Padded bras for kindergarteners with growing breasts to make them more comfortable? Sixteen percent of U.S. girls experiencing breast development by the age of 7? Thirty percent by the age of 8? Clearly something is affecting the hormones of U.S. girls—a phenomenon also seen in other developed countries. Girls in poorer countries seem to be spared—until they move to developed countries.
No scientists dispute that precocious or early-onset puberty is on the rise but they do not agree on the reasons. Is it bad diets and lack of exercise that cause growing obesity? Is it soft drinks themselves, even when not linked to obesity? Is it the common chemicals known as endocrine disrupters that exert estrogen-like effects (and also cause obesity)? Is it the many legal, unlabeled hormones used in the U.S. to fatten livestock? Some researchers even believe precocious puberty could be triggered by sociological factors like having no father in the home or even stress.
Puberty in girls is defined by three things: breast development (thelarche), appearance of pubic hair (pubarche) and the onset of menstrual periods (menarche), the latter coming last. In the 1700s, girls did not menstruate until age 17 or 18, and 100 years ago the average age when a girl got her first period was 16–17.
“The reason why weight matters is because when the body senses it has extra calories, enough to sustain a pregnancy, the fat tissues release a signal into the bloodstream,” reports KATU 2 News. “That signal then travels to the brain, telling it that sexual development is a ‘go.’ Doctors see the opposite happen in girls who suffer from anorexia. When the body is starved of calories, the first thing it does is shut down sex hormones.”
Leptin, a protein produced by fatty tissue and believed to regulate fat storage in the body, is also a factor. Fat children have high levels of the protein leptin, which through a complicated chain involving the hypothalamus and pituitary gland, can stimulate the release of the three main hormones in puberty: hypothalamic ￼gonadotropin-releasing hormone, luteinizing hormone and follicle-stimulating hormone which encourage puberty.
What’s wrong with precocious puberty?
There are many reasons precocious puberty is undesirable.
“Girls with earlier maturation are at risk for lower self-esteem and higher rates of depression. They are more likely to be influenced by older peers and more deviant peers, and initiate intercourse, substance use, and other norm-breaking behaviors at younger ages,” writes Frank M. Biro in the journal Pediatrics. “The biologic impact of earlier maturation includes greater risk of several cancers, including breast, ovarian, and endometrial cancer, as well as obesity, hyperinsulinemia, and hypertension.”
Heart disease risk is also increased.
Finally, precocious puberty usually means reduced stature through accelerated growth and accelerated bone maturation that stops sooner than girls who mature later.
“The early occurrence of puberty shortens the duration of pre-pubertal growth in a fashion that is not compensated for by an increase in peak amplitude,” says a paper in the Oxford journal. In historical studies, “there was a negative correlation between the age of onset of precocious puberty and adult height, confirming the poor height prognosis of the most severe and early cases.”
Meat—especially hormone-raised meat—may be a factor
A 2010 study in Public Health Nutrition of 3,000 girls found that girls who ate eight portions of meat a week by age three, and 12 portions of meat a week by age seven were likely to have an early start of menstruation. In fact, the girls were 75 percent more likely to have begun their periods by the age of 12 if they were eating a high-meat diet when they were seven years old. Not mentioned in the study, led by Imogen Rogers from the University of Brighton, was whether the meat had been grown with livestock hormones, a practice that also raises concerns.
“We have always had access to junk food, but never in human history have we been the subjects of such an intense ingestion of chemicals and hormones,” writes Christina Pirello on the Huffington Post. “Dr. Andrew Weil states that more than two-thirds of the cattle raised in the U.S. are given hormones, usually testosterone and estrogen to boost growth. According to Cornell, there are actually six hormones commonly used in meat and dairy production: estradiol and progesterone (natural female sex hormones); testosterone (natural male sex hormone); zeranol, trenbolone acetate and melengesterol (synthetic growth promoters that make animals grow faster).”
Pirello urges people to eat more produce and avoid hormone-fed meat, noting, “If hormones can make an animal fat, what do you think will happen to us?” AlterNet has covered the wide use of the drug ractopamine in livestock production, which also produces unnatural weight gain.
More than a decade ago, milk made by giving cows genetically modified recombinant bovine growth hormone (rBGH) was thought to be linked to precocious puberty. The persistence of food safety advocates has largely driven rBGH, originally made by Monsanto, out of the milk supply.
While some suspect soy, which has some estrogen-like actions, could be another precocious puberty culprit, “a recent longitudinal study by our colleagues in the NIH-funded Breast Cancer and the Environment Research Program (BCERP) suggests that soy intake might even delay pubertal onset in girls,” write Julianna Deardorff and Louise Greenspan, authors of The New Puberty: How to Navigate Early Development in Today’s Girls. Also, “There is epidemiologic evidence that women who consume soy as young girls have lower breast cancer risk,” the authors write.
Endocrine disrupters: A new and dangerous factor
While meat and obesity have been around for a long time, endocrine-disrupting toxins found in everyday products like hand soap, shampoos, cosmetics, cleaning products and of course plastics have not. From carpets, couches and food containers to thermal receipts given at gas stations, chemicals that mimic estrogen and change our hormonal balance are now everywhere.
A 2012 Centers for Disease Control and Prevention study found dichlorobenzene, a solvent used in mothballs, solid block toilet bowl deodorizers and air fresheners is linked to precocious puberty, reported Lindsey Konkel of Environmental Health News. Dichlorobenzene is a common indoor contaminant. Nationwide tests found dichlorobenzene residue in 98 percent of people tested, Konkel writes. The chemical passes to the fetus in the womb and is widely found in breast milk.
Precocious puberty has been linked to other common endocrine disrupters.
“Adolescent girls with high levels of brominated flame retardants had their first periods earlier than other girls in a 2011 study,” writes Konkel. “Also, girls prenatally exposed to other, now-banned flame retardants called PBBs began to menstruate at a younger age, according to one study of Michigan women who in 1973, while pregnant, ate food contaminated with the chemicals. In-the-womb exposure to the banned insecticide DDT was associated with early menarche in a study of mothers and daughters in the Great Lakes region in the 1970s and 1980s.”
Even puberty in animals has been affected by these chemicals, says Konkel.
Unpredictable households could play a role
Emotional stress in a girl’s family with high levels of conflict can “jump-start” precocious puberty, write Greenspan and Deardorff.
“So does early sexual abuse. A girl who grows up without her biological father is twice as likely to get her period before age 12 compared with a girl reared with her father in the home. The effects of fathers may or may not be linked to stress, but a father’s presence in the home does seem to matter when it comes to puberty.”
Some have even suggested that stressed-out single mothers, having to provide the only paycheck while caring for their children, are more likely to feed girls fattening and processed food that is linked to precocious puberty.
Precocious puberty treated through lifestyle changes
While there are drug treatments doctors can give to girls exhibiting precocious puberty that will block the effects of the soaring hormones, prevention is clearly preferable. Certainly a “green household,” with as few endocrine disrupting chemical products as possible is a good start, as is a “green diet” without excess chemicals, hormones and calories.
Martha Rosenberg is an investigative health reporter and the author of “Born With a Junk Food Deficiency: How Flaks, Quacks and Hacks Pimp the Public Health” (Random House).