Low sex hormone may increase autism symptoms

A lack of anti-M?llerian hormone in boys with autistic spectrum disorder (ASD) may lead to a greater number of symptoms.

Michael Pankhurst and Ian McLennan from the University of Otago in New Zealand say hormones like anti-M?llerian hormone (AMH) that control the speed at which the body and brain develop might play a central role in the way that ASD progresses through childhood.

The pair analysed the level of AMH in 82 boys with ASD. The lower the level of AMH in their blood, the greater the number of autistic traits they displayed.

In an earlier study, McLennan and his colleagues found that an increased level of AMH was associated with slower overall growth and development in boys. Together, he thinks the two studies suggest that a lack of AMH could cause the brain to develop too quickly, leading to an increased number of symptoms in boys with ASD.

"Rapid development is associated with a greater frequency of developmental disorders," says McLennan. A complex system that develops quickly is more likely to contain errors than one that develops more slowly, he explains.

Surprisingly, there was no difference between the average level of anti-M?llerian hormone in the children with ASD and 16 boys without autism. McLennan says this shows that the hormone doesn't cause ASD, but may increase the number of symptoms in people who have the condition.

Not extreme males?

If confirmed, the study would challenge the idea that ASD is an exaggerated version of normal male cognition caused by an excess of testosterone during early development. This "extreme male brain" hypothesis holds that men are typically systematisers while women are empathisers. Accordingly, autism is said to be a condition where a person is extremely male: a great systematiser but a poor empathiser.

Besides slowing development and suppressing the growth of female sex organs in males, AMH has also been linked to male behavioural traits in mice. McLennan says that because they found less of this hormone in boys with more severe autism, the results don't sit well with the extreme male brain hypothesis.

"At present, the evidence is still too preliminary to draw any strong conclusions," says Simon Baron-Cohen at the University of Cambridge, the leading proponent of the extreme male brain hypothesis. He says that the study is too small and looks for too many associations, increasing the chances of stumbling across some by accident.

Rhoshel Lenroot, a psychiatrist at Neuroscience Research Australia in Sydney, says that because many children with ASD have a larger head, the idea of accelerated brain development is plausible. She adds that it is "terrific to have findings that suggest a role for hormones other than just testosterone".

Everyone that New Scientist spoke to agreed that the work is too preliminary for speculation on using the hormones as a treatment to decrease autistic symptoms.

Journal Reference: Translational Psychiatry, DOI: 10.1038/tp.2012.72

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