So-called normal levels of testosterone are approximations, but can help researchers investigate disease and treatments.
Disorders affecting penis development are among the most common birth defects seen in humans, and rates are on the rise.
Populations of freshwater species are in a state of deep decline. But we know why and we can reverse the trend.
Having a 'period' on the pill is far from necessary.
Studies show oestrogen protects against depression and psychotic symptoms. So falls in the hormone, as happens before menstruation, can lead to depressive and other symptoms of mental illness.
Two theories on autism and sex differences are confirmed in half a million people.
Worker naked mole-rats take care of their colony's young even though they aren't the pups' actual parents. New research suggests the queen gets them ready via hormones in her poop.
Seasonal animals such as the Siberian hamster can teach us a lot about appetite suppression.
Endometriosis is cut or vaporised with an electric current or laser. It ranges from a simple, 20 minute operation to complex surgery involving important organs such as the bowel and bladder.
Dogs have the same hormones and experience the same chemical changes that humans do.
Women on the pill are able to manipulate or suppress their menstrual cycles to have fewer "periods", or to avoid bleeding at important or inconvenient times.
We usually focus on the physical health effects of the pill, yet the most common reason women stop or change the pill is mental health side effects.
New research with elite sportswomen found half use hormonal contraceptives.
If you need an alarm to get up in the morning, you're probably not getting enough sleep.
Many women are prescribed the pill without a definitive diagnosis of endometriosis.
Women shouldn't be disheartened by the latest finding that exercise doesn't lead to weight loss in the first month or two. There are other reasons to persist.
The "love hormone" system starts to develop in the womb and is important in helping us deal with stress.
...just don't call it the new phrenology.
Teenagers aren't just lazy. Their sleep hormones aren't calibrated to let them get up and go until later in the morning – which has academic and health consequences when school starts too early.
Parents' DNA try to manipulate one another in a bid to shape junior in their mould.