For reasons that remain unclear, boys in the US are hitting puberty as much as two years earlier than in previous decades, according to a new study from the American Academy of Pediatrics.
Theories as to why range from higher levels of obesity to inactivity to chemicals in food and water, or any other number of variables that might interfere with normal hormone production. What the change could mean for public health concerns also remains unclear.
The study, based on data on more than 4,000 boys in 41 states, provided by their pediatricians' offices, echoes an already well-documented trend of girls hitting adolescence earlier than in the past.
African-American boys were generally the earliest to start puberty, with boys as young as nine years old showing signs of maturation. Non-Hispanic whites were next, with the average age of puberty onset coming at just over 10 years old, while Hispanic boys hit puberty on average a few months later, at just under 10 and a half.
The ages were calculated based on when the pediatricians saw "stage two genital and pubic hair growth."
"Following changes in growth and development is an important part of assessing the health of the nation's children," wrote study author Marcia Herman-Giddens in a statement.
The study, to be printed in next month's edition of the journal "Pediatrics" was put online Saturday to coincide with an AAP conference in New Orleans.
Have you noticed that boys are coming of age a little earlier than they used to? Let us know your take.