A study published in the journal of Molecular Psychiatry discusses a link between children who later develop autism with exposure to elevated levels of steroid hormones such as testosterone, progesterone, and cortisol when they are in the womb; offering a potential explanation as to why more boys are impacted by autism than girls.
The study out of Denmark sampled nearly 20,000 amniotic fluid samples from children born between 1993-1999. The amniotic fluid was collected from women who chose to have amniocentesis during the 15-16 weeks of pregnancy, allowing scientists to view what is going on in the crucial time period in fetal development. Researchers looked at steroid hormones including progesterone, 17a-hydroxy-progesterone, androstenedione, testosterone as well as cortisol. The children who later developed autism were noted to have higher than average levels of all these hormones compared to typically developing children. These results were found to hold steady across the entire autism spectrum – uniting those with Asperger’s, PDD-NOS and classical autism.
Autism experts note that this is one of the earliest non-genetic biomarkers recognized in the disorder. One expert, Dr. Simon Baron-Cohen states. "We previously knew that elevated prenatal testosterone is associated with slower social and language development, better attention to detail, and more autistic traits. Now, for the first time, we have also shown that these steroid hormones are elevated in children clinically diagnosed with autism. Because some of these hormones are produced in much higher quantities in males than in females, this may help us explain why autism is more common in males."
Because the hormones were found in the amniotic fluid, researchers believe the source of the hormones is more likely the baby than the mother – but they are not certain. Further research needs to be completed for further understanding. It is suspected that children with autism are more sensitive to hormone levels or their bodies use them differently than other children. Boys produce about twice as much testosterone as girls when they are in the womb and the autism group had even HIGHER levels – a significant difference that can impact brain development.
The journal Frontiers in Neuroendocrinology also discussed the link between testosterone and autism spectrum disorder earlier this year. They also discovered that early exposure to androgenic hormones and early maternal immune activation comprise environmental factors that cause more boys to be susceptible to autism. Several months earlier the same journal found that the effect of testosterone remained in the ‘gentle touch’ response for four generations – meaning there is an epigenetic component to this.
LiveScience reported back in 2011 that autism had a sexual bias and that fetal testosterone levels can put a fetus at risk. A gene nicknamed RORA normally turns on several other genes. When a cell has high levels of testosterone, RORA levels run low, which impact all genes that RORA is supposed to turn on. The RORA gene is also supposed to protect neurons against the effects of stress and inflammation which are both higher in children with autism. Further, the brain tissue of people with autism contains lower levels of RORA than neuro-typical people. This also explains why females have lower rates of autism; if RORA levels are low, estrogen can pick up some of the slack and protect neurons.
References
http://www.nature.com/mp/journal/vaop/ncurrent/full/mp201448a.html
http://www.theguardian.com/society/2014/jun/03/boys-with-autism-likely-exposed-to-more-hormones-in-the-womb
http://www.ncbi.nlm.nih.gov/pubmed/24705124
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3940884/
http://www.livescience.com/12920-autism-common-males-testosterone-affects-gene.html