A new study released by the American Academy of Pediatrics suggests that boys are entering puberty much earlier now than was the case several decades ago, with that rapid physical development especially more prevalent among young African-American males.
The study, widely considered the most reliable attempt to measure puberty in American boys, estimates that boys are showing signs of puberty six months to two years earlier than was reported in previous research done in Britain 40 years ago that taught that 11 ½ was the general age puberty began in boys. Experts, however, cautioned that because previous studies were smaller or used different approaches, it is difficult to say how much earlier boys might be developing.
The study echoes research on girls, which has now established a scientific consensus that they are showing breast development earlier than in the past.
The study, which was to be announced at the Academy of Pediatrics national conference on Saturday and published online in the journal Pediatrics, did not try to determine what might be causing earlier puberty, although it mentioned changes in diet, less physical activity and other environmental factors as possibilities. Experts said that without further research, implications for boys are unclear.
“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, according to the New York Times. She was not involved in the study.
The new study found that African-American boys began puberty earlier than whites and Hispanics, a result that other studies have shown also applies to African-American girls. Researchers said that difference is most likely driven by the role of genes in puberty.
On average, black boys in the study showed signs of puberty, primarily identified as growth of the testicles, at a little older than 9, while white and Hispanic boys were a little older than 10.
Several experts said the study should not be seized upon as cause for alarm, but rather as a way to help parents and doctors gauge what to be aware of in boys’ development and whether to start conversations about social issues sooner.
“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.
For the study, researchers enlisted about 200 pediatricians in 41 states to record information on 4,131 healthy boys ages six to 16 during their well-child exams. Physicians were trained to use an orchidometer, a string of oval wooden or plastic beads of increasing size that are compared against the size of the testicles. Urologists use orchidometers to measure testicular volume when men have fertility concerns. Normal adult size is about 22 to 25 milliliters, Dr. Lamb said. In boys, two milliliters is pre-pubertal; some doctors consider three milliliters and others four milliliters as an indicator of puberty, so the study included analysis for both sizes.
The study’s lead author, Dr. Marcia E. Herman-Giddens, is a child and maternal health specialist at University of North Carolina Chapel Hill whose large study on girls’ puberty in 1997, and its conclusion that girls were developing earlier generated great controversy. Now, though, experts generally agree that subsequent research has shown breast development as young as seven or eight. With girls, there is also scientific consensus that heavier girls enter puberty earlier, which makes sense, experts said, because body fat is tied to estrogen production.
In the study of boys, weight was not analyzed intensively, but the heaviest boys were developing earlier than what Dr. Herman-Giddens called “the little bitty skinny boys.” Experts said it is unclear if weight gain precipitates puberty or is a consequence.
