Testosterone is a male sex hormone (androgen) that helps male features develop. Most

testosterone is made in the testes (in men) and the ovaries (in women). A small amount is

made in the adrenal glands.Testosterone causes the changes that occur in boys during

puberty. It helps hair and muscles grow. It also helps the penis and testes grow. Testosterone

also causes a boy's voice to deepen. Men continue to make testosterone. It boosts sex drive

and helps make sperm.