00Nov15b Early puberty 2 (Fwd)
October 20th 2000
Teens Before Their Time
With budding breasts and pubic hair, girls are developing earlier than ever. What's causing it?
Marissa Carter, a Galveston, Texas, housewife, could not believe it when her daughter Sharon, at the tender age of 4, seemed to be developing breasts. The tiny buds that appeared on the little girl's chest were gone within a couple of weeks, but three years later, they reappeared, and this time they grew -- along with pubic hair and hair in Sharon's armpits. "I felt this was too early for her to be developing," recalls Carter. "Gosh, I was flat as a board at her age."
So after a series of medical consultations, the Carters (all these names have been changed at the families' request) put Sharon on lupron, a hormone that slams the brakes on puberty -- only to see their happy little girl go into terrible mood swings. "I had a child acting like she was in menopause," says Carter. The parents decided to stop the treatment, and by age 9, Sharon had full-blown breasts and was getting her period.
Laura Stover took her daughter Karen to a specialist when the girl began growing pubic hair at age 5. The doctor put Karen through a battery of blood tests to rule out ovarian tumors (which can force glands to churn out puberty-triggering hormones). But there was no apparent medical problem, and by age 8, Karen had full pubic growth. "We didn't allow her to go to any slumber parties," says Stover. "Or to change bathing suits in front of other children."
Cecilia Morton, in Santa Maria, Calif., has not one but two daughters who developed early. Clara, now 13, started sprouting breasts and pubic hair when she was 8 and began menstruating a year later, at summer camp. Says her mother: "It was scary and embarrassing because the girls in her cabin didn't have their periods yet." Then Clara's little sister Susan, a kindergartner, began developing at the same time. Although Susan's tests were normal, Morton put her on hormone treatments. "We already see how men look at Clara," she says. "If my younger one didn't have the medication, I can't even imagine the problems we'd be having."
If these were isolated cases, they might be chalked up to statistical flukes. But it seems as if everywhere you turn these days -- outside schools, on soccer fields, at the mall -- there are more and more elementary schoolgirls whose bodies look like they belong in high school and more and more middle schoolers who look like college coeds. "Young girls [in the 5-to-10-year-old range] with breasts or pubic hair -- we encounter this every day we're in clinic," says Dr. Michael Freemark, chief of pediatric endocrinology at Duke University Medical Center in Durham, N.C.
It's as if an entire generation of girls had been put on hormonal fast-forward: shooting up, filling out, growing like Alice munching on the wrong side of the mushroom -- and towering Mutt and Jeff-like over a generation of boys who seem, next to the girls, appear to be getting smaller every year.
What's going on? Is it something in the water? That's a possibility. Scientists think it may be linked to obesity, though they've also proposed a witches' brew of other explanations, from chemicals in the environment to hormones in cow's milk and beef. But the truth is that all anyone knows for certain is that the signs of sexual development in girls are appearing at ever younger ages. Among Caucasian girls today, 1 in every 7 starts to develop breasts or pubic hair by age 8. Among African Americans, for reasons nobody quite understands, the figure is nearly 1 out of every 2.
In retrospect, pediatricians and psychologists say, there have been hints for the past decade or so that something strange was going on. But it wasn't until 1997 that anyone put her finger on it. That's when Marcia Herman-Giddens, now an adjunct professor at the University of North Carolina School of Public Health, published her famous paper in the journal Pediatrics. Herman-Giddens noticed in her clinical work that more and more young girls were coming in with breasts and pubic hair. Intrigued, she launched a major study of 17,000 girls to get a statistical handle on the problem.
What she and her colleagues found was that the changes of puberty were coming in two stages, each with its own timetable. The average age of menarche, or first menstruation, had already fallen dramatically (from 17 to about 13) between the middle of the 19th century to the middle of the 20th -- mostly owing to improvements in nutrition. (Menstruation is considered the technical start of puberty; the outward signs of sexual maturity usually come earlier.) But since the 1960s, average age of first menstruation has basically remained steady at 12.8 years. For African Americans, it's currently about six months earlier, possibly reflecting genetic or nutritional differences.
What was striking about Herman-Giddens' report was the onset of secondary sexual characteristics: breast buds and pubic hair. Significant numbers of white girls -- some 15% -- were showing outward signs of incipient sexual maturity by age 8, and about 5% as early as 7. For African Americans, the statistics were even more startling. Fifteen percent were developing breasts or pubic hair by age 7, and almost half by age 8.
The Pediatrics report answered many questions, but much about the subject remains a mystery. The study couldn't accurately gauge, for example, how much the average age of onset of breast development (as opposed to menstruation) has dropped or over what period. That's because a key piece of research that helped set the standard age at 11 was a small study in the 1960s of white girls raised in English orphanages. But Dr. John Dallas, a pediatric endocrinologist with the University of Texas Medical Branch in Galveston, points out that the British girls may have been poorly nourished -- a factor known to delay puberty. African- American girls were studied even less rigorously. "For all we know," says Dallas, "African-American girls could have been earlier developers for a long time."
The Pediatrics study is also limited because it does not include enough Asian-American or Hispanic girls to draw conclusions about these groups. Herman-Giddens agrees: "We in the public health and medical community really need to get data on American girls of all racial and ethnic groups." They also need to get data on boys, who haven't been studied in any systematic way. Herman-Giddens is pursuing the question now but says it isn't easy. "With girls," she says, "you can see breasts budding. With boys, the equivalent sign is an increase in size of the testes. It's very subtle. Even a physician may not be aware of it if they are not looking carefully."
Finally, somebody needs to compare studies going on in other countries. Is this a peculiarly American phenomenon? Or are girls developing breasts and reaching puberty at younger and younger ages all over the world?
The uncertainties swirling around the phenomenon make it difficult for scientists to nail down a cause, but that hasn't stopped them from coming up with a long list of potential candidates. The theory that has the broadest support among scientists holds that early puberty is somehow tied up with a much more familiar phenomenon: weight gain. America is in the midst of an epidemic of overweight and obese kids; between the late '70s and the early '90s, the percentage of children ages 6 to 11 who were overweight nearly doubled, from 6.5% to 11.4%, according to the National Center for Health Statistics. Dr. Paul Kaplowitz, a pediatric endocrinologist with the Virginia Commonwealth University School of Medicine in Richmond, Va., explains, "We've known for a long time that very overweight girls tend to mature earlier, and very thin girls, such as anorexics, tend to mature later than normal. We think mildly overweight girls may be maturing early as well." Kaplowitz emphasizes that the correlation is merely statistical; not every girl with a little extra baby fat will develop breasts early.
Exactly why obesity and early development should be linked is not well understood. But Kaplowitz suspects early breast development may be encouraged by a protein called leptin. "We know that fat cells produce leptin," he says. "And leptin is necessary for the progression of puberty." Another clue, according to Duke's Freemark, is that overweight girls have more insulin circulating in their blood. Says Freemark: "Those higher levels of insulin appear to stimulate the production of sex hormones from the ovary and the adrenal gland."
While the consensus favors a fat connection, other explanations haven't been ruled out. One is chemical pollution in the food chain -- specifically, DDE, a breakdown product of the pesticide DDT, and PCBs, once used as flame retardants in electrical equipment. Both chemicals are plausible suspects because they mimic hormones that play a key role in the development of the reproductive system. Beyond that, says Dr. Walter Rogan, an epidemiologist at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., both chemicals are ubiquitous in the environment, and they persist in the body for years after exposure.
For that reason, he chose PCBs and DDE for one of the very few large, long-term studies of chemical exposure and puberty in humans. Rogan and his colleagues began with some 600 pregnant women, measuring concentrations of the chemicals in their bodies. When their babies were born, the researchers then measured levels in the mothers' breast milk. Finally, the team monitored the children as they grew and entered puberty.
The most prominent effect, reported last spring in the Journal of Pediatrics, was that boys exposed to DDE and girls exposed to PCBs were heavier than their unexposed peers at age 14. The study also noted an intriguing fact: girls with high prenatal PCB exposure tended to hit the first stages of puberty a bit earlier than others. Rogan stresses that the numbers were too low to be statistically significant. "If there is an effect of environmental chemicals on puberty," he says, "it's pretty small, because we studied these kids in detail over a long period of time, and we didn't see it." But, Rogan adds, "I can't rule it out."
Could other substances besides PCBs and DDE influence sexual development? Perhaps, Rogan says. But few compounds are as persistent and pervasive. Hormones given to livestock, for instance -- another frequently invoked possibility -- break down very quickly in the body. "I have not studied the effects of hormones in beef or dairy cattle," Rogan says. "It's not something I'm running out to study either."
What merits another look, some researchers believe, is a suite of chemicals used to make plastics. One is Bisphenol A, or BPA. Like DDE and PCBs, it is a chemical cousin of estrogen's, and it has been shown to affect the reproductive systems of lab mice. Another category of plastics ingredients, phthalates, may have played a role in a rash of cases of very early puberty in Puerto Rico back in the 1980s, with girls as young as 2 growing breasts and pubic hair. And while no cause has yet been determined, a study published last month suggests that a possible culprit could be phthalates, which are used, among other things, to make plastics flexible. It's by no means an ironclad case, however, and the plastics industry doubts that there's any link. But, says Rogan, "what went on in Puerto Rico is a good question and one that needs more study."
Whatever the cause -- and it may eventually turn out to be a mix of some of or all these factors and more -- doctors say early development has become too widespread to be treated as a medical aberration. In the past, girls who developed breasts before age 8 were often given hormone therapy to slow things down. But in a report being prepared for the Pediatric Endocrine Society, Kaplowitz and co-author Dr. Sharon Oberfield of Columbia University argue that most girls between 6 and 8 who develop breasts or pubic hair should be reclassified as normal and left untreated. "Three-, four- and five-year-old girls should still be managed aggressively," he says, "but there are far fewer of these."
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