"The biological cause of Autism spectrum disorder (ASD) is unknown, but we have shown that one of the many risk factors—low vitamin D in mothers—causes an increase in testosterone in the brain of the male foetuses, as well as the maternal blood and amniotic fluid," said Professor Darryl Eyles, who co-authored the research with Dr. Asad Ali from UQ's Queensland Brain Institute. "In addition to its role in calcium absorption, vitamin D is crucial to many developmental processes. Our research also showed that in vitamin D-deficient male foetuses, an enzyme which breaks down testosterone was silenced and could be contributing to the presence of high testosterone levels."
Previous research led by Professor Eyles showed that vitamin D plays a critical role in brain development, and that that giving D supplements to mice during pregnancycompletely prevented ASD-like traits in their offspring.
Excessive exposure of the developing brain to sex hormones like testosterone was thought to be an underlying cause of ASD, Dr. Ali added in the release, but the reasons remained unclear. "Vitamin D is involved in pathways controlling many sex hormones. When the rat mothers were fed a low vitamin D diet, it caused male foetal brains to have high levels of exposure to testosterone."
This is the first to show that a known risk factor for ASD alters testosterone in both the foetal brain and the mother's blood, according to Professor Eyles, who noted that this is one possible contributor to why ASD is more prevalent in males. He added that UQ research only studied one risk factor for ASD (vitamin D deficiency during development). The next step: to look at other possible risk factors, such as maternal stress and hypoxia, to see if those factors have the same effect.