On the one hand, the serum calcitonin level is considered to be the most sensitive and specific marker of MTC; on the other hand, it must be taken into consideration that not all MTCs produce calcitonin [9], and hypercalcitoninemia is known to be associated with chronic thyroiditis and C-cell hyperplasia besides MTC [8]. This evidence concerns the gene CALCA and Hashimoto thyroiditis.