TG and medullary thyroid gland carcinoma: Other research concerning the changes in serum Ct and carcinoembryonic antigen (CEA) values over time in patients with MTC who had persistent disease postoperatively and studies of the serum thyroglobulin values in patients with papillary thyroid carcinoma (PTC) after a total thyroidectomy has demonstrated that these values changed exponentially and that the DTs of these tumor marker values were very strong prognostic factors, supporting the concept described by Collins et al. [1, 7].