Serum Tg--A Sensitive Marker of Thyroid Abnormalities and Iodine Deficiency in Epidemiological Studies

Abstract

Serum Tg is widely used in the control of thyroid cancer but also in the diagnosis of certain other thyroid diseases. Serum Tg may be useful in the characterization of the iodine status of a population, but little is known about determinants of serum Tg levels. We examined a random selection of 4,649 subjects from 2 regions in Denmark with different iodine status. Thyroid volume and structure were determined with ultrasonography, and thyroid function tests and Tg analysis were performed. The factor with the closest association with serum Tg levels was thyroid volume at ultrasonography (P < 0.001). Also thyroid nodularity (P < 0.001) and iodine excretion (P < 0.001) had close associations to serum Tg, even after adjusting for the influence of the other parameters. Thyroid dysfunction had a less pronounced but still highly significant association with serum Tg (P < 0.001), but no relation was found to serum TSH in general. The association with age seemed to rely on differences in the prevalence of thyroid abnormalities, and men had lower Tg levels than women of the same age. There was a marked difference in serum Tg between the two regions with slightly different iodine excretion also after adjusting for the other factors. In conclusion, serum Tg reflects thyroid abnormalities and thyroid function and is a sensitive marker of iodine deficiency in a population.

Thyroid hyperactivity with high thyroglobulin in serum despite sufficient iodine intake in chronic cold adaptation in an Arctic Inuit hunter population

“…The intake of the traditional Inuit food items decreases with increasing Westernisation and explains the rather marked differences in iodine excretion between the participant groups (32). In populations, serum TG increases with increasing iodine deficiency (16,21,22). We would thus expect lower TG among hunters and settlement dwellers.…”

“…Reference intervals were 0.3-4.5 mU/l for TSH, 9.8-20.4 pmol/l for fT 4 and 3.6-6.9 pmol/l for fT 3 . The TG assay had a working range from 1 to 500 mg/l, and median values of around 9, 10 and 15 mg/l are seen in iodine-replete, mild and moderately deficient Caucasian Danes respectively (21,22). TG antibodies (TGAb) were measured using Dynotest RIA (BRAH-MS Diagnostica) with a functional sensitivity of 20 kU/l for TGAb (35).…”

“…However, serum TG is raised in patients with goitre (13,15), in pregnancy (16,17) and hyperthyroidism (18,19,20) where thyroid hormone production is increased. Moreover, elevated serum TG is a sign of iodine deficiency in population studies (21,22). Thus, serum TG is a marker of overall thyroid gland activity.…”

Thyroglobulin in smoking mothers and their newborns at delivery suggests autoregulation of placental iodide transport overcoming thiocyanate inhibition

“…To evaluate autoregulation of placental iodide transport, we used Tg in maternal and cord serum at delivery as markers of iodine deficiency in the mother and the fetus respectively (27,28,29).…”

“…We studied a unique cohort of iodine-deficient pregnant women with a high frequency of smoking and their newborns. Tg in maternal serum at delivery and in cord serum was used as a marker of iodine deficiency (27,28,29), and we examined the impact of thiocyanate from maternal smoking on the degree of iodine deficiency in the mother and in the fetus by comparing serum Tg in smoking and nonsmoking mothers and cord serum Tg.…”