Testosterone

Lore & Background

Testosterone drives the development of male reproductive tissues such as testicles and prostate, and promotes secondary sexual characteristics including increased muscle and bone mass, body hair growth, and voice deepening. It is associated with increased aggression, sex drive, dominance, and courtship display. In both sexes, testosterone affects mood, cognition, social and sexual behavior, metabolism, cardiovascular health, and osteoporosis prevention. Insufficient levels in men may lead to frailty, fat accumulation, anxiety, depression, sexual deficits, and bone loss, while excessive levels may be linked to hyperandrogenism, heart failure risk, increased mortality in prostate cancer, and male pattern baldness.

Reader's Guide

Testosterone is a steroid hormone from the androstane class, with a ketone and hydroxyl group at positions three and seventeen. It is biosynthesized from cholesterol and converted in the liver to inactive metabolites, exerting its action through binding to the androgen receptor. In humans, it is secreted primarily by the testicles of males and, to a lesser extent, the ovaries of females. Adult male levels average seven to eight times those of females, with daily production about 20 times greater.

Testosterone is used medically to treat hypogonadism and breast cancer, and illicitly by athletes to enhance physique and performance, leading to its prohibition by the World Anti-Doping Agency. Its effects include anabolic (muscle and bone growth) and androgenic (sex organ maturation, hair growth) actions, with some effects mediated by metabolites like dihydrotestosterone and estradiol. Conflicting results regarding testosterone's role in cardiovascular health.

Did You Know?

• The World Anti-Doping Agency lists testosterone as an S1 Anabolic agent substance prohibited at all times.
• Testosterone can be metabolized by 5α-reductase into dihydrotestosterone or aromatized to estradiol.