To detect an abnormal testosterone level in males and females: In males, to help diagnose the cause of symptoms, such as erectile dysfunction. In females, to help diagnose the cause of masculine physical features (virilization), excess body hair (hirsutism), infertility, or polycystic ovary syndrome (PCOS) In children, to help determine the cause of delayed or early (precocious) puberty, or the cause of genitals that are not clearly male or female (ambiguous genitalia)