Scientist have identified a link between exposure to high levels of estrogen sex hormones in the womb and the likelihood of developing autism. The findings are published today in the journal Molecular Psychiatry. The discovery adds further evidence to support the prenatal sex steroid theory of autism first proposed 20 years ago.
Levels of estrogen
In 2015, a team of scientists at the University of Cambridge; also the State Serum Institute in Denmark measure the levels of four prenatal steroid hormones, including two known as androgens; so in the amniotic fluid in the womb and discover that they were higher in male foetuses who later develop autism. These androgens are produce in higher quantities in male than in female foetuses on average; so might also explain why autism occurs more often in boys.
They are also known to masculinise parts of the brain; and also to have effects on the number of connections between brain cells. Today, the same scientists have built on their previous findings; hence by testing the amniotic fluid samples from the same 98 individuals sample from the Danish Biobank; which has collect amniotic samples from over 100,000 pregnancies; but this time looking at another set of prenatal sex steroid hormones called estrogens.
This is an important next step because some of the hormones previously study are directly convert into estrogens. All four estrogens were significantly elevate, on average, in the 98 foetuses who later develop autism; hence compare to the 177 foetuses who did not. High levels of prenatal estrogens were even more predictive of likelihood of autism than were high levels of prenatal androgens. Contrary to popular belief that associates estrogens with feminisation, prenatal estrogens have effects on brain growth and also masculinise the brain in many mammals.
Sex steroid hormones
Professor Simon Baron-Cohen, Director of the Autism Research Centre at the University of Cambridge, who led this study and who first propose the prenatal sex steroid theory of autism, said: “This new finding supports the idea that increase prenatal sex steroid hormones; hence are one of the potential causes for the condition. Genetics is well establish as another; also these hormones likely interact with genetic factors to affect the developing foetal brain.”
Alex Tsompanidis, a Ph.D. student in Cambridge who work on the study, said: “These elevate hormones will be coming from the mother, the baby or the placenta. Our next step should be to study all these possible sources; also how they interact during pregnancy.” Dr. Alexa Pohl, part of the Cambridge team, said: “This finding is exciting because the role of estrogens in autism has hardly been studied; also they hope that we can learn more about how they contribute to foetal brain development in further experiments. They still need to see whether the same result holds true in autistic females.”
However, the team caution that these findings cannot; also should not be use to screen for autism. “They are interest in understanding autism, not preventing it,” add Professor Baron Cohen. Dr. Arieh Cohen, the biochemist on the team; so base at the State Serum Institute in Copenhagen, said: “This is a terrific example of how a unique biobank set up 40 years ago is still reaping scientific fruit today in unimagined ways, through international collaboration.”