Higher levels of testosterone are correlated with financial risk-taking behavior, according to a new study in which men's testosterone levels were assessed before participation in an investment game. The findings help to shed light on the evolutionary function and biological origins of risk taking.

Anabolic steroids are synthetic hormones derived from the human male hormone testosterone. The use of steroids has been suspected in professional baseball and other sports where building muscle strength, rather than endurance, is paramount.

Exposure to an excess of sexual steroids, like testosterone, during fetal development may be a potential risk factor for low sperm count and motility, according to a new study accepted for publication in Endocrinology, a journal of The Endocrine Society.

High levels of testosterone may be a key factor in spreading disease among mice, according to biologists. The findings could help explain why males in a population are often more likely to get infected, and transmit disease.

For young male offspring who suffer a dominant mother, a brother may be on the way to help bear the burden. And all because of follicular testosterone. A growing body of evidence suggests a maternal influence on sex determination: dominant human females conceive more sons.

When City traders have high morning testosterone levels they make more than average profits for the rest of that day, researchers at the University of Cambridge have discovered.

The risk of osteoporosis (bone fracture) in women is highly recognized by the public. Less appreciated is the fact that the disorder also occurs in men. Some two million males have been diagnosed with osteoporosis and another three million are at risk.

Testosterone appears to protect people against eating disorders, providing further evidence that biological factors – and not just social influences – are linked to anorexia and bulimia, according to new research findings at Michigan State University.

Aggression, testosterone and nepotism don’t necessarily help one climb the social ladder, but the support of a good female can, according to new research on the social habits of an unusual African species of fish.

Older men with low testosterone levels who received testosterone supplementation increased lean body mass and decreased body fat, but were no stronger and had no improvement in mobility or cognition compared with men who did not use the supplement, according to a study in the January 2 issue of JAMA.

Two reports from physician-scientists at NewYork-Presbyterian Hospital/Weill Cornell Medical Center shed new light on male infertility. A first report shows that a common cause of male infertility -- varicoceles, or varicose veins in the scrotum -- also results in a depletion of testosterone.

The ability to ramp up testosterone production appears to drive male dark-eyed juncos to find and win mates, but it comes with an evolutionary cost. Big fluctuations in testosterone may also cause males to lose interest in parenting their own young, scientists have learned.