A girl’s genes affect when she will get her first period, and many of these genes cause childhood weight gain, which is a risk factor for early puberty, according to a University of Cambridge study.
In the largest-ever genetic study of puberty onset in girls, published on Monday in Nature Genetics, researchers analyzed the DNA of around 800,000 women. They identified 1,000 DNA changes that influence the age at which a girl will have her first menstrual period. Forty-five percent of these DNA changes are involved in early-childhood weight gain.
“Many of the genes we’ve found influence early puberty by first accelerating weight gain in infants and young children,” professor John Perry, a corresponding author of the study, said in a news release. “This can then lead to potentially serious health problems in later life, as having earlier puberty leads to higher rates of overweight and obesity in adulthood.”
Early Puberty, Poorer Adult Health
Puberty in girls typically occurs between the ages of 10 and 15, though trends have shown that the average age of puberty has lowered in recent decades.
Researchers noted that though the trend is not fully understood, early puberty is associated with an increased risk of adverse health conditions, including Type 2 diabetes, obesity, cardiovascular disease, and certain cancers. Conversely, delayed puberty has been associated with better adult health and a longer lifespan.
The authors recognized a “bidirectional causal relationship” between the age of a girl’s first period and her body size.
“Greater early weight gain leading to earlier [onset of menses] and also earlier [onset of menses] leading to higher adult BMI (body mass index),” the authors wrote.
The researchers also found that a few genes that influence the onset of menses are also linked to the age of menopause onset.
During a previous investigation alongside the University of Cambridge’s Medical Research Council Metabolic Diseases Unit, the researchers found a receptor in the brain that detects the body’s nutritional state. The receptor, MC3R, also regulates the timing of puberty and children’s growth rate. Other genes were observed to control the brain’s release of reproductive hormones.
In addition, a few people carry rare genetic variants that have a profound effect on the timing of puberty. One variant, found in one in 3,800 women, causes girls to start puberty 1.3 years later than the average girl.
Predicting Puberty May Aid Future Health Outcomes
“This is the first time we’ve ever been able to analyse rare genetic variants at this scale. We have identified six genes which all profoundly affect the timing of puberty,” lead study investigator Katherine Kentistou said in the news release. “While these genes were discovered in girls, they often have the same impact on the timing of puberty in boys. The new mechanisms we describe could form the basis of interventions for individuals at risk of early puberty and obesity.”
The research team was able to develop a genetic score to predict whether a girl was likely to reach puberty very early or very late. Girls with the highest 1 percent of the genetic score were 11 times more likely to have highly delayed puberty after the age of 15. Meanwhile, girls with the lowest 1 percent of the score were 14 times more likely to undergo puberty very early, before age 10.
Researchers said the ultimate goal would be to use DNA sequencing to help predict when a child might reach puberty. Doing so would enable parents and health care providers to offer the most appropriate medical care as the child matures.
“Children who present … with very early puberty—at age seven or eight—are offered puberty blockers to delay it,” professor and pediatrician Ken Ong, a senior author of the study, said in the press release. “But age of puberty is a continuum, and if they miss this threshold, there’s currently nothing we have to offer. We need other interventions, whether that’s oral medication or a behavioural approach, to help. This could be important for their health when they grow up.”