We’ve known for a while that testosterone is associated with aggressive behavior. But a fascinating new experiment reveals that these hormones are a two-way street: Simply acting aggressive can also raise levels of testosterone, in both women and men.
Women know that menopause can put a “sell by” date on getting pregnant, but common wisdom says that men retain much of their fertility well into old age. That common wisdom is wrong.
Hormone surges at puberty trigger a lot of physical changes in both men and women, morphing child-bodies into adult forms. Genitals, hips, and muscle mass change, obviously–but so do faces. A new study suggests those facial changes are primed to happen by the presence of testosterone in utero.
One of the fastest growing areas in pharmacology today is testosterone supplementation in men. But while low-T is a genuine problem for some men, it's not as prevalent as you may think – and the treatment is not without its risks. Here's what men need to know about testosterone replacement therapy, and why it should…
Male aggression is commonly pinned on testosterone, and estrogen is credited with imparting females with maternal instinct – but the true story of the sex hormones, and their roles in male and female behavior, is a lot more subtle. Here's why estrogen is an important hormone for males and females alike.
Male or female, most of us have body hair—some far, far more than others. This video explains how testosterone fuels the growth of hair all over your body.
Researchers from Emory University have discovered that fathers with smaller testicles are more likely to be involved in caregiving activities like diaper changes, feeding, and nap time. Brains scans also show higher activity in their reward system. But the study is far from complete in its assessment.
Last year, we reported on the strongest evidence yet that becoming a father is linked to a drop in a man's testosterone levels. Now it seems a family's sleeping arrangements actually have an even more specific effect on dad's biology.
South African sprinter Caster Semenya created a stir a few years back on account of her "intersexed" characteristics — prompting some to demand that sporting authorities screen for these sorts of biological anomalies in the name of fairness. But a Stanford University School of Medicine bioethicist and her colleagues…
You might have a friend who has to take them for asthma. You might know someone else who denies taking them but has gotten crazy ripped really fast and angers easily. Famous athletes are denying or being caught with them in their blood stream seemingly every day—just yesterday, MLB slugger Ryan Braun successfully…
Major League Baseball MVP Ryan Braun reportedly tested positive for steroid use on Saturday, a shock for a game whose marquee players had largely overcome their collective reputation as a tainted bunch of juicers.
A recent study published in the Proceedings of the National Academy of Sciences suggests men's testosterone levels fluctuate when they have children.
No matter how sophisticated and complex we get as a species, we're still influenced by evolutionary drives millions of years in the making. Case in point: A new study argues that human women are seemingly drawn to deep male voices. But is this study reliable, or just playing on our preconceptions about how men and…
Becoming a parent means making a lot of sacrifices in your life, from giving up sleep to giving up your paycheck. But new research shows that if you're becoming a dad, you should also be prepared to give up some testosterone — but don't worry, it's all so you can better provide for your child.
The wider a man's face is, the more likely he is to deceive others and cheat to get ahead...or so a new study claims. Is this just the new phrenology, or could there be something to the idea?
Late last year, a British hen named Gertie stopped laying eggs. She then started crowing like a rooster, and suddenly her entire appearance seemed to morph into a male. So just what is going on here?
If you voted for John McCain in last year's election, you may have felt a twinge of disappointment when Barack Obama took the stage. If you're male, that twinge was more than political disagreement; Obama may have lowered your testosterone.
Although thousands of women take estrogen replacement therapy (ERT) to avoid the unpleasantness of menopause, study after study has shown that ERT may shorten life. But today researchers announced results from a study of testosterone therapy that suggested the substance known as T may become a crucial ingredient in…
Check out this video, where these guys have created a chainsaw using a V-8 engine. A chainsaw is already the most dangerous object you can hold in your hands, but take a look at what this one can do to a gigantic log. Cuts through it like butta.