New research has found that boys exposed to high levels of testosterone before birth are twice as likely to experience delays in language development, while the opposite is true for girls.
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SYDNEY: Exposure to high levels of testosterone in boys before birth is linked to an increased risk of language development delays, according to a new study. But for girls, the opposite is true.
These findings, published in the current issue of the Journal of Child Psychology and Psychiatry could help scientists to identify and treat children at risk of delays in language development from a very early stage. Uncovering the biological mechanisms that are active in language development, such as the role hormones like testosterone play, could also lead to a better understanding of how conditions such as autism are caused.
"It's not just the levels of testosterone that affect the biological mechanisms, but also the way the body processes that testosterone. That's what we're thinking might be going on here," said lead author Andrew Whitehouse, a speech pathologist and psychologist at the Telethon Institute for Child Health Research in Perth, Western Australia.
How language problems develop
Delays in language development are very common and boys are generally affected more often than girls. Even though most cases resolve without intervention, therapy can be important, as about 20% of affected children suffer from lifelong language difficulties if not treated. "The earlier we intervene, the better we can change the trajectory of brain development," said Whitehouse.
For many years, a poor language environment - for example parents not reading to their children - was believed to cause language delay. "But more and more we are starting to think that biological mechanisms may be just as important," said Whitehouse.
The researchers analysed umbilical cord blood samples taken at the delivery stage of around 700 children to determine the testosterone concentrations they were exposed to during the late stages of pregnancy. Using detailed questionnaires, the parents were then asked to assess the language development of their children until the age of three. "To follow that number of children for that length of time and also study the biological mechanisms [involved in speech development] is quite unique," said Whitehouse.
Boys vs girls
Male foetuses are generally exposed to 10 times higher levels of sex steroids such as testosterone than females, which makes a direct comparison between the sexes impossible. But among the boys, those whose umbilical cord blood contained the most testosterone were found to be much more likely to develop language delays. For the girls, high levels of the hormone were found to reduce that risk.
In most people, it is the left hemisphere of the brain that is most important for language development and it has long been speculated that language difficulties could be a result of complications with this specialisation. Whitehouse's research suggests that testosterone affects the development of the male and female brain differently, and prenatal exposure to the steroid could hamper this left-hemisphere language 'lateralisation' in males while facilitating it in females.
While scientists still have to figure out how exactly this works on a cellular level, it is presumed that "the way [testosterone] affects the DNA is what might be a little bit different" among boys and girls, said Whitehouse
