Early puberty may be linked to a commonly used chemical in personal care products

The age at which girls reach puberty has been dropping at an alarming rate for decades, and scientists have struggled to explain why. New research suggests that a compound found in a wide range of products — from cosmetics to air fresheners to detergents and soaps — may send a signal to an area of ​​the brain that triggers the onset of puberty.

It’s the first time researchers have looked at the potential impact of environmental chemicals on the brain to explain the increase in early puberty, said Dr. Natalie Shaw, a pediatric endocrinologist at the National Institute of Environmental Health Sciences in Durham, North Carolina.

The significantly early onset of puberty — younger than 8 for girls, 9 for boys — can have health effects that last into adulthood, including a higher risk of breast cancer, diabetes and heart disease. It can also lead to shorter stature in both girls and boys. In May, a study from the Harvard T.H. Chan School of Public Health found that 15.5 percent of girls had their periods early — younger than 11 — and 1.4 percent started their periods younger than 9.

Previously, scientists have suggested possible causes, including obesity, diet, socioeconomic status and possible exposure to substances such as phthalates that can disrupt sex hormones.

Shaw, a co-senior author of the new study, acknowledged a link between early puberty and obesity in young girls. “I think it plays a role, but in my practice, it’s not just those who are overweight or obese who have early puberty,” she said.

While the timing of puberty may be at least partly dependent on genetics, a rapid change “points 100% to environmental factors,” Shaw said. That’s what led the researchers to look for a compound that kids might be exposed to frequently.

If Shaw and her team have found a compound that might affect when the brain sends the signal to start puberty, they will have also discovered the mechanism underlying the change in timing, something population studies have not yet been able to do.

By scouring 10,000 compounds in a library of licensed pharmaceuticals, environmental chemicals and dietary supplements, the researchers found several that could affect the timing of puberty. But children were likely exposed to only one: musk ambrette, according to the report, published in Endocrinology.

Musk ambrette, a synthetic form of the scent, is thought to bind to a receptor in the hypothalamus associated with puberty, triggering the release of GnRH, a hormone involved in the maturation of the sex 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, Shaw said. But it has also shown up in studies of sewage and in the bodies of freshwater fish, the researchers noted.

The next step for the researchers was to test the impact of musk ambrette on human hypothalamus cells and on zebrafish larvae.

They found that the substance triggered GnRH production in both fish larvae and human cells.

The new study is just a first step, Shaw said. Future studies will look at the impact of musk ambrette on mammals, such as rodents, and blood levels of the compound in humans, she added.

Shaw advises parents who want to prevent precocious puberty to check the musk ambrette ingredient list on cosmetics, perfumes and household products their children use until more is known.

The new study addresses a very important topic, said Dr. Apisadaporn Thambundit, a pediatric endocrinologist who is also an assistant clinical professor of pediatrics at UCLA.

“I don’t think it’s strong enough to suggest that parents can do anything about it,” she said. She was surprised that phthalates, which have been linked to early puberty, didn’t show up in the study.

Jasmine McDonald, an associate professor in the department of epidemiology at Columbia University Mailman School of Public Health in New York City, said the new findings “are great as a first step.”

A key strength 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 ban or restrict any substance, McDonald said. But families may want to limit products with strong scents.

“If you need a lotion, it can be unscented,” McDonald said. “In the shower, avoid scented body washes and shampoos.”