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, increased energy, and protection against osteoporosis. On average, an adult human male body produces about eight to ten times more testosterone than an adult female body. 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.