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Reasons for Early Puberty in Girls

Puberty is the start of sexual maturity, when a child changes physically and hormonally. In girls, physical changes include development of breasts, appearance of underarm and pubic hai, and the onset of menstruation. There also is an overall increase in growth rate. Puberty normally occurs between 9 and 16 years of age for girls. Various reasons for early puberty are possible, but most cases have no known cause.

  1. Prevalence

    • Early puberty in girls, also called precocious puberty, involves signs of puberty occurring before age 8. Early puberty is more frequent in girls than boys, and much more common in African-American girls than in white girls. According to the National Research Center for Women and Families, by age 8, a total of 48 percent of African-American girls show clear signs of puberty, while only 15 percent of white girls do.

    Hormonal and Ovary Abnormalities

    • Certain physical conditions are associated with early puberty in girls, as noted by the University of Michigan Health System. The pituitary gland, which regulates most hormones, may signal the ovaries to begin hormone production early. Ovary abnormalities, such as tumors, also can cause early puberty.

    Genetic Disorders and Birth Defects

    • Early puberty also is associated with McCune-Albright syndrome, a genetic disorder involving the bones and pigmentation of the skin. Children born with spina bifida, in which the backbone and spinal canal are not fully closed, along with hydrocephalus, a build up of fluid in the skull that causes pressure on the brain, have a tendency to begin puberty early.

    Weight and Social Factors

    • Obesity also is linked to early puberty in girls, according to the University of Michigan Health System. Additionally, family conflict and the absence of the girl's father during childhood predicted an earlier onset of menstruation than normal, as indicated by a study published in a 1992 issue of the journal Child Development. If the girl also was overweight, the combination of those factors was an even better predictor.

    Environmental Toxins

    • Animal studies have indicated that exposure to contaminants that mimic estrogen activity can hasten the beginning of puberty. The University of Michigan Health Center lists several environmental toxins that may contribute to precocious puberty. Bisphenol A, phthalates and polybrominated biphenyls (PBBs), for instance, are used in manufacturing certain types of plastics. DDT (dichloro diphenyl trichloroethane) pesticide metabolites also may contribute to early puberty. Endocrine disruptors that may wind up in the environment include the synthetic estrogen hormone diethylstilbestrol (DES), the industrial byproduct dioxin and polychlorinated biphenyls (PCBs), once commonly included in a wide variety of products.

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