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Randomized Controlled Trial
. 2021 Sep;60(6):3411-3422.
doi: 10.1007/s00394-021-02515-1. Epub 2021 Feb 23.

A randomized, double-blind study of iodine supplementation during pregnancy in Sweden: pilot evaluation of maternal iodine status and thyroid function

Sofia Manousou  1   2 , Robert Eggertsen  3 , Lena Hulthén  4 , Helena Filipsson Nyström  4   5   6
Affiliations
Randomized Controlled Trial

A randomized, double-blind study of iodine supplementation during pregnancy in Sweden: pilot evaluation of maternal iodine status and thyroid function

Sofia Manousou et al. Eur J Nutr. 2021 Sep.

Abstract

Purpose: Pregnant women in Sweden are mildly iodine deficient. We investigated the effect of daily iodine supplementation on the iodine and thyroid status of pregnant women.

Methods: In this pilot, randomized, double-blind trial, 200 thyroid-healthy pregnant women were recruited at mean (standard deviation) pregnancy week 8.85 (1.62) and assigned (1:1) to daily intake of a multivitamin tablet with or without 150 μg of iodine. Urine and serum samples were collected at baseline and once during the second and third trimesters. Urinary iodine concentration (UIC), serum thyroglobulin (Tg), thyroid-stimulating hormone (TSH), free thyroxine (FT4), and thyroid peroxidase antibodies (TPOabs) were analyzed. Neonatal TSH data were collected. UIC and Tg were also analyzed in a group of 89 thyroid-healthy non-pregnant women of reproductive age (WRA).

Results: At baseline, the intervention and the control groups had similar median UIC (interquartile range (IQR)): 110 μg/L (74-119) and 111 μg/L (66-168), respectively. The intervention group reached iodine sufficiency with median UIC (IQR) 139 μg/L (89-234) and 136 μg/L (91-211) in the second and third trimester, respectively, without significant difference from the lower limit of the recommended range, i.e. 150-250 μg/L (p = 0.42 and p = 0.87, respectively). The intervention group had higher median UIC and lower median Tg compared to the control group during the second (p < 0.001 and p = 0.019, respectively) and third trimester (p < 0.001 and p = 0.003, respectively), whereas thyroid hormones, serum TPOabs, and neonatal TSH were similar. The WRA group presented median UIC (IQR) 65 μg/L (30-98) and median Tg (IQR) 18 μg/L (13-27).

Conclusion: A daily supplement containing 150 μg of iodine to a group of pregnant women with mild iodine deficiency improved the iodine status from mild ID to iodine sufficiency. This improvement seems to have had a positive impact on maternal thyroglobulin. This study is now under extension to investigate the children's neuropsychological development.

Trial registration: ClinicalTrials.gov Identifier NCT02378246, May 3, 2015, retrospectively registered.

Keywords: Iodine supplementation; Pregnancy; Randomized controlled trial; Sweden; Thyroglobulin; Urinary iodine concentration.

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Conflict of interest statement

The authors declare that they have no conflicts of interest. The funding sponsors had no role in the design of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.

Figures

Fig. 1
Fig. 1
Boxplots comparing a urinary iodine concentration, b estimated urinary iodine excretion, and c serum thyroglobulin at baseline, and during the second and third trimesters for the intervention and control groups. Boxplots show median, interquartile range, and range. Dotted line in panel a represents the lower recommended median urinary iodine concentration during pregnancy
See this image and copyright information in PMC

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