Precocious puberty and pseudoprecocious puberty are sexual maturation that begins before age 7 in a girl or before age 9 in a boy. True precocious puberty is caused by the early release of certain sex hormones (gonadotropins) from the pituitary gland. These hormones cause the ovaries or testes to develop and begin secreting other sex hormones, such as estrogen or testosterone. The estrogen or testosterone causes the development of puberty and the appearance of adult physical characteristics. This early hormone release may be caused by a tumor or other abnormality in the pituitary gland or the hypothalamus (the region of the brain that controls the pituitary gland).

In pseudoprecocious puberty, high levels of testosterone or estrogen are produced by a tumor or other abnormality in the adrenal gland or in a testis or ovary. These hormones do not cause the testes or ovaries themselves to mature but do cause a child to look more like an adult.

In both conditions, pubic and underarm hair grows, adult body odor develops, and the child's body shape changes. Acne may appear. A boy develops facial hair, his penis lengthens, and his appearance becomes more masculine. A girl develops breasts and may start to have menstrual periods, especially if she has true precocious puberty. Height increases rapidly but stops at an early age. Therefore, the final height is shorter than would be expected. In true precocious puberty, the sex glands (ovaries or testes) also mature and enlarge, whereas in pseudoprecocious puberty, the sex glands remain immature. True precocious puberty is 2 to 5 times more common in girls.

Testotoxicosis is a rare hereditary form of pseudoprecocious puberty that affects boys; it results directly from maturation of the testes, independent of the hypothalamus or pituitary gland. Similarly, McCune-Albright syndrome is a genetic (but not hereditary) disorder that results in pseudoprecocious puberty; this disorder is more common in girls.

Doctors measure blood hormone levels and take x-rays of the hand and wrist to estimate bone maturity. They perform an ultrasound of the pelvis and adrenal glands and computed tomography (CT) or magnetic resonance imaging (MRI) of the head to check for tumors in the adrenal glands, hypothalamus, or pituitary gland. A test to measure the effect of gonadotropin-releasing hormone on pituitary hormone levels can help doctors diagnose the cause.

In true precocious puberty, taking a drug such as long-acting injections of leuprolide (synthetic gonadotropin-releasing hormone) or daily injections of deslorelin or histrelin stops the pituitary gland from producing sex hormones by desensitizing it to the effects of the body's own gonadotropin-releasing hormone. In pseudoprecocious puberty, a doctor may try to inhibit the action of the sex hormones with various drugs. The antifungal drug ketoconazole reduces the levels of testosterone circulating in the blood in boys who have testotoxicosis. A drug called testolactone reduces the levels of estrogen in adolescents who have McCune-Albright syndrome. In both of these conditions, spironolactone or cyproterone may also be useful.

When a tumor is responsible for true precocious or pseudoprecocious puberty, removing it may cure the condition.