Growing Up Fast
Are young girls today reaching puberty prematurely—and if so, what can parents do to slow the process?

By Dagny Scott Barrios

These days it's not unusual for a mother to groan when her 9-year-old daughter attempts to leave the house in belly-baring pants and a halter top. But for today's preteen girls, clothing choice might not be the only thing developing ahead of pace. Many researchers are convinced that girls are reaching the milestones of puberty earlier than previous generations did. Although pediatricians are still heatedly debating whether or not the actual age of puberty is dropping—and if so, why it is—they do agree that the potential developments are worrisome.

Pediatricians first reconsidered the normal age of puberty onset in response to a 1997 study published in the journal Pediatrics (vol. 99, no. 4). That survey of some 17,000 girls showed that by age 8, 14.7 percent of white girls and 48.3 percent of black girls had begun breast development, and the average age of pubic-hair development was 10.5 years for white girls and 8.78 years for black girls. (For all characteristics measured, the black girls developed earlier than the white girls, though researchers aren't sure why.) Accordingly, many pediatricians concluded that it was not abnormal for girls of age 7 or even 6 to show signs of puberty. But the firestorm of debate was just beginning.

"In response to that study, some pediatricians said, 'Let's redefine what's normal now,' but it's still not a good thing for an 8-year-old to have breasts," says Diana Zuckerman, PhD, executive director of the National Center for Policy Research for Women and Families. It's not a good thing, Zuckerman and other researchers contend, because girls' psychological development isn't keeping up with their bodies; developing early forces girls to deal with their own sexuality before they are emotionally mature enough.

Defining a "normal" age of puberty is critical because that marker helps determine whether a girl is in fact showing signs of precocious puberty and needs to see a physician. Early puberty can be a warning sign of certain medical conditions, such as a brain tumor. And early-onset puberty in the absence of such serious conditions can cause problems of its own. For example, growth plates—the area of developing tissue near the end of bones—can fuse early, leading to stunted growth. If diagnosed in time, these girls can take medication to correct and slow their development. "It's fine to redefine normal so that we are not treating all these girls with powerful drugs, but it's not OK to pretend that everything's OK," Zuckerman contends.

Flipping The Switch
Indeed, redefining the normal age of puberty onset doesn't begin to answer the question of why girls might be developing earlier. The fact is, scientists are not sure. One theory is that hormones in the food supply and chemicals that are ubiquitous in plastics, pesticides, and cosmetic products are acting as endocrine disrupters, which in turn mimic estrogens in the body. "There are a lot of ways a normal healthy girl in the United States will be exposed to more chemicals that act like estrogens than her mother was, whether from nail polish, microwaving in plastics, or the foods she's eating," Zuckerman says.

To be cautious, avoid microwaving in plastic or with plastic wrap and don't let young children use nail polish. Theo Colborn, PhD, a senior scientist at the World Wildlife Fund and coauthor of Our Stolen Future (Plume, 1996), points out that one chemical that disrupts the endocrine system—bisphenol A (BPA)—is a component of practically everything from telephones to the lining of food cans. Other known endocrine disruptors—phthalates—are common in glues, cosmetics, plastic wrap, and children's toys. Colborn's book documents several animal studies that show how chemicals that interfere with development prior to birth can affect sexual development. Another study, she says, showed high blood levels of phthalates in girls who experience early breast development.

"For years we've used many products thinking they're benign," says Colborn. "But in the body, if there are hormone or other receptors in a cell, certain chemicals have been shown to turn them on." In other words, these chemicals could flip the switch to begin or reduce the production of hormones and disrupt normal female development. BPA and some phthalates are among this class of chemicals that can prevent normal messaging of a number of vital systems.

It's not that dialing a plastic telephone will bring on early puberty, Colborn points out. Rather, "it is the timing of exposure, especially before one is born, where we are most vulnerable," she says. There's also the threat that contact with so many such items-lotions, CDs, and the list goes on-means that inexorably these chemicals find their way into women's bodies and ultimately the womb during the earliest stages of development. And this can undermine how we function the rest of our lives.

For more information and current research on precocious puberty and chemical endocrine disrupters, visit the following Web sites.

  • The National Center for Policy Research for Women and Families offers an online overview of research about early-onset puberty.

  • Health Care Without Harm's site offers information on phthalates in cosmetics and more.

  • This Web site is packed with links to the latest scientific studies involving endocrine-disrupting chemicals and other impacts of toxins on the immune and nervous systems.

Both Colborn and Zuckerman hope continued research will offer proof of what is now a largely theoretical danger and that that will prompt government control over the implicated chemicals. For now, Zuckerman says, it's hard to know how to protect yourself and your family from such items. "Even I don't know exactly what to avoid," she says. "Reading the labels doesn't necessarily show the presence [of suspect hormones or chemicals]. But to be cautious, I avoid microwaving in plastic or with plastic wrap and suggest that young children don't use nail polish or other products that are known to contain phthalates, or hair products or creams with 'placenta' or hormones," says Zuckerman. "It also makes sense to peel or avoid fresh fruits and vegetables that are known to contain high levels of pesticides, since they can also act like estrogens." But, she says, little research exists on these precautions, which is why opinions vary on what to do.

The Fat Factor
Before you start throwing away your computer keyboard and all the other plastic in your house, consider another side of the issue. It turns out there's a problem—well, a few problems—with the research that caused all the fuss in the first place. For one thing, no definitive measurements of previous generations' ages of pubic-hair and breast development exist, making scientific comparisons virtually impossible.

Ora Pescovitz, MD, director of the pediatric endocrinology division at Indiana University School of Medicine and former president of the Society for Pediatric Research, points out that no study has shown a change in the average age of first menses, which remains 12.8 years for white girls and has dropped only slightly to 12.1 years for black girls. "That's a very important reason I don't believe the age of the onset of puberty has really dropped," she says.

So how to explain the budding of breasts on so many young girls? Even though no studies exist from previous generations, few researchers disagree that, anecdotally, girls are developing in that way earlier than before. One theory is that we're not seeing advanced puberty at all, but rather another impact of the obesity epidemic in this country. In one of the most common criticisms of the landmark 1997 study, some pediatric endocrinologists question whether what was believed to be breast tissue might in actuality have been fat tissue.

"Body fat tends to be deposited in the area of the breast, so it's sometimes difficult to tell if it's breast tissue or fat tissue," says Pescovitz, who specializes in early-onset puberty. In addition, fat tissue throughout the body contributes to the production of the female hormone estrogen. Therefore, estrogen produced by excess fat could be stimulating sexual development. In fact, data from the original 1997 study, when reanalyzed with an eye toward weight, did show that girls with a higher body mass index were most likely to show earlier pubic-hair and breast development (Pediatrics, 2001, vol. 108, no. 2).

As of today, some pediatricians who earlier agreed that the normal age of puberty onset had dropped have backed off their stand to reconsider. One thing everyone agrees upon is that more research is necessary. If girls are developing early due to obesity, that's a serious health issue in itself. And if another factor is responsible for such changes, it's important to determine what it is. Meanwhile, Pescovitz recommends that a girl showing signs of puberty prior to age 8 see a physician to rule out serious medical concerns.

Writer Dagny Scott Barrios has a 2-year-old daughter who already insists on wearing nail polish.