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Why are Young Kids Entering Puberty Earlier? 

5 min read  |  July 03, 2024  | 

More children, particularly girls, are entering puberty earlier than in past generations, but pediatricians and endocrinologists can’t point to a definitive reason why.

Typically, girls begin puberty between the ages of 8 and 13. (For boys, that’s 9 to 14.) In precocious puberty — or puberty that starts early, however, the body shows signs of change before the age of 8 in girls and before 9 in boys. “There’s always been a range in the onset of puberty,” says Gary D. Berkovitz, M.D., a pediatric endocrinologist with the University of Miami Health System. “But in early-onset puberty, the body begins to show signs at an even younger age than is considered within the normal range.”

The beginning of puberty is marked by physical signs.

This stage is primarily the beginning of breast development and/or growth of pubic hair in girls. In boys, it’s the enlargement of the testes and the growth of pubic hair. This usually launches a years-long process that includes other bodily changes, most noticeable growth spurts, voice deepening in boys and menstruation in girls.

Early puberty happens more frequently among girls than boys. It is estimated that it is diagnosed in about 20 out of every 10,000 girls but in fewer than 5 in every 10,000 boys.

A generation or two ago, the average age of puberty onset in girls — called thelarche in medical terms —  was about 11 years old, with the start of menstruation, on average, at 13. Today, thelarche begins closer to 10, and menarche (the start of menstruation) also begins earlier.

In fact, a study published in the journal Pediatrics in 2010 found that 18% of white girls, 31% of Hispanic girls, and 43% of Black girls had entered thelarche by the time they were eight years old. But this trend isn’t limited to the U.S. As early as 2009, researchers found the rate of early breast development increasing among girls in Denmark.

More recent studies have confirmed those findings. For example, a retrospective study analyzing data in South Korea found that children diagnosed with precocious puberty nearly doubled in the five years between 2016 and 2021, according to an August 2022 paper published in Frontiers in Pediatrics. A 2020 study of girls on six continents revealed that the age at which girls begin experiencing breast development has dropped by about three months every decade since 1977, a downward movement from about 10.5 to 9.5 years old.

Not all early signs of puberty result in too-early progressive sexual development.

However, parents need to seek help to understand what is happening to their child. In some cases, a girl may develop early pubic hair growth without other typical puberty changes. This condition is known as premature adrenarche. “This can be an isolated incident,” Dr. Berkovitz says. “It may not be followed by an acceleration of growth or other signs, such as enlargement of breasts.”

This is a benign condition, he adds, but a pediatrician should monitor the child’s development for other signs of puberty.

The precocious puberty cases Dr. Berkovitz sees in his UHealth are different. Many are diagnosed with central precocious puberty, which is puberty that starts too soon and continues developing through its stages — accelerated growth and menstruation, for example — as usual. Central precocious puberty happens when the brain begins producing LH and FSH hormones that instruct the body to make more estrogen in the ovaries. (In the case of boys, it leads to more production of testosterone in the testes.)

In rare instances, central precocious puberty may be caused by tumors, radiation or a genetic disease, but in most cases there is no known cause. Endocrinologists like Dr. Berkovitz theorize that something in the environment is stimulating the start of menses.

“The onset of periods in girls is earlier by a few months than it was 20 years ago,” he explains. “Twenty years is too short a time span for it to be explained by genetic conditions.”

Researchers believe that endocrine disruptors, called xenoestrogens, may be to blame.

These are chemicals that mimic the body’s natural female sex hormone and interact with our organs and neurological systems to create the same changes that estrogen does. These foreign chemicals can be found in pesticides or the production of plastics. Another factor is a child’s weight. Girls who are overweight tend to have earlier puberty development.

Regardless of the cause, complications can be serious. Kids who begin puberty before their peers may be confused and upset about their bodies. Dealing with periods in elementary school may also be stressful.

 “Some studies show an increase in depression, moodiness and anxiety,” Dr. Berkovitz says. “However, the risk for development of significant psychological problems is controversial.”

Early puberty may result in shorter stature as well.

Children who begin their growth spurt earlier also finish earlier, which results in shorter than average height as adults. Precocious puberty is also related to earlier menopause.

Since it appears that obesity can stimulate early signs of puberty, Dr. Berkovitz recommends parents help their children keep a healthy weight. In addition, avoid products that might contain xenoestrogens. These include pesticides and plastics, as well as certain skincare products, including soaps, shampoos, and perfumes that use parabens as a preservative and phenols such as triclosan. Also, read food labels to avoid preservatives and dyes. (For a detailed list, visit womenindistress.org.)

If your daughter shows signs of earlier-than-normal puberty, consult your pediatrician. However, Dr. Berkovitz says parents should not stress over early pubic hair or breast development.

“Parents should understand there’s a huge variance in the beginning of onset of puberty,” he says. “It’s a pretty wide range.”


Headshot of Ana Veciana, author (2023)

Ana Veciana-Suarez is a regular contributor to the University of Miami Health System. She is a renowned journalist and author who has worked at The Miami Herald, The Miami News, and The Palm Beach Post. Visit her website at anavecianasuarez.com or follow @AnaVeciana on Twitter.


Tags: child develepment, Dr. Gary Berkovitz, growth spurts, sexual health

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