tag:theconversation.com,2011:/us/topics/ghrelin-19613/articlesGhrelin – The Conversation2020-09-04T12:13:12Ztag:theconversation.com,2011:article/1450582020-09-04T12:13:12Z2020-09-04T12:13:12ZWhy sleep is so important for losing weight<figure><img src="https://images.theconversation.com/files/356525/original/file-20200904-22-2y4l9y.jpg?ixlib=rb-1.1.0&rect=55%2C22%2C7293%2C4880&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sleep is important for many aspects of our health.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-african-woman-sleeping-her-bed-555427036">Stock-Asso/ Shutterstock</a></span></figcaption></figure><p>When it comes to weight loss, diet and exercise are usually thought of as the two key factors that will achieve results. However, sleep is an often-neglected lifestyle factor that also plays an important role. </p>
<p>The recommended sleep duration for adults is seven to nine hours a night, but many people often sleep for less than this. <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/jsr.12504">Research has shown</a> that sleeping less than the recommended amount is linked to having greater body fat, increased risk of obesity, and can also influence how easily you lose weight on a calorie-controlled diet. </p>
<p>Typically, the goal for weight loss is usually to decrease body fat while retaining as much muscle mass as possible. Not obtaining the correct amount of sleep can determine how much fat is lost as well as how much muscle mass you retain while on a calorie restricted diet. </p>
<p><a href="https://www.acpjournals.org/doi/10.7326/0003-4819-153-7-201010050-00006?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dpubmed&">One study</a> found that sleeping 5.5 hours each night over a two-week period while on a calorie-restricted diet resulted in less fat loss when compared to sleeping 8.5 hours each night. But it also resulted a greater loss of fat-free mass (including muscle). </p>
<p><a href="https://academic.oup.com/sleep/article/41/5/zsy027/4846324">Another study</a> has shown similar results over an eight-week period when sleep was reduced by only one hour each night for five nights of the week. These results showed that even catch-up sleep at the weekend may not be enough to reverse the negative effects of sleep deprivation while on a calorie-controlled diet. </p>
<h2>Metabolism, appetite, and sleep</h2>
<p>There are several reasons why shorter sleep may be associated with higher body weight and affect weight loss. These include changes in <a href="https://www.sciencedirect.com/science/article/pii/S1521690X10000722?casa_token=qLbO2fWDtKkAAAAA:a5v3LKYaVsJK4jIJyNCHAwy-TxmyWPBAoeEbKI3s7xgDM4nFZ0YBCX6ZMNqC6RaUu4S3dNc-76eR">metabolism, appetite</a> and <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/oby.21321">food selection</a>. </p>
<p>Sleep influences two important appetite hormones in our body – leptin and ghrelin. <a href="https://ijpeonline.biomedcentral.com/articles/10.1155/2009/141753">Leptin</a> is a hormone that decreases appetite, so when leptin levels are high we usually feel fuller. On the other hand, <a href="https://ijpeonline.biomedcentral.com/articles/10.1155/2009/141753">ghrelin</a> is a hormone that can stimulate appetite, and is often referred to as the “hunger hormone” because it’s thought to be responsible for the feeling of hunger.</p>
<p>One study found that sleep restriction <a href="https://www.acpjournals.org/doi/10.7326/0003-4819-141-11-200412070-00008">increases levels</a> of ghrelin and decreases leptin. <a href="https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.0010062">Another study</a>, which included a sample of 1,024 adults, also found that short sleep was associated with higher levels of ghrelin and lower levels of leptin. This combination could increase a person’s appetite, making calorie-restriction more difficult to adhere to, and may make a person more likely to overeat. </p>
<p>Consequently, increased food intake due to changes in appetite hormones may result in weight gain. This means that, in the long term, sleep deprivation may lead to weight gain due to these changes in appetite. So getting a good night’s sleep should be prioritised.</p>
<p>Along with changes in appetite hormones, reduced sleep has also been shown to impact on food selection and the way the brain perceives food. Researchers <a href="https://academic.oup.com/ajcn/article/95/4/818/4576711">have found</a> that the areas of the brain responsible for reward are more active in response to food after sleep loss (six nights of only four hours’ sleep) when compared to people who had good sleep (six nights of nine hours’ sleep). </p>
<p>This could possibly explain why sleep-deprived people <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/oby.21321">snack more often</a> and tend to choose <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/oby.21321">carbohydrate-rich foods and sweet-tasting snacks</a>, compared to those who get enough sleep.</p>
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<img alt="Person's hands typing on keyboard while eating unhealthy snacks." src="https://images.theconversation.com/files/356522/original/file-20200904-22-zqjr2t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/356522/original/file-20200904-22-zqjr2t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/356522/original/file-20200904-22-zqjr2t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/356522/original/file-20200904-22-zqjr2t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/356522/original/file-20200904-22-zqjr2t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/356522/original/file-20200904-22-zqjr2t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/356522/original/file-20200904-22-zqjr2t.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">
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<span class="caption">Sleep deprivation may make you eat more unhealthy food during the day.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/unhealthy-snack-workplace-hands-woman-working-1117577912">Flotsam/ Shutterstock</a></span>
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<p>Sleep duration also influences <a href="https://www.sciencedirect.com/science/article/abs/pii/S1521690X10000722">metabolism</a>, particularly glucose (sugar) metabolism. When food is eaten, our bodies release insulin, a hormone that helps to process the glucose in our blood. However, sleep loss can impair our bodies’ response to insulin, reducing its ability to <a href="https://academic.oup.com/sleep/article/34/3/371/2433844">uptake glucose</a>. We may be able to recover from the occasional night of sleep loss, but in the long term this could lead to health conditions such as obesity and type 2 diabetes. </p>
<p>Our own research has shown that a <a href="https://journals.humankinetics.com/view/journals/ijsnem/30/2/article-p139.xml">single night</a> of sleep restriction (only four hours’ sleep) is enough to impair the insulin response to glucose intake in healthy young men. Given that sleep-deprived people already tend to choose foods high in glucose due to increased appetite and reward-seeking behaviour, the impaired ability to process glucose can make things worse. </p>
<p>An excess of glucose (both from increased intake and a reduced ability to uptake into the tissues) could be <a href="https://nutritionandmetabolism.biomedcentral.com/articles/10.1186/1743-7075-8-74">converted</a> to fatty acids and stored as fat. Collectively, this can accumulate over the long term, leading to weight gain.</p>
<p>However, physical activity may show promise as a countermeasure against the detrimental impact of poor sleep. Exercise has a <a href="https://www.mdpi.com/2072-6643/10/9/1140">positive impact on appetite</a>, by reducing ghrelin levels and increasing <a href="https://journals.physiology.org/doi/full/10.1152/ajpregu.90706.2008?rfr_dat=cr_pub++0pubmed&url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org">levels of peptide YY</a>, a hormone that is released from the gut, and is associated with the feeling of being satisfied and full. </p>
<p>After exercise, people tend to <a href="https://www.nature.com/articles/ijo2017181">eat less</a>, particularly when the energy expended by exercise is taken into account. However, it’s unknown if this still remains in the context of sleep restriction. </p>
<p>Research has also shown that exercise training may <a href="https://www.frontiersin.org/articles/10.3389/fphys.2017.00992/full">protect against</a> the metabolic impairments that result from a lack of sleep, by improving the body’s response to insulin, leading to improved glucose control. </p>
<p>We have also shown the potential benefits of just a <a href="https://journals.humankinetics.com/view/journals/ijsnem/30/2/article-p139.xml">single session</a> of exercise on glucose metabolism after sleep restriction. While this shows promise, studies are yet to determine the role of long-term physical activity in people with poor sleep. </p>
<p>It’s clear that sleep is important for losing weight. A lack of sleep can increase appetite by changing hormones, makes us more likely to eat unhealthy foods, and influences how body fat is lost while counting our calories. Sleep should therefore be considered as an essential alongside diet and physical activity as part of a healthy lifestyle.</p><img src="https://counter.theconversation.com/content/145058/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Walshe receives funding from Society for Endocrinology. </span></em></p><p class="fine-print"><em><span>Emma Sweeney 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 lack of sleep increases appetite, makes us more likely to eat unhealthy foods, and even affects how body fat is lost while dieting.Emma Sweeney, Lecturer in Exercise and Health, Nottingham Trent UniversityIan Walshe, Lecturer in Health and Exercise Sciences, Northumbria University, NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/355452015-09-25T04:20:43Z2015-09-25T04:20:43ZChemical messengers: how hormones make us feel hungry and full<figure><img src="https://images.theconversation.com/files/92377/original/image-20150819-10873-1ee6q7n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Whether or not you feel inclined to eat depends on the balance of the activity between two sets of neurons.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/dskley/6694869343/">Dennis Skley/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>The need to find fuel to generate energy is a profound drive within the biology of all living organisms: we all need food to survive. So it’s not surprising that our bodies have such a complex system to control food intake, driven by hormones. </p>
<p>Hormone levels also change when we lose weight. As much as we battle to trim down via diets and eating patterns, they’re also the reason most of us <a href="https://theconversation.com/weight-loss-and-the-brain-why-its-difficult-to-control-our-expanding-waistlines-3522">will regain the weight</a> we lose – or more. </p>
<p>The body’s system for regulating food intake is coordinated by the hypothalamus, which is located under the midline of the brain, behind the eyes: </p>
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<p>Within the hypothalamus are nerve cells that, when activated, produce the sensation of hunger. They do so by producing two proteins that cause hunger: <a href="http://www.wisegeek.com/what-is-neuropeptide-y.htm">neuropeptide Y</a> (NPY) and <a href="http://medical-dictionary.thefreedictionary.com/agouti-related+peptide">agouti-related peptide</a> (AGRP). </p>
<p>Quite close to these nerve cells is another set of nerves that powerfully inhibit hunger. They produce two different proteins that inhibit hunger: <a href="https://en.wikipedia.org/wiki/Cocaine_and_amphetamine_regulated_transcript">cocaine and amphetamine-regulated transcript</a> (CART) and <a href="http://www.yourhormones.info/hormones/melanocytestimulating_hormone.aspx">melanocyte-stimulating hormone</a> (αMSH).</p>
<p>These two sets of nerve cells initiate and send hunger signals to other areas of the hypothalamus. So, whether you feel inclined to eat or not depends on the balance of the activity between these two sets of neurons. </p>
<p>But what determines which set of neurons dominates at any given time?</p>
<p>The activity is mainly controlled by hormones that circulate in the blood. These come from tissues in various parts of the body that deal with energy intake and storage, including the gut (which receives and digests the food), the fat (which stores the energy) and the pancreas (which makes hormones that are involved in energy storage, such as insulin). </p>
<h2>Hormones in the blood</h2>
<p>Let’s take a closer look at how each of these blood-circulating hormones work. </p>
<p><strong>Ghrelin</strong> is made in the stomach. It stimulates hunger by entering the brain and acting on the neurons in the hypothalamus to increase the activity of the hunger-causing nerve cells and reducing the activity of hunger-inhibiting cells. As the stomach empties, the release of ghrelin increases. As soon as the stomach is filled, it decreases. </p>
<p><strong>Insulin-like peptide 5 (ILP-5)</strong> was found to stimulate hunger in 2014. It is the second circulating hormone to have this effect and is mainly produced in the colon. But we still don’t know its physiological role. </p>
<p><strong>Cholecystokinin (CCK)</strong> is produced in the upper small bowel in response to food and gives a feeling of fullness. It is released soon after food reaches the small bowel. Researchers have found CCK can stop a mouse from eating as soon as it’s injected into the brain.</p>
<p><strong>Peptide YY, glucagon-like peptide 1 (GLP-1), oxyntomodulin and uroguanilin</strong> are all made from the last part of the small bowel and make us feel full. They are released in response to food in the gut. </p>
<p><strong>Leptin</strong> is the most powerful appetite-suppressing hormone and is made in fat cells. It was discovered in 1994. The more fat cells we have, the more leptin the body produces. </p>
<p><strong>Amylin, insulin and pancreatic polypeptide</strong> are made in the pancreas. Studies in the United States have shown that when insulin enters the brain it inhibits hunger, telling the brain “there is enough energy in the body, take a rest”. </p>
<p>Amylin, discovered in 1981, is made in the same cells that make insulin (the beta cells). It has been shown to inhibit food intake. </p>
<p>The exact role of pancreatic polypeptide is not yet known, but there is evidence that it inhibits hunger. </p>
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<a href="https://images.theconversation.com/files/92193/original/image-20150818-25727-11n4ddz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/92193/original/image-20150818-25727-11n4ddz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92193/original/image-20150818-25727-11n4ddz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=499&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92193/original/image-20150818-25727-11n4ddz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=499&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92193/original/image-20150818-25727-11n4ddz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=499&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92193/original/image-20150818-25727-11n4ddz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=627&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92193/original/image-20150818-25727-11n4ddz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=627&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92193/original/image-20150818-25727-11n4ddz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=627&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<p>The hypothalamus also receives signals from pleasure pathways that use <a href="http://www.utexas.edu/research/asrec/dopamine.html">dopamine</a>, <a href="http://www.sciencedaily.com/releases/2005/07/050720065810.htm">endocannabinoids</a> and <a href="http://www.medterms.com/script/main/art.asp?articlekey=5468">serotonin</a> as messengers, which influence eating behaviour.</p>
<p>Once full, the stomach reduces the desire to eat both by lowering ghrelin production and by sending a message to the hypothalamus. Ghrelin levels reach a low around 30 to 60 minutes after eating. </p>
<p>Levels of hormones that make us feel full – CCK, PYY, GLP-1, amylin and insulin – all increase following a meal to reach a peak about 30 to 60 minutes later.</p>
<p>All the hormones then gradually return to their fasting levels three to four hours after a meal.</p>
<h2>How weight loss affects our hormones</h2>
<p>Several studies have found that diet-induced weight loss is <a href="https://theconversation.com/weight-loss-and-the-brain-why-its-difficult-to-control-our-expanding-waistlines-3522">associated with</a> hormone changes that, together, promote weight regain. </p>
<p>Following weight loss, leptin levels decrease profoundly. Other hormonal changes include increases in circulating ghrelin, GIP and pancreatic polypeptide and reductions in PYY and CCK. Almost all of these changes favour regaining lost weight, by increasing hunger, reducing satiety and improving the capacity to store fat. These hormonal changes seem to be present for at least one year after weight loss, leading to a persistent increase in hunger. </p>
<p>These findings suggest suppressing hunger after weight loss – preferably with a replacement of hormones – may help people maintain their new weight. </p>
<p>Several of these agents have recently been approved by different regulatory bodies in the United States, Europe or Canada, but only one – liraglutide – is a version of one of the naturally occurring appetite suppressants (GLP-1). The ideal medication to maintain weight loss would be a long-acting mixture of three or more of the blood-circulating hormones we examined above: leptin, amylin, GLP-1, PYY, CCK and oxyntomodulin. </p>
<p>But producing such a mixture is proving a considerable challenge, so researchers continue to investigate how this might be done. </p>
<p><em>This article is part of an occasional series, <a href="https://theconversation.com/au/topics/chemical-messengers">Chemical Messengers</a>, on hormones and the body.</em></p><img src="https://counter.theconversation.com/content/35545/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joseph Proietto is Chair of The medical Advisory Board for Liraglutide 3mg for Novo Nordisk. He receives funding from the NH&MRC.</span></em></p>Our bodies have a complex system to control food intake, driven by hormones. Hormone levels also change when we gain and lose weight.Joseph Proietto, Professor of Medicine, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/449832015-09-09T04:45:31Z2015-09-09T04:45:31ZChemical messengers: how hormones help us sleep<figure><img src="https://images.theconversation.com/files/92331/original/image-20150819-12421-1sn7w0v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The activities we do during the day – from having a fight with a partner to using our iPhones at night – also affect our hormone levels and, in turn, our quality of sleep.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-194744459/stock-photo-young-beautiful-woman-sleeping-in-bed-in-closeup-shot.html?src=5CZs4Zr5KIdPffy940ybLg-6-20">Jan Faukner/Shutterstock</a></span></figcaption></figure><p>When it comes to motives for getting a good night’s sleep we don’t usually think about our body’s hormones. But sleep allows many of our hormones to replenish so we have the optimal energy, immunity, appetite and coping ability to face the day’s highs and lows.</p>
<p>The activities we do during the day – from having a fight with a partner, using our iPhones at night, running in a race, to travelling overseas – also affect our hormone levels and, in turn, our quality of sleep.</p>
<p>For both men and women, changes in our levels of sex hormones can affect how well we sleep. These differences also change with age. </p>
<p>Understanding the connections between hormones and sleep may help improve your own sleep and well-being. </p>
<h2>What are hormones?</h2>
<p>Our body’s hormones are like <a href="http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Hormonal_(endocrine)_system?open">chemical messages</a> in the bloodstream which cause a change in a particular cell or organ and surrounding tissues. The hormone <a href="http://www.yourhormones.info/Hormones/Adrenaline.aspx">adrenaline</a>, for example, is produced by the adrenal glands (on top of the kidneys) and helps prepare the body’s “fight or flight” response during times of stress. </p>
<p>Hormones control many of the <a href="http://www.pearson.com.au/9781292057200?gclid=CJzzzKGkiccCFdgnvQodjFwHxg">body’s processes</a>, including growth, development, reproduction, responding to stress, metabolism and energy balance.</p>
<p>Hormones are linked with sleep in a number of ways.</p>
<h2>Hormones affect sleep through our stress levels</h2>
<p>Some hormones, such as <a href="http://www.yourhormones.info/Hormones/Adrenaline.aspx">adrenaline</a>, make us feel more alert and prepared for action. This then makes it hard for us to go to sleep. To prevent this effect it’s best to do relaxing activities before bedtime, rather than stressful work tasks or intense exercise.</p>
<p>When stress is long lasting, <a href="http://www.sleepdex.org/acth.htm">adrenocorticotrophic hormone</a> within the pituitary gland (attached to the base of the brain) triggers the release of <a href="http://www.britannica.com/science/cortisone">cortisone</a> and <a href="http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Hormones_-_cortisol_and_corticosteroids">cortisol</a> from the adrenal glands. </p>
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<p>Levels of adrenocorticotrophic hormone tend be higher in people with <a href="https://theconversation.com/explainer-what-is-insomnia-and-what-can-you-do-about-it-36365">insomnia</a> than in good sleepers. This suggests that excessive arousal and ongoing stressors contribute to the insomnia.</p>
<p><a href="http://sock-doc.com/cortisol-and-sleep/">Elite athletes</a> can have difficulty getting to sleep because they tend to have high levels of cortisol throughout the day, including in the evening.</p>
<h2>Hormones released during sleep boost our immune system and make us hungry</h2>
<p>Sleep is a time when several of the body’s hormones are <a href="http://sleepfoundation.org/how-sleep-works/what-happens-when-you-sleep">released</a> into the bloodstream. These include growth hormone, which is essential for growth and tissue repair, including in adults. </p>
<p>Sleep helps to balance our <a href="http://sleepfoundation.org/how-sleep-works/what-happens-when-you-sleep">appetite</a> by maintaining optimal levels of the hormones <a href="http://www.ncbi.nlm.nih.gov/pubmed/17212793">ghrelin and leptin</a>. So, when we get less sleep than normal we may feel an urge to eat more. </p>
<p>Sleep also controls levels of the hormones <a href="http://draliciastanton.com/how-poor-sleep-effects-our-health-hormones-and-weight">insulin and cortisol</a> so that we wake up hungry, prompting us to eat breakfast, and we are prepared for facing daytime stress. </p>
<p>If we get less sleep than normal our levels of <a href="http://draliciastanton.com/how-poor-sleep-effects-our-health-hormones-and-weight">prolactin</a> may get out of balance and we can end up with a weakened immune system, difficulty concentrating and carbohydrate cravings during the day.</p>
<h2>Hormones stop us from having to get up in the night to go to the bathroom</h2>
<p>Changes in hormonal levels during sleep, including higher levels of aldosterone and <a href="https://myhealth.alberta.ca/health/pages/conditions.aspx?hwid=hw211268&">antidiuretic hormone</a>, prevent us from needing to go to the toilet. In children, while the hormonal system is still developing, bedwetting may be partly influenced by low levels of antidiuretic hormone.</p>
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<h2>Hormones make us feel sleepy at night</h2>
<p>Hormone levels also influence the timing of when we feel sleepy and awake – our body clock or sleep-wake cycle. The hormone melatonin is released with <a href="http://draliciastanton.com/how-poor-sleep-effects-our-health-hormones-and-weight">darkness</a> and tells our body it’s time to sleep. This is why being around too much <a href="http://sleepfoundation.org/sleep-topics/melatonin-and-sleep/page/0/1">bright light</a> before bed can affect our sleep as it can stop the release of melatonin. It’s also why it can be hard for night-time <a href="http://www.sleepeducation.com/essentials-in-sleep/shift-work/">shift workers</a> to sleep during the day. </p>
<p>While <a href="http://sleepfoundation.org/sleep-topics/melatonin-and-sleep/page/0/1">artificial melatonin</a> is available, taking the wrong dosage and at the wrong time of day can make things worse, so it’s best used with the guidance of a medical doctor.</p>
<h2>Hormones give us a wake-up call in the morning</h2>
<p>Levels of the hormone <a href="http://sleepfoundation.org/how-sleep-works/what-happens-when-you-sleep">cortisol</a> dip at bedtime and increase during the night, peaking just before waking. This acts like a <a href="http://www.brainfacts.org/across-the-lifespan/stress-and-anxiety/articles/2012/stress-the-role-of-glucocorticoids/">wake-up signal</a>, turning on our appetite and energy. </p>
<p>When we travel <a href="http://www.brainfacts.org/across-the-lifespan/stress-and-anxiety/articles/2012/stress-the-role-of-glucocorticoids/">long distances</a> our body’s sleep-wake cycle takes a while to adjust. So increased cortisol levels and hunger may occur at inappropriate times of the day.</p>
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<h2>For women, changes in sex hormones affect sleep</h2>
<p>The relationship between hormones and the sleep-wake cycle in women is further influenced by the <a href="http://www.hindawi.com/journals/ije/2010/259345/">menstrual cycle</a>. Just before a woman’s period, hormonal changes, including the sudden drop in levels of <a href="http://www.yourhormones.info/Hormones/Progesterone.aspx">progesterone</a>, affect the body’s temperature control, which in turn can reduce the amount of “REM” sleep. This is the stage of sleep when most of our dreams occur. </p>
<p>For women with <a href="http://www.hindawi.com/journals/ije/2010/259345/">severe premenstrual symptoms</a> reduced levels of melatonin before bedtime just before their menstrual period can cause poor sleep, including night-time awakenings or daytime sleepiness.</p>
<p>Changes in hormone levels also contribute to sleeping difficulties during <a href="http://sleepfoundation.org/sleep-topics/pregnancy-and-sleep">pregnancy</a>. Increased progesterone levels can cause daytime sleepiness, particularly in the first trimester. High levels of <a href="https://theconversation.com/the-brain-also-produces-the-sex-hormone-oestrogen-21194">oestrogen</a> and progesterone during pregnancy can also cause nasal swelling and lead to snoring.</p>
<p>During <a href="http://www.sleephealthfoundation.org.au/fact-sheets-a-z/212-menopause-and-sleep.html">menopause</a>, low levels of oestrogen may contribute to sleeping difficulties. Changes in hormone levels mean that body temperature is less stable and there may be increases in adrenaline levels, both of which can affect sleep. </p>
<p>The loss of oestrogen causes body fat to move more to the stomach area, which increases the chances of women having snoring and <a href="https://theconversation.com/health-check-heres-what-you-need-to-know-about-sleep-apnoea-26402">sleep apnoea</a>.</p>
<h2>For men, testosterone levels affect sleep</h2>
<p>For men, levels of <a href="http://www.ncbi.nlm.nih.gov/pubmed/24435056">testosterone</a> are highest during sleep and require at least three hours sleep to reach this peak. Low levels of testosterone in men, which can occur with sleep deprivation, ageing and physical problems, have been associated with a reduction in sleep efficiency and changes to the stages of sleep men experience. </p>
<p>Testosterone can be taken as a <a href="http://www.smrv-journal.com/article/S1087-0792(07)00166-9/">drug</a> but abuse of it can lead to other sleep problems.</p>
<h2>Hormones influence our dreams</h2>
<p>Finally, as we sleep, our hormones, including levels of <a href="https://www.psychologytoday.com/blog/dream-catcher/201108/oxytocin-sleep-and-dreams">oxytocin</a> and <a href="http://www.ncbi.nlm.nih.gov/pubmed/15576884">cortisol</a>, may influence the content of our dreams.</p>
<p>By doing things to promote good sleep, such as reducing stress, engaging in relaxing evening routines before bed, going to bed and getting up at regular times, or seeking professional help for sleeping difficulties, we can facilitate the replenishing activities of our hormones that help us make the most of our day and optimise our well-being.</p>
<p><em>This article is part of an occasional series, <a href="https://theconversation.com/au/topics/chemical-messengers">Chemical Messengers</a>, on hormones and the body. Stay tuned for other articles on hunger, mood and sexual desire.</em></p><img src="https://counter.theconversation.com/content/44983/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jo Abbott 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>Sleep allows many of our hormones to replenish so we have the optimal energy, immunity, appetite and coping ability to face the day’s highs and lows.Jo Abbott, Research Fellow / Health Psychologist, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.