The study, which was unveiled Saturday at the organization's national conference in New Orleans, found boys show signs of puberty six months to two years earlier than was reported by previous research, The New York Times reported.
Previous studies generally found boys begin puberty at 11.5 years of age.
"This should perhaps set a standard going forward for being very attentive to puberty in boys and being mindful that they're developing earlier," said Dolores J. Lamb, a molecular endocrinologist at Baylor College of Medicine and president of the American Society for Reproductive Medicine.
She was not involved in the study.
"Whether the difference is as large as what they say on some papers 40 years ago is not clear," Lamb said, adding, "this is going to be incredibly useful to pediatricians and urologists."
Researchers in the study called on about 200 pediatricians in 41 states to record information on 4,131 boys ages 6 to 16 during their well-child exams.
"It was an important study to do, and their methodology is improved over prior studies in that they based their assessment of puberty in boys on what I consider to be the gold standard: the size of the testicles," said Dr. Laura Bachrach, a professor of pediatric endocrinology at Stanford University.