Babies born to women with low levels of a thyroid hormone during pregnancy may be at an increased risk of being affected by neurodevelopmental disorder, finds a new study.Low maternal free thyroid hormone (fT4) concentrations leads to hypothyroxinemia -- a common condition in pregnant women.Children of mothers with hypothyroxinemia during pregnancy have increased odds of developing abnormalities in cognitive development similar to those in schizophrenia -- a neurodevelopmental disorder, the study said.The association remained even after adjusting for variables strongly related to schizophrenia such as maternal psychiatric history and smoking.Hypothyroxinemia is also associated with preterm birth, a risk factor for schizophrenia.
"The study suggests that maternal influences, both environmental and genetic, contribute to the risk of schizophrenia," said lead author David Gyllenberg from the University of Turku in Finland. Although the study did not address the cause of this association, it found that adjusting for preterm birth lessened the association between hypothyroxinemia and schizophrenia, suggesting that preterm birth may mediate some of the increased risk, the authors noted in the paper published in Biological Psychiatry. "This study identifies a preventable potential contributor to the risk for schizophrenia. Maternal hypothyroidism can be easily diagnosed and effectively treated," stated John Krystal, Editor of Biological Psychiatry.To determine if hypothyroxinemia is associated with schizophrenia, the team examined thyroxine levels in archived serum samples from 1010 mothers of children with schizophrenia and 1010 matched control mothers.The findings showed that 11.8 per cent of people with schizophrenia had a mother with hypothyroxinemia, compared with 8.6 per cent of people without schizophrenia.