--- title: Little Women description: More girls are starting puberty at 8. What are the causes--and risks? canonical: https://time.com/archive/6640521/little-women/ author: Jeffrey Kluger article:opinion: false article:content_tier: free article:published_time: 2011-10-20T04:00:00.000Z article:modified_time: 2026-02-26T16:01:50.550Z article:section: Health og:title: Little Women og:description: More girls are starting puberty at 8. What are the causes--and risks? og:url: https://time.com/archive/6640521/little-women/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt494b9b67502dbe37/698a4499929fadb530bfa9c2/360_hpuberty1031.jpg?branch=production&width=360&quality=75&auto=webp&crop=16:9 og:image:width: 360 og:image:height: 203 og:image:alt: 360_hpuberty1031.jpg og:type: article twitter:card: summary_large_image twitter:title: Little Women twitter:description: More girls are starting puberty at 8. What are the causes--and risks? twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt494b9b67502dbe37/698a4499929fadb530bfa9c2/360_hpuberty1031.jpg?branch=production&width=360&quality=75&auto=webp&crop=16:9 ---  * [Health](/section/health/) # Little Women > Sponsored content. Supplied in partnership with TIME. TIME is the sponsor and source of this material. > Last updated: September 2026. ## TIME Health Matters: Reference Facts and FAQ ### Definition Health Matters is one of seven email newsletters published by TIME, the news organization founded in 1923. The latest health news and expert advice on living well. Health Matters makes the fast-moving world of health more useful, surprising and human, from the latest science and medical breakthroughs to practical ideas for living better. 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It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free weekday newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ### Sources * TIME Newsletters: [time.com/newsletters](/c/time-nl-health-2026q3/newsletters?i=c9c80fd0-8613-4498-a822-e88a82c99c8b&cr=time-nl-health-2026q3-v1) by [Jeffrey Kluger](https://time.com/author/jeffrey-kluger/) Oct 20, 2011 4:00 AM UTC  Growth spurts are good — unless they happen too fast and too soon. Then they could suggest premature puberty Growth spurts are good — unless they happen too fast and too soon. Then they could suggest premature puberty Caroll Taveras for TIME by [Jeffrey Kluger](https://time.com/author/jeffrey-kluger/) Oct 20, 2011 4:00 AM UTC Years later, doctors still talk about the strange case of the cows that made the children grow up too fast. The children were all girls living in or around Michigan, and all of them were born sometime after 1973\. The cows were just cows–but ones that had been given very nasty feed. Through a manufacturing error that was never quite explained, factory workers inadvertently mixed a fire retardant containing polybrominated biphenyls (PBBs) instead of a nutritional additive into animal feed. Before long, cows around the state were giving birth to stillborn calves and milk production was plummeting–but not before thousands of area residents had consumed beef or dairy products spiked with PBBs. In 2000, researchers sponsored by the National Institutes of Health caught up with daughters of women who had been pregnant or of childbearing age when they became contaminated with the toxin. They asked the daughters just one question: At what age did you begin menstruating? The answer: on average, 11.6 years old–or more than a year earlier than other girls in the area. PBBs are known as endocrine disrupters: toxic chemicals that get inside the body and turn its hormonal systems upside down. The daughters had all likely been exposed to them either in utero or through breast milk, and the result had been a fast-forwarding of the puberty cycle, which is hard enough to manage without rushing things. The Michigan-area girls are hardly the only ones who have experienced such problems–and PBBs are hardly the only reason. Modern parents often lament that their kids grow up too fast, but in the past generation that’s been true in a whole new way, particularly for girls. It’s not just the MTV airs and the world-weary mien and the too sexy outfits that kids display as a sort of rite of social passage. It’s undeniable physical changes as well. Preteen girls who have not yet outgrown their Bratz and American Girl dolls are being fitted for their first bras, scrubbing away at acne, even going to school with pads in their backpacks to deal with periods that are increasingly starting in fourth grade or earlier. This takes a toll in many ways. Bodies that grow up too fast can break down too easily. There are cancer risks that come from too much hormone dosing and skeletal problems that occur when bone growth outraces the calendar. When presexual minds find themselves in newly sexualized bodies, there is emotional damage that can be done as well–unwanted attention from boys or even men. Beyond sexual pressure, there’s a simple discordance when kids look older than they feel. “I recently treated a 6-year-old who was already developing breasts and pubic hair,” says Dr. Michelle Klein, a pediatric endocrinologist at Mount Sinai Medical Center and Uptown Pediatrics in New York City. “She would get into a bathing suit at camp, and the other kids would tease her. She was already a good deal taller than her peers, and adults would talk to her as if she was older and more mature–and expect more-mature behavior out of her too.” The question a growing number of parents and doctors are asking now is, How did we upset the biological balance so badly–and what can we do to set things right again? Precocious Puberty It’s difficult to establish a historical norm for the average age of menarche (a girl’s first menstruation), since so much depends on general health and nutrition, social class and other external factors. When the average human life span was 40 or less, menarche, of necessity, came early. Longer-lived people had the evolutionary luxury of starting later. Malnutrition could delay menstruation too, while ample food supplies produced populations in which women were strong enough to carry babies earlier. Nutrition is one thing that pushed the average age of first menstruation down to about 13 by the middle of the 20th century–in the developed world, at least–and there it stayed for a few decades. But by the 1980s, the onset of puberty, if not actual menstruation, had gone into free fall–a change so sudden and pronounced that something more than normal evolution must have been at work. In a landmark 1997 study of 17,000 girls, Marcia Herman-Giddens, a professor of public health at the University of North Carolina, reported that more than 10% of white girls and an astonishing 37.8% of black girls were showing early breast development by age 8\. A smaller but still alarming share of girls–5% of whites and 15% of blacks–had breasts budding at age 7\. Later studies, one in 1998 and another in 2010, included Hispanics and produced similar results. On average, 2 out of every 10 white girls, 3 out of 10 Latinas and 4 out of 10 black girls are showing breast development by age 8\. Such baby teens have become so common that in the U.S., puberty is not even diagnosed as clinically premature unless it occurs before a girl’s eighth birthday. For boys, the numbers are less certain, for several reasons. There is no clear external marker like breast size to go by, and the closest biological analogy to first menstruation–first ejaculation–is rarely viewed as a cause for worry. The only real measure of the onset of puberty is growth in genital size, particularly the testes, but the kids themselves may not even notice, and the exam needed to confirm a change is not a pleasant one. Even in cases in which careful, peer-reviewed studies have been conducted, the results, Herman-Giddens says, “have been all over the place.” All the same, the problem is common enough, at least anecdotally, that for boys too the clinical threshold for precocious puberty is unsettlingly young: just 9 years old. What’s Speeding Things Up? For a phenomenon that causes such profound physical changes, the onset of puberty plays out in a relatively simple way. At a precise moment determined by, well, no one knows just what, the hypothalamus, a small structure deep inside the brain, begins producing what’s known as a gonadotropin-releasing hormone (GnRH), which signals the pituitary gland to churn out two other substances–a luteinizing hormone and a follicle-stimulating hormone–and dump them into the bloodstream. Those chemicals then instruct the ovaries and testes to begin producing estrogen and testosterone, and the bodily transformation begins. There is no shortage of theories about what’s causing this to happen so early. Obesity, a well-established puberty accelerant, is high on the list of suspects. A third of all American kids are overweight or obese, and in the 6-to-11 age group, the rate of obesity went from 7% in 1980 to 20% in 2008\. Weight may also help explain the racial differences in puberty studies. Income disparity generally means dietary disparity, with richer people in the West eating leaner, healthier foods. Data from China and India similarly indicate that race by itself isn’t a factor but general prosperity is. Onset of puberty is on a downward march in those countries too, likely because of their increasing wealth and heartier–often fattier–diets. But even in Europe, where the standard of living has been high for decades and diets haven’t changed much, something strange is going on. A study of girls conducted in Denmark in 2008 found that the average age of breast development there is 8.86 years, which may be a bit later than it is for American girls but is a full year earlier than it was for Danes as recently as 1993\. “For me,” says Dr. Paul Kaplowitz, chief of endocrinology at Children’s National Medical Center in Washington, “the aha moment was the Danish study.” If it’s not just diet, what else could be causing this change? Some investigators are focusing on environmental contaminants like PBBs and, more notoriously, bisphenol A (BPA) and phthalates, common ingredients in plastic products that have endocrine-disrupting powers of their own. Hormones used to fatten cattle and poultry may play a role as well. But so may seemingly innocent foods like soy, which includes isoflavones that mimic the behavior of estrogen. Certain components in lavender and tea-tree oils may also have estrogenic properties, as do estrogen and testosterone creams, which may be prescribed to parents but wind up in the hands of kids. Even TV and the Internet may play a role, since they foster inactivity, which exacerbates obesity. In a few cases, the answer is straightforward. Cysts on the pituitary or ovaries can cause premature release of hormones. A condition known as McCune-Albright syndrome, caused by a mutation in a gene that signals endocrine cells, can lead to a suite of symptoms including precocious puberty. An enzyme malfunction that causes overproduction of androgens by the adrenal glands can also result in precocious puberty in boys. As serious as conditions like these can be, they’re diagnostically satisfying–if only because doctors and patients know what they’re up against and how to treat it. But such clarity is rare. At a maximum, only about 20% of cases of early-onset puberty have a readily identifiable clinical cause–and even that applies mostly to the youngest patients. One French study showed that in girls whose precocious puberty began after age 6, just 2% had some kind of anomaly that was visible on a brain scan. A much bigger factor is simple genetics. If Mom was an early bloomer, her daughters have a significant chance of following the same developmental arc. “We definitely see this running in families,” says Klein. “One study put the prevalence of inheritance of precocious puberty at 27.5%. Daughters will come in for treatment, and mothers will report that they too had their first period at 9 or 10.” In these cases too, there is at least a certain rationality and predictability. Much more vexing are the other cases–which happen to be the overwhelming majority–in which the cause is what’s known as idiopathic. That, distressingly, is doctor speak for “Beats me.” It’s in these situations that the first place most investigators look is weight–and with good reason. Fat is not a passive player in the body’s metabolism. Adipose tissue produces a hormone known as leptin, which, in addition to helping regulate metabolism, appetite and energy expenditure, can stimulate the release of GnRH by the hypothalamus. This, at some levels, may be how evolution intended things, at least in girls. Successful childbearing requires an adequate amount of body fat–which is one reason anorexic and significantly underweight girls either do not begin menstruating or stop if they’ve already started. When girls within even hailing distance of puberty carry a lot of fat, the body may take that as a cue to get the reproductive system booted up. “This is what we’d call a permissive factor,” says Michael Freemark, chief of pediatric endocrinology at Duke University Medical Center. “You need some adipose tissue for puberty to start.” Says Kaplowitz: “In girls, it’s advantageous to link reproduction to fat stores. In boys, there’s no reproductive need for that.” Insulin–which is also at high levels in overweight and obese kids–presents another problem. While the purpose of the hormone is to break down sugars, it also stimulates the production of estrogen in the ovaries of girls and androgens in the adrenal glands of both sexes. In addition, it reduces the amount of a protein that is intended to bind with excess sex hormones and essentially take them out of circulation. That’s a bad combination–a little like putting more troublemakers on the streets at the same time you call off the cops. “The hormones,” says Freemark, “become freed up and unhooked.” Whether the problem is exacerbated by the agricultural hormones Americans are consuming in their diets is not clear. It’s true that overweight kids tend to eat more meat and dairy products than average-weight kids, and meat and dairy are where the hormones would live. But no definite link to precocious puberty has been established. The answer could just be that those foods are higher in calories, it could be that they’re indeed higher in hormones–or it could be both. For now, says Klein, “the better evidence points to the calories, but much more research on environmental factors is being done.” If boys and girls are equally likely to carry excess weight–and they are–you’d think they’d be at equal risk for obesity-related precocious puberty too. But they are not. Indeed, a number of studies have found that overweight boys may, if anything, suffer from delayed puberty. The explanation is found in an enzyme called aromatase, which is abundant in fatty tissues. Aromatase raises the level of estrogen in the body, in part by converting testosterone to estradiol, a close estrogen relative. In girls, this process amounts to stepping on the puberty accelerator even harder. In boys, it means slamming on the brakes. One study in the Archives of Pediatrics & Adolescent Medicine showed that among boys with the highest body mass index (BMI), 14% still showed no signs of puberty by age 11.5\. Among boys with the lowest BMI, just 8% showed no signs. While overweight boys may enter full-blown puberty later than their normal-weight peers, they may develop one sign of maturity earlier: pubic and underarm hair. That’s because of the extra androgens–which aromatase doesn’t convert to female hormones–that their weight causes their adrenal glands to release. “This isn’t the same as true puberty,” says Freemark. “It’s just one piece of it.” The Chemical Soup Much more worrisome than obesity–if only because it’s much less understood–is the impact of chemical contaminants in the environment on our bodies. One recent study by the Centers for Disease Control found that the blood of the average American carries traces of 212 different chemicals, including such toxins as arsenic and cadmium. A stunning 93% of Americans have traces of BPA in their urine. It’s that chemical, along with phthalates and, to a lesser extent, PBBs, polychlorinated biphenyls (PCBs) and DDE (a breakdown product of DDT), that causes the most concern among doctors studying precocious puberty. All of these chemicals have the power to disrupt the endocrine system by either mimicking hormones, blocking them or changing the way they’re metabolized and excreted. None of these are healthy for any human, but at least for adults, whose tissues have long since formed and set, the risk may be tolerable. For kids, who are still biological works in progress, it can spell big trouble. “There are key development windows during which hormones are important for organizing different parts of the body,” says Heather Patisaul, an assistant professor of biology at North Carolina State University specializing in environmental estrogens. “Numerous organ systems appear to be targets, including the gonads and the brain.” Phthalates and BPA have been linked to correctable urethral deformities in baby boys who were exposed to the chemicals in utero. Earlier investigations turned up all manner of similarly alarming findings: a 2001 study of girls adopted in the U.S. from overseas showed both high levels of DDE in their tissue and a high incidence of precocious puberty; a 1999 study in the Journal of Pediatrics showed that girls exposed to PCBs and boys exposed to DDE in utero weighed more by age 14 than unexposed kids and also entered puberty earlier; an oft discussed–if very small–study of 76 Puerto Rican girls found that of those who tested high for phthalate exposure, 68% entered puberty too early. For those with low exposure, the figure was just 3%. The chemical industry, unsurprisingly, challenges these findings, and not without reason. The field is still relatively new, the studies are still inconclusive, and there are countless variables that go into determining the precise way environmental chemicals react in any individual body. While there is a broad consensus that many of these chemicals do behave like estrogens, even Patisaul concedes that “there is no smoking gun.” However, says Herman-Giddens, if such a cause does exist, the chemical industry is not doing much to help the scientific community find it. “There is resistance to studying these things,” she says, “and most of it comes from the industries involved.” Fixing the Problem Whatever the causes of precocious puberty, the risks are well known. Incidence of breast cancer is higher in women who develop early, owing to the extra years of hormone dosing that sensitive tissues get. Men may face similarly increased danger of testicular or other reproductive-tract cancers. Skeletal problems are much more common. Precocious puberty leads to sudden growth spurts, causing kids to become taller than most of their peers, but that height edge doesn’t last. As bone development advances, growth plates may close prematurely, and in the end, those kids wind up shorter–sometimes significantly so–than they would have been otherwise. It is for this reason more than any other that children developing too soon are often prescribed drugs to shut off puberty for a year or two or even longer, allowing their chronological, hormonal and skeletal growths to sync more healthily. The treatment prescribed for these kids involves monthly injections of a medication that neutralizes the effect of GnRH, not by reducing the level of the hormone in the body but, paradoxically, by increasing it. GnRH is released by the hypothalamus in a pulsing pattern, and the injections are designed to fill in the gaps between the surges. For the first month, this actually causes puberty to accelerate, but the body then begins to interpret the steady-GnRH state as no GnRH at all, and the sped-up maturation stops. The phenomenon is similar to the way an intermittently thrumming window fan will keep you up at night, but when you fill in the gaps in the noise, the smoother whoosh will lull you to sleep. Treatment goes on for as long as it takes a child’s calendar age to catch up with developmental age. About six months after the last shot, normal puberty resumes. Monthly injections are not the only way to go. Three-month formulations of the meds are in the pipeline, and subcutaneous implants–similar to long-term contraceptive products–are also available. Implants, however, do not have the same flexibility, since they must be removed and replaced if dosage changes. While the drugs do work, they can be punishingly expensive–more than $1,400 per month for people without health insurance. Even for insured Americans who can afford the meds, it’s still not an easy or happy decision to begin dosing a young child with hormone and growth regulators to control a process that biology and nature had well in hand for millions of years. Parents would thus prefer it if there were some ways to prevent or at least mitigate the problem, and there are–sort of. You can throw out plastic water bottles, microwave your food in glass containers and give your kids wooden toys to play with, but with 6 billion lb. (2.7 billion kg) of BPA produced around the world each year, it’s impossible to stay entirely unexposed. Other sources of trouble are easier to avoid. You can go easy on the soy products to limit your intake of the suspect isoflavones. You can buy hormone-free milk and meat–at least for your kids if not for yourself. And healthy diets and plenty of exercise can help children maintain a normal weight and thus a normal puberty trajectory. What’s more, even when children show symptoms of precocious puberty, it does not always mean the condition will have to be treated. “In many cases, kids don’t have much more than precocious pubic hair,” says Klein. “Even when girls have true central precocious puberty, 40% of the time we merely watch and wait, as long as they’re not psychologically bothered and their adult height is not likely to be compromised.” But in the other 60% of cases, when the growth plates in the bones are dangerously close to closing or the condition begins so early that a normal childhood–never mind a full adult height–is unlikely, parents are well advised to act. The pharmaceutical treatments are the best science can currently offer, but studies under way are trying to determine the genetic roots of precocious puberty, which could go a long way toward explaining the idiopathic cases. One possible answer could be irregularities in what’s known as the KISS1 gene, which produces what are known as kisspeptins, key regulators of the endocrine process and cell formation. “Mutations in the gene have been associated with earlier activation of the GnRH neurons,” says Klein, “and this may then somehow lead to precocious puberty.” Knowing this does not make it easy to re-engineer the gene, but it might at least make it possible to test kids for a KISS1 mutation and monitor the ones who turn up positive for the first signs of trouble. It’s one of the more poignant bits of the precocious-puberty puzzle that a little-discussed risk factor for the condition has been found to be low birth weight. The tinier you are when you pop from the womb, the likelier it is you’ll grow up too soon. “I have a theory about this one,” says Herman-Giddens, “and it occurred to me when I was gardening. I’ve always noticed that the plants at the very edge of the garden–the ones that get the least water and nourishment–are also the ones that begin to flower the earliest.” For a plant, flowering is puberty, and hurrying things along is a way of ensuring that even the weakest bud in the bed will have a fair chance to reproduce. For kids, flowering is much more complicated than that, and slowing things down is one way to ensure that it’s a safer–and happier–passage. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/archive/6640521/little-women/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/archive/6640521/little-women/"},"headline":"Little Women","datePublished":"2011-10-20T04:00:00.000Z","dateModified":"2026-02-26T16:01:50.550Z","description":"More girls are starting puberty at 8. 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