There is a school of thought, as championed by Simon Baron-Cohen, that thinks of autistic disorders as ‘an exaggerated version of maleness’. The theory goes that autists are systematic, unable to articulate feelings, not great at empathising. They tend to gravitate towards logical subjects like maths and science. They often don’t have close friends. The same things are broadly more true of men than of women. Female diagnoses of high-functioning autism are much rarer (4:1 for profound autism, maybe even 9:1 for Aspergers). Ergo, maybe autism = extreme maleness. Girls are less likely to be diagnosed because a particularly “male” girl is… well, a tomboy. Whereas an extra-“male” boy is more of an anomaly.
It’s a nice theory, but has not been conclusively shown to have a physiological or endocrinological basis. The empathising / systemising nature of humans in general has been shown to correlate well with testosterone levels in foetuses. Testosterone has been shown in vitro (i.e. in a petri dish) to have an inhibitory effect upon a transcription factor called RORA, and biopsies show that autists have lower levels of RORA in their brains than the general population. There could very well be a link, but it’s not conclusive. It also doesn’t tell us much about why there is a link.
Anyway, I could talk about this stuff for hours, but this isn’t (particularly) new news. What is new is that a group from New Zealand have started looking at another hormone called AMH (anti-Mullerian hormone), which – amongst other things – regulates the production of testosterone. Females do need AMH but at much lower levels, and males with inadequate AMH can develop a syndrome called PMDS, which means they grow us as hermaphrodites with a small uterus and undescended testes.
Anyway what Ian McLennan and Michael Pankhurst found was that, firstly, 82 boys with an autistic spectrum disorder have AMH levels that on average match the general population. Dead end? Actually no. They also looked at the variation within the autistic group. They found that boys with a higher ADI-R score (autism diagnostic interview: basically, ‘how autistic are you?’) had lower levels of AMH.
So what does that mean?
Well what it doesn’t mean is that low AMH makes you autistic: if it did then there would be a noticeable difference between the autistic kids and the neurotypical ones. But it does suggest that low AMH could exacerbate autistic tendencies.
Having said all of that, of course there are the usual problems. 82 isn’t a massive sample size, which means that the correlation isn’t amazing. It can’t say for definite how the hormone affects autists. However in a previous paper the same group found that that increased AMH in young boys lead to slower growth and development. Off the back of that the authors suggested in this New Scientist article that by slowing overall development, low levels of AMH make lead to faster brain development. It doesn’t tell us anything about preventative measures or treatment options.
But then I’m just morbidly curious about what might be going on in my own brain…
Pankhurst MW, McLennan IS. (2012) Transl Psychiatry. Inhibin B and anti-Müllerian hormone/Müllerian-inhibiting substance may contribute to the male bias in autism. doi: 10.1038/tp.2012.72.
Knickmeyer, R, Baron-Cohen, S, Raggatt, P & Taylor, K (2006) Foetal testosterone and empathy. Hormones & Behaviour, 49, 282-292.