tag:theconversation.com,2011:/fr/topics/endocrinology-6704/articlesEndocrinology – The Conversation2023-10-12T16:37:24Ztag:theconversation.com,2011:article/2151102023-10-12T16:37:24Z2023-10-12T16:37:24ZThe ‘male menopause’ – what you need to know<p><a href="https://www.itv.com/news/central/2023-10-04/nhs-trust-to-give-staff-paid-leave-for-male-menopause">East Midlands Ambulance Service</a> is reportedly giving men up to a year of paid leave for “<a href="https://www.nhsemployers.org/system/files/2021-06/East%20Midland%20Ambulance%20Service%20andropause%20in%20the%20workplace%20guidance.pdf">andropause related issues</a>”, which some are calling the “male menopause”.</p>
<p>This move has <a href="https://www.thetimes.co.uk/article/mariella-frostrup-men-get-your-hands-off-our-menopause-zccdh78hg">angered some commentators</a> who question whether there really is such a thing as the male menopause or “manopause”.</p>
<p>The andropause is not a condition that was recently invented. The medical establishment has been talking about it since <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4046605/#:%7E:text=%E2%80%9CAndras%E2%80%9D%20in%20Greek%20means%20human,of%20testosterone%20in%20older%20man">the 1940s</a> when it was known as the “male climacteric”. Symptoms of this condition include a lack of energy, weight gain (including “man boobs”), sexual difficulties, sleep problems, anxiety, irritability, depression and even hot flushes.</p>
<p>While many private clinics recognise and treat andropause, it is not recognised as a syndrome by the <a href="https://www.nhs.uk/conditions/male-menopause/">NHS</a>, nor is it usually caused by a radical drop in “male hormones”, such as testosterone. Testosterone levels do naturally decline in men, but the average decrease is around <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4046605/#:%7E:text=%E2%80%9CAndras%E2%80%9D%20in%20Greek%20means%20human,of%20testosterone%20in%20older%20man">1% per year</a> after <a href="https://health.clevelandclinic.org/declining-testosterone-levels/#:%7E:text=The%20average%20drop%20is%20about,1987%2C%201995%20and%202002.">the age of 30</a>. </p>
<p>Less common – only seen in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4046605/#:%7E:text=%E2%80%9CAndras%E2%80%9D%20in%20Greek%20means%20human,of%20testosterone%20in%20older%20man">6% of adult men under 80</a> – are chronically low levels of testosterone, also known as androgen deficiency. This may result from accidents affecting their testes, experiencing severe illness, or treatment for prostate cancer. </p>
<p>The natural drop in testosterone can be worsened by obesity, extreme stress and some medications or diseases, including drinking too much alcohol. So the andropause is probably more of a lifestyle symptom and therefore should be tackled as such.</p>
<p>The recent media <a>spotlight</a> on female menopause has highlighted just how badly women can be affected by midlife reduction in hormone levels. So much so that the <a href="https://www.theguardian.com/society/2022/apr/24/sajid-javid-appoint-hrt-tsar-acute-shortages-menopause">UK government</a> had to appoint a dedicated “menopause tsar” to deal with the resulting shortage of oestrogel, a popular <a href="https://www.fertifa.com/post/hrt-shortage-and-how-to-get-hrt">form of HRT</a>, as more and more women seek menopause treatment.</p>
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<a href="https://theconversation.com/menopausal-women-often-turn-to-doctors-who-know-little-about-the-symptoms-heres-what-needs-to-change-207450">Menopausal women often turn to doctors who know little about the symptoms – here's what needs to change</a>
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<p>The East Midlands Ambulance Service is commendable in wanting to support men in making mid-life lifestyle changes, but calling it the “male menopause” undermines the magnitude of the physiological changes women experience as part of female menopause. </p>
<p>For men, lifestyle <a href="https://www.emerald.com/insight/content/doi/10.1108/WWOP-12-2016-0036/full/html">changes</a> can have huge benefits. Taking care of heart health, exercise and healthy diets <a href="https://pubmed.ncbi.nlm.nih.gov/36697895/">in midlife</a> are known to be good for brain function and can help prevent dementia and heart disease later on.</p>
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<img alt="Middle-aged man stretching in a park." src="https://images.theconversation.com/files/553480/original/file-20231012-15-y9c82z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553480/original/file-20231012-15-y9c82z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553480/original/file-20231012-15-y9c82z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553480/original/file-20231012-15-y9c82z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553480/original/file-20231012-15-y9c82z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553480/original/file-20231012-15-y9c82z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553480/original/file-20231012-15-y9c82z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Exercise can stave off some of the effects of declining male hormones.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/staying-active-after-retirement-happy-joyful-2131333251">Evgeny Atamanenko/Shutterstock</a></span>
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<h2>Hormone replacement</h2>
<p>While many women report that taking sex hormones helps with brain problems, actual studies do not show overall long-term benefit of hormone treatment on <a>memory or mood</a>. There are also <a href="https://www.nhs.uk/medicines/hormone-replacement-therapy-hrt/benefits-and-risks-of-hormone-replacement-therapy-hrt/">small risks linked with taking hormone therapy</a>. </p>
<p>In contrast, for those who have had their ovaries or testes removed, or take hormone blockers because of cancers, a significant drop in memory and mood can occur and reduced testosterone has been associated with an increased risk for dementia, such as <a href="https://pubmed.ncbi.nlm.nih.gov/21696899/">Alzheimer’s disease</a> and heart disease – the two main causes of death in the UK. </p>
<p>However, it is unclear whether testosterone treatment helps to reduce this risk in men, as some studies showed an increased risk of heart disease, while others found testosterone treatment to be protective or have <a href="https://www.thelancet.com/journals/lanhl/article/PIIS2666-7568(22)00115-5/fulltext">no effect</a>.</p>
<p>In men with low testosterone levels, overall <a href="https://www.thelancet.com/journals/lanhl/article/PIIS2666-7568(23)00169-1/fulltext#:%7E:text=We%20observed%20that%20testosterone%20treatment,testosterone%20but%20without%20classic%20hypogonadism">studies</a> suggest that taking testosterone reduced depression and improved erections and libido. There may also be benefits of oestrogen or <a href="https://www.ohsu.edu/sites/default/files/2019-09/CPD%20AMH919-Adams%20handouts.pdf">testosterone</a> gel on sexual function in women. </p>
<p>However, study results have been mixed and caution should always be taken with interpreting the results of research sponsored by the industries producing the treatments. Also, libido is not simply linked to hormones, and a dry vagina or limp penis can be influenced by factors such as relationship stress or work stress – or both.</p>
<h2>The stress effect</h2>
<p>Could andropause be a manifestation of midlife stress? Most likely. And this is not a matter of hormone change. Rather, while dips in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7347230/">life satisfaction</a> are only seen in 10-20% of adults in middle age (and often not shown over time), this is probably the result of an evaluation of life at this important new stage.</p>
<p>Importantly, <a href="https://www.mentalhealth.org.uk/explore-mental-health/a-z-topics/men-and-mental-health">suicide risk</a> is highest in men between 40 and 49 and is the most common cause of death in men under 50. Many men may mask their depression with alcohol, drugs and overwork. This risk is highest in the poor.</p>
<p>We should applaud the East Midlands Ambulance Service for paying attention to men’s mental health, but maybe not because of the andropause. Rather, interventions that tackle <a href="https://www.glassdoor.co.uk/Salaries/emergency-ambulance-crew-salary-SRCH_KO0,24.htm">poor pay</a>, working conditions, job stress, <a href="https://aace.org.uk/vaa/#:%7E:text=Every%20day%20during%20the%202020,over%20the%20last%20five%20years">public harassment</a> and work-life satisfaction may help improve mental health more than framing these concerns as male menopause.</p>
<p>In the full statement by the East Midlands Ambulance Services, it was made clear that there is no separate or special leave policy for andropause with 12 months off on full pay. Instead, decisions are made on a case-to-case basis, trying to keep staff in work where possible and supporting them with their mental health in a wide variety of ways.</p><img src="https://counter.theconversation.com/content/215110/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Eef Hogervorst received funding from the Alzheimer's Association and RIA to investigate sex hormone levels and dementia. She also received funding from the British Council Newton Trust to investigate soy and dementia risk. Eef reviewed evidence for dementia risk after taking menopausal HRT for NICE in 2022-2023. </span></em></p><p class="fine-print"><em><span>Emma D'Donnell and Gemma Witcomb do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Testosterone in men declines at a rate of around 1% a year from age 30. That doesn’t mean that men go through the ‘manopause’.Eef Hogervorst, Professor of Biological Psychology, Loughborough UniversityEmma D'Donnell, Senior Lecturer in Exercise Physiology, Loughborough UniversityGemma Witcomb, Senior Lecturer in Psychology, Loughborough UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1732102022-01-28T13:27:13Z2022-01-28T13:27:13ZNew insights from biology can help overcome siloed thinking in cancer clinical trials and treatment<figure><img src="https://images.theconversation.com/files/441611/original/file-20220119-25-164wpa0.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C537%2C420&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Metabolic conditions like obesity and diabetes can influence how cancer develops and responds to treatment.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/chemo-therapy-royalty-free-image/1134307405?adppopup=true">Eric Kitayama/iStock via Getty Images Plus</a></span></figcaption></figure><p>Rarely does an oncologist closely question a breast cancer patient about their blood glucose, body weight, lipid profile, or medications for diabetes and cardiovascular disease. Instead, these issues are usually the concern of the patient’s primary care provider. </p>
<p>Medical experts have <a href="https://doi.org/10.1152/physrev.00030.2014">recognized that obesity</a>, defined as a body mass index of 30 or greater, increases the <a href="https://doi.org/10.1016/j.canep.2016.01.003">risk of several cancers</a>. They include cancers of the breast, esophagus, kidney, gallbladder, liver, colon and several other organs. We have been aware of this relationship for <a href="https://doi.org/10.1038/sj.onc.1207751">about 20 years</a>. Despite this awareness, medicine is still missing a holistic view of people with cancer.</p>
<p>When testing new cancer drugs, clinical trials traditionally exclude patients with a history of heart disease, kidney disease, diabetes or similar chronic conditions related to obesity. The purpose is to make <a href="https://doi.org/10.1001/jamaoncol.2019.1187">study results easier to interpret</a>. But this practice leaves cancer researchers with a weak understanding of how patients could be monitored and treated for <a href="https://doi.org/10.1038/nrc1550">obesity-driven cancers</a>. One way it limits their knowledge is by leaving out significant numbers of patients. Among them are patients of color, who are already underrepresented in <a href="https://doi.org/10.3233/SHTI190369">scientific studies</a> generally and <a href="https://doi.org/10.1002/cncr.23157">cancer treatment treatment trials</a> in particular.</p>
<p>As a <a href="https://profiles.bu.edu/Gerald.Denis">molecular oncologist</a> at Boston Medical Center, I explore how metabolic conditions like <a href="https://scholar.google.com/citations?user=2f8xa-oAAAAJ&hl=en">obesity and diabetes</a> can influence whether someone develops cancer. I look closely at how these conditions can affect how the cancer grows, spreads or responds to treatment.</p>
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<img alt="Blue-gloved hand holding clear vial of blood." src="https://images.theconversation.com/files/441767/original/file-20220120-8584-1uztb33.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441767/original/file-20220120-8584-1uztb33.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441767/original/file-20220120-8584-1uztb33.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441767/original/file-20220120-8584-1uztb33.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441767/original/file-20220120-8584-1uztb33.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441767/original/file-20220120-8584-1uztb33.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441767/original/file-20220120-8584-1uztb33.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Less invasive cancer detection and treatment is one potential benefit of better communication between endocrinologists and cancer specialists.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/blood-sample-for-lipid-profile-testing-medical-royalty-free-image/1354714222?adppopup=true">Juan Ruiz Parmo/iStock via Getty Images Plus</a></span>
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<p>Our teams at Boston Medical Center’s Cancer Center have have identified how obesity and diabetes may provoke cancer to spread in potentially deadly ways. In particular, <a href="https://doi.org/10.1016/S0026-0495(78)80007-9">insulin-resistant fat cells</a> are likely to play a critical role in provoking breast cancer cells to move from the original tumor to distant organs like the lungs, liver, bones or brain. These distant metastases commonly define the end stage before someone with breast cancer dies.</p>
<p>Our results show that in the <a href="https://doi.org/10.1126/scisignal.abj2807">microscopic neighborhood inside or near a tumor</a>, cancer cells and noncancerous fat cells sit right next to each other, like neighbors on a park bench. Our research has shown that these two cell types engage in active “cross-talk.” This communication may inhibit or promote a tumor’s ability to grow and spread. How that happens is not well understood, partly because oncologists – whether studying cancer or treating it – generally don’t take nearby fat cells into consideration. </p>
<h2>Strategic diagnosis and treatment</h2>
<p>Acknowledging the relationship between fat cells and cancer cells offers opportunities to find and treat cancer less invasively. With molecules isolated from just a teaspoon or less of a patient’s blood, specialists can learn the risk that the cancer might be growing and spreading. These molecules, <a href="https://doi.org/10.1016/j.molonc.2012.01.010">called biomarkers</a>, can also show which patients are in the greatest danger of treatment failure. Taking occasional blood samples is less invasive than repeated biopsies, which involves getting samples of breast or other tissue. </p>
<p>When endocrinologists and oncologists consult with one another, they can consider obesity and metabolism alongside the current standard of care for patients with cancer. This combination would likely benefit populations, like <a href="https://doi.org/10.1200/JCO.2003.08.010">older adults</a>, in which both obesity and metabolic disease are more prevalent. </p>
<p>Furthermore, the cancer patient population may soon include more <a href="https://doi.org/10.1038/s41571-020-00445-1">young people</a>. A 2019 study found that people age 50 or younger have a <a href="https://doi.org/10.1016/S2468-2667(18)30267-6">disproportionately elevated risk</a> for certain obesity-driven cancers, including obesity-associated colorectal cancer. The relationship between fat cells and cancer cells could explain some of these trends.</p>
<h2>Closing gaps in care</h2>
<p>And already, more young African American adults are developing <a href="https://doi.org/10.1097/MEG.0000000000001205">aggressive colorectal cancers</a> than young adults of <a href="https://doi.org/10.3322/caac.21555">other races</a>. This fact came to the nation’s attention in 2020, when actor <a href="https://doi.org/10.2196/29387">Chadwick Boseman died</a> from an <a href="https://doi.org/10.1002/cncr.33919">aggressive colon cancer</a> at age 43. </p>
<p>Although Boseman was not overweight, his death brought attention to the community of African American adults who experience higher risks not only <a href="https://doi.org/10.1007/s10549-015-3353-z">for obesity</a> and <a href="https://doi.org/10.2105/ajph.92.4.543">diabetes</a> but also for several cancers including <a href="https://doi.org/10.1007/s11934-017-0724-5">prostate</a>, <a href="https://doi.org/10.1158/1055-9965.EPI-07-0336">breast</a> and <a href="https://doi.org/10.1053/j.gastro.2019.10.029">colorectal</a>. And despite their higher risks, Black patients are often not effectively counseled <a href="https://doi.org/10.1093/jnci/djab073">by physicians</a> regarding cancer risk and treatment.</p>
<p>[<em>Get fascinating science, health and technology news.</em> <a href="https://memberservices.theconversation.com/newsletters/?nl=science&source=inline-science-fascinating">Sign up for The Conversation’s weekly science newsletter</a>.]</p>
<p>At Boston Medical Center, 50% of our patients have diagnoses of obesity and 30% have Type 2 diabetes. We see similar numbers and patterns in our cancer patient population. One potential reason is that Boston Medical Center is a <a href="https://doi.org/10.1177/1077558708315440">safety-net hospital</a>, providing essential and excellent care to a very diverse range of patients regardless of insurance, immigration status or medical literacy. Such hospitals are often located in neighborhoods with high rates of <a href="https://doi.org/10.1001/archinternmed.2011.287">obesity and diabetes</a>.</p>
<p>Black and Latino adults with cancer tend to be overrepresented in <a href="https://doi.org/10.1007/BF02345673">safety-net hospital systems</a>. They receive cancer screenings <a href="https://doi.org/10.1016/j.athoracsur.2019.11.052">less often</a>. They also experience
<a href="https://doi.org/10.1080/03630242.2010.530928">longer wait times</a>, first for diagnosis and then for treatment. These factors contribute to <a href="https://doi.org/10.1016/j.canep.2017.05.003">worse survival rates</a> among Black and Latino cancer patients. Some of these worse outcomes may be a result of cancer and diabetes <a href="https://doi.org/10.1530/ERC-16-0222">interacting in these patients</a>.</p>
<p>Addressing disparities like these would be a natural benefit of bringing together previously disconnected clinical specialties. Research on the linkage among obesity, diabetes and cancer is revealing new pathways and molecules that tie these different diseases together. These new insights could improve outcomes for patients who are at greatest risk, and prompt more holistic assessments and treatments for all patients.</p><img src="https://counter.theconversation.com/content/173210/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gerald Denis receives funding from the National Cancer Institute.</span></em></p>Fat cells and cancer cells talk to each other. Specialists in both systems can do the same.Gerald Denis, Professor of Medicine and Pharmacology, Boston UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1688202021-10-01T19:17:35Z2021-10-01T19:17:35ZTylenol could be risky for pregnant women – a new review of 25 years of research finds acetaminophen may contribute to ADHD and other developmental disorders in children<figure><img src="https://images.theconversation.com/files/424065/original/file-20210930-22-wgb0x.jpg?ixlib=rb-1.1.0&rect=123%2C22%2C1993%2C1387&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Nearly 100 scholars and health care professionals are urging women to limit their use of acetaminophen during pregnancy. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/midsection-of-pregnant-woman-holding-her-belly-royalty-free-image/1310443783?adppopup=true"> Oscar Wong/Moment via Getty Images</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p>A mounting body of evidence shows that the use of acetaminophen - widely known by its brand name Tylenol - during pregnancy may pose risks to the fetus and to early childhood development. That was the conclusion of a <a href="https://doi.org/10.1038/s41574-021-00553-7">new review study</a> on which I was a lead author. </p>
<p>Acetaminophen, which has the chemical name paracetamol, is a go-to over-the-counter medication that is widely recommended by doctors to relieve pain and reduce fever.</p>
<p>Our study, based on an assessment of 25 years of research in the areas of human epidemiology, animal and in-vitro studies, concludes that prenatal acetaminophen exposure may increase the risks of reproductive organs developing improperly. We identified a heightened risk of <a href="https://doi.org/10.1111/ppe.12632">neurodevelopmental disorders</a>, primarily attention deficit hyperactivity disorder and related behaviors, but also autism spectrum disorder, as well as language delays and decreased IQ. </p>
<p>In our consensus statement – a broad agreement by our multidisciplinary international panel of experts – published in Nature Reviews Endocrinology in September 2021, 91 clinicians and researchers are calling for caution and additional research.</p>
<h2>Why it matters</h2>
<p>Acetaminophen is an active ingredient in <a href="https://www.chpa.org/our-issues/otc-medicines/acetaminophen">over 600 prescription and over-the-counter medications</a>, including Tylenol. It is used by more than <a href="https://doi.org/10.1002/aur.1591">50% of pregnant women</a> worldwide and at least <a href="https://doi.org/10.1016/j.ajog.2005.02.100">65% of pregnant women</a> in the U.S. Research suggests that acetaminophen is an endocrine disruptor and may interfere with the hormones essential for healthy neurological and <a href="https://doi.org/10.1289/EHP2478">reproductive development</a>.</p>
<p>A spokeswoman for Johnson & Johnson, which makes Tylenol, <a href="https://www.cnn.com/2021/09/23/health/acetaminophen-pregnancy-wellness/index.html">told CNN</a> in September that the product label tells women who are pregnant or breastfeeding to ask a health care professional before using it.</p>
<p>Current <a href="https://mothertobaby.org/fact-sheets/acetaminophen-pregnancy/">guidance recommends</a> acetaminophen as the pain reliever of choice during pregnancy, as <a href="https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/expert-answers/aspirin-during-pregnancy/faq-20058167">other pain relievers</a> such as <a href="https://www.fda.gov/drugs/drug-safety-and-availability/fda-recommends-avoiding-use-nsaids-pregnancy-20-weeks-or-later-because-they-can-result-low-amniotic">ibuprofen and aspirin are not considered safe</a> after <a href="https://mothertobaby.org/fact-sheets/ibuprofen-pregnancy/">midpregnancy</a>.</p>
<p>Rates of <a href="https://doi.org/10.1152/physrev.00017.2015">reproductive disorders</a> and neurodevelopmental disorders, <a href="https://www.cdc.gov/ncbddd/adhd/timeline.html">such as ADHD</a> and <a href="https://autismsciencefoundation.org/what-is-autism/how-common-is-autism/">autism spectrum disorder</a>, have <a href="https://doi.org/10.1542/peds.2019-0811">been increasing</a> over the last 40 years. </p>
<p>Over the same time period, the use of acetaminophen during pregnancy <a href="https://doi.org/10.1016/j.ajog.2005.02.100">has gone up</a>. We conclude that because <a href="https://doi.org/10.1016/j.annepidem.2017.09.003">acetaminophen is so commonly taken during pregnancy</a>, if its use is responsible for even a small increase in individual risk, it could contribute substantially to these disorders in the <a href="https://doi.org/10.1136/bmj.k757">overall population</a>.</p>
<h2>What still isn’t known</h2>
<p>It’s unethical to do experiments that could harm a human life, so to gain a better understanding of the direct effects of acetaminophen during pregnancy, we must rely on human observational and experimental studies to assess the possibility of causal connections. But to really get at these questions, we need human cohort studies that can precisely capture when and why acetaminophen is taken during pregnancy. Additionally, we would like to see research that gives us a better understanding of the biologic pathways. </p>
<p>Notably, acetaminophen is also the medication <a href="https://doi.org/10.1542/peds.2008-2869">most commonly</a> <a href="https://doi.org/10.1016/j.jped.2014.03.004">given to infants</a>. More research is needed to determine whether this practice is safe for the developing brain. </p>
<h2>What’s next</h2>
<p>The current near-ubiquitous use of acetaminophen during pregnancy is due in part to the <a href="https://doi.org/10.2174/1381612825666190321110420">widespread perception</a> – even among doctors – that it has limited side effects and negligible risk. But a growing body of research suggests that the <a href="https://doi.org/10.1016/j.yhbeh.2018.01.003">indiscriminate use</a> of acetaminophen during pregnancy – especially for conditions such as <a href="https://doi.org/10.1111/bcpt.12527">chronic pain</a>, <a href="https://doi.org/10.1002/14651858.CD012230">low back pain</a> and <a href="https://doi.org/10.1002/14651858.CD011889.pub2">headaches</a> – may be unwarranted and unsafe.</p>
<p>In our consensus statement, we urge education of health professionals and pregnant women about the risks and benefits of acetaminophen use during pregnancy.</p>
<p>Based on our extensive review of the evidence – and the recognition that there are limited alternatives for the necessary treatment of high fever and severe pain – we recommend that pregnant women refrain from using acetaminophen unless it is medically recommended by a doctor. Women should also minimize risk to the fetus by using the lowest effective dose for the shortest possible time.</p>
<p><em>This article was updated on Oct. 4, 2021, to include a statement from Johnson & Johnson.</em></p>
<p>[<em>Get the best of The Conversation, every weekend.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybest">Sign up for our weekly newsletter</a>.]</p><img src="https://counter.theconversation.com/content/168820/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ann Z. Bauer does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Tylenol has long been considered a go-to medication for low to moderate pain and for fever reduction, even during pregnancy. But mounting evidence suggests that it is unsafe for fetal development.Ann Z. Bauer, Postdoctoral Fellow in Epidemiology, UMass LowellLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1558412021-02-26T13:25:21Z2021-02-26T13:25:21ZWhat are phthalates, and how do they put children’s health at risk?<figure><img src="https://images.theconversation.com/files/386581/original/file-20210225-19-1wfq2w3.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5362%2C3583&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Phthalates can be found in many common products and types of plastic packaging.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/plastic-bags-and-bottles-royalty-free-image/1127955502">Curtoicurto via Getty Images</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>You may not realize it, but you likely encounter phthalates <a href="https://www.cdc.gov/biomonitoring/Phthalates_FactSheet.html">every day</a>. These chemicals are found in many plastics, including food packaging, and they can migrate into food products during processing. They’re in personal care products like shampoos, soaps and laundry detergents, and in the vinyl flooring in many homes. </p>
<p>They’re also in the news again after an editorial by scientists in the <a href="https://ajph.aphapublications.org/doi/pdf/10.2105/AJPH.2020.306014">American Journal of Public Health</a> included an urgent call for better federal regulation of the chemicals.</p>
<p>In particular, scientists are urging state and federal agencies to eliminate phthalates (pronounced THAL-ates) from products used by pregnant women and children. Despite evidence of the harm these chemicals can cause, federal regulation in the United States has been minimal beyond <a href="https://www.federalregister.gov/documents/2018/01/26/2018-01451/prohibition-of-childrens-toys-and-child-care-articles-containing-specified-phthalates-revision-of">children’s toys</a>. A recent move by the General Mills-owned food brand Annie’s to <a href="https://www.annies.com/faq/">eliminate phthalates from its macaroni and cheese</a> suggests stricter rules are feasible.</p>
<p>So, what’s the risk, and what can you do about it? </p>
<p>I’m an <a href="https://scholar.google.com/citations?user=wKXbh1UAAAAJ&hl=en">environmental epidemiologist</a> who studies the impact of pregnant women’s exposure to environmental chemicals. Here are answers to three important questions about phthalates.</p>
<h2>Who’s at risk?</h2>
<p>Ortho-phthalates, commonly referred to as phthalates, are synthetic chemicals that are used to manufacture plastic. They help make plastic more flexible and harder to break. </p>
<p>Despite their abundance in many products, phthalates can be harmful to <a href="https://www.sciencedirect.com/science/article/pii/S0160412018329908">pregnant women</a> and <a href="https://www.sciencedirect.com/science/article/pii/S0013935115001899?via%3Dihub">their children</a>. These chemicals can disrupt the endocrine system, the glands that release hormones as the body’s chemical messengers. Studies suggest that can lead to pregnant women <a href="https://www.sciencedirect.com/science/article/pii/S0160412021000684">delivering their babies early</a>. Other studies have found that children born to mothers exposed to high levels of phthalates can have a <a href="https://www.sciencedirect.com/science/article/pii/S0013935115001899?via%3Dihub">lower IQ</a> and poorer social communication development, and that these children are also more likely to develop <a href="https://ehp.niehs.nih.gov/doi/10.1289/EHP2358">ADHD</a> and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0161813X18303255?via%3Dihub">behavior problems</a>. Researchers have also found effects on the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1280349/">genital development of male infants</a> born to mothers exposed to phthalates during pregnancy.</p>
<p>While phthalates can be found in nearly everyone, <a href="https://www.sciencedirect.com/science/article/pii/S0160412018329908">minority women have been found to be especially burdened</a>. Studies show that many <a href="https://doi.org/10.1016/j.envres.2018.03.030">beauty products</a> targeted at these communities contain high levels of chemicals.</p>
<p><a href="http://doi.org/10.1097/MOP.0b013e32835e1eb6">Infants and young children</a> may experience high phthalate levels because they often put plastic products in their mouths as they explore the world.</p>
<p>Phthalates can enter food at <a href="https://www.cdc.gov/biomonitoring/Phthalates_FactSheet.html">many places</a> in the supply chain, including through plastic tubing for liquids during production, plastic storage containers and even food preparation gloves. Foods that are <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4050989/">high in fat</a> in particular can absorb phthalates through exposure during processing. Eating out doesn’t avoid the risk. A <a href="https://doi.org/10.1016/j.envint.2018.02.029">study of U.S. children and adults</a> showed that those who ate food outside of their homes had higher phthalate levels.</p>
<h2>How do I know if a product has phthalates?</h2>
<p>Figuring out which products have high levels of phthalates isn’t always easy. While <a href="https://phthalates.americanchemistry.com/">phthalates</a> are required to be listed on ingredients labels, they are sometimes included instead as part of the fragrance, which <a href="https://www.safecosmetics.org/fragrance-disclosure/learn-more/trade-secrets/">allows them to be excluded</a> from the ingredients list. </p>
<p>Many companies have voluntarily removed phthalates, and many consumer products are now labeled “phthalate free.” The <a href="https://www.ewg.org/skindeep/">Environmental Working Group</a>’s Skin Deep website also offers a way to search for details about chemicals in cleaning and personal care products.</p>
<h2>How do I keep my family safe?</h2>
<p>Phthalates are <a href="https://www.cdc.gov/biomonitoring/Phthalates_FactSheet.html">rapidly metabolized</a> and generally removed from the body once exposure stops. Until there is better regulation, a few simple changes can make a big difference in promoting health and reducing phthalate levels in the home. </p>
<p>One <a href="http://doi.org/10.1289/ehp.1003170">easy change</a> is to swap out all plastic food packaging containers with glass containers. If that’s not possible, it’s best to let food cool to room temperature before placing it in plastic food storage containers. </p>
<p>Don’t microwave anything in plastic, because phthalates can <a href="http://doi.org/10.3390/ijerph110100507">migrate from food storage containers</a> into food. </p>
<p>You can also reduce phthalate exposure by checking labels to avoid using products that include phthalates, by <a href="http://doi.org/10.1289/ehp.1003170">eating less processed food</a> that might have absorbed phthalates during production, and by cooking more meals at home.</p><img src="https://counter.theconversation.com/content/155841/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephanie Eick does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Scientists issued an urgent call for better federal regulation of these endocrine-disrupting chemicals. Here’s what you can do to reduce your family’s risk.Stephanie Eick, Postdoctoral Researcher in Reproductive Health, University of California, San FranciscoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1135872019-04-16T09:29:51Z2019-04-16T09:29:51ZTestosterone: why defining a ‘normal’ level is hard to do<figure><img src="https://images.theconversation.com/files/267612/original/file-20190404-123413-1emyzsy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/509354542?size=medium_jpg">Marc Bruxelle/Shutterstock</a></span></figcaption></figure><p>Testosterone is the main sex hormone in men. It’s best known for its role in the development of male sexual characteristics and physical features, but there are also many surprising and lesser known functions of testosterone that make it an important hormone in health and disease. Identifying whether someone has too much or too little testosterone can predict future diseases and even treat them. But knowing what is high, low or normal for an individual isn’t straightforward.</p>
<p>Testosterone plays an important role in how male reproductive tissues – such as the testicles and the prostate – develop, as well as promoting what are known as secondary sexual characteristics, such as increased muscle, bigger bones, deep voice and the growth of body hair – all the things we associate with being male. Females also produce testosterone, although in much lower amounts. It helps with the growth and maintenance of a woman’s reproductive tissue, strengthens bones and can influence mood and behaviour. </p>
<p>As with many hormones, the importance of testosterone becomes even more apparent when we look at people who don’t have enough. </p>
<p>Doctors measure testosterone in nanomoles per litre (nmol/l) and the reported “normal” healthy range in males is anywhere from <a href="https://academic.oup.com/jcem/article/102/4/1161/2884621">9.2 to 31.8 nmol/L</a>. It is about ten times lower in females, with “normal” levels considered to be between <a href="https://www.mayocliniclabs.com/test-catalog/Clinical+and+Interpretive/83686">0.3 and 2.4 nmol/L</a>. Despite these lower levels in women, testosterone circulates in the blood at higher concentrations than oestrogen, the typical female hormone.</p>
<p>But it is difficult to know what is the right level of testosterone, and these ranges are often <a href="https://www.ncbi.nlm.nih.gov/pubmed/17100942?dopt=Abstract&holding=npg">not agreed on</a> by experts from different societies, countries or laboratories. </p>
<p>Nevertheless, low levels of testosterone in men can result in a lack of energy and strength, a reduced sex drive and putting on weight. Many of these symptoms are actually the same in women who also have low testosterone, and now research suggests that low testosterone can be a risk factor for developing heart disease, diabetes and obesity in both men and women.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/267618/original/file-20190404-123397-1edkq1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/267618/original/file-20190404-123397-1edkq1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267618/original/file-20190404-123397-1edkq1s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267618/original/file-20190404-123397-1edkq1s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267618/original/file-20190404-123397-1edkq1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267618/original/file-20190404-123397-1edkq1s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267618/original/file-20190404-123397-1edkq1s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Low testosterone can increase the risk of obesity, in men and women.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/1212097219?size=medium_jpg">India Picture/Shutterstock</a></span>
</figcaption>
</figure>
<h2>The Goldilocks zone</h2>
<p>Really high testosterone levels in men tend not to occur naturally, but it is known that male athletes abusing testosterone or other similar steroids for performance gains often have problems with their heart. Likewise, certain diseases in women that result in high testosterone also lead to similar risks for heart disease. This means that testosterone appears to be best for health when it stays within a certain range: not too high and not too low. </p>
<p>Complicating this matter is the fact that testosterone levels don’t stay the same through life, through the year or even through the day – at least in men. Testosterone levels change throughout the day in men, peaking at around <a href="https://www.sciencedirect.com/science/article/pii/0039128X73901104">4-8am and falling to their lowest at about 12 hours later</a>. They can also vary across the year, although these seasonal highs and lows will differ around <a href="https://www.ncbi.nlm.nih.gov/pubmed/22790643">the world</a>. These daily and seasonal variations can see levels change by as much as 19%.</p>
<p>Men’s testosterone levels in the blood are thought to fall with age, although this may actually be more related to diseases that occur with age. Women’s testosterone levels are a bit more stable, without any known daily or yearly changes. As with men, however, they also decrease a little with age. And it is these falling levels that increase the risk of disease. </p>
<p>Complicating matters even further is the fact that everybody is different, particularly in the way that testosterone works. </p>
<h2>Approximations of the truth</h2>
<p>Testosterone takes action when it joins onto its receptor in any particular cell in our body. But how well it does this to bring about the functions mentioned above differs from person to person, which is influenced by genetics. So what might be considered a low level for one person may actually be OK if they have a more sensitive receptor capable of carrying out testosterone’s actions at lower concentrations. In fact, when we look at some diseases in men that are thought to result from low testosterone, not everyone below the normal range develops the disease.</p>
<p>It is unclear whether it is also due to similar genetic factors, but testosterone can also be different depending on where you <a href="https://www.nature.com/articles/s41559-018-0567-6">live and how wealthy you are</a>. So a universal “normal range” may not apply to all groups of people. </p>
<p>Establishing a “normal” level is complex, and measuring testosterone on its own may not be enough to estimate what is the correct level to have in the blood for any one person. Still, research tries to define levels that are healthy, and levels that may be related to disease so patients can be identified and treated. Still, these are approximations of the truth in specific populations with specific genetics, backgrounds and disease. Like the story of the <a href="https://www.allaboutphilosophy.org/blind-men-and-the-elephant.htm">blind men feeling different parts of an elephant</a>, we can only build up a picture of the truth from small parts in the search to find the answers.</p>
<p>Using average levels of testosterone from lots of people from different populations to establish normal ranges is useful to help identify people outside of this range with a related disease. But many factors have to be considered when deciding whether someone has normal testosterone or not and whether there truly is a “normal” testosterone level at all.</p><img src="https://counter.theconversation.com/content/113587/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Kelly does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>So-called normal levels of testosterone are approximations, but can help researchers investigate disease and treatments.Daniel Kelly, Lecturer in Biochemistry, Sheffield Hallam UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/758972017-05-11T06:23:03Z2017-05-11T06:23:03ZEveryday chemicals may affect brain development, including foetal IQ<figure><img src="https://images.theconversation.com/files/167513/original/file-20170502-17281-1warhub.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Disruption of the thyroid hormones can prevent tadpoles from becoming frogs. </span> <span class="attribution"><a class="source" href="https://pixabay.com/en/tadpole-frog-nature-wildlife-1328874/">Coffee/Pixabay</a></span></figcaption></figure><p>All vertebrates – from frogs and birds to human beings – require the same thyroid hormone to thrive. Every stage of brain development is modulated by <a href="https://www.ncbi.nlm.nih.gov/pubmed/25905404">thyroid hormone</a> and, over millions of years, the structure of this critical hormone has remained unchanged. </p>
<p>But, increasingly, the trappings of modern life are preventing it from playing its critical role in human brain development. Thyroid hormone signalling is very vulnerable to interference by chemicals that can scramble the endocrine communication routes between cells. </p>
<p>These endocrine disruptors, as they are called, include ubiquitous chemicals such as pesticides, plastifiers, flame retardants and surfactants, all of which are found in our food, non-stick pans, furniture, cleaning products, clothes and cosmetics. They are even found in the air we breath and the water we drink.</p>
<p>This is bad news for our brains, and children’s brains in particular. Thyroid hormone serves multiple functions in orchestrating the production and differentiation of the 100 billion cells that make up the human brain. Without the right amount of thyroid hormone at the right time, human babies will suffer <a href="https://www.ncbi.nlm.nih.gov/pubmed?db=pubmed&cmd=link&linkname=pubmed_pubmed&uid=7744994">severe intellectual disabilities</a>, developing an IQ of only about 35.</p>
<p>In a <a href="http://umr7221.mnhn.fr/spip.php?article66">recent experiment</a>, conducted on tadpoles, we tested the hypothesis that common chemicals in the environment, singly and as a mixture, can interfere with brain development in humans.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/166964/original/file-20170427-15112-1365mli.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166964/original/file-20170427-15112-1365mli.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166964/original/file-20170427-15112-1365mli.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166964/original/file-20170427-15112-1365mli.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166964/original/file-20170427-15112-1365mli.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166964/original/file-20170427-15112-1365mli.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166964/original/file-20170427-15112-1365mli.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tadpoles help scientists understand how human brains develop, as we share similar thyroid hormones.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/benimoto/2548615317">Benny Mazur/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Previous work had showed that tadpoles with endocrine disorders <a href="https://doi.org/10.1016/j.ydbio.2015.02.018">couldn’t metamorphose</a>, that is, they never become frogs. Our paper, published on March 7 in <a href="https://www.nature.com/articles/srep43786">Scientific Reports</a>, shows that young tadpoles exposed to a mixture of common chemicals at concentrations routinely found in human amniotic fluid not only modified thyroid hormone signalling but also reduced the total number and size of neurons and inhibited tadpole movement.</p>
<p>Even with limited exposure of three days, we observed significant effects on the tadpoles’ brain development. Tadpoles have long been used to study human developmental processes, including in the first cloning experiments <a href="https://doi.org/10.1242/dmm.002014">back in the late 1950s</a> because they offer important insights into how brains develop.</p>
<h2>The autism debate</h2>
<p>These findings raise a number of concerns. </p>
<p><a href="http://web.unep.org/">Global chemical production has increased 300 times</a> over the last 50 years, according to the United Nations Environment Programme. Given that all of the common molecules we used in our experiment are found at similar concentrations in human amniotic fluid, one must be concerned about the potential effects of this mixture on foetal brain development. </p>
<p>In recent years, <a href="https://www.ncbi.nlm.nih.gov/pubmed/26497402">we have learned</a> that small variations in a woman’s thyroid hormone levels during early pregnancy significantly impact her child’s IQ and brain structure, including the ratio of grey matter (neurons) to white matter (glia cells). </p>
<p>Similarly, it has been repeatedly shown in <a href="https://doi.org/10.1289/ehp.0901340">longitudinal epidemiological studies</a> that children born to mothers with high levels of certain thyroid disrupting chemicals, <a href="https://doi.org/10.1016/j.envres.2014.05.024">such as PCBs or flame-retardants</a>, have lower IQs. Children born to mothers exposed to pesticides or other chemicals can also display <a href="https://doi.org/10.1289/ehp.1307044">more neurodevelopmental problems</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/167518/original/file-20170502-17245-1r4m579.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/167518/original/file-20170502-17245-1r4m579.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/167518/original/file-20170502-17245-1r4m579.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/167518/original/file-20170502-17245-1r4m579.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/167518/original/file-20170502-17245-1r4m579.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/167518/original/file-20170502-17245-1r4m579.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/167518/original/file-20170502-17245-1r4m579.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Clean, perhaps, but not so safe.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/121935927@N06/13690615265">Siyavula Education/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Might intra-uterine exposure to thyroid-disrupting chemicals, then, be linked to the apparent rise in neurodevelopmental diseases, such as autism and attention deficit hyperactivity disorder (ADHD)? </p>
<p><a href="https://www.cdc.gov/ncbddd/autism/data.html">Different data sets</a> from Asia, Europe and North America have shown increases in autism spectrum disorders and ADHD. Today in the United States, one in 42 boys is diagnosed as <a href="https://doi.org/10.15585/mmwr.ss6503a1">on the autism spectrum</a>. </p>
<p>The incidence of autism in the US increased significantly between the data sets published <a href="https://www.cdc.gov/ncbddd/autism/features/impact-dsm5.html">in 2000 and 2014</a>. The human genome did not change during this time, nor can changed diagnosis criteria or increased awareness entirely account for the <a href="https://doi.org/10.1038/479022a">increase</a>.</p>
<p>Research emphasises the genetic bases of autism spectrum disorders, but it is highly plausible that environmental factors could exacerbate genetic susceptibilities. In studies conducted on <a href="https://doi.org/10.3389/fendo.2014.00146.">gestating rats</a>, autism-like behaviour in offspring <a href="https://doi.org/10.1111/1471-0528.12681">has been linked</a> to disruptions in thyroid-hormone signalling, specifically hypothyroidism. </p>
<h2>Dropping IQs</h2>
<p>Endocrine disruption may also tell us something about the IQ decreases observed in certain populations. </p>
<p>Comparing IQ in different populations at different time points is, of course, not scientifically rigorous. But measuring IQ at a given time point in a given population exposed to different levels of chemicals can be meaningful. </p>
<p><a href="http://www.nejm.org/doi/full/10.1056/NEJM199609123351104">Several data sets</a> from around the world have shown <a href="https://www.sciencedaily.com/releases/2016/01/160127052555.htm">IQ scores dropping</a> over time. Military recruitment <a href="http://dx.doi.org/10.1016/j.intell.2013.05.008">boards in Finland</a> and <a href="http://doi.org/10.1016/j.intell.2007.01.007">Denmark</a> demonstrate this decrease, and <a href="http://www.sciencedirect.com/science/article/pii/S0160289615000653">similar losses are seen in other populations</a>, including adults in France and children in the United Kingdom. </p>
<p>Other data shows that reaction time in <a href="http://www.odilejacob.fr/catalogue/sciences/neurosciences/cerveau-endommage_9782738133915.php">young people is slowing</a>. This is surprising, perhaps, given that many young people today play screen games that require rapid responses. </p>
<p>But the speed of neuronal transmission is dependent on myelination, the formation of the <a href="https://www.ncbi.nlm.nih.gov/pubmed/25905404">lipid sheath around the neurons</a>, which requires thyroid hormone. Thus, reaction time is vulnerable to interruption by the endocrine disruptors present in our everyday lives. </p>
<p>The mechanisms that may link chemical thyroid-hormone disruption with increased brain disorders and decreasing IQ are further explored in my 2017 book, <a href="https://global.oup.com/academic/product/toxic-cocktail-9780190260934?cc=es&lang=en&">Toxic Cocktail: How chemical pollution is poisoning our brains</a>.</p>
<h2>The takeaway</h2>
<p>Today, chemical contamination is such that we are all exposed to hundreds of chemicals, few of which have <a href="https://doi.org/10.1093/toxsci/kfl103">been fully tested</a> for their toxic effects. Little is known about their potential effects on our hormonal systems, and even less about how they act together as mixtures to have a “cocktail effect”. </p>
<p>Our findings showing adverse effects on tadpoles’ thyroid-hormone signalling, including reduced neuronal number and mobility, indicate the urgent need to revisit the way chemicals are tested before they hit the market.</p>
<p>As a cautionary tale, recall that paracetamol, the main ingredient in many painkillers, which was previously considered safe during pregnancy, is now linked <a href="https://doi.org/10.1093/ije/dyw296">to behavioural problems in children</a>. Doctors now suggest that pregnant women avoid all medications, acknowledging the acute susceptibility of fetuses to drugs and chemicals. The concept is scientifically grounded in the developmental origin of adult disease: prenatal factors, we now know, can cause disease later in life. </p>
<p>In modern life, every pregnant woman is exposed to hundreds of chemicals. Not only are these chemicals found in her bloodstream but also in the amniotic fluid that surrounds her developing child. </p>
<p>Our tadpole experiments show that this exposure compromises the hormonal regulation that underlies brain development. Processes honed through millions of years of evolution are now very much endangered.</p><img src="https://counter.theconversation.com/content/75897/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Barbara Demeneix is a cofounder of Watchfrog that screens chemicals for potential endocrine disrupting properites. Research in her lab is supported by national (ANR) and European Funding.</span></em></p>Research shows thyroid hormone, which is required for brain development in all vertebrates, is severely affected by chemicals present in our everyday cleaning products, clothing and cookware.Barbara Demeneix, Professeur en endocrinologie, Muséum national d’histoire naturelle (MNHN)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/714312017-01-18T14:34:28Z2017-01-18T14:34:28ZFrom diet to blood pressure – it’s not just chromosomes that help determine the sex of a baby<figure><img src="https://images.theconversation.com/files/153228/original/image-20170118-3929-cv6znk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">nattanan726/Shutterstock</span></span></figcaption></figure><p>The concept of being able to predict the sex of a baby during early pregnancy or even influence it by eating or doing certain things when trying to conceive has been the subject of public fascination and debate for many centuries. But surely the sex of a foetus is exclusively determined by the father’s sperm, carrying an X chromosome for girls and a Y chromosome for boys? </p>
<p>It turns out this is not the full story. Since the 17th century, it has been recognised that slightly more boys are born than girls. This is strange – if the sex were determined solely by chromosomes, the probability of either should be 50% and not variable. This must mean that, although the same number of boys and girls are conceived initially, more female foetuses than male ones are lost during the pregnancy. </p>
<p>While the mechanisms underlying these findings are not fully understood, it seems plausible that there may be underlying physiological factors in the mother that make the spontaneous miscarriage of a male or female foetus more likely – thereby influencing the likelihood of delivering a boy or a girl.</p>
<p>An important and <a href="http://www.pnas.org/content/112/16/E2102.abstract">fascinating study</a>, which mapped the trajectory of the human sex ratio from conception to birth, indicated that gender-specific foetal loss varies across gestation. The authors confirmed that the sex ratio of foetuses is indeed balanced at conception. They observed an increased loss of male foetuses very early and very late during pregnancy. Female mortality, however, was higher in the remainder of the pregnancy. The net result was a greater total loss of female foetuses – consistent with observations of more boys being born. Why this is the case, however, is still a bit of a mystery.</p>
<h2>Hormones and diet</h2>
<p>A number of studies have observed that factors such as disasters, terrorism and economic collapse may <a href="https://theconversation.com/stress-leads-to-decline-in-male-births-4718">reduce the numbers of boys</a> born in a population. It <a href="https://www.ncbi.nlm.nih.gov/pubmed/26549774">has been proposed</a> that stress caused by these adverse conditions results in higher levels of maternal testosterone which is associated with increased risk of miscarriage. If male foetuses are weaker than female ones, they may be disproportionately affected by this.</p>
<p>Indeed, studies have shown that exposure to substances that disrupt the hormonal system – including toxic man-made pollutants – have resulted in <a href="http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(00)02290-X/fulltext?version=printerFriendly">subsequent increases in female births</a>. This has further fuelled the theories proposing that frailer and weaker male foetuses have a survival disadvantage in times of overwhelming environmental stress.</p>
<p>It remains unclear whether high maternal concentrations of testosterone play a role in these processes. It is also uncertain whether adverse social, economic and political situations result in higher androgen levels in mothers at all. </p>
<p>The influence of maternal diet on offspring sex ratio has also been widely debated. Studies in rodents and mammals have indicated a higher likelihood of males being born <a href="https://www.ncbi.nlm.nih.gov/pubmed/4682135">from well-fed, healthy mothers</a>. In humans, however, there have been conflicting results, with higher proportions of males being born both in <a href="http://news.bbc.co.uk/1/hi/health/7358384.stm">women with high energy intake</a> prior to pregnancy, but also during famine and war.</p>
<h2>Blood pressure</h2>
<p>Meanwhile, a recent study found a link between blood pressure and the sex of the baby. The research evaluated 1,411 Chinese newly-married women at about 26 weeks before conception. It identified that systolic blood pressure <a href="http://www.iflscience.com/health-and-medicine/womens-blood-pressure-before-pregnancy-could-determine-the-sex-of-their-baby/">was almost 3mmHg higher at this time in mothers who would go on to give birth to a son</a>. This held true even after they adjusted for factors including age, education, BMI, smoking, cholesterol and glucose. </p>
<p>The likelihood of delivering a boy rose progressively with higher pre-pregnancy systolic blood pressure and at a reading of 123 mmHg, the chance of having a boy was 1.5 times higher than that of having a girl. Importantly, systolic blood pressure before pregnancy was the only independent predictor of having a male baby. Notably, these differences in blood pressure between mothers of male and female babies were not observed during pregnancy.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/153229/original/image-20170118-3929-1kctkj1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/153229/original/image-20170118-3929-1kctkj1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/153229/original/image-20170118-3929-1kctkj1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/153229/original/image-20170118-3929-1kctkj1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/153229/original/image-20170118-3929-1kctkj1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/153229/original/image-20170118-3929-1kctkj1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/153229/original/image-20170118-3929-1kctkj1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A boy?</span>
<span class="attribution"><span class="source">Bacho/Shutterstock</span></span>
</figcaption>
</figure>
<p>It is unclear how blood pressure may affect offspring gender. The processes involved in <a href="https://www.researchgate.net/profile/Henning_Tiemeier/publication/261186598_Fetal_sex_specific_differences_in_human_placentation_A_prospective_cohort_study/links/559a263b08ae793d138074a6.pdf?origin=publication_list">formation of the placenta</a> appear to be different dependent on the sex of the foetus. A woman’s circulation has to undergo important adaptations in early pregnancy to accommodate increased blood flow to the foetus and it is possible that maternal blood pressure may therefore affect whether you are more likely to lose male or female foetuses.</p>
<p>While the findings of this study are extremely fascinating, there are a number of important limitations. The study was performed in young, healthy Chinese women with normal weight and may not be applicable to other populations. Moreover, the findings do not indicate a causal link but merely an association. In other words, it has not been demonstrated that a woman can increase her chance of delivering a boy by raising her blood pressure. It is more likely that the systolic blood pressure measurement before pregnancy is an indicator of the mother’s underlying physiology and ability to carry a baby of a specific gender. Either way, only more research can provide reliable answers.</p>
<p>All this research has important clinical and ethical implications. In particular, there’s a risk that women <a href="https://theconversation.com/little-china-girls-how-historys-worst-famine-shifted-the-sex-ratio-6312">in cultures where the birth of one sex over the other is preferred</a> engage in dangerous experimentation with trying to change blood pressure, diet or hormonal balance prior to pregnancy.</p><img src="https://counter.theconversation.com/content/71431/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kristien Boelaert does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A recent study found that a woman’s blood pressure before pregnancy can help predict her child’s gender. And it’s not the only indicator.Kristien Boelaert, Reader in Endocrinology, School of Clinical and Experimental Medicine, University of BirminghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/542112016-03-11T11:12:18Z2016-03-11T11:12:18ZBPS, a popular substitute for BPA in consumer products, may not be safer<figure><img src="https://images.theconversation.com/files/114883/original/image-20160312-11302-13acr2b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What's in your water bottle?</span> </figcaption></figure><p>The industrial chemical Bisphenol A (BPA) is an ingredient in dozens of everyday products – baby and water bottles, sports equipment, medical and dental devices, dental filling sealants, CDs and DVDs, household electronics, eyeglass lenses, foundry castings and the lining of water pipes. Manufacturers worldwide use <a href="https://doi.org/10.1289/ehp.0901716">at least 3.6 billion kilograms</a> (8 billion pounds) of BPA to make polycarbonate plastic and epoxy resins every year.</p>
<p>Over the past decade, studies have shown that BPA is widely present in the environment and in our bodies. BPA can be measured in <a href="https://doi.org/10.1016/S0731-7085(02)00516-2">human serum</a>, <a href="https://doi.org/10.1289/ehp.10753">urine</a>, umbilical cord blood, <a href="https://doi.org/10.1016/S0890-6238(02)00051-5">amniotic fluid</a> and placental tissue. Some <a href="https://doi.org/10.1021/es9028292">studies</a> have suggested that BPA may affect human reproductive and other systems by <a href="https://doi.org/10.1006/bbrc.2002.6407">behaving like human hormones</a>. Many countries, including the United States, Australia, Canada, New Zealand, the United Kingdom, Japan and those in the European Union, have <a href="http://www.mts-global.com/en/technical_update/CPIE-018-13.html">banned the use of BPA in baby bottles</a> and other polycarbonate items produced for babies and toddlers.</p>
<p>In response, manufacturers have introduced “BPA-free” products made with substitute chemicals. Bisphenol S (BPS) is one of the most widely used BPA replacements. A 2012 <a href="https://doi.org/10.1021/es300876n">analysis</a> of urine samples taken in the United States, Japan, China and five other Asian countries confirmed that humans are widely exposed to BPS from drinking from containers or cans lined with the chemical or contamination through the water supply. </p>
<p>However, BPS may not be safer than BPA. Two recent studies have found that BPS is <a href="https://doi.org/10.1021/es300876n">as hormonally active as BPA</a> and, like BPA, it <a href="https://doi.org/10.1073/pnas.1417731112">interferes with the endocrine (hormone) system</a> in ways that may produce harmful effects, such as obesity, cancer and neurological disorders. In a <a href="http://dx.doi.org/10.1210/en.2015-1785">paper</a> published last month, we showed that both of these endocrine-disrupting chemicals alter normal development of the reproductive system.</p>
<h2>Impacts on reproductive development</h2>
<p>As endocrinologists concerned about public safety, we wanted to know whether BPS had effects similar to BPA during embryonic development of brain cells and genes that control puberty and fertility later in life. We chose to study the embryo because animals are particularly susceptible to toxins at this stage. </p>
<p>As our subjects, we used <a href="https://www.theguardian.com/science/2013/sep/15/zebrafish-human-genes-project">zebrafish</a> because their embryos are transparent, making it possible to watch their cells and organs develop in real time. And the zebrafish genome has been sequenced, which allows us to study genes that are involved in reproduction.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/114489/original/image-20160309-13740-ipod5w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/114489/original/image-20160309-13740-ipod5w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=821&fit=crop&dpr=1 600w, https://images.theconversation.com/files/114489/original/image-20160309-13740-ipod5w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=821&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/114489/original/image-20160309-13740-ipod5w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=821&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/114489/original/image-20160309-13740-ipod5w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1032&fit=crop&dpr=1 754w, https://images.theconversation.com/files/114489/original/image-20160309-13740-ipod5w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1032&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/114489/original/image-20160309-13740-ipod5w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1032&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Zebrafish embryo 22 hours after fertilization.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nihgov/24226476920">National Institutes of Health/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>To understand whether BPA and BPS affected normal development of our target genes and brain cells, we studied how exposure to low levels of each chemical affected embryos’ survival, hatching rate and development of gonadotropin-releasing hormone (GnRH) neurons. These are the brain cells that control reproduction. We also measured their levels of reproduction-related genes during embryonic and early larval development.</p>
<p>In addition to looking for these effects, we wanted to understand the process through which BPA and BPS could be impacting development of embryos. Studies have shown that BPA mimics the actions of estrogen, but there is also evidence that it interferes with normal thyroid hormone signaling. Thyroid hormones play essential roles in regulating fetal brain development, so we wanted to know whether BPA and BPS also influence that hormonal pathway in a way that affects reproductive development.</p>
<p>We already know that BPA is widely present in the environment worldwide. It is <a href="http://www.epa.gov/sites/production/files/2015-09/documents/bpa_action_plan.pdf">released</a> in two ways: directly from manufacturing waste, or through leaching from products containing BPA that are buried in landfills. Currently BPA can be found in river water at levels up to 21 micrograms per liter. Concentrations as low as 0.1 micrograms per liter can <a href="https://doi.org/10.1002/etc.634">harm</a> fish and other aquatic organisms <a href="https://doi.org/10.1080/02772248.2010.530136">over time</a>. </p>
<p>In our <a href="http://dx.doi.org/10.1210/en.2015-1785">study</a>, we found that when zebrafish embryos were exposed to levels of BPA that can be detected in the environment during development, they hatched early and had increased numbers of GnRH neurons and reproduction-related genes expressed in their brains and pituitary glands. This indicates that BPA has significant effected the reproductive development. We also found that equally low levels of BPS produced similar effects.</p>
<p>BPA and BPS alter reproductive development in ways that we don’t fully understand yet. Further work needs to be performed to understand how chronic exposure to low levels of the chemicals affects an organism’s development through its life.</p>
<h1>Mimicking hormones</h1>
<p>Next we investigated whether BPA and BPS acted like other hormones in addition to estrogen. Hormones act like messengers in the body, delivering instructions to target cells. Those target cells have receptors – areas that detect the hormone and allow it to bind to the target cell and trigger certain responses。 </p>
<p>We wanted to compare BPA and BPS to estrogen, thyroid hormone and aromatase, an enzyme that influences sexual development by converting testosterone to estrogen. We used inhibitors for each of these substances – chemicals that block the actions of estrogen and thyroid hormone at their receptors, and block the enzymatic activity of aromatase so that it is not functional. </p>
<p>If these inhibitors could also prevent BPA and BPS from their actions in cells, that would be further evidence that BPA and BPS behave like hormones in the body. When we combined these treatments with either BPA or BPS, they blocked those chemicals’ stimulatory actions on many reproduction-related genes. By showing that the inhibitors for estrogen, thyroid hormone and aromatase blocked BPA and BPS from affecting target cells, we demonstrated that BPA and BPS behave like several different hormones.</p>
<p>Altogether, these data suggest that both BPA and BPS have the potential to impact development of the reproductive system. And although BPA is often referred to as a chemical that mimics estrogen, our findings indicate that both BPA and BPS affect a wider wider range of cellular processes.</p>
<p>The GnRH neurons and reproduction-related genes that we studied ultimately control development of testes and ovaries, puberty and fertility. Our work provides important supporting evidence that both BPA and BPS alter fundamental characteristics of the developing reproductive system in ways that could have later impacts on reproductive health. In sum, BPS is not necessarily a safer alternative to BPA.</p>
<p><em>An earlier version of this article included a photo of bottles that do not contain BPA.</em></p><img src="https://counter.theconversation.com/content/54211/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wenhui Qiu receives funding from the China Scholarship Council.</span></em></p><p class="fine-print"><em><span>Ming Yang receives funding from the National Nature Science Foundation of China.</span></em></p><p class="fine-print"><em><span>Nancy Wayne does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Manufacturers have removed the industrial chemical BPA from many products over concerns that it mimics hormones in the body. Now studies show that BPS, a popular substitute, has similar effects.Wenhui Qiu, Ph.D. Candidate in Environmental and Chemical Engineering , Shanghai UniversityMing Yang, Professor of Environmental Science and Engineering, Shanghai UniversityNancy Wayne, Professor of Physiology, University of California, Los AngelesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/170802013-08-14T13:33:24Z2013-08-14T13:33:24ZGut feeling: how bacteria can mess with your mood<figure><img src="https://images.theconversation.com/files/29259/original/cqcxg63b-1376482957.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It's not you, it's the bacteria in your gut.</span> <span class="attribution"><span class="source">Alaina Abplanalp Photography</span></span></figcaption></figure><p>Probiotics are something of a new dietary craze. Foods contain healthy “probiotic” bacteria, and these microbes can promote good gastrointestinal (GI) health.</p>
<p>But what about your brain? Apparently, bacteria influence what’s going on up there, too. Within the past several years, a blossoming field of study called “<a href="http://www.ncbi.nlm.nih.gov/pubmed/18191570">microbial endocrinology</a>” has provided some provocative insights about the relationship between our GI microbiota and our mood and behaviour.</p>
<p>Studies in this field of have implicated GI microbes as a factor that can regulate the endocrine system. This could have both good and bad effects since the endocrine system is responsible for the production of hormones and coordinates metabolism, respiration, excretion, reproduction, sensory perception and immune function.</p>
<p>Consider the action of stress on the body. The endocrine system responds by sending out stress molecules called catecholamines that function as neurotransmitters and hormones. These molecules account for that fight-or-flight response that we feel when we encounter a stressful event. Conversely, there are molecules of the endocrine system that are deemed “feel good” molecules, such as dopamine, gamma-aminobutyric acid (GABA), oxytocin, endorphin and serotonin. </p>
<p>The implication is that, by influencing the endocrine system, GI microbiota could possibly influence our mood and behaviour by helping us “feel good” or enhancing our flight-or-flight reactions.</p>
<p>Most of what we know about this GI microbe-endocrine connection comes about due to an unusual side effect of irritable bowel syndrome (IBS). It is <a href="http://www.apa.org/monitor/2012/09/gut-feeling.aspx">well documented</a> that people suffering from IBS are more vulnerable to feelings of anxiety or depression or both. In fact, these psychological conditions can exacerbate IBS symptoms, indicating a reciprocal relationship between IBS and anxiety and depression.</p>
<p>One of the “feel good” molecules of the endocrine system, GABA, is a neurotransmitter that when low in abundance can lead to anxiety or depression. Two different GI bacteria, <em>Lactobacillus</em> and <em>Bifidobacterium</em> have been shown to <a href="http://www.microbialcellfactories.com/content/9/1/85">produce GABA</a>. Although it is unknown if GABA is playing a role in the resolution of symptoms, several studies have recently shown that supplements of either <em>Lactobacillus</em> or <em>Bifidobacterium</em> can relieve anxiety in both animals and humans suffering from IBS.</p>
<p>In other words, these bacteria have now become “psychobiotic”.</p>
<p>Another GI bacterium, <em>Clostridium difficile</em> is typically acquired during infancy. Usually harmless, this often antibiotic-resistant microbe can cause severe problems for older people on antibiotics, who subsequently succumb to diarrhoea’s or inflammation of the colon caused by <em>C. difficile</em> unrestrained in growth due to the lack of sufficient bacterial competition. <em>C. difficile</em> synthesises at least two toxins that <a href="http://www.cnrs.fr/cw/en/pres/compress/ScienceDefense/13.htm">interfere with neurons</a> and possibly the endocrine system, as well. Intriguingly, patients with autism and schizophrenia have been shown to have higher than normal levels of this bacterial species.</p>
<p>Because of antibiotic resistance, one treatment that appears to have a good success rate is called a fecal transplant. This technique requires a healthy donor sample of fecal matter to be transplanted in the affected patient. While most of us might cringe at the thought, sufferers of <em>C. difficile</em> often feel they have little choice. Patients who have undergone the fecal transplant have described feeling better mere moments after the procedure is complete.</p>
<p>Combined, what these studies indicate is that an imbalance in the GI microbiota can manifest as both physiological and psychological pathologies. And it appears these pathologies may be resolved with the use of proper “psychobiotic” bacteria.</p>
<hr>
<p><em>This article was first published on <a href="http://www.realclearscience.com/articles/2013/08/13/can_psychobiotic_bacteria_affect_our_mood_106629.html">Real Clear Science</a>.</em></p><img src="https://counter.theconversation.com/content/17080/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Camille Zenobia does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Probiotics are something of a new dietary craze. Foods contain healthy “probiotic” bacteria, and these microbes can promote good gastrointestinal (GI) health. But what about your brain? Apparently, bacteria…Camille Zenobia, Postdoctoral Researcher, University of PennsylvaniaLicensed as Creative Commons – attribution, no derivatives.