The carcinoma of thyroid associated with hypocalcemia is -

In Medullary carcinoma serum, calcitonin is increased, whose function is to lower serum calcium levels. So hypocalcemia may be found associated with MTC. "The calcitonin excess (in MTC) is not associated with hypocalcemia." "Notably hypocalcemia is not a prominent feature despite the presence of raised calcitonin levels." Also, know - MTC secrets not only calcitonin but also some other peptides such as : CEA CGRP (Calcitonin gene-related peptide) histaminase prostaglandin E2 and F2a Serotonin ACTH (may lead to Cushing syndrome in about 2 to 4% of pts.) Ref : Schwaz Sx 9/e p1367