Serum Tg - A sensitive marker of thyroid abnormalities and iodine deficiency in epidemiological studies

Serum Tg is widely used in the control of thyroid cancer but also in the di agnosis of certain other thyroid diseases. Serum Tg may be useful in the ch aracterization of the iodine status of a population, but little is known ab out determinants of serum Tg levels. We examined a random selection of 4,64 9 subjects from 2 regions in Denmark with different iodine status. Thyroid volume and structure were determined with ultrasonography, and thyroid func tion tests and Tg analysis were performed. The factor with the closest association with serum Tg levels was thyroid vo lume at ultrasonography (P < 0.001). Also thyroid nodularity (P < 0.001) an d iodine excretion (P <0.001) had close associations to serum Tg, even afte r adjusting for the influence of the other parameters. Thyroid dysfunction had a less pronounced but still highly significant association with serum T g (P < 0.001), but no relation was found to serum TSH in general. The assoc iation 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. Ther e 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.