We know that autism is more common among males: for every girl diagnosed there are four boys with the disorder.
There is much debate about the hormonal and genetic explanations for the disparity — but not much in the way of direct scientific evidence.
But today, a study from George Washington Medical Center in Washington DC reports that researchers may have found one of the underlying reasons for the male autism bias. It could help explain why the developmental disorder is so much more common for boys.
Here’s what they found:
The scientists looked at one particular gene that has been linked with autism — retinoic acid-related orphan receptor-alpha (RORA). RORA has been shown to be important in the cerebellum, and on average people with autism expressed this gene less than others. In animal studies, mice with less RORA expression show characteristic autism signs like repetitive behaviors and difficulty with spacial learning.
The researchers took human brain cells that express the RORA gene and bathed them in either female hormones (oestradiol) or male hormones (dihydrotestosterone, derived from testosterone). They found that when bathed in the female sex hormones, the gene was strongly expressed, whereas when exposed to male sex hormones, the RORA gene was suppressed.
So male hormones may have a direct effect in downplaying this gene, which could contribute to the development of autism symptoms.
If it holds up to further testing, this is one piece of a very complex puzzle. If you follow my writing, you know that when it comes to autism research I always qualify: autism is a highly complicated disorder with perhaps hundreds of genes involved – add to it that autism is not likely to be one disorder (even though we put one label on it). It’s probably multiple disorders, each with its own unique genetic and environmental makeup.
The male hormone findings are interesting, though — now researchers have another marker to work from in this complicated road map.