Health

Deciphering the reason why girls hit puberty earlier and earlier


AmericaExperts surmise that early puberty in children is due to overweight, obesity, exposure to certain chemicals in the environment or psychology.

In 1980, while serving as director of child abuse at Duke University Medical Center in Durham, Marcia Herman-Giddens discovered that girls there developed breasts between the ages of six and seven, earlier. much more than the normal threshold.

A decade later, she published the results of a study of more than 17,000 girls who had physical exams at pediatricians’ offices around the country. Accordingly, in the mid-1990s, girls developed breasts at about 10 years of age, a year earlier than previously recorded.

This work marks a turning point in the field of puberty medicine. Subsequent studies throughout the following decades have shown that puberty in girls worldwide has decreased by about 3 months every 10 years since 1970.

Although the consequences are unclear, experts say early puberty can have harmful effects, especially for girls. Girls with precocious puberty are at greater risk of depression, anxiety, substance abuse tendencies, and psychological problems than their late pubertal peers. Girls who start menstruating early also have a higher risk of breast or cervical cancer as adults.

Experts do not know the risk factors associated with early puberty. However, most conjecture that obesity, environmental changes, and chemicals in food may be involved.

Comparing the age of puberty for American and Danish children, the scientists found that Danish girls have a menstrual period at the same age as the previous average, 11 years old, different from American children. Meanwhile, American children have higher rates of obesity. From there, the team showed that overweight or obese female children started menstruating earlier than children of average weight.

A decades-long study of nearly 1,200 girls in Louisiana, published in 2003, found that each standard deviation from average childhood weight can double the chance of precocious puberty before age 12.

In 2021, experts from the UK discovered that leptin, a hormone secreted by fat cells, has the effect of limiting hunger. Leptin acts on the part of the brain that regulates sexual development. Mice and humans with certain genetic mutations experience later puberty or outbreaks.

Dr. Natalie Shaw, a pediatric endocrinologist at the National Institute of Environmental Health Sciences, also believes that obesity is a cause of early puberty. However, this is not the only cause. She points out that many children hit puberty early even though they are not overweight.

A decade after Herman-Giddens’ study, Dr Anders Juul, of the Department of Endocrinology at the University of Copenhagen, found an increase in the number of children with precocious puberty in Copenhagen. Girls sometimes develop breasts between the ages of 7 and 8.

In a 2009 study of nearly 1,000 female schoolchildren, he and his colleagues found that the average age of breast development in girls decreased by about a year compared with the previous study, to less than 10 years old. Most girls go through puberty between the ages of 7 and 12. They also started menstruating at age 13, about four months earlier than in previous analyses.

“Very big change happens in a short amount of time,” says Dr. Juul.

Unlike doctors in the US, he considers that Exposure to chemicals in the environment and food is the cause of early puberty. In a 2009 study, girls with early breast development had high levels of phthalates in their urine. This is the substance used to plasticize plastics, found in almost every household item, from vinyl flooring to food packaging.

Phthalates are part of a larger class of chemicals, called “endocrine disruptors,” that can affect hormone action, that have become ubiquitous in the environment over the past few decades.

In a report published earlier this year, Dr. Juul and colleagues analyzed hundreds of studies on endocrine disruptors, which may affect puberty. Research methods varied, some were done in boys, others in girls. Experts assess exposure to chemicals at different ages. They compared 23 studies, but found no other chemical that could cause girls to go through puberty early.

Other factors that are also associated with early puberty are psychological stress. Children who were sexually abused in childhood may have earlier puberty, however, scientists have not confirmed a cause-and-effect relationship. Stress and trauma can promote growth in general.

Girls whose mothers are psychologically disturbed, or who do not live with their biological father, often reach puberty earlier. Lifestyle factors such as lack of physical activity also lead to changes during puberty.

During the pandemic, pediatric endocrinologists worldwide are also seeing an increase in the number of girls experiencing precocious puberty. Research published in Italy in February found that more than 300 children were referred to five clinics across the country in the last seven months of 2020, twice as many as 140 children in the same period of 2019. in India, Turkey and the US.

“I’ve asked my colleagues around the country. They see similar trends. It’s unclear if this is due to stress,” said Paul Kaplowitz, professor emeritus of paediatrics at the National Children’s Hospital in Washington. increased stress, a sedentary lifestyle, or because parents are closer to their daughters and notice changes earlier.

For decades, the medical literature has determined the stage of puberty in children using the Tanner Scale, based on rigorous analysis between 1949 and 1971 of about 700 children living in the UK.

This scale determines the average age of puberty in boys is 9 years old, girls is 8 years old. If puberty begins earlier than that threshold, doctors need to screen children for a rare hormonal disorder. The children will have brain scans and prescribed puberty-blocking drugs to delay sex development until an appropriate age.

Thuc Linh (According to NY Times)

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