Developing problems

Why are today’s young girls experiencing the onset of puberty at such an early age?

LITTLE GIRLS really are growing up faster. A new study shows that girls are now reaching puberty, on average, before the age of 10. Examining a group of 1,000 Danish children, paediatric endocrinologist Prof Anders Juul discovered that in 1991-2006 the average age of breast development – the first and most reliable sign of imminent puberty in girls – has come down from 10.88 to 9.86 years.

While striking, the finding isn’t unexpected: for a long time, the age at which puberty occurs has been falling rapidly – in the 19th century, 15 was the norm – and there are similar findings from other parts of Europe and North America. And if nine is the new average, that means there are plenty of youngsters reaching puberty even younger.

The study showed that the average age of menarche – a girl’s first period – has not changed so dramatically: in the girls studied in 2006-2008, menstruation began less than four months earlier than the girls studied from 1991-1993. What these findings seem to show is that while the age of full sexual maturity has changed relatively little over the past decades, the process of puberty is drawn out much longer than it used to be.

Dr Juul of Copenhagen University Hospital in Denmark says there are serious consequences for the physical and emotional wellbeing of girls starting puberty while still at primary school. “If girls mature early, they run into teenage problems at an early age and they’re more prone to diseases later on.”

Beginning puberty early can mean longer exposure to oestrogen, which is a factor in breast cancer, and there is also a greater risk of heart disease. “We should be worried about this regardless of what we think the underlying reasons might be,” adds Juul. “It’s a clear sign that something is affecting our children; whether it’s junk food, environmental chemicals or lack of physical activity.”

The possible reasons behind the earlier onset of puberty range from benign to more sinister explanations. Some experts reason that girls today are better nourished than they’ve been in the past, gaining in weight and height more quickly than they would have done several generations ago, which may encourage hormonal changes to start.

But others believe it’s rising levels of obesity that is pushing the age of puberty down. Fatter children have high levels of the protein leptin, which stimulates the release of the three main hormones in puberty: hypothalamic gonadotropin-releasing hormone, luteinizing hormone and follicle-stimulating hormone.

Could higher consumption of meat play a part? A recent study by the University of Bristol reviewed the dietary intake of 3,000 girls at ages three and seven, then recorded the onset of puberty. Girls who had a higher intake of meat (and protein) at ages three and seven were more likely to begin menstruation at age 12.5. Scientists working in the US and Canada are concerned that hormone residues in beef could be exacerbating this effect.

A variety of artificially produced chemicals could also be helping to hasten puberty. Questions have been raised about the actions of phthalates – used to make plastics flexible and durable – and parabens, the preservatives used in some shampoos and sunscreens. But it’s bisphenol-A – a plastic found in the lining of babies’ feeding bottles and tin cans – that has come under particular scrutiny. In fact, Juul’s research team is currently testing urine and blood samples from girls in the study, to see if there is a definite link between the endocrine-disrupting chemical and early sexual maturity.

While girls’ bodies are developing at a more marked rate, the timetable of brain changes associated with adolescence has not shifted. Cambridge University zoologist Prof David Bainbridge says, “The quest for autonomy, more complex thought process and the ability to think about other people: these start aged 12-14, as they always did. Whereas these used to occur before puberty, now they come afterwards.”

So that leaves a whole generation of little girls stuck in what is rapidly becoming an adult’s body, while they still have the minds of children. The fact that we live in a hyper-sexualised society only makes the problem worse.

Educational psychologist Madelene Portwood says young girls should be concentrating on friendship and education, not feeling under pressure to behave like adults, while paediatric endocrinologist Richard Stanhope says “these children are also at a much higher risk of being sexually abused because it is hard for some adults to understand and behave appropriately towards them.”

Early puberty poses a physical, social and emotional challenge to primary school age girls. It’s difficult coping with an embarrassing unruly body when you’re a teenager, but it’s even harder when you’re only nine.