Present in much greater levels in men than women, testosterone initiates the development of the male internal and external reproductive organs during foetal development and is essential for the production of sperm in adult life. It is an androgen, meaning that it stimulates the development of male characteristics.

Testosterone is produced by the gonads (by the Leydig cells in testes in men and by the ovaries in women), although small quantities are also produced by the adrenal glands in both sexes.

Testo (brand name for testosterone formulations) 4-androsten-17β-ol-3-one What is testosterone?