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 look at what's 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.
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, to be getting smaller every year (see box).
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.
Even more troubling than the physical changes is the potential psychological effect of premature sexual development on children who should be reading fairy tales, not fending off wolves. The fear, among parents and professionals alike, is that young girls who look like teenagers will be under intense pressure to act like teenagers. Childhood is short enough as it is, with kids bombarded from every direction by sexually explicit movies, rock lyrics, MTV videos and racy fashions. If young girls' bodies push them into adulthood before their hearts and minds are ready, what will be forever lost?
The danger, as authors Whitney Roban and Michael Conn pointed out in a report for the Girls Scouts of America called Girls Speak Out, is that the stages of childhood development--cognitive, physical and emotional--have got out of synch. Roban and Conn call this "developmental compression" and pepper their study with poignant quotes from girls struggling to cope with pressures they are ill equipped to handle. "Boys," complains a fourth-grader in their report, "are gaga over girls with breasts."
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.
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."
Then there are those who believe the sexualized messages bombarding kids from all sides could be triggering changes in the brain that are jump-starting development. Drew Pinsky, a physician and co-host of MTV's recently canceled Loveline advice program, is a proponent of this notion. "MTV," he asserts, "is absolutely one of the factors in early puberty." But even though the idea sounds nutty, says Herman-Giddens, "it would not be scientific to dismiss it. If someone cuts a nice juicy grapefruit in front of you, you salivate. Seeing things can affect us physiologically."
Whatever the cause--and it may eventually turn out to be a mix of some of or all these factors--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."
That doesn't mean that breasts on seven-year-olds can simply be ignored. Mentally and emotionally, these kids are no different from their undeveloped peers. "They're not dyeing their hair purple and talking on the phone all the time," says Dr. Francine Kaufman, head of pediatric endocrinology at Childrens Hospital Los Angeles. "They're still 7."
But they don't look it, which can lead to all sorts of problems. For one thing, it makes these girls very obviously different from their peers--a position that can be deeply embarrassing for early and late developers alike. More ominously, says Susan Millstein, a professor of pediatrics at the University of California, San Francisco, "people think they're older, and the kinds of pressures put on them are more than they can handle." Marissa Carter, Sharon's mother, puts it more bluntly. "Girls who look more mature for their age are like honey," she says. "They attract older boys."
For Chicago friends Angelica Andrews, 13, and Emily Jacobson Ranalli, 12, that kind of attention is such a source of pride that the girls are willing to use their real names. Says Angelica: "The boys tease me. They ask me, 'Have you had plastic surgery?' My friends get kind of jealous." Emily, giggling, says, "I've been mistaken for 17." But even they see a downside to looking a half-decade older than they really are. "Life gets harder and harder when you're developed," admits Angelica. "Boys walk up and hit your butt. They won't stay away. They're like dogs."
The physical dangers of sexual harassment and sexually transmitted diseases--and, for those who start menstruating early as well, pregnancy--are only the most obvious fallout of premature development. Academic pressure, drugs and alcohol in the schools, peer pressure and sexually explicit media are all conspiring to foreshorten childhood, with consequences that are still not well understood. "One of the big shocks during the whole Clinton debacle," says William Damon, director of Stanford's Center on Adolescence, "was that people were trying to filter out phrases like 'oral sex,' when in fact there were no eight-year-olds who didn't already know what that was." One result of these influences is that girls are wearing highly sexualized, adult clothing in middle school and below--even when they don't have adult bodies.
Yet this acceleration of growing up comes precisely at a time when life should be less about Eminem and more about M&M's. Between 8 and 12, explains psychologist Mary Pipher, author of Reviving Ophelia, a best-selling book on female adolescence, girls are in the so-called latency period, when they turn their backs on boys and bond with their peers--other girls. "Theoretically, it's a time when they're really gathering a lot of strength--they're doing well in sports, they're investigating the world, they're confident learners, and they're confident socially. They're marshaling their forces to be able to go into puberty."
Cultural pressure alone tends to short-circuit the latency period, when a child usually develops a sense of who she is and where she fits in the world. When a girl's body develops early, she is more likely to hook up with a boy--and leave her group of girl friends--before the developmental work of the latency period is done. "That," says Pipher, "has all sorts of harmful social, academic and psychological consequences."
Moreover, says MTV's Pinsky, early development feeds into what's already one of the toughest aspects of being a young person in the U.S. today. "Kids don't feel good about themselves," he says. "There's a pandemic of that. Society says, 'Here's how you feel good: get lots of money, look like Britney Spears, have sex, do drugs, do extreme sports.' And it works--in the moment." Eventually, though, the high wears off, and, he says, kids' self-esteem is lower than ever.
So if worried parents shouldn't medicate their prematurely pubescent daughters, what can they do? "If I had a daughter who had a period at 9," says Pipher, "I'd say, 'This does not mean you're a woman; it means you're a nine-year-old having a period, and we are going to proceed accordingly.'" That means clothing, books and music appropriate to a girl's chronological age, not her physical age. It also means having her hang out with her family, where peer pressure to act sophisticated isn't a problem. "One of the best things for a nine-year-old," says Pipher, "is having her spend a lot of time with grandparents, cousins and so on--people who value her for something besides how sexy and popular she is."
Most important, agree virtually all the experts, is that parents keep communicating with their daughters (see box). "It doesn't matter what you tell them," argues Pinsky. "Just get the dialogue going, because when they hit puberty, they'll have questions and they will ask you if they feel comfortable." Nothing is more important than that connection, he says. "It's the child that can't trust adults who is going to do whatever their biological impulses or their peers or the ambient culture suggests to them."
It was family support that got Sharon Carter safely though her bout with early puberty. "I am really very excitable," says her mom, "and I had to get all that under control and make her feel that what she was going through was normal." The result, says Sharon: "I don't remember much about all that. I couldn't go swimming when I had my period. And I still can't, and I love to swim. That's the only difference it made with me."
Angelica Andrews also has her parents watching out for her. Recently, the teenager experienced her first French kiss--but her family knew all about it, and the boy was immediately instructed not to call again until she was 16, or maybe 18. It's unfortunate that such vigilance has become necessary for the families of many 12- and 13-year-olds, whereas a generation ago, most parents could relax until a girl was 16 or 17. But as Angelica puts it, "Welcome to the 21st century."
--REPORTED BY DAN CRAY/LOS ANGELES, DEBORAH FOWLER/HOUSTON, JULIE GRACE/CHICAGO, ALISON JONES/DURHAM AND DICK THOMPSON/WASHINGTON