[Measurement of plasma calcitonin gene-related peptide (CGRP) level in patients with thyroid disease].

To elucidate the pathophysiology of CGRP in patients with medullary thyroid carcinoma (MTC), we measured the plasma CGRP level in patients with thyroid disease employing RIA. The plasma CGRP level (normal level 12.7 pg/ml) was elevated in all five preoperative patients with MTC, ranging from 128 pg/ml to 2010 pg/ml, and in ten of 17 postoperative patients who indicated possible recurrence. On the other hand, CGRP levels showed low frequencies of elevation in 96 patients with other thyroid tumors (anaplastic carcinoma, malignant lymphoma, follicular adenoma and adenomatous goiter), subacute thyroiditis, chronic thyroiditis and Graves' disease. Provocation test (calcium gluconate plus pentagastrin) in 12 MTC patients showed that, although the CGRP level fluctuated in parallel with the calcitonin level, the elevation rate (maximum level after administration/basal level) of CGRP was lower than that of calcitonin. Particularly, the rate of elevation of CGRP in three virulent and advanced patients with poorly differentiated MTC was below 2.0, while that in nine patients with well-differentiated MTC ranged from 2.8 to 23.3. These results suggest that CGRP may be a humoral marker of MTC and is possibly related to the degree of malignancy.