Radioimmunoassay of Human Calcitonin in Serum and Tissue from Healthy Individuals and Patients with Medullary Carcinoma of the Thyroid Gland

A specific radioimmunological method for measurement of immunoreactive calcitonin (iCT) in human serum and tissue is described. Of healthy individuals of both sexes, 85% had measurable iCT in serum (mean, 0.23 ng/ ml). Of 29 patients who had received treatment for medullary carcinoma of the thyroid gland (MCT), 19 had increased serum iCT (0.60 ng/ml to 205 ng/ ml). Elevated serum iCT was also found preoperatively in 2 MCT patients. Eleven of the patients with abnormal elevations of serum iCT were alive 4 to 13 years after the operation. Concentration of iCT in extracts from MCT varied from 0.5 to 540 ng/ml wet weight. The diagnostic value of this method and its importance for pre- and post-operative evaluation of these patients are improved by the use of selective venous catheterization in basal state and during stimulation of CT secretion.