Testosterone is a male hormone which is responsible for the development of male genitalia, their maturation & male pattern of hair growth at puberty. It is present in females also & helps in the production of female hormone Estrogen. In males, your doctor will prescribe this test if you have problems of erection or if your partner is unable to get pregnant. In females, your doctor will prescribe this test if you develop male features with excess hair on the face or if you are not able to conceive or if you suffer from polycystic ovaries. This test is useful in boys who are maturing much before the puberty. This test is also recommended in newborns whose genitalia are not well formed.