Hormone sorts men from boys

Fairfax

MAN MADE: New Zealand scientists are uncovering what makes the male population so varied.

Relevant offers

Health

A burning issue: When coffins get too big Promoter dismisses bike helmet harm study Plucky mother intent on recovery ACC beneficiary admits he cheated Cafe's stub-out stance a winner Doctor sceptical about boy's alternative cancer care Calls to stop the spread of fast food outlets Information withheld puts children 'at risk' Kiwi scientist urges halt to doomsday flu research City doctors earn less than country cousins

It's a tale of mice and manliness - New Zealand scientists are uncovering what makes the male population so varied, from rugby-heads and warrior types to poets and ballet dancers.

The secret is in a hormone previously thought to only stop boys from developing a uterus. Now it seems that hormone, called Mullerian inhibiting substance, plays a larger role in making men different to women, and to one another.

Though it might potentially make men throw balls further or grunt more, it appears to have no influence on their sexuality. The finding has implications for treating diseases such as anorexia and Alzheimer's, which affect mainly females, and ADHD, autism and motor neurone disease, which typically affect males.

Otago University neurobiologists Ian McLennan and Kyoko Koishi led the study, which is published in the latest edition of the American journal Proceedings of the National Academy of Sciences.

The scientists tested mice with both high and low levels of MIS by putting them in a box. Males with high levels of MIS were "about three times more likely to try to climb out and explore beyond the confines of the box" an established male-biased trait, Dr McLennan said.

The mice with low MIS explored the box in a way similar to females but were still interested in the females and able to get them pregnant.

The research was supported through a $750,000 Marsden Fund grant and an Otago research grant.

The researchers had now begun a three-year trial with Dunedin five-year-olds and six-year-olds to try to replicate the findings. "We're looking at things like their rough-and-tumble play, the way they throw a ball, the way they draw a picture," Dr McLennan said.

After testing the children's blood, scientists could work out if their behaviour was linked to their particular MIS level. Boys and girls clearly developed differently before puberty, which was down to both social and biological reasons.

"Science is just slowly catching up with what everyone knew in their general life," Dr McLennan said, but he cautioned that the results were useful only in describing general tendencies. "Empathy, for example, has a female bias, but some of the greatest men are empathetic."

- © Fairfax NZ News