The age of puberty in girls has been falling at an alarming rate for decades, and scientists have struggled to explain why. New research suggests that a compound found in a variety of products – from cosmetics to air fresheners to cleaning products and soaps – could send a signal to an area of the brain that triggers the onset of puberty.
It is the first time researchers have examined the possible effects of environmental chemicals on the brain to explain the increase in early puberty rates, said Dr. Natalie Shaw, a pediatric endocrinologist at the National Institute of Environmental Health Sciences in Durham, North Carolina.
A significantly earlier onset of puberty — before age 8 for girls, before age 9 for boys — can have health consequences that last into adulthood, including a higher risk of breast cancer, diabetes and heart disease. It can also cause short stature in both girls and boys. In May, a study from the Harvard TH Chan School of Public Health found that 15.5% of girls started their periods early — before age 11 — and that 1.4% began menstruating before age 9.
Scientists had previously suspected possible causes including obesity, diet, socioeconomic status and possible contact with substances such as phthalates, which can disrupt sex hormone levels.
Shaw, one of the lead authors of the new study, confirmed a link between early puberty and obesity in young girls. “I do think it plays a role, but in my practice it’s not just the overweight or obese who have early puberty,” she said.
While the timing of puberty may depend at least in part on genetic factors, rapid change “points 100% to environmental factors,” Shaw said, leading researchers to look for a link to what children might be commonly exposed to.
If Shaw and her team have found a compound that may influence when the brain sends the signal to start puberty, then they have also discovered the mechanism underlying this change in timing, something population studies have previously failed to do.
The researchers combed through 10,000 compounds in a library of approved drugs, environmental chemicals and dietary supplements and found several that could affect puberty timing. But the children were most likely exposed to only one of these compounds: ambrette musk, according to the report published in Endocrinology.
Musk ambrette, a synthetic form of the fragrance, could bind to a puberty receptor in the hypothalamus, causing 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 commonly used in cheap or counterfeit perfumes and other scented personal care products, Shaw said. But it has also been detected in sewage tests and in the bodies of freshwater fish, the researchers noted.
In the next step, the researchers tested the effect of musk ambrette on human hypothalamus cells and on zebrafish larvae.
They found that the compound triggered the production of GnRH in both the fish larvae and human cells.
The new study is just a first step, Shaw said. Future studies will examine the effects of musk ambrette on mammals such as rodents and blood concentrations of the compound in humans, she added.
Until more is known, Shaw recommends that parents who want to prevent early puberty should check the ingredient list of all their children’s cosmetics, perfumes and household products for ambrette musk.
The new study addresses a very important issue, said Dr. Apisadaporn Thambundit, a pediatric endocrinologist and assistant professor of pediatrics at UCLA.
“However, I don’t think the results are strong enough to suggest anything parents can do,” she said. She was surprised that phthalates, which have been linked to early puberty, were not mentioned 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 were “great as a first step.”
A major strength of the study is that it did not start with a candidate drug, 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, it’s too early to consider banning or restricting a compound, McDonald said, but families could limit consumption of products with strong scents.
“If you need a lotion, it can be fragrance-free,” McDonald said. “In the shower, you can avoid perfumed shower gels and shampoos.”
