A new study, published in the journal Molecular Psychiatry, suggests that exposure to high levels of estrogen in the womb may be linked to an increased risk for autism.
“This finding is exciting because the role of estrogens in autism has hardly been studied, and we hope that we can learn more about how they contribute to foetal brain development in further experiments,” said Dr. Alexa Pohl from the University of Cambridge in the U.K.
In 2015, a team of scientists from the University of Cambridge and the State Serum Institute in Denmark measured the levels of four prenatal steroid hormones, including two known as androgens, in the amniotic fluid. They found levels were higher in male fetuses who later developed autism.
On average, these androgens are produced in higher quantities in male fetuses, so this could also explain why autism occurs more often in boys. These hormones are also known to masculinize parts of the brain, and to have effects on the number of connections between brain cells.
For the new study, the same team of scientists built on their previous findings by testing the amniotic fluid samples from the same 98 individuals sampled from the Danish Biobank.
This time, however, they looked at another set of prenatal sex steroid hormones called estrogens. This is an important next step because some of the hormones previously studied are directly converted into estrogens.
The team discovered that, on average, all four estrogens were significantly elevated in the 98 fetuses who later developed autism, compared to the 177 fetuses who did not.
“These elevated hormones could be coming from the mother, the baby or the placenta. Our next step should be to study all these possible sources and how they interact during pregnancy,” said Alex Tsompanidis, a Ph.D. Cambridge student who worked on the study.
High levels of prenatal estrogens were even more predictive of likelihood of autism than were high levels of prenatal androgens (such as testosterone).
Contrary to the popular belief that estrogen is tied to feminization only, prenatal estrogens also have effects on brain growth and even masculinize the brain in many mammals.
The new finding adds to the growing body of research supporting the prenatal sex steroid theory of autism first proposed decades ago by study leader Professor Simon Baron-Cohen, director of the Autism Research Centre at the University of Cambridge.
“This new finding supports the idea that increased prenatal sex steroid hormones are one of the potential causes for the condition,” he said. “Genetics is well established as another, and these hormones likely interact with genetic factors to affect the developing foetal brain.”
However, the researchers caution that these findings cannot and should not be used to screen for autism. Baron-Cohen clarifies that his research team is working on “understanding autism, not preventing it.”
Source: University of Cambridge