Causes of Early Puberty in Girls

Early puberty in girls is becoming a serious problem. A recent Pediatrics study of 1,239 girls found that the rates of early puberty, measured by breast development at age 7, has spiked over the past decade. The rates of early puberty have doubled for white girls (from 5% to 10%) and also increased for black non-Hispanic girls (from 15% to 23%). Fifteen percent of Hispanic girls also show signs of early puberty at age 7.

Along with large racial/genetic differences in early puberty onset in girls, there are two other potential causes. It might be caused by chemicals in the environment that mimic estrogen or cause other hormonal disruptions, triggering the body to begin puberty. Prime chemical suspects include pesticides and herbicides, flame retardants, and bisphenol A (BPA) (a chemical I've blogged about before), according to an article on early puberty by USA Today's Liz Szabo.

Weight also plays a role. The study found that obese and overweight girls, as measured by their body mass index (BMI), are more likely to start puberty early than normal-weight girls. Fat cells in their bodies create and release the hormone leptin, which can trigger puberty.

Puberty onset is a tricky thing, though, because it is also influenced by other medical, social, or environmental factors. Certain rare medical problems, such as a tumor or meningitis, can cause early puberty. Some studies have suggested that girls are more likely to start puberty earlier than average if they are adopted internationally, don't live with their biological fathers, or if their mothers are depressed.

Whatever the cause, early onset of puberty is both physically and emotionally unhealthy for girls. These girls are more likely to have low self-esteem, have a poor body image, become sexually active earlier, and develop certain cancers later in life, the Pediatrics study stated.

With one in three U.S. children overweight or obese, the rates of early puberty will probably continue to increase. Early puberty is yet another reason to substantively address the many causes of obesity in this country, and to substantively regulate how certain chemicals are used in the environment, food packaging, and foods.

Resources:

• The Environmental Working Group's Body Burden page contains extensive information on the toxic chemicals found in the human body, particularly BPA
• Follow this CDC link to calculate your child's BMI
  
  

BPA and Baby Bottles

A chemical often used to manufacture infant bottles, water bottles, and food packaging might be harmful to humans, according to a draft brief released this week by the NIH-funded National Toxicology Program's (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR). The NTP reviewed a number of mostly animal studies that indicated that Bisphenol A (BPA), used in resins and polycarbonate plastics, might cause neural changes, precancerous prostate and breast lesions, and early puberty, among other problems, at fairly low doses. At significantly higher doses than humans are likely to encounter, BPA has been proven to slow puberty and growth, and decrease survival rates in animal studies.

Although BPA is also sometimes found in tableware, medical devices, dental sealants, and automobiles, among other places, the draft brief stated that humans primarily absorb BPA though food and drink. The U.S. produces 2.3 billion pounds of BPA yearly, and infants and children have the greatest exposure to the chemical "because they eat, drink and breathe more than adults on a pound for pound basis," the report stated.

The draft brief points out that most ingested BPA is metabolized and eliminated in the urine. The remaining ("free") BPA in the body is probably harmful. Based on evidence from animal studies, infants and young children are thought to be less efficient at metabolizing and excreting BPA than adults, the draft brief states, so they retain higher levels of free BPA in their bodies. The draft brief also says that BPA seems to leach more easily from plastic into foods when the food is heated. As such, baby bottles (often heated up, of course, before given to the baby) seem like an especially potent source of exposure in infants.

Formula-fed infants aged 0 to 6 months, who are exposed to BPA primarily though baby bottles but also through the packaging of formula containers, might absorb about ten times the amount of BPA as a breast-fed infant, according to the draft brief.

I find this information, and the pervasiveness of BPA in the environment, disturbing news. I first read about the NTP draft brief in a story on the Washington Post online, and the writer considered the report's findings worrisome. A number of other online news outlets, such as Fox Business, on the other hand, chose to run the press release on BPA from the American Chemistry Council as an article. The American Chemistry Council press release, not surprisingly, states that the NTP draft brief proves that there are no serious human reproduction concerns about BPA.

Yes, the data is based primarily on animal rather than human studies, and the authors of the NTP draft brief pointed out a number of limitations to the studies they looked at, such the reproducibility and structure of some studies. I still think that the information in the NTP draft brief is too important to be dismissed – especially for parents, who have been concerned about the plastics in baby bottles for years.