(CNN) -- Boys in the United States are starting puberty earlier
than ever, according to a new study publishing in the November
issue of the journal Pediatrics. In the study, lead author
Marcia Herman-Giddens from the University of North Carolina's
School of Public Health and her colleagues show that boys are
starting to sexually develop six months to two years earlier
than medical textbooks say is standard. 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. 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. For
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. Researchers
responded: " 'Yikes, we don't want to ask about that!' " Herman-
Giddens said with a laugh. But as