(HealthDay News) – For U.S. boys, the mean age for development of secondary sexual characteristics is earlier than reported previously, and varies depending on race.

Marcia E. Herman-Giddens, PA, MPH, DrPH, from the University of North Carolina at Chapel Hill, and colleagues examined data from racially and ethnically diverse U.S. boys to determine the age of onset of secondary sexual characteristics. Tanner stage and testicular volume data for 4,131 boys were collected by 212 practitioners in 144 pediatric offices. The prevalence and mean age of onset of sexual maturity markers were assessed.

The researchers found that, for non-Hispanic white, African-American, and Hispanic boys, the mean ages of onset of Tanner 2 genital development were 10.14, 9.14, and 10.04 years, respectively. For stage 2 pubic hair, the mean ages of onset were 11.47, 10.25, and 11.43, respectively. Testicular volumes of ≥3mL were achieved at a mean age of 9.95 for whites, 9.71 for African-Americans, and 9.63 for Hispanics, with the corresponding ages of 11.46, 11.75, and 11.29 for ≥4mL. Compared with white and Hispanic boys, African-American boys showed significantly earlier mean ages for stage 2–4 genital development and stage 2–4 pubic hair.

“The causes and public health implications of this apparent shift in U.S. boys to a lower age of onset for the development of secondary sexual characteristics in U.S. boys needs further exploration,” the authors write.

Several authors disclosed financial ties to pharmaceutical companies, including Novo Nordisk and Abbott, which manufacture growth hormone and testosterone, respectively.

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