Serum thyroglobulin as a biomarker of iodine deficiency in adult populations

Summary Objective To clarify which factors may influence the serum Tg level in an adult population and how this may affect Tg as a biomarker of iodine deficiency (ID). Design and methods Two identical cross‐sectional studies were performed before (C1a: 1997–98, n = 4649) and after (C2: 2004–05, n = ...

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Published in:Clinical endocrinology (Oxford) 2016-09, Vol.85 (3), p.475-482
Main Authors: Krejbjerg, Anne, Bjergved, Lena, Bülow Pedersen, Inge, Carlé, Allan, Knudsen, Nils, Perrild, Hans, Ovesen, Lars, Banke Rasmussen, Lone, Laurberg, Peter
Format: Article
Language:English
Subjects:
Adolescent
Adult
Aged
Biomarkers - blood
Cross-Sectional Studies
Dietary Supplements
Female
Follow-Up Studies
Humans
Iodine - administration & dosage
Iodine - deficiency
Iodine - standards
Iodine - urine
Male
Middle Aged
Netherlands - epidemiology
Thyroglobulin - blood
Thyrotropin - blood
Young Adult
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Summary:Summary Objective To clarify which factors may influence the serum Tg level in an adult population and how this may affect Tg as a biomarker of iodine deficiency (ID). Design and methods Two identical cross‐sectional studies were performed before (C1a: 1997–98, n = 4649) and after (C2: 2004–05, n = 3570) the Danish mandatory iodine fortification (IF) of salt (2000). Additionally, a follow‐up study of C1a was performed after IF (C1b: 2008–10, n = 2465). The studies took place in two regions with mild (Copenhagen) and moderate (Aalborg) ID before IF. Serum Tg was measured by immunoradiometric method and investigated as outcome variable in multivariate models. Results Multiple factors were associated with serum Tg. Some were directly related to iodine intake (cohort, urinary iodine concentration (UIC) level and region), and some were likely mediators of iodine intake effects on Tg (thyroid nodularity, thyroid size and autonomy with low TSH). Others were caused by Tg assay interference (Tg‐Ab positivity), aggravation of ID (childbirths and smoking) or TSH stimulation of the thyroid. Estimated 24‐h urinary iodine excretion was a more sensitive predictor of Tg than UIC. Iodine supplement users had low median Tg values compared with nonusers both before and after IF. Conclusions Multiple factors should be taken into consideration when evaluating Tg as a marker of ID in adult populations, and the Tg results may depend on the assay used. Still, Tg is a sensitive marker of ID. We suggest including a reference population with known sufficient iodine intake when Tg is used to evaluate ID.
ISSN:0300-0664
1365-2265
DOI:10.1111/cen.13037