Prenatal iodine supplementation and neurocognitive outcomes in moderately deficient populations

Abstract

Over the past 100 years, there has been significant progress in limiting the development of iodine deficiency disorders globally. The recognition that congenital cretinism can be eradicated through early iodine supplementation along with the implementation of salt iodination in many countries has substantially decreased the prevalence of severe iodine deficiency. Yet, there are still populations that are mildly iodine deficient, likely due to lack of mandated iodine supplementation programs. While some countries are qualified as iodine sufficient based upon the general population’s median urinary iodine concentration, the sub-population of pregnant women may be mildly to moderately iodine deficient. Thyroid hormone demand increases during gestation to support fetal thyroid function and neurodevelopment. Pregnant women require increased iodine intake during pregnancy to account for this increased demand and to make up for increased renal iodide losses. The American and European Thyroid Associations both recommend that pregnant women in mild to moderately deficient populations take a daily 150mcg iodine supplement while planning a pregnancy, pregnant, and lactating. Studies into the impact of mild to moderate iodine deficiency in pregnancy on long-term neurocognitive outcomes of offspring have shown varied results. Some have found that iodine sufficiency or supplementation in pregnancy is associated with higher intelligence quotient scores in offspring. Others have found no significant effect of iodine sufficiency and iodine supplementation on developmental outcomes. This proposal is a double-blind, placebo-controlled, randomized study evaluating the effect of iodine supplementation in pregnancy on long-term neurocognitive outcomes of offspring. The study will be implemented in the mildly iodine deficient population of Southern England. Results from this study will contribute to and likely expand upon the current body of literature. They will also bolster current recommendations for iodine supplementation in pregnancy. In addition, this study may have important public health consequences including discussions around mandatory salt iodization in mild to moderately deficient populations.