Mouse Anti-Testosterone monoclonal antibody for EIA. Testosterone is the principal androgen, or male sex hormone. One of the group of compounds known as anabolic steroids, testosterone is secreted by the testes but is also synthesized in small quantities in the ovaries, cortices of the adrenal glands, and placenta, usually from cholesterol. Testosterone is necessary in the fetus for the development of male external genitalia. Testosterone also stimulates protein synthesis and accounts for the greater muscular development of the male. For many years, synthetic steroids similar to testosterone have been used by athletes with the goal of improving performance, although recent medical research has shown that these drugs may have a wide range of harmful side effects.