California mother Jennifer was stunned when her 6-year-old daughter started developing breasts and experienced her first period shortly before turning 8.

With no family history of early puberty and no signs of obesity or underlying health issues, Jennifer, who requested only her first to protect her child’s privacy, embarked on a long and frustrating search for answers. 

Now part of a growing group of parents grappling with this jarring trend, Jennifer is left questioning the role of environmental toxins, plastics, and chemicals in everyday life — while science and regulation scrambles to keep up.

Late last month, Health and Human Services Director Robert F. Kennedy brought high-level scrutiny to the matter, emphasizing that “girls are hitting puberty six years early.”

That figure might be more of an outlier, but the issue is glaring and bound to worsen. 

“Over the past century, girls worldwide have been entering puberty at progressively younger ages,” Academic Endocrinologist and Obesity Specialist at Harvard Medical School, Dr. Mehmet Burak, tells the New York Sun. 

“Although this change differs per area, puberty is starting earlier than it did in previous generations, and health authorities are therefore reconsidering clinical definitions in ‘precocious puberty’.”

A recent major study published in JAMA Network Open finds that girls in the United States are getting their first period — known as menarche — about six months earlier on average than in previous generations, with a sharp rise in those menstruating before age 9. Among girls born between 2000 and 2005, 16.9 percent experienced early or very early menarche, compared to just 9.2 percent of those born from 1950 to 1969. 

Experts say the shift is likely driven by biological and environmental factors. Yet getting to the bottom of the causes is a challenge. Further complicating the matter, as medical definitions currently stand, “early puberty” isn’t a straightforward term. 

Professor emeritus of pediatrics in the Division of Endocrinology at the University of California, Robert Lustig, tells the Sun that what many professionals may diagnose as “early puberty” is often the body mimicking puberty symptoms. 

“Breast development is usually the first sign of puberty in girls, but it can also occur from any exposure to estrogen. Now that estrogen might be produced by the ovaries because the brain told them to — and that would be real puberty,” Dr. Lustig explained. 

“In girls, the normal age range for puberty is between 8 and 13. So, suppose breast development starts before age 8. In that case, we need to ask: is this true precocious puberty, or is it from some other exposure to estrogen that has nothing to do with the brain-pituitary-ovary axis? What’s clearly happening is that premature breast development — often due to obesity or environmental estrogens — is increasing. That’s not the same as early true puberty.”

The Drivers

So, what is going on? It is likely not one thing, but a key factor stands out: obesity. 

“There are two major alternative sources of estrogen besides the ovaries. One is fat tissue. Fat tissue contains an enzyme — aromatase — that converts androgens, which are male hormones, into estrogens,” Dr. Lustig said. 

“Around ages 6 to 8, the adrenal glands start producing androgens in a process called adrenarche. That’s totally normal. In obese children, this fat-derived estrogen can lead to breast development between ages 6 and 8.”

He noted that medical professionals “started seeing this more with the rise of the obesity epidemic around 1980.”

Childhood obesity rates in the United States have risen significantly over recent decades. Approximately 19.3 percent of children and adolescents aged 2–19 are classified as obese, with 6.1 percent experiencing severe obesity. The prevalence increases with age. Factors contributing to this trend include diets high in added sugars and saturated fats, reduced physical activity, and socioeconomic challenges. 

“Ultra-processed foods and insulin resistance further disrupt the reproductive system development,” Dr. Burak of Harvard Medical School said. 

What may be the murkiest driving force behind early puberty, however, is the abundance of endocrine disruptors lurking everywhere, from our food, personal products, furniture and electronics to plastic packaging, cleaning agents, the air we breathe, and the water we drink. 

“The second source of estrogen is environmental chemicals — endocrine disruptors. These include phthalates, parabens, flame retardants, and others. They started becoming widespread in the 1960s,” Mr. Lustig said. “So, we’re exposed to all kinds of compounds daily that act like estrogens. Some are even in personal care products.”

Dr. Lustig recalled a case when a 5-year-old girl came into his clinic “with very large breasts.”

“She wasn’t obese — just a normal-sized child. We ran every test we could: no signs of puberty, no tumors, no estrogen in the blood,” he recounted. “I asked the mother, ‘What do you bathe her in?’ She said, ‘Victoria’s Secret bubble bath.’ Sure enough, the label said, ‘For Adults Only.’ It contained plant-based compounds like genistein — a phytoestrogen. That was the cause.”

On the flipside but equally alarming, boys are experiencing the opposite trend. According to Dr. Lustig, their puberty is also affected by increased estrogen exposure, which can disrupt the brain-pituitary-testis axis and actually delay the onset of puberty.

A 2024 study published in Endocrinology, backed by the National Institutes of Health, identified musk ambrette — a synthetic fragrance found in some soaps and personal care products — as a potential trigger for early puberty in girls. 

The chemical activated puberty-related hormone receptors in human brain cells and zebrafish models, prompting concern over its continued use in consumer products despite restrictions in Canada and Europe.

Researchers screened 10,000 compounds and flagged musk ambrette for its ability to mimic hormones and disrupt normal development. 

The 2024 study also determined cholinergic agonists — found in certain medications for Alzheimer’s disease and myasthenia gravis — as potential endocrine-disrupting chemicals that may contribute to early puberty. While children rarely use these drugs, structurally similar compounds can be found in pesticides, industrial cleaners, and some disinfectants, raising concerns about indirect environmental exposure. 

What has experts most worried, however, is the prevalence of plastics in our everyday lives. 

“Chemicals like phthalates, which are found in plastics, also contribute to heart disease and possibly brain issues. Microplastics are a big concern, too — they’re in the air, food, and even our brains. Every one of us is walking around with microplastics in our body,” Dr. Lustig underscored. “Plastics act like estrogens in the body. Estrogens are double-edged: they’re essential for reproduction, but too much — or from the wrong source — can be harmful.”

Beyond environmental and chemical exposures, psychosocial and lifestyle factors also appear to influence early puberty in girls. Recent data indicates a concerning rise in childhood stress: around 35 percent of American children experience stress-related health problems, and 18.5 percent of children aged 5–17 have encountered one or more stressful life events, such as parental incarceration or exposure to violence. 

Additionally, from 2016 to 2021, the prevalence of mental, behavioral, and developmental disorders among children aged 3 to 17 years jumped from 25.3 percent to 27.7 percent, highlighting a growing mental health concern.

“Chronic stress and prolonged psychosocial stressors during early childhood have been linked to earlier puberty,” Dr. Burak explained, adding that the stress experienced by significant life events, from changes in family circumstances to the COVID-19 pandemic led to “a temporary spike in cases of early puberty.”

Childhood trauma, including sexual abuse and the absence of a biological father, have thus been linked to earlier development.  

“A girl’s hormone system will interpret that absence as a signal – stemming from caveman times — that it’s time to become a woman and start repopulating the tribe. So, the absence of a biological father can actually trigger early menstruation by a couple of years,” Tennessee-based physician Dr. Matt Tipton tells the Sun. 

“Also, exposure to sexual stimuli — whether actual or just through media—can also signal the endocrine system to ‘grow up.’ That’s another factor beyond just environmental endocrine disruptors.”

Girls with mothers who have mood disorders or who engage in little physical activity also face higher risks of early puberty.

The Ramifications 

In any case, the health consequences of early puberty are a cause for concern and are associated with a range of long-term health risks.

“It has been shown to increase the risk of obesity and type 2 diabetes, as well as cardiovascular disease, independent of Body Mass Index. Women who experience menarche at an earlier age are at a greater risk of developing breast cancer later in life, as well as endometrial cancer,” Dr. Burak asserted. “Additionally, girls who experience early puberty are more vulnerable to mental health challenges, including higher rates of depression, anxiety, eating disorders, and substance abuse. Early menarche may increase the risk of premature or early menopause and potentially shorten reproductive lifespan.”

Whether precocious or true puberty or late-onset for boys, the long-term health consequences are worrisome. 

“Earlier and longer exposure to estrogen over a lifetime increases the risk for hormone-related cancers, like breast cancer,” Dr. Lustig said. “That may also apply to prostate cancer in men.”

Taking Action 

Experts urge parents to avoid products with vague terms like “fragrance,” opt for those with full ingredient transparency, and make lifestyle changes where necessary. 

“Although genetics and lifestyle factors such as diet and weight play a much larger role in determining puberty timing, everyday exposures to these chemicals could significantly impact hormonal development,” Dr. Burak added. 

“Reducing exposure is possible by taking simple precautions such as consuming fresh fruits and vegetables instead of canned ones, using glass rather than plastic receptacles, and promoting good day-to-day hygiene practices. These little steps, though small, lower the unwarranted exposure to the chemicals which are possibly detrimental.”

The United States Department of Health and Human Services did not respond to a request for comment.