n.1. A steroid hormone, C19H28O2, produced primarily in the testes and responsible for the development and maintenance of male secondary sex characteristics. Testosterone synthesized from plant sources, often in the form of an ester, is used in the medical treatment of testosterone deficiency.
2. Any of several synthetic compounds that mimic the physiologic activity of testosterone, used as drugs in the medical treatment of testosterone deficiency and as doping agents by athletes.