Why puberty now begins at seven - pesticides? obesity? genetic epidemic?

[Guest guest]

Why puberty now begins at seven

By

BBC News health reporter

England's children getting fatter

<http://news.bbc.co.uk/2/hi/health/4496947.stm>

EU alarmed by spread of obesity

<http://news.bbc.co.uk/2/hi/europe/4351509.stm>

Whether it is sprouting hair, budding breasts or a breaking voice, the

signs that herald puberty can be distressing and difficult to cope with.

In the western world children are reaching puberty at younger and

younger ages - some girls at the age of seven.

The reasons for this trend is unknown, although several theories have

been suggested.

Swedish scientists at the Karolinska Institute aim to find out by

tackling the puzzle from different angles.

Precocious puberty

It is accepted that the normal age for a girl to begin to develop the

first signs of puberty is 10 and above. Boys develop slightly later,

generally at eleven-and-a-half.

However, the age has been decreasing in developed countries.

In 1990, the first signs of puberty were around the age of eight for

girls - the whole process taking two years to complete.

Now, according to researchers, some enter puberty as young as seven.

Boys, too, are entering puberty at an earlier stage, albeit still

slightly later than girls.

But it is unclear whether this is a simply a shift of the norm, or a if

more children are experiencing a phenomenon called precocious puberty -

when they develop the first signs of puberty abnormally early.

Controversial theories have been put forward, including how watching too

much television could distort the hormonal balance of adolescents and

push many of them into early puberty.

Psychologists have said young girls who have close relationships with

their fathers might enter puberty later than girls with distant or

non-existent links.

Now 12 European teams are carrying out research as part of a three-year

project to get to the root of the problem, looking at the most likely

culprits.

Calories

Professor Olle Söder from the Karolinska Institute is leading one study

which will look at whether rising obesity rates are to blame.

His team will study whether animals that are overfed produce more of the

male and female sexual hormones that trigger puberty.

" We believe that this has a nutritional background and that the obesity

explosion we have seen in the US, and which is coming to Europe, is

important, " he said.

Colleagues in Germany will gather data on around 50,000 children to look

at whether those who are plumper reach puberty earlier.

A London group will look at strains of mice renowned for early or late

onset of puberty and see whether they can modify this with diet.

Researchers have shown that overfed and rapidly growing newborn babies

go on to reach puberty earlier than other babies.

Also, adoption studies show undernourished children who have catch-up

growth after being placed with more affluent families have earlier onset

of puberty than siblings who remain in their home place.

Pesticides and pollution

" Another thing that might be important is environmental factors that

mimic hormones, such as pesticides, " said Professor Söder.

A team of Belgian researchers pointed the finger at a chemical

derivative of the controversial pesticide DDT.

Jean-Pierre Bourguignon and colleagues from the University of Liege

found children who had emigrated from countries such as India and

Colombia were 80 times more likely to start puberty unusually young.

Three-quarters of these immigrant children with " precocious " puberty had

high levels of a chemical derivative of DDT in their blood.

However, there is no firm evidence. Some of the European researchers

will probe this further.

Equally, he said it might be down to genetics.

Genes

A team of researchers in the UK and the US recently pinpointed a gene

that they believe controls puberty through the regulation of a protein

called GPR54.

The US scientists, from Massachusetts General Hospital, found that the

gene that codes for GPR54 was mutated in all members of a Saudi Arabian

family who failed to reach puberty.

At the same time, scientists at the UK biotechnology company Paradigm

Therapeutics contacted the US doctors to tell them they had bred mice

that had failed to reach puberty.

They had " knocked out " the gene for GPR54 in these mice.

Regardless of whether it is down to one factor or many, it is not clear

whether children entering puberty earlier is a problem, said Professor

Söder.

Some say girls who reach puberty earlier are more likely to drop out of

school and have lower incomes.

Data shows that they are also more likely to become mums earlier.

With more and more women putting off having a baby until later life,

this might help be a good thing and help reverse trends of top heavy

ageing population, said Professor Söder.

But equally, it might mean more women reach the menopause earlier too

and miss their chance to become a mum, he said.

Either way, " it will have a societal impact, " he warned.

Story from BBC NEWS:

http://news.bbc.co.uk/go/pr/fr/-/2/hi/health/4530743.stm

Published: 2005/05/15 23:08:01 GMT

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