THERAPY OF ENDOCRINE DISEASE: Impact of iodine supplementation in mild-to-moderate iodine deficiency: systematic review and meta-analysis

Abstract

Background: Although the detrimental effects of severe iodine deficiency are well recognised, the benefits of correcting mild-to-moderate iodine deficiency are uncertain. Objectives: We undertook a systematic review of the impact of iodine supplementation in populations with mildto-moderate iodine deficiency. Methods: We searched Medline and the Cochrane library for relevant articles published between January 1966 and April 2013, which investigated the effect of iodine supplementation on maternal and newborn thyroid function, infant neurodevelopment and cognitive performance in school-age children. The quality of studies was graded and eligible trials were evaluated in the meta-analysis. Results: Nine randomised controlled trials (RCTs) and eight observational studies met the inclusion criteria. Controlled trials on infant neurodevelopment were lacking; gestational iodine supplementation reduced maternal thyroid volume and serum thyroglobulin and in some studies prevented a rise in serum thyroid-stimulating hormone. None of the intervention trials recorded an excess frequency of thyroid dysfunction in contrast to observational studies. A pooled analysis of two RCTs which measured cognitive function in school-age children showed modest benefits of iodine supplementation on perceptual reasoning (standardised mean difference (SMD) 0.55; 95% CI 0.05, 1.04; PZ0.03) and global cognitive index (SMD 0.27; 95% CI 0.10, 0.44; PZ0.002) with significant heterogeneity between studies. Conclusion: Iodine supplementation improves some maternal thyroid indices and may benefit aspects of cognitive function in school-age children, even in marginally iodine-deficient areas. Further large prospective controlled studies are urgently required to clarify these findings and quantify the risk/benefits of iodine supplementation in regions previously believed to be iodine sufficient such as the UK.

Suboptimal Maternal Iodine Intake Is Associated with Impaired Child Neurodevelopment at 3 Years of Age in the Norwegian Mother and Child Cohort Study

“…To isolate the effect of long-term iodine intake, we restricted these analyses to participants who did not report the use of supplements containing iodine in the FFQ. Previous studies have indicated that long-term iodine intake might be more important for thyroid function during pregnancy than recent supplement use (39). Indeed, we also found that the associations between iodine FIGURE 3 Associations between maternal iodine intake from food in pregnancy and internalizing (A, B) and externalizing (C, D) child behavior problems at the age of 3 y in the Norwegian Mother and Child Cohort Study.…”

“…Previous studies on iodine supplement use in pregnancy and child neurodevelopmental outcomes in areas with mild-to-moderate ID have shown inconsistent results (3,39,48), and to our knowledge there are no randomized controlled trials published to date. In this study we examined the associations in women with iodine intake from food below and above the EAR (160 mg/d) separately because the effect of supplemental iodine might depend on previous iodine status.…”

Assessment of iodine importance and needs for supplementation in school-aged children in Portugal

“…While many countries have mandatory iodizes salt programmes in Portugal only two recommendations are ongoing; DGS suggests supplementation for pregnant women [32] and Directorate-General for Education (DGE) the iodized salt use for school canteens [44]. However, although Universal salt iodine can eliminate specific supplementation [45], such as pregnancy and lactation periods [32,35], our results showed that iodine supplementation is not a current practice. Obstetricians and pediatrics medical practice and mothers did not present consistent information regarding this subject.…”

Iodine deficiency: current status

“…В метаанализ были включены 9 рандомизи-рованных контролируемых исследований и 8 описа-тельных исследований. Было выявлено, что у детей школьного возраста на фоне йодопрофилактики было отмечено умеренное улучшение способности рассуждать и повышение общего когнитивного ин-декса [44].…”