1. An androgen isolated from the testes of a number of animals, including man, and considered to be the principal testicular hormone produced in men.
2. It accelerates growth in tissues on which it acts and stimulates blood flow.
3. It stimulates and promotes the growth of secondary sexual characteristics and is essential for normal sexual behavior and the occurrence of erections.
4. It is responsible for deepening of the male voice at puberty, greater muscular development in men, development of the beard and pubic hair, and the distribution of fat in adult men.

WESTPORT, February 16, 2000 (Reuters Health) - Testosterone therapy provides short-term relief of hypogonadal symptoms in men with symptomatic HIV infection, according to a multicenter group. Specifically, after six weeks of therapy, the subjects showed improvements in libido, energy levels, mood and muscle mass.