Serum thyroglobulin levels in hypofunctioning nodules before and after surgery.

Serum thyroglobulin (Tg) level was determined in 34 biologically euthyroid patients having benign hypofunctioning nodule, before and after surgery. Based on the results of thyroid scanning with radioiodine, 2 groups of patients were considered. Group 1 (n = 18) had solitary hypofunctioning nodule with an otherwise normal thyroid gland and group 2 (n = 16) had hypofunctioning nodule inside an enlarged and/or heterogeneous thyroid. Results were compared to a group of 30 control subjects. Mean Tg level was significantly elevated in both groups 1 and 2 before surgery. No significant difference was found between group 1 and group 2. After surgical removal of the hypofunctioning nodule (follicular adenoma), mean Tg level was normalized in group 1 and decreased but still remained elevated in group 2. It is concluded that the observed elevated serum Tg level is due to the presence of hypofunctioning nodule and/or heterogeneous thyroid tissue. Thus, Tg determination may be useful in the follow-up of operated hypofunctioning nodules in order to detect abnormality in the remaining thyroid tissue.