Thyroglobulin as a Biomarker of Iodine Deficiency: A Review

Abstract

Background: Thyroglobulin, produced exclusively by the thyroid gland, has been proposed to be a more sensitive biomarker of iodine status than thyrotropin or the thyroid hormones triiodothyronine and thyroxine. However, evidence on the usefulness of thyroglobulin (Tg) to assess iodine status has not been extensively reviewed, particularly in pregnant women and adults. Summary: An electronic literature search was conducted using the Cochrane CENTRAL, Web of Science, PubMed, and Medline to locate relevant studies on Tg as a biomarker of iodine status. Since urinary iodine concentration (UIC) is the recommended method to assess iodine status in populations, only studies that clearly reported both Tg and UIC were included. For the purpose of this review, a median Tg <13 lg/L and a median UIC ‡100 lg/L (UIC ‡150 lg/L for pregnant women) were used to indicate adequate iodine status. We excluded studies conducted in subjects with either known thyroid disease or those with thyroglobulin antibodies. The search strategy and selection criteria yielded 34 articles of which nine were intervention studies. The majority of studies (six of eight) reported that iodine-deficient pregnant women had a median Tg ‡13 lg/L. However, large observational studies of pregnant women, including women with adequate and inadequate iodine status, as well as well-designed intervention trials that include both Tg and UIC, are needed. In adults, the results were equivocal because iodine-deficient adults were reported to have median Tg values of either <13 or ‡13 lg/L. Only studies in school-aged children showed that iodine-sufficient children typically had a median Tg <13 lg/L. Some of the inconsistent results may be partially explained by the use of different methodological assays and failure to assess assay accuracy using a certified reference material. Conclusions: These data suggest that Tg does hold promise as a biomarker of iodine deficiency. However, it is associated with limitations. A median Tg cutoff of 13 lg/L warrants further investigation, particularly in adults or pregnant women, as there is a lack of both observational and intervention studies in these groups.

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

“…In accordance with our results, these studies found an inverse relation between serum Tg and iodine intake even in regions with small differences in iodine intake. Several studies concluded that even if serum Tg concentration is a non-specific marker of thyroid disease in the individual and even if Tg-Ab may influence measurements, Tg is a good marker of iodine intake in a population and that it is a useful tool in monitoring the iodine status (14,18,21,28,29). However, only one previous longitudinal population-based cohort study has investigated serum Tg in relation to iodine intake.…”

Factors associated with serum thyroglobulin in a Ukrainian cohort exposed to iodine-131 from the accident at the Chernobyl Nuclear Plant

“…In contrast, high thyroid volume is an indicator of longterm iodine deficiency that may persist for years after iodine repletion (Zimmermann et al, 2006). Serum thyroglobulin (Tg), a thyroid protein that facilitates the uptake and storage of iodine in the thyroid gland, has been proposed as a biomarker of intermediate-term population iodine nutrition status (weeks to months) based on associations with UIC (Knudsen et al, 2001;Krejbjerg et al, 2016;Swanson et al, 2012;Vejbjerg et al, 2009), and sensitivity to changes in iodine status following iodine supplementation (Gordon et al, 2009;Ma and Skeaff, 2014;Skeaff and Lonsdale-Cooper, 2013;Vejbjerg et al, 2009;Zimmermann et al, 2006).…”

Evaluating of significance of thyroglobulin (Tg) level in blood as a biomarker of iodine deficiency disorders severity in Uzbekistan

“…Тиреоглобулин предлагается как перспективный биомаркер для оценки дефицита йода в регионе [6]. Большинством исследований рекомендуется исполь-зование ТГ в качестве биомаркера йодного статуса у школьников с использованием порога <13 мкг/л [7].…”

“…Имеются многочисленные исследования роли ТГ в качестве биомаркера дефицита йода [6]. Так как у детей практически не встречаются АтТГ, его кон-центрация показывает истинную картину йододе-фицита в регионе.…”

“…В последнее время привлекает внима-ние использование тиреоглобулина (ТГ) крови как многообещающего биомаркера йододефицитных со-стояний, однако остается открытым вопрос о поро-говых значениях ТГ в крови при оценке йододефи-цита и его тяжести в регионе [6,7].…”