Blood lead concentration and delayed puberty in girls

By influencing growth, exposure to lead might indirectly alter the timing of puberty in girls. Lead-exposed rats have exhibited altered hormone levels and delayed puberty. The investigators attempted to relate blood leadconcentrations to pubertal development in females 8-18 years of age who were enrolled in the third National Health and Nutrition Examination Survey (NHANES III). The nationally representative patient population of 2186 girls included 600 non-Hispanic whites, 805 non-Hispanic African-American girls, and 781 Mexican-Americans. Puberty was assessed by taking note of pubic hair stage, breast development stage, and age at menarche. Mean age was comparable in the 3 study groups, and blood lead levels generally declined with advancing age. Mean blood lead levels were less than 3 μg/dL in all groups. All stages of pubertal development occurred earliest in African-American girls. After adjusting for age and race but not body mass index, lead levels of 3 μg/dL, compared with 1 μg/dL, were associated with decreased height. Levels on this order also were associated with significantly delayed breast and pubic hair development in the African-American and Mexican-American groups. Delayed pubertal development was most evident in African-American girls. Higher lead levels correlated significantly with delayed menarche only in African-American girls. In those with levels of 3 μg/dL, compared with I μg/dL, menarche was delayed by 3.6 months on average. White girls with blood lead levels of 3 μg/dL exhibited directionally similar but nonsignificant delays in all measures of pubertal development, including age at menarche. Delayed pubertal development in girls with relatively high blood lead levels might be a result, at least in part, of mechanisms independent of body growth. Possibly changes in endocrine function are responsible.