Preliminary Findings Show Maternal Hypothyroidism May Contribute to Abnormal Cortical Morphology in Offspring.

Julieta E Lischinsky,Hayyah Clairman,Joanne Rovet,Jovanka Skocic

doi:10.3389/fendo.2016.00016

Abstract

In rodents, insufficient thyroid hormone (TH) gestationally has adverse effects on cerebral cortex development. Comparable studies of humans examining how TH insufficiency affects cortical morphology are limited to children with congenital hypothyroidism or offspring of hypothyroxinemic women; effects on cortex of children born to women with clinically diagnosed hypothyroidism are not known. We studied archived MRI scans from 22 children aged 10–12 years born to women treated for preexisting or de novo hypothyroidism in pregnancy (HYPO) and 24 similar age and sex controls from euthyroid women. FreeSurfer Image Analysis Suite software was used to measure cortical thickness (CT) and a vertex-based approach served to compare HYPO versus control groups and Severe versus Mild HYPO subgroups as well as to perform regression analyses examining effects of trimester-specific maternal TSH on CT. Results showed that relative to controls, HYPO had multiple regions of both cortical thinning and thickening, which differed for left and right hemispheres. In HYPO, thinning was confined to medial and mid-lateral regions of each hemisphere and thickening to superior regions (primarily frontal) of the left hemisphere and inferior regions (particularly occipital and temporal) of the right. The Severe HYPO subgroup showed more thinning than Mild in frontal and temporal regions and more thickening in bilateral posterior and frontal regions. Maternal TSH values predicted degree of thinning and thickening within multiple brain regions, with the pattern and direction of correlations differing by trimester. Notably, some correlations remained when cases born to women with severe hypothyroidism were removed from the analyses, suggesting that mild variations of maternal TH may permanently affect offspring cortex. We conclude that maternal hypothyroidism during pregnancy has long-lasting manifestations on the cortical morphology of their offspring with specific effects reflecting both severity and timing of maternal TH insufficiency.

Highlights

Thyroid hormone (TH) is essential for normal brain development from the start of pregnancy until the first few years of life [1, 2]
It is relevant to note we recently reported that children with CH, who underwent a brief circumscribed period of thyroid hormone (TH) insufficiency that occurred somewhat later and extended longer than in hypothyroidism in pregnancy (HYPO), showed that cortical thinning and thickening relative to controls and effects reflected the severity of their hypothyroidism [45]
Our findings revealed that thickening effects in some regions, such as the postcentral gyrus and sulcus and pericallosal sulcus, which are important for sensory processing, but these disappeared once outliers were removed, suggesting that central regions may be especially vulnerable to severe TH deficiency in pregnancy

Summary

Introduction

Thyroid hormone (TH) is essential for normal brain development from the start of pregnancy until the first few years of life [1, 2]. Diverse cortical abnormalities [18, 19] reflecting both severity and timing of maternal TH deficiency [20] include neuronal migration defects, atypical layering [21, 22], reduced growth of axons and dendrites [23, 24], and increased apoptosis [25] These effects are generally localized to middle and posterior brain regions, especially parietal and occipital cortices [26,27,28,29], which underlie sensorimotor, visual, and auditory functions [2, 30]. The frontal lobes, which are important for executive processing and attention require TH in the postnatal period [31], signifying a posterior-to-anterior progression of TH need within the cortex

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Conclusion