Secondary Sexual Characteristics in Boys

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Abstract
Background Descriptive data on pubertal stages for a representative population of racially and ethnically diverse boys in the United States have not been published to our knowledge. Objective To determine at what ages boys in the United States reach each of the 5 sexual maturity stages for genital and pubic hair growth. Design and Setting Cross-sectional survey from the National Health and Nutrition Examination Survey III (NHANES III), 1988-1994. Participants A population-based sample of 2114 boys aged 8 to 19 years representing 16 575 753 boys according to NHANES III sampling strategies. The sample included white, African American, and Mexican American boys. Main Outcome Measures Sexual maturity stages for genital maturation and pubic hair growth. Results The median (equivalent mean) ages at stage 2 for pubic hair development of white, African American, and Mexican American boys were 12.0 (95% confidence interval [CI], 11.7-12.3), 11.2 (95% CI, 10.9-11.4), and 12.3 (95% CI, 12.1-12.6) years, respectively, and at stage 2 for genital growth were 10.1 (95% CI, 9.6-10.6), 9.5 (95% CI, 8.9-10.0), and 10.4 (95% CI, 9.6-11.1) years, respectively. All 3 groups were significantly taller and heavier than boys in previous NHANES reports and showed earlier genital maturation and pubic hair growth than previous studies based on Tanner staging. Statistically significant differences among the 3 racial/ethnic groups were found in the median ages of onset of pubic hair growth and genital development at stage 5 with and without controlling for height and weight, indicating an earlier age of attainment for the African American boys. Conclusions The median (mean) ages at the onset of genital and pubic hair growth were younger than in past studies. Additional studies are required to further evaluate these findings and to explore the public health implications.