Serum clearance rates of immunologically reactive thyroglobulin.

Serum thyroglobulin levels have been shown to have a role in detecting the presence of residual or recurrent disease in most patients who have undergone total thyroidectomy for thyroid cancer. It has not yet been determined at what interval postoperatively to begin following serum thyroglobulin levels in these patients to detect residual disease. Eight patients who underwent total thyroidectomy were studied to determine the clearance rate of this glycoproteint. Serial samples were obtained pre- and postoperatively and clearance rate curves were plotted for each patient. The average half-life of thyroglobulin was 14 hours, with a range of 8 to 22 hours. Based upon these results, it appears that 4 weeks is a sufficient period of time to allow for the clearance of the residual thyroglobulin in patients undergoing total thyroidectomy. Elevated levels of serum thyroglobulin after this time represent residual thyroid tissue or the presence of metastatic thyroid carcinoma.