Boys Hit Puberty Sooner Now, Study Finds

SATURDAY Oct. 20, 2012 -- American boys are entering puberty at a younger age now than they did several decades ago, new research reveals.

Specifically, investigators discovered that males are showing the first signs of sexual maturity six months to two years earlier, with blacks having a significant head start relative to whites and Hispanics.

The study does not pinpoint what exactly is driving the trend toward earlier puberty, nor does it identify an underlying mechanism that might explain any racial differences.

However, the finding builds on what most experts consider definitive research from the 1990s, which confirmed that American girls are also entering puberty at a younger age today than in decades past.

"When I was studying the subject in girls, I wasn't surprised with the findings because I was seeing it every day in clinic," said study author Marcia Herman-Giddens, an adjunct professor of maternal and child health at the University of North Carolina School of Public Health in Chapel Hill. "And it's also more obvious, since breast development is the first sign of puberty and everybody can see it."

"By contrast, testicular development in boys is very subtle," she noted. "To the point where even the boy himself doesn't necessarily notice it at the beginning. And also the environmental issues that we have long associated with earlier puberty in girls, such as being overweight and environmental exposure to endocrine [hormone]-disruptive chemicals, would actually be expected to slow puberty in boys, not hasten it. So, to see the same thing in boys is actually somewhat surprising."

Herman-Giddens and her colleagues report their findings online Oct. 20 in Pediatrics, to coincide with a presentation at the American Academy of Pediatrics annual meeting in New Orleans. The report will also be published in the November print issue of the journal.

For the study, the authors tracked more than 4,000 boys seen as patients between 2005 and 2010 at one of 144 pediatric health providers in 41 states and one Canadian province.

Puberty onset was determined by the first signs of genital and pubic hair growth and testicular enlargement.

The result: Black boys were found to begin maturing sexually at an average age of just over 9, followed by white boys at just over 10 and Hispanic boys at between 10 and 11.

The study authors stressed that more research is needed to explore why earlier maturation is happening among boys.

Should the findings concern parents?

"The problem is that as a culture we are encouraging a longer and longer adolescence," noted Herman-Giddens. "We're delaying maturity in our culture, by staying longer in school, being later to leave the parent's home, later to marry, later to get financial security. And that means that we have now a huge discrepancy between when the body starts to mature physically and when overall maturity is achieved, which may mean that a boy's or girl's cognitive and social skills do not necessarily mature earlier just because the body does. So, there may be a big and growing gap here, which can cause all sorts of concern for guidance and teaching."

Parents need to be aware that boys might enter into sexual maturity earlier than they might have thought, and they need to discuss what that means sooner rather than later, she said. "When we talk about age 9 and age 10 we're actually talking about averages; for some boys this is actually beginning quite a bit earlier," she said. "Which means that this is an issue that needs to be addressed probably by the third grade, because by the fourth grade it may be too late."

Dr. Frank Biro, director of adolescent medicine at Cincinnati Children's Hospital Medical Center, described the study's conclusions as "a major finding," and agreed that the growing gap between physical and social maturation should be viewed with concern.

"This is the first study, I believe, that looks at this question closely in a contemporary U.S. setting," he noted, "and I feel comfortable in saying that it confirms that puberty is occurring earlier in boys."

Biro said he isn't sure that an earlier maturing boy is going to be sexually active any earlier. However, "I do think that it may lead to a little greater disparity between social maturation and physical maturation. And that is certainly something to think about," he said.

More information

For more on puberty, visit the U.S. National Institutes of Health.

Posted: October 2012


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