Is puberty before the age of 10 a “new normal” for girls? asks a long article in the New York Times magazine. The phenomenon of early breast budding and growth of pubic hair in girls as young as six has been studied since at least the late 1980s. Now, US researchers seem to be agreed that breast development is starting earlier. They are just not sure what it means, since the age of menarche (first period) has dropped only slightly -- from 12.8 years to 12.5.
There’s “early” and then there’s “very early” breast development -- the latter often distressing for parents, and for the little girls as they become aware that they are different. In extreme cases doctors will prescribe hormone shots to stop the process, but otherwise they are reluctant because this treatment carries a risk of osteoporosis and also reinforces to the child that there is something “wrong” with her. One expert prefers a “process of normalising”.
The burning question is, Why is this happening? Researchers have suggested several causes:
* Being overweight. More precisely, being too fat. It’s excess fat tissue that which produces “higher levels of the hormone leptin, which can lead to early puberty, which leads to higher estrogen levels, which leads to greater insulin resistance, causing girls to have yet more fat tissue, more leptin and more estrogen, the cycle feeding on itself, until their bodies physically mature.” * Environmental chemicals. Endocrine disrupters such as estrogen mimics, notably the ubiquitous BPA, found in products ranging from dental sealant to till slips.
* Family stress. The Times article notes:

Girls who from an early age grow up in homes without their biological fathers are twice as likely to go into puberty younger as girls who grow up with both parents. Some studies show that the presence of a stepfather in the house also correlates with early puberty. Evidence links maternal depression with developing early. Children adopted from poorer countries who have experienced significant early-childhood stress are also at greater risk for early puberty once they’re ensconced in Western families.

Bruce Ellis, a professor of Family Studies and Human Development at the University of Arizona, discovered along with his colleagues a pattern of early puberty in girls whose parents divorced when those girls were between 3 and 8 years old and whose fathers were considered socially deviant (meaning they abused drugs or alcohol, were violent, attempted suicide or did prison time). In another study, published in 2011, Ellis and his colleagues showed that first graders who are most reactive to stress — kids whose pulse, respiratory rate and cortisol levels fluctuate most in response to environmental challenges — entered puberty earliest when raised in difficult homes. Evolutionary psychology offers a theory: A stressful childhood inclines a body toward early reproduction; if life is hard, best to mature young. But such theories are tough to prove. For these same reasons, probably, early physical development is linked with low self esteem, depression, and high-risk behaviour such as drinking and sexual activity.
Some experts, however, wonder whether girls with early breast growth are in puberty at all. Robert Lustig, of Benioff Children’s Hospital explains:

True puberty starts in the brain, he explains, with the production of gonadotropin-releasing hormone, or GnRH. “There is no puberty without GnRH,” Lustig told me. GnRH is like the ball that rolls down the ramp that knocks over the book that flips the stereo switch. Specifically, GnRH trips the pituitary, which signals the ovaries. The ovaries then produce estrogen, and the estrogen causes the breasts to grow. But as Lustig points out, the estrogen that is causing that growth in young girls may have a different origin. It may come from the girls’ fat tissue (postmenopausal women produce estrogen in their fat tissue) or from an environmental source. “And if that estrogen didn’t start with GnRH, it’s not puberty, end of story,” Lustig says. “Breast development doesn’t automatically mean early puberty. It might, but it doesn’t have to.” Don’t even get him started on the relationship between pubic-hair growth and puberty. “Any paper linking pubic hair with early puberty is garbage. Gar-bage. Pubic hair just means androgens, or male hormones. The first sign of puberty in girls is estrogen. Androgen is not even on the menu.” Research by Anders Juul in Denmark tends to confirm Lustig’s view. It “shows some of the girls with early breast development had unexpectedly low levels of estradiol, the predominant form of estrogen in women’s bodies from the onset of puberty through menopause.” Still, if a girl is 10 and she looks 15 she may attract sexual attention even if she has no interest in sex herself. So what are parents to do? This seems sound advice from one expert, who stresses the importance of secure family life:

“I know they can’t change the fact that their daughter started developing early, but they can change what happens downstream,” Louise Greenspan, the pediatric endocrinologist at Kaiser Permanente, told me. Parents can keep their daughters active and at healthy body weights. They can treat them the age they are, not the age they look. They can defend against a culture that sells push-up bikinis for 7-year-olds and otherwise sexualizes young girls. “Most of the psychological issues associated with early puberty are related to risk-taking behaviors,” Greenspan continued, and parents can mitigate those. “I know it sounds corny and old-fashioned, but if you’re in a supportive family environment, where you are eating family meals and reading books together, you actually do have control.” Early breast growth may be just that — early breast growth: disconcerting, poorly understood, but not a guarantee of our worst fears. “You don’t go directly from the first signs of early puberty to anorexia, depression, drinking and early sexual debut.” There are some other points in my earlier post on this: the role of television or other screen use at night; the physical mechanism whereby the presence of a father inhibits sexual precociousness in girls; concerns about a link between early estrogen exposure and breast cancer; and the environment in the mother’s womb, including being pregnant for the first time (after years on the pill?).
As for "normalising" early breast development, that hardly seems the way to go. A mother can reassure her daughter that it happens to other girls too, but, given the risks, it could hardly be a professional or public health strategy. Could it?