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Type: Journal article
Title: Comparison of iodine status pre- and post-mandatory iodine fortification of bread in South Australia: a population study using newborn thyroid-stimulating hormone concentration as a marker
Author: Wassie, M.M.
Yelland, L.N.
Smithers, L.G.
Ranieri, E.
Zhou, S.J.
Citation: Public Health Nutrition, 2019; 22(16):3063-3072
Publisher: Cambridge University Press
Issue Date: 2019
ISSN: 1368-9800
Statement of
Molla Mesele Wassie, Lisa N Yelland, Lisa G Smithers, Enzo Ranieri and Shao Jia Zhou
Abstract: Objective: The present study aimed to evaluate the effect of mandatory iodine fortification of bread on the iodine status of South Australian populations using newborn thyroid-stimulating hormone (TSH) concentration as a marker. Design: The study used an interrupted time-series design. Setting: TSH data collected between 2005 and 2016 (n 211 033) were extracted from the routine newborn screening programme in South Australia for analysis. Iodine deficiency is indicated when more than 3 % of newborns have TSH > 5 mIU/l. Participants: Newborns were classified into three groups: the pre-fortification group (those born before October 2009); the transition group (born between October 2009 and June 2010); and the post-fortification group (born after June 2010). Results: The percentage of newborns with TSH > 5 mIU/l was 5·1, 6·2 and 4·6 % in the pre-fortification, transition and post-fortification groups, respectively. Based on a segmented regression model, newborns in the post-fortification period had a 10 % lower risk of having TSH > 5 mIU/l than newborns in the pre-fortification group (incidence rate ratio (IRR) = 0·90; 95 % CI 0·87, 0·94), while newborns in the transitional period had a 22 % higher risk of having TSH > 5 mIU/l compared with newborns in the pre-fortification period (IRR = 1·22; 95 % CI 1·13, 1·31). Conclusions: Using TSH as a marker, South Australia would be classified as mild iodine deficiency post-fortification in contrast to iodine sufficiency using median urinary iodine concentration as a population marker. Re-evaluation of the current TSH criteria to define iodine status in populations is warranted in this context.
Keywords: Thyroid-stimulating hormone; newborns; iodine deficiency; iodine fortification; population iodine status
Rights: © The Authors 2019
DOI: 10.1017/S1368980019001915
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