Girls who are overweight in childhood may be at greater risk of early puberty, genetic research has revealed.
In the largest study of its kind to date, a team from the University of Cambridge studied the DNA of around 800,000 women from around the world.
They discovered more than 1,000 variants – small changes in DNA – that influence the age of when girls started their first period.
Just under half of these variants affected puberty by increasing weight gain in early childhood.
The age at which girls hit puberty and start having periods normally occurs between the ages of 10 to 15, though this has been getting earlier and earlier in recent decades.
University of Cambridge researchers discovered more than 1,000 genetic variants that influence the age of when girls started their first period. Just under half of these variants affected puberty by increasing weight gain in early childhood
The increased risk starts in those aged under-13 at menarche, and increases the younger they are. Experts believe this could be due to higher levels of oestrogen, which they are exposed to for longer
Doctors have not been able to identify a single or even a handful of causes for precocious puberty, though experts told DailyMail.com that some underlying factors include obesity, stress, and genetics
Early puberty is linked with increased risk of a number of diseases in later life, including type 2 diabetes, cardiovascular disease and certain cancers.
Previous studies have already shown that being overweight is linked to early puberty in both boys and girls.
Professor John Perry, one of the study’s authors, said: ‘Many of the genes we’ve found influence early puberty by first accelerating weight gain in infants and young children.
‘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.’
The researchers also generated a genetic score that predicted whether a girl was likely to hit puberty very early or very late.
Girls with the highest 1 per cent of this genetic score were 11 times more likely to have extremely delayed puberty, after the age of 15.
On the other hand, girls with the lowest 1 per cent genetic score were 14 times more likely to have extremely early puberty before the age of 10.
Senior author Professor Ken Ong said: ‘In the future, we may be able to use these genetic scores in the clinic to identify those girls whose puberty will come very early or very late.
‘The NHS is already trialling whole genome sequencing at birth, and this would give us the genetic information we need to make this possible.
‘Children who present in the NHS with very early puberty – at age seven or eight – are offered puberty blockers to delay it.
‘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.’
Lead study investigator Dr Katherine Kentistou added: ‘The new mechanisms we describe could form the basis of interventions for individuals at risk of early puberty and obesity.’
Previous work by the team showed that a receptor in the brain, known as MC3R, detects the nutritional state of the body and regulates the timing of puberty and rate of growth in children.
Other identified genes appeared to be acting in the brain to control the release of reproductive hormones.
The findings were published in the journal Nature Genetics.
