Serum thyroglobulin before and after iodization of salt: An 11-year DanThyr follow-up study

Anne Krejbjerg Motavaf, Lena Bjergved, Inge Bülow Pedersen, Allan Carle, Nils Knudsen, Hans Perrild, Lars Ovesen, Lone Banke Rasmussen, Peter Laurberg

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5 Citations (Scopus)


OBJECTIVE: Our objective was to investigate individual serum thyroglobulin (Tg) changes in relation to iodine fortification (IF) and to clarify possible predictors of these changes.

DESIGN: We performed a longitudinal population-based study (DanThyr) in two regions with different iodine intake at baseline: Aalborg (moderate iodine deficiency (ID)) and Copenhagen (mild ID). Participants were examined at baseline (1997) before the mandatory IF of salt (2000) and again at follow-up (2008) after IF.

METHODS: We examined 2,465 adults and a total of 1,417 participants with no previous thyroid disease and without Tg-autoantibodies were included in the analyses. Serum Tg was measured by immunoradiometric method. We registered participants with a daily intake of iodine from supplements in addition to IF.

RESULTS: Overall, the follow-up period saw no change in median Tg in Copenhagen (9.1/9.1μg/l, p=0.67) while Tg decreased significantly in Aalborg (11.4/9.0μg/l, p<0.001). Regional differences were evident before IF (Copenhagen/Aalborg, 9.1/11.4μg/l, p<0.001), whereas no differences existed after IF (9.1/9.0μg/l, p=1.00). Living in Aalborg (p<0.001) and not using iodine supplements at baseline (p=0.001) predicted a decrease in Tg whereas baseline thyroid enlargement (p=0.02) and multinodularity (p=0.01) were associated with an individual increase in Tg during follow-up.

CONCLUSIONS: After IF we observed a decrease in median Tg in Aalborg and the previously observed regional differences between Aalborg and Copenhagen had levelled out. Likewise, living in Aalborg was a strong predictor of an individual decrease in serum Tg. Thus, even small differences in iodine intake at baseline were very important for the individual response to IF.

Original languageEnglish
JournalEuropean Journal of Endocrinology
Issue number5
Pages (from-to)573-581
Number of pages9
Publication statusPublished - 2015


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