When puberty comes knocking early

The research is just the latest in a flood of reports over the last decade that have led to concern and heated debate about whether girls are reaching puberty earlier, and why it might be happening.

Increased rates of obesity are thought to play a major role, because body fat can produce sex hormones. Some researchers also suspect that environmental chemicals that mimic the effects of estrogen may be speeding up the clock on puberty, but that idea is unproved.

The issue is of concern for both medical and psychosocial reasons. Studies suggest that earlier puberty, as measured by the age at first menstruation, can slightly increase the risk of breast cancer, probably because it results in longer lifetime exposure to the hormones estrogen and progesterone, which can feed some tumors.

Although the new study did not look at menstrual age, breast growth is also a sign of hormone exposure, and some researchers fear that early development might also mean an increased cancer risk.

Socially and emotionally, life can be difficult for a girl who has a child’s mind in a woman’s body and is not ready to deal with sexual advances from men and boys, or cope with her own hormone-spiked emotions and sexual impulses.

“Our analysis shows clearly that the white participants entered puberty earlier than we anticipated,” said Dr Frank M Biro, the first author of the study and the director of adolescent medicine at Cincinnati Children’s Hospital Medical Center.

Factors responsible

Overweight girls were more likely to have more breast development, the study showed. But Biro said he did not think weight was the whole story. He said it was possible that environmental chemicals were also playing a role, and added that he and his colleagues were now studying the girls’ hormone levels and lab tests measuring their exposures to various chemicals.

“It’s certainly throwing up a warning flag,” Biro said. “I think we need to think about the stuff we’re exposing our bodies to and the bodies of our kids. This is a wake-up call, and I think we need to pay attention to it.”

The new study is being published on Monday in the journal Pediatrics.
If there is an ideal age when girls should reach puberty, no one knows what it is, said Dr Marcia E Herman-Giddens, a researcher at the University of North Carolina, Chapel Hill. A girl needs a certain amount of body fat to start menstruating, and girls who are malnourished or ill may have delayed puberty.

In developed countries, the age of puberty dropped from the 19th to 20th centuries, as nutrition improved and infectious diseases were brought under better control, and it was seen as a sign of progress. But if the drop continues, at what point does it become pathological?

The debate over this issue started with a study published in 1997 by a research team led by Herman-Giddens. In the study, pediatricians around the US rated sexual maturation in 17,077 girls ages 3 to 12. The study found that breasts or pubic hair, or both, were far more common in 7- and 8-year-olds than medical textbooks had been reporting.

Dozens of studies have been published in the years since. Arguments continue, but many doctors accept the idea that heavier girls often develop earlier. Though breasts may be sprouting earlier, the average age of first menstruation, between 12 and 13, has not really changed.

Dr Vaneeta Bamba, director of the Diagnostic and Research Growth Center at the Children’s Hospital of Philadelphia, said that the 1997 study had “somewhat reshaped” endocrinologists’ thinking about the onset of puberty, but that most would still urge a thorough medical evaluation for any girl under 8 who was showing significant breast development or other signs of puberty. She said she doubted that the new study would change medical practice.

Objection raised

One objection to the 1997 study was that the pediatricians may have mistaken fat deposits for breast tissue in some girls, or differed in other ways in assessing the stage of breast development.

In the new study, the researchers went to great lengths to train examiners and make sure all were on the same page when it came to checking girls’ breasts and rating their stage of development.