Puberty is the body's natural process of sexual maturation. Puberty's trigger lies in a small part of the brain called the hypothalamus, a gland that secretes gonadotropin-releasing hormone (GnRH). GnRH stimulates the pituitary gland, a pea-sized organ connected to the bottom of the hypothalamus, to emit two hormones: luteinizing (pronounced LOO-tee-uh-nize-ing) hormone (LH) and follicle-stimulating hormone (FSH). These two hormones signal the female and male sex organs (ovaries and testes, respectively) to begin releasing the appropriate sex hormones, including estrogens and testosterone, which launch the other signs of puberty in the body.1
In approximately 90% of girls who experience precocious puberty, no underlying cause can be identified—although heredity and being overweight may contribute in some cases. When a cause cannot be identified, the condition is called idiopathic precocious puberty. In boys with precocious puberty, approximately 50% of cases are idiopathic. In the remaining 10% of girls and 50% of boys with precocious puberty, an underlying cause can be identified.
Sometimes the cause is an abnormality involving the brain. In other children, the signs of puberty occur because of a problem such as a tumor or genetic abnormality in the ovaries, testes, or adrenal glands, causing overproduction of sex hormones.
Precocious puberty can be divided into two categories, depending on where in the body the abnormality occurs—central precocious puberty and peripheral precocious puberty.
- Central Precocious Puberty
This type of early puberty, also known as gonadotropin-dependent precocious puberty, occurs when the abnormality is located in the brain. The brain signals the pituitary gland to begin puberty at an early age. Central precocious puberty is the most common form of precocious puberty and affects many more girls than boys. The causes of central precocious puberty include:
- Brain tumors
- Prior radiation to the brain
- Prior infection of the brain
- Other brain abnormalities
Often, however, there is no identifiable abnormality in the brain; this is called idiopathic central precocious puberty.
- Peripheral Precocious Puberty
This form of early puberty is also called gonadotropin-independent precocious puberty. In peripheral precocious puberty, the abnormality is not in the brain but in the testicles, ovaries, or adrenal glands, causing overproduction of sex hormones, like testosterone and estrogens.
Peripheral precocious puberty may be caused by2:
- Tumors of the ovary, testis, or adrenal gland
- In boys, tumors that secrete a hormone called hCG, or human chorionic gonadotropin (pronounced kawr-ee-ON-ik goh-nad-uh-TROH-pin)
- Certain rare genetic syndromes, such as McCune-Albright syndrome or familial male precocious puberty
- Severe hypothyroidism, in which the thyroid gland secretes abnormally low levels of hormones
- Disorders of the adrenal gland, such as congenital adrenal hyperplasia
- Exposure of the child to medicines or creams that contain estrogens or androgens
Many children with delayed puberty will eventually go through an otherwise normal puberty, just at a late age. Sometimes, this delay occurs because the child is just maturing more slowly than average, a condition called constitutional delay of puberty. This condition often runs in families.
Puberty can be delayed in children who have not gotten proper nutrition due to long-term illnesses. Also, some young girls who undergo intense physical training for a sport, such as running or gymnastics, start puberty later than normal.3
In other cases, the delay in puberty is not just due to slow maturation but occurs because the child has a long-term medical condition known as hypogonadism (pronounced HI-poe-GO-nad-iz-uhm), in which the sex glands (the testes in men and the ovaries in women) produce few or no hormones. Hypogonadism can be divided into two categories: secondary hypogonadism and primary hypogonadism.
- Secondary hypogonadism (also known as central hypogonadism or hypogonadotropic hypogonadism), is caused by a problem with the pituitary gland or hypothalamus (part of the brain). In secondary hypogonadism, the hypothalamus and the pituitary gland fail to signal the gonads to properly release sex hormones. Causes of secondary hypogonadism include4:
- Kallmann syndrome, a genetic problem that also diminishes the sense of smell
- Isolated hypogonadotropic hypogonadism, a genetic condition that only affects sexual development but not the sense of smell
- Prior radiation, trauma, surgery, or other injury to the brain or pituitary
- Tumors of the brain or pituitary
- In primary hypogonadism, the problem lies in the ovaries or testes, which fail to make sex hormones normally. Some causes include4:
- Genetic disorders, especially Turner syndrome (in women) and Klinefelter syndrome (in men)
- Certain autoimmune disorders
- Developmental disorders
- Radiation or chemotherapy
- Jones, R. E., & López, K. H. (2006) Human Reproductive Biology, 3rd Edition. Academic Press. [top]
- Lavin, N. (2009). Manual of Endocrinology and Metabolism. Lippincott Williams & Williams. [top]
- Lindholm, C., Hagenfeldt, K., & Ringertz, B. M. (1994). Pubertal development in elite juvenile gymnasts: Effects of physical training. Acta Obstetricia et Gynecologica Scandinavica, 73, 269–273. [top]
- U.S. National Library of Medicine. (2010). Hypogonadism. Retrieved June 4, 2012, from http://www.nlm.nih.gov/medlineplus/ency/article/001195.htm [top]