NBC News
The age at which girls reach puberty has been declining at an alarming rate for decades, and scientists have been scrambling to explain why. New research suggests that a compound found in a wide variety of products – from cosmetics to detergents to soaps – can send a signal to an area of the brain that triggers the onset of puberty.
This is the first time researchers have looked at the possible impact of environmental chemicals on the brain to explain the rise in early puberty, said Dr. Natalie Shaw, a pediatric endocrinologist at the National Institute of Environmental Health Sciences in Durham, North Carolina.
Starting puberty at a significantly early age — younger than 8 for girls and younger than 9 for boys — can have health effects that extend into adulthood, including an increased risk of breast cancer, diabetes and heart disease. It can also shorten the height of both boys and girls. In May, a study from the Harvard T.H. Chan School of Public Health found that 15.5 percent of girls started menstruating before age 11 and that 1.4 percent started menstruating before age 9.
Previously, scientists had suggested possible causes, including obesity, diet, socioeconomic status and possible exposure to substances such as phthalates, which can disrupt sex hormones.
Shaw, co-lead author of the new study, acknowledged that there is a link between precocious puberty and excess weight in girls. “I think it plays a role, but in my practice it’s not just those who are overweight or obese who have precocious puberty,” she said.
While the timing of puberty may depend at least in part on genetics, a rapid change points “100 percent to environmental factors,” Shaw said. That’s what led researchers to search for a compound to which minors might be routinely exposed.
If Shaw and his team find a compound that can affect when the brain sends the signal to start puberty, they will also have discovered the mechanism that causes the timing change, something that population studies have failed to do.
After screening 10,000 compounds from a library of approved drugs, environmental chemicals and dietary supplements, researchers found several that could influence the timing of puberty. However, according to the report, published in the journal Endocrinology, boys were most likely to be exposed to just one of them: musk ambrette.
Musk ambrette, a synthetic form of the fragrance, may hook onto a puberty-related receptor in the hypothalamus, triggering the release of GnRH, a hormone involved in the maturation of sexual organs and the production of estrogen, testosterone and progesterone.
Musk ambrette is widely used in cheap or counterfeit fragrances and other scented personal care products, according to Shaw. But it has also turned up in studies of wastewater and in the bodies of freshwater fish, the researchers said.
The researchers’ next step was to test the effect of musk ambrette on human hypothalamic cells and zebrafish larvae.
They found that in both fish larvae and human cells, the compound triggered GnRH production.
According to Shaw, the new study is just a first step. He added that future studies will look at the impact of musk ambrette on mammals such as rodents and at blood levels of the compound in humans.
Until more is known, Shaw suggests that parents who want to prevent precocious puberty should check the ingredient lists of cosmetics, fragrances and household products their children use for the substance.
For Dr. Apisadaporn Thambundit, a pediatric endocrinologist and clinical assistant professor of pediatrics at UCLA, the new study addresses a very important issue.
However, “I don’t think it’s strong enough to suggest anything parents can do,” she said. She was surprised that phthalates, which have been linked to early puberty, didn’t come up in the research.
Jasmine McDonald, an associate professor in the department of epidemiology at Columbia University’s Mailman School of Public Health in New York, said the new findings “are great as a first step.”
One of the main strengths of the study is that it didn’t start with a candidate compound, McDonald said. Instead, the researchers had a biological mechanism in mind and then looked for compounds that might play a role.
Based on this study alone, it’s too early to consider banning or restricting a compound, McDonald added. But families could cut back on products with strong scents.
“If you need a lotion, it can be unscented,” McDonald said. “In the shower, you can avoid fragranced body washes and shampoos.”
