Growing Pains: What Causes Early Puberty in Girls Today?
Margaret, the iconic protagonist in Judy Blume’s 1970 young-adult book, Are You There God? It’s Me, Margaret., is a sixth-grade girl just dying to hit puberty and become a woman. It’s surprising that Margaret still resonates with young female readers nowadays, because, well, most of them aren’t waiting very long for their bodies to change. Puberty is hitting girls earlier and earlier, and while scientists and doctors have theories about why this is so, no one fully understands what’s turning girls into women at younger ages than ever before.
Hormones in milk and meat were the first suspects when early puberty, which researchers define as “the presence of breast development before age nine,” became a recognizable trend in the early 1990s, according to Christopher Wanjek, author and “Bad Medicine” columnist for LiveScience.com. Specifically, those concerned with prematurely developing children blamed artificial bovine growth hormone (rBGH) for disrupting the normal hormonal balance in young girls. But while many in the organic-food movement still worry about rBGH’s effects on humans, the U.S. Food and Drug Administration (FDA) argues that the hormone does not survive pasteurization, so the FDA does not consider its use on dairy farms unsafe.
We Are What We Eat
Wanjek dismisses the growth-hormone theory in favor of one that pegs childhood obesity as the culprit behind early puberty. Unless girls suffer from an underlying medical condition, such as congenital adrenal hyperplasia, McCune-Albright syndrome, or spina bifida with hydrocephalus (all of which can cause early puberty), they begin puberty once they achieve a certain weight and fat distribution. This is why female gymnasts and ballerinas with lower-than-normal body mass indexes (BMIs) for their age tend to develop much later than their peers. It also means that girls who have higher-than-normal BMIs may develop much earlier. The body doesn’t make a distinction between an eight-year-old girl who weighs as much as a normal twelve-year-old and the actual twelve-year-old.
Also, according to Wanjek, overweight children have high levels of the protein leptin, which stimulates the release of the three main hormones in puberty: hypothalamic gonadotropin–releasing hormone, luteinizing hormone, and follicle-stimulating hormone. Paul B. Kaplowitz, MD, PhD, wrote in the February 2008 issue of Pediatrics that a “growing body of evidence” supports this link between leptin and early puberty, which may have evolved in mammals as a way to ensure that pregnancy will not occur unless there are adequate fat stores to sustain both the mother and the growing fetus.
To support his argument, Wanjek cites a 2003 study by Kirsten Krahnstoever Davison, of Penn State, documenting that over 50 percent of overweight girls start puberty early. Few studies, however, have found a link between a high BMI and puberty in boys, according to Kimberly A. Loux, a contributor to LiveStrong.com.
Wanjek also believes that environmental pollutants play a role in early puberty: plastics and insecticides break down into chemicals that have an estrogenlike effect on both animals and humans. Some scientists blame these chemicals for causing hermaphroditic fish, which have been appearing more and more in U.S. river basins over the past few years. Ivelisse Colón of the University of Puerto Rico, who led the landmark study behind this theory, and her colleagues measured the presence of certain phthalates in the blood of forty-one girls experiencing early breast development and compared these girls with a control group, discovering that 68 percent of the more pubescent girls had high levels of phthalates in their blood.
Bisphenol A (BPA), an environmental estrogen used to manufacture polycarbonate plastic, is likely as responsible as phthalates are when it comes to early puberty in girls. A study published in the August 2005 issue of Environmental Health Perspectives reveals that even small amounts of this substance can have “significant” effects on women, especially young women; early-onset sexual maturation is associated with as few as 2.4 micrograms of BPA per day. Fortunately, manufacturers have begun to market BPA-free products.
Slow and Steady Wins the Race
Whatever factors, or confluence of factors, are contributing to early puberty, the trend has far-reaching implications beyond what Blume’s Margaret ever considered. Not only are girls under age ten mentally and emotionally unprepared to handle breasts, monthly periods, and the sexual desires that come with puberty, but early growth spurts retard fuller growth in adolescence and may cause osteoporosis in later life because the brain will tell the bones to stop growing. Early puberty is also associated with alcohol abuse, behavioral problems, adult obesity, depression and anxiety, and reproductive cancers. If this trend doesn’t stop, childhood will be just a memory, even for children.