Long-term observation of serum thyroglobulin after resection of nontoxic goiter and relation to ultrasonographically demonstrated relapse.

The object was to carry out a prospective study of the changes in serum thyroid hormones and thyroglobulin (Tg) following resection of nontoxic goiter and to investigate if there was a correlation to the pattern of relapse. A group of 39 consecutive patients, mainly with nodular, nontoxic goiter, were studied for 13 years following thyroidectomy. No thyroid hormone replacement therapy was given after surgery. The preoperative serum Tg level was elevated. After operation the mean serum Tg declined to a nadir of 43 micrograms/L at 1 year and subsequently increased to 90 micrograms/L at 10 years, with large individual differences. In 19 patients the serum Tg increased, in 1 it decreased, and in 19 no significant alteration was observed. Serum free thyroxine and triiodothyronine indices decreased following resection but achieved normal levels within 6 to 12 months. Serum thyroid-stimulating hormone increased after resection, with a peak level 1 month after surgery, but it returned to normal levels at 1 year and remained stable for the rest of the period. At 13 years after resection the thyroid volume was determined by ultrasonography in 30 of the patients. In 10 patients the thyroid volume was enlarged (>/= 28 ml). In this group a rise of average serum Tg after resection [DeltaTg(10-1 year)] of 133 micrograms/L was observed, compared to 26 micrograms/L in the 20 patients without sonographic relapse (volume < 28 ml). A positive correlation was demonstrated between serum DeltaTg(10-1 year) postsurgically and thyroid volume 13 years after surgery. However, an overlap was observed between the groups with and without ultrasonographic relapse, probably in part due to large differences in the Tg synthesis activity of different follicle cell clones. It is concluded that repeated serum Tg determinations may provide biochemical evidence of increased growth activity of thyroid remnants monitored after goiter resection.