Endocrine Abstracts

Iodine deficiency was common in the UK until the 1960s and was eradicated mainly through the adventitious increase in milk-iodine concentration. Iodine sufficiency was subsequently assumed in the UK, until a recent national study revealed mild iodine deficiency in adolescent girls, giving cause for concern. Iodine, as a component of the thyroid hormones, is crucial for brain development, and particularly during gestation. This study aimed to evaluate the relationship between iodine status in UK pregnant women and offspring cognition. As urinary iodine is a biomarker of iodine status, iodine concentration (and creatinine for adjustment of urine volume) was measured in urine samples collected during pregnancy from 1000 women of the Avon Longitudinal Study of Parents and Children (ALSPAC). Women were grouped as iodine-deficient or sufficient according to WHO criteria. The relationships between maternal iodine status and child IQ (age 8), reading ability (age 9), and key stage 2 (age 11) were analysed using logistic regression and up to 21 confounders were included in the analyses. Suboptimal outcome was defined as the bottom quartile of scores. The group was mildly-to-moderately iodine deficient based on a median iodine concentration of 91.8 μg/l (123 μg/g creatinine). The children of women deficient in iodine were more likely to have scores in the bottom quartile for total IQ (OR 1.58, 95% CI 1.09–2.29), reading accuracy (OR 1.83, 95% CI 1.22–2.74) and key stage 2 mathematics score (OR 1.60, 95% CI 1.07–2.41). When the iodine deficient category was subdivided into ‘severe’ and ‘mild-to-moderate’ there was evidence of a trend of increasing cognitive scores with improved maternal iodine status. Although these results cannot prove causality, they are suggestive of the importance of achieving adequate iodine status during pregnancy and suggest that iodine deficiency can pose a risk to the developing infant, even in regions of mild iodine deficiency.