Calcitonin gene-related peptide in patients with endocrine tumors.

The plasma level of calcitonin gene-related peptide (CGRP) was measured by RIA in 41 patients with endocrine tumors [22 medullary thyroid carcinomas (MTC), seven parathyroid adenomas, four benign insulinomas, five carcinoids, and three pheochromocytomas]. Of the 22 patients with MTC, all five preoperative patients had elevated CGRP levels. The correlation between CGRP and calcitonin levels was significant (P less than .001) in 22 patients with MTC. Six of 19 patients with endocrine tumors other than MTC showed elevated CGRP levels. Immunohistochemical study showed that tumor tissues from all 22 cases of MTC and seven from other endocrine tumors contained immunoreactive CGRP. CGRP reactivity was found in only small numbers of tumor cells. Thus, although CGRP appeared to be a useful additional marker for MTC, the role of CGRP in the pathophysiology of endocrine tumors was not elucidated.