What is precocious puberty?

Causes and Symptoms

Secondary sexual development is commonly known as puberty. It is typically characterized by growth of pubic and underarm hair, acne, and rapid physical development until about age eighteen. During puberty, a boy also grows facial hair, his penis and testes enlarge, and he begins to produce sperm. A girl develops breasts and begins to menstruate and ovulate.

Puberty is the result of hormonal changes triggered by the hypothalamus region of the brain. The brain releases luteinizing hormone-releasing hormone (LHRH) in periodic bursts, which causes the pituitary gland to secrete gonadotropin-releasing hormone (GnRH). Gonadotropins stimulate the ovaries in girls and the testes in boys to secrete sex hormones. These hormones—estrogen and progesterone in girls and testosterone in boys—start the sexual maturation process and stimulate rapid physical growth.

Puberty usually begins at about age twelve in boys and age eleven in girls. Approximately one in every ten thousand children begins puberty abnormally early, between infancy and approximately age nine. This condition, known as precocious puberty, affects both sexes but is two to five times more common among girls than boys. Early onset of puberty is also more likely to occur in overweight children.

In addition to prematurely developing secondary sexual characteristics, children with precocious puberty are initially tall for their ages. Left untreated, however, they rarely reach their full adult height potential because the same sex hormones that trigger early growth also end it prematurely. Males often grow no taller than 5 feet 2 inches, and many females remain under 5 feet. Precocious puberty frequently results in adolescent behaviors such as moodiness, irritability, and aggressiveness, as well as the early development of a sex drive. Children with precocious puberty reach sexual maturity at varying rates, and some characteristics may even begin to regress to their normal state.

When an underlying cause for precocious puberty cannot be determined, the condition is known as idiopathic precocious puberty. About 80 percent of cases in females and 40 percent of male cases are idiopathic. Common causes for precocious puberty that can be identified include genetic disorders or tumors in the hypothalamic region of the brain. Such tumors, known as hypothalamic hamartomas, are usually benign. Between 5 and 10 percent of boys with precocious puberty genetically inherit the condition from their fathers or indirectly from their maternal grandfathers. This genetic transmittal of precocious puberty only occurs in about 1 percent of girls with the condition. Less common causes of precocious puberty include other kinds of brain tumors, ovarian tumors or cysts, and adrenal gland disorders such as adrenogenital hyperplasia or congenital adrenal hyperplasia. Precocious puberty can also be caused by pituitary lesions, hydrocephalus, radiation therapy, nervous system disorders such as neurofibromatosis, thyroid disorders (specifically severe hypothyroidism), and a rare condition called McCune-Albright
syndrome.

Children with precocious puberty are often self-conscious about their early physical and sexual development, since they appear older than their ages. Mental development is not affected by the condition, however, so children with precocious puberty are usually not as emotionally mature as they appear.

Treatment and Therapy

Underlying causes of precocious puberty, if known, are often difficult or impossible to treat. Surgical removal of noncancerous hypothalamic hamartomas and other brain tumors, for example, may not be feasible and rarely halts sexual development. Other causes such as neurofibromatosis are incurable, and treatments for conditions such as adrenal disorders may not stop the effects of precocious puberty.

Therefore, many forms of precocious puberty are treated by changing patients’ hormonal balance. Synthetic hormones called LHRH analogs and gonadotropin-releasing hormone agonists (GnRHa) block the body’s production of sex hormones and thus slow down or stop pubertal symptoms. The synthetic hormone histrelin acetate, also known by its brand name Supprelin, has been shown to be effective in reducing early sexual changes in both sexes and to slow bone growth. Leuprolide acetate, sold under the brand name Lupron-Depot PED, is another successful treatment for this condition. Daily injections of these drugs are stopped when the patient reaches the appropriate age for onset of puberty.

Synthetic versions of GnRH or LHRH interrupt the chain of hormonal events that result in sexual maturation. Some research, however, suggests a link between these therapies and bone mineral density loss. Treatments are administered in daily or monthly injections.

Girls with precocious puberty caused by congenital adrenal hyperplasia can be treated by suppressing the hormone known as ACTH with a glucocorticoid. Precocious puberty associated with McCune-Albright syndrome can be treated with testolactone, which blocks the production of estrogens. Some forms of precocious puberty involving the gonadotropins can be treated with the hormone suppressant nafarelin acetate.

Genetic counseling is recommended for families of patients with inherited precocious puberty. Psychological counseling may also benefit patients, since they may not fit in with peers because of the physical ramifications of the condition.

Perspective and Prospects

Previous treatments for precocious puberty included the use of synthetic progesterone, an artificial version of a sex hormone secreted by the ovaries. Synthetic progesterone frequently stops menstruation and reduces breast size in girls, but it has little or no effect on boys. Unfortunately, it fails to stop rapid growth in either sex. Synthetic progesterone can also result in several serious side effects.

Experimental treatments for idiopathic precocious puberty include a combination of spironolactone and testolactone for male patients, as well as another drug called deslorelin or Somagard for either sex.

Bibliography

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Grave, Gilman D., and Gordon B. Cutler, Jr., eds. Sexual Precocity: Etiology, Diagnosis, and Management. New York: Raven Press, 1993.

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