Testosterone is a steroid hormone from the androgen group. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid.In both men and women, testosterone plays a key role in health and well-being as well as in sexual functioning. Examples include enhanced libido, energy, immune function, and protection against osteoporosis. On average, an adult human male body produces about eight to ten times more testosterone than an adult female body.James McBride Dabbs, 2000 However the overall ranges for male and female are very wide, such that the ranges actually overlap at the low end and high end respectively.
Testicular action was linked to circulating blood fractions — now understood to be a family of androgenic hormones — in the early work on castration and testicular transplantation in fowl by Arnold Betho