Researchers led by Marcia Herman-Giddens from the University of North Carolina's School of Public Health found that boys are starting to sexually develop six months to two years earlier than medical standards.
This research has been a long time coming. Herman-Giddens first documented early puberty in girls in 1997, and several studies have since backed up those findings, the CNN reported.
One of the reasons it took so long to do a comprehensive study on early puberty in boys, Herman-Giddens said, is that the onset is more difficult to identify.
In girls, breast development and the start of a menstrual cycle are obvious clues. For boys, the onset of puberty comes in the form of enlarged testes and the production of sperm.
" Yikes, we don't want to ask about that," Herman-Giddens said.
As many as 212 practitioners across US examined more than 4,100 boys aged 6 to 16. The practitioners recorded information on the boys' genital size and pubic hair appearance.
Researchers assigned each boy's data to one of five stages
- Stage 1 being pre-puberty, Stage 2 being the onset of puberty and Stage 5 being adult maturity.
They then compared the ages and puberty stages of all the boys. The rigorous study was designed to report on only physical changes, not hormonal.
The results were broken down by race - African-American boys start hitting Stage 2 first, at about 9 years old, while non-Hispanic white and Hispanic boys begin developing around 10 years old.
"This should have an impact on the public health community," Herman-Giddens said.
Researchers are worried that the environment may be playing a role in accelerating puberty.
"The changes are too fast," Herman-Giddes said.
"Genetics take maybe hundreds, thousands of years. You have to look at something in the environment. That would include everything from (a lack of) exercise to junk food to TV to chemicals," said Herman-Giddens.
