Like girls, US boys may hit puberty earlier

2012-10-21 19:49

(Supplied)

New York - Boys in the United States may be entering puberty earlier than in generations past, a new study has found, suggesting it's not just girls who are developing at younger ages.

In comparison with decades-old data, boys who were seen for well-child visits between 2005 and 2010 were maturing six months to two years sooner, based on their genital development.

The finding is significant for researchers seeking to understand why the age of puberty may be decreasing.

The discovery is also important for parents, who have to know how and when to discuss changing bodies with their children, according to the lead author of the study published by the journal Paediatrics.

"They need to talk to their boys earlier than they would have thought about puberty and sexual development and all of those related issues," said Marcia Herman-Giddens at the University of North Carolina at Chapel Hill.

Recent studies from the United States and elsewhere have shown that girls are maturing at a younger age, with many starting to develop breasts as early as age seven or eight.

Doctors haven't necessarily thought the same early puberty trend applied to boys.

Some doctors blame oestrogen-like chemicals in the environment for girls' earlier development.

Those same chemicals would be expected to delay sexual maturation in boys.

But even if boys are developing earlier than in the past, that doesn't mean they are more mature socially and psychologically at younger ages, researchers said.

Puberty

"Now there's probably a bigger disparity between their physical maturation and their psychosocial maturation," said Dr Frank Biro, head of adolescent medicine at Cincinnati Children's Medical Centre, who wasn't involved in the new analysis.

"People are going to interact with them like they're older," he said.

Data for the new study came from 144 US paediatric practices and included 4 131 boys aged six to 16.

Based on the so-called Tanner stages of development - a technique doctors use to measure how far along in puberty a young person is - genital changes in boys started around the age of nine or 10 and pubic hair appeared between age 10 and 11½, on average.

Testicle size hit a common measure for the start of puberty just before age 10 and full sexual maturity happened at 15 to 16.

In general, African-American boys developed earlier than their white and Hispanic peers, Herman-Giddens and her colleagues reported.

A study from the 1950s through 1970s of white boys in England - for which the Tanner scale is named - found boys started genital development at age 11.6, on average.

Other data through the 1970s also put the start of genital changes between age 11 and 12, and pubic hair development typically between 12 and 13 - about two years later than in the new study.

Despite strong evidence showing girls are developing breasts and getting their periods at younger and younger ages, Herman-Giddens said it is still not clear why boys may also be hitting puberty sooner than in years past. One possible explanation is high rates of obesity, which alters the body's hormone levels.

"The reasons it is happening may not be healthy," she said.

- Reuters