One of a group of male sex hormones that stimulate development of the testes and of male secondary sexual characteristics (such as growth of facial and pubic hair in men). Testosterone is the most important. Androgens are produced principally by the testes when stimulated with luteinizing hormone but they are also secreted in smaller amounts by the adrenal glands and the ovaries. Injections of natural or synthetic androgens are used to treat hormonal disorders of the testes and breast cancer and to build up body tissue (see anabolic steroid).