Women with high early pregnancy urinary iodine levels have an increased risk of hyperthyroid newborns: the population‐based Generation R Study. (9th October 2013)

• Record Type: Journal Article
• Authors: Medici, Marco; Ghassabian, Akhgar; Visser, Willy; de, Sabine M. P. F.; Jaddoe, Vincent W. V.; Visser, W. Edward; Hooijkaas, Herbert; Hofman, Albert; Steegers, Eric A. P.; Bongers‐Schokking, Jacoba J.; Ross, H. Alec; Tiemeier, Henning; Visser, Theo J.; de, Yolanda B.; Peeters, Robin P.
• Is Part Of: Clinical endocrinology. Volume 80:Number 4(2014:Apr.)
• Page Start: 598
• Page End: 606
• Publication Date: 2013-10-09
• Subjects: Endocrinology -- Periodicals; 616.4005
• DOI: 10.1111/cen.12321
• Languages: English
• ISSNs: 0300-0664

Abstract

<abstract abstract-type="main" id="cen12321-abs-0001"> <title>Abstract</title> <sec id="cen12321-sec-0001" sec-type="section"> <title>Objective</title> <p>Iodine deficiency during pregnancy results in thyroid dysfunction and has been associated with adverse obstetric and foetal effects, leading to worldwide salt iodization programmes.</p> <p>As nowadays 69% of the world's population lives in iodine‐sufficient regions, we investigated the effects of variation in iodine status on maternal and foetal thyroid (dys)function in an iodine‐sufficient population.</p> </sec> <sec id="cen12321-sec-0002" sec-type="section"> <title>Design, Participants and Measurements</title> <p>Urinary iodine, serum TSH, free T4 (FT4) and TPO‐antibody levels were determined in early pregnancy (13·3 (1·9) week; mean (SD)) in 1098 women from the population‐based Generation R Study. Newborn cord serum TSH and FT4 levels were determined at birth.</p> </sec> <sec id="cen12321-sec-0003" sec-type="section"> <title>Results</title> <p>The median urinary iodine level was 222·5 μg/l, indicating an iodine‐sufficient population. 30·8% and 11·5% had urinary iodine levels <150 and >500 μg/l, respectively.</p> <p>When comparing mothers with urinary iodine levels <150 <italic>vs</italic> ≥150 μg/l, and >500 <italic>vs</italic> ≤500 μg/l, there were no differences in the risk of maternal increased or decreased TSH, hypothyroxinaemia or hyperthyroidism. Mothers with urinary iodine levels >500 μg/l had a higher risk of a newborn with decreased cord TSH levels (5·6 ± 1·4 (mean ± SE) <italic>vs</italic> 2·1 ± 0·5%, <italic>P </italic>=<italic> </italic>0·04), as well as a higher risk of a hyperthyroid newborn (3·1 ± 0·9 <italic>vs</italic> 0·6 ± 0·3%, <italic>P </italic>=<italic> </italic>0·02). These mothers had newborns with higher cord FT4 levels (21·7 ± 0·3 <italic>vs</italic> 21·0 ± 0·1 p<sc>m</sc>, <italic> P </italic>=<italic> </italic>0·04).</p> <p>Maternal urinary iodine levels <150 μg/l were not associated with newborn thyroid dysfunction.</p> </sec> <sec id="cen12321-sec-0004" sec-type="section"> <title>Conclusions</title> <p>In an iodine‐sufficient population, higher maternal urinary iodine levels are associated with an increased risk of a hyperthyroid newborn.</p> </sec> </abstract>