By Makiko Kitamura, Bloomberg News | June 03, 2014
LONDON — Boys who develop autism are exposed to higher levels of steroid hormones in the womb than those who don't develop the condition, according to a study that further dispels the role of vaccines.
Prenatal levels of substances such as testosterone, progesterone and cortisol were greater on average in boys who were later diagnosed with autism, scientists at the University of Cambridge in England and the Statens Serum Institute in Copenhagen said in a report released Tuesday.
The finding, published in the journal Molecular Psychiatry, provides a possible explanation for how autism develops during pregnancy, countering fears that external factors such as vaccines play a role. Autism spectrum disorders, a group of brain development disorders, affect about one child in 160, according to the World Health Organization.
"We previously knew that elevated prenatal testosterone is associated with slower social and language development, better attention to detail and more autistic traits," Simon Baron- Cohen, professor of developmental psychopathology at Cambridge, said in a statement. "Now, for the first time, we have also shown that these steroid hormones are elevated in children clinically diagnosed with autism."
The study drew on 19,500 amniotic-fluid samples stored in a Danish biobank from individuals born between 1993 and 1999. The researchers identified samples from mothers who gave birth to 128 boys later diagnosed with an autism-spectrum condition. Because some of the hormones are produced in much higher quantities in males than in females, the finding may help explain why autism affects more boys, the researchers said.
"We now want to test if the same finding is found in females with autism," Baron-Cohen said.
Mothers shouldn't rush to use steroid-hormone blockers, as this may have unwanted side effects, according to Baron-Cohen. The study also shouldn't be interpreted as indicating a need to develop a prenatal screening test as the results were found at the average group level and may not predict diagnosis for an individual, he said.
The study results suggest there's variation in individual sensitivity to hormones or that the investigated time window is too early to detect a true elevation of hormone levels, said Richard Sharpe, a professor specializing in male reproductive health at the University of Edinburgh.
"Researching this in humans is incredibly difficult because of the obvious limitations in accessing what is happening in the fetus inside the womb, so investigations such as the present study have to be viewed as pioneering," Sharpe said in an e-mailed statement.
The study adds to earlier research suggesting that autism is linked to prenatal developments.
A paper published in March in the New England Journal of Medicine found that those diagnosed with autism missed key genetic markers for brain cells that are supposed to develop prior to birth.
A Norwegian study published last year found that taking folic acid supplements in early pregnancy was linked to a lower risk of autistic disorder. Folic acid is needed to fuse the spinal cord in early fetal development.
Vaccination has been feared as a potential cause of autism after a study by Andrew Wakefield, published in the Lancet medical journal in 1998, linked the measles-mumps-rubella vaccine to an increased risk of developing the condition. The Lancet retracted the study in 2010, citing "false" claims, and the British Medical Journal called it a fraud in a report the following year.
A study published about 14 months ago in the Journal of Pediatrics by researchers at the Centers for Disease Control and Prevention in Atlanta confirmed earlier research findings that autism risk isn't increased by the use of childhood vaccines.