Maternal Iodine Status is Associated with Offspring Language Skills in Infancy and Toddlerhood.

Maria Markhus,Anne Brantsæter,Marianne Abel,Lisbeth Dahl,Ingvild Graff,Marian Kjellevold,Kjell Stormark,Jannike Øyen,Vibeke Moe,Helle Meltzer,Lars Smith

doi:10.3390/nu10091270

Abstract

Inadequate iodine status affects the synthesis of the thyroid hormones and may impair brain development in fetal life. The aim of this study was to explore the association between maternal iodine status in pregnancy measured by urinary iodine concentration (UIC) and child neurodevelopment at age 6, 12 and 18 months in a population-based cohort. In total, 1036 families from nine locations in Norway were enrolled in the little in Norway cohort. The present study includes n = 851 mother-child pairs with singleton pregnancies, no use of thyroid medication in pregnancy, no severe genetic disorder, data on exposure (UIC) in pregnancy and developmental outcomes (Bayley Scales of Infant and Toddler Development, third edition). Data collection also included general information from questionnaires. We examined associations between UIC (and use of iodine-containing supplements) and repeated measures of developmental outcomes using multivariable mixed models. The median UIC in pregnancy was 78 µg/L (IQR 46–130), classified as insufficient iodine intake according to the WHO. Eighteen percent reported use of iodine-containing multisupplements. A UIC below ~100 was associated with reduced receptive (p = 0.025) and expressive language skills (p = 0.002), but not with reduced cognitive or fine- and gross motor skills. Maternal use of iodine-containing supplements was associated with lower gross motor skills (b = −0.18, 95% CI = −0.33, −0.03, p = 0.02), but not with the other outcome measures. In conclusion, an insufficient iodine intake in pregnancy, reflected in a UIC below ~100 µg/L, was associated with lower infant language skills up to 18 months. The use of iodine-containing supplements was not associated with beneficial effects.

Highlights

Iodine deficiency (ID) is considered one of the most common nutritional disorders globally and is the world’s largest single cause of preventable brain impairment [1]
We found that an insufficient iodine intake in pregnancy, reflected in a urinary iodine concentration (UIC) below ~100 μg/L, was associated with lower infant language skills up to 18 months
This study provides further evidence for a potential negative impact of insufficient iodine status in pregnancy on child neurodevelopment

Summary

Introduction

Iodine deficiency (ID) is considered one of the most common nutritional disorders globally and is the world’s largest single cause of preventable brain impairment [1]. Infants and pregnant women are vulnerable population groups [2], as ID may impair normal growth and development of the child, especially affecting brain development [3]. Iodine is an essential nutrient for the synthesis of the thyroid hormones triiodothyronine (T3 ). Dietary iodine is rapidly absorbed and the thyroid gland is dependent on regular and adequate supply through the diet in order to produce these vital hormones [4]. Inadequate thyroid hormone levels impair differentiation, maturation, cell migration, and myelination [3]. The iodine turnover during pregnancy is increased because the mother synthesizes approximately 50% more T4 to maintain maternal euthyroidism and transfer thyroid hormones to the fetus, and because iodine needs to be transferred to the fetus for fetal thyroid hormone production

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