Exposure to High levels of Steroid Homones in Womb Ups Autism Risk

A new study, conducted by researchers at the University of Cambridge, explains why autism is more common in boys than in girls.

According to researchers at the University of Cambridge and the Statens Serum Institute in Copenhagen, Denmark, increased levels of steroid hormones in the womb might up the chances of the child developing autism. These steroid hormones - testosterone, progesterone and cortisol - are found in higher levels in male children, which might explain why boys have high autism risk.

Researchers have warned that the study doesn't recommend any screening test or use of drugs that block steroids. Steroid-blockers can lead to unwanted side-effects in babies. The study is important because it shows that certain biological mechanisms that occur before birth are associated with autism.

Autism Spectrum Disorders are a group of developmental problems that affect a child's social and learning abilities. At least one in every 68 children in the U.S has ASD.

Data for the present study came from Danish biobank. Researchers used 19,500 amniotic fluid samples stored in the biobank from 1993 to 1999. Amniotic fluid surrounds the baby in the womb and is used to diagnose chromosomal abnormalities in babies. The samples were derived from women who chose to undergo amniocentesis around 15-16 weeks of pregnancy. The database provided researchers with key information about fetal development at this key stage of pregnancy.

Around 128 males in the samples were later found to be diagnosed with autism, according to a news release.

The team used the amniotic fluid sample to look at levels of four sex steroids that are made from the preceding hormone - progesterone, 17α-hydroxy-progesterone, androstenedione and testosterone. The pathway is called 'Δ4 sex steroid' pathway. The team even looked at another steroid called cortisol that is also a hormone, but is not a product of the aforementioned pathway.

Researchers found that the hormones were all associated with each other and that males diagnosed with autism were more likely to have higher levels of these steroids before birth than other children.

The study was funded by the Medical Research Council (MRC) and is published in the journal Molecular Psychiatry.

"This is one of the earliest non-genetic biomarkers that has been identified in children who go on to develop autism. 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," said Simon Baron-Cohen from Cambridge.

The study shows that science hasn't fully understood why some children are at an increased risk of developing autism. Recent study had found that environmental changes are strongly associated with autism risk in some children.