Effect of Gestational Subclinical Hypothyroidism on the IQ of Offspring

Abstract

Subclinical hypothyroidism (SCH) is the most common endocrine dysfunction during pregnancy. Its impact on the intellectual development of the offspring is not entirely clear. We aimed to evaluate the association between maternal SCH in pregnancy and the Intellectual Quotient (IQ) of offspring and assess benefits from prenatal maternal thyroid hormonal replacement. IQ scores were compared among 8-9-year-old offspring of 146 healthy mothers (control group) whose thyroid-stimulating hormone (TSH) concentrations were < 4.1 mIU/l, of 32 untreated hypothyroid women whose TSH was between 4.1-5.0 mIU/l, and of 29 women (TSH 5-10 mIU/l) who underwent thyroid hormone replacement during pregnancy. In all cases the serum free thyroxine (fT4) was within their respective reference ranges. The IQs of children of healthy and treated for hypothyroid mothers were 105.7 +14.1 and 108.5+14.7, respectively, which was significantly higher (p<0.05) than the mean IQs (98.3+11.4) of offspring from untreated hypothyroid women. Our study demonstrates that the treatment of maternal hypothyroidism during pregnancy appears to be beneficial for the child's intellectual development.