Among the 12 sporadic MTC patients and in the earlier half-period of the surveillance, ten patients showed a gradual increase in their serum calcitonin levels with the median Ct-DT of 8.0 years, and the other two patients showed a gradual decrease in these levels with the median Ct-DT of −22.9 years. Here, CALCA is linked to medullary thyroid gland carcinoma.