• Akhgar Ghassabian, Hanan El Marroun, Robin P Peeters, Vincent W Jaddoe, Albert Hofman, Frank C Verhulst, Henning Tiemeier, and Tonya White.
• Departments of Child and Adolescent Psychiatry (A.G., H.E.M., F.C.V., H.T., T.W.) and Pediatrics (V.W.J.), Erasmus Medical Center-Sophia's Children Hospital, 3000 CB Rotterdam, the Netherlands; and The Generation R Study Group (A.G., H.E.M.) and Departments of Internal Medicine (R.P.P.), Epidemiology (V.W.J., A.H., H.T.), Psychiatry (H.T.), and Radiology (T.W.), Erasmus Medical Center, 3000 CA Rotterdam, The Netherlands.
• J. Clin. Endocrinol. Metab. 2014 Jul 1; 99 (7): 2383-90.

ContextAlthough maternal hypothyroxinemia is suggested to be related to various adverse consequences in a child's neurodevelopment, the underlying neurobiology is largely unknown.ObjectiveThe objective of the study was to examine the relationship between maternal hypothyroxinemia in early pregnancy and children's nonverbal intelligence quotient (IQ). Furthermore, we explored whether global brain volumes, cortical thickness, and brain surface area differed between children exposed prenatally to hypothyroxinemia and healthy controls.Design And SettingThe study included a large population-based prospective birth cohort in The Netherlands.ParticipantsA total of 3727 mother-child pairs with data on prenatal thyroid function at less than 18 weeks of gestation and nonverbal IQ at 6 years participated in the study. In 652 children, brain imaging was performed at 8 years of age.Main MeasuresMaternal hypothyroxinemia was defined as free T4 in the lowest 5% of the sample, whereas TSH was in the normal range. At 6 years, children's IQ was assessed using a Dutch test battery. Global brain volumetric measures, cortical thickness, and surface area were assessed using high-resolution structural magnetic resonance imaging.ResultsThe children of mothers with hypothyroxinemia in early pregnancy scored 4.3 points IQ lower than the children of mothers with normal thyroid status (95% confidence interval -6.68, -1.81; P = .001). After adjustment for multiple testing, we did not find any differences in brain volumetric measures, cortical thickness, and surface area between children exposed prenatally to hypothyroxinemia and controls.ConclusionsOur findings confirm a large adverse effect of maternal hypothyroxinemia on children's nonverbal IQ at school age. However, we found no evidence that maternal hypothyroxinemia is associated with differences in brain morphology in school-age children.

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