CALCA and medullary thyroid gland carcinoma: Among the 14 hereditary MTC patients and in the earlier half-period of the study period, 13 patients showed a gradual increase in their serum calcitonin levels with the median Ct-DT of 7.2 years, and the other hereditary MTC patient showed a gradual decrease in the level with the Ct-DT of −7.6 years.