an organic compound belonging to the steroid family and occurring as the androgenic, or masculinizing, hormone produced by the testis. Testosterone is responsible for development of the male sex organs and such masculine characteristics as facial hair and deepening of the voice. The hormone was isolated from testicular extracts in 1935, after it had been shown that they contain an androgen more potent than androsterone, which had been obtained from urine in 1931. Androsterone was later shown to be a biochemical product (a metabolite) of testosterone. Testosterone can be manufactured by chemical and microbiological modification of inexpensive steroids, such as diosgenin. It is used clinically for treatment of testicular insufficiency, the suppression of lactation, the therapy of certain types of breast cancer, and the treatment of frigidity in women.