Earlier Onset and Racial Differences of Puberty in Boys

In a 1997 report, researchers noted that girls were undergoing puberty earlier than had been reported 30 to 40 years previously. Now, the same research group finds that boys also are undergoing pubertal changes at younger ages than reported earlier. As part of a U.S. government study, a representative sample of 2395 white, black, and Mexican-American boys (age range, 8 to 19 years) were assessed by specially trained physicians; the boys' genital and pubic-hair development were classified according to the widely used Tanner stages.

Mean ages of boys at Tanner pubic-hair stage 2 (i.e., onset of hair growth) was 12.0, 11.2, and 12.3 years for white, black, and Mexican-American boys, respectively. Significant racial and ethnic differences were n…