Human Calcitonin Radioimmunoassay in Normal and Pathological Conditions*

A radioimmunoassay for human calcitonin (CT) has been established and each of its steps has been analysed in detail. The assay is extremely sensitive allowing the detection of 10 pg/ml in serum incubated in presence of human serum proteins using a standard curve. The specificity of our system has been established on the basis of immunological and biological criteria. The method is sufficiently sensitive to allow the study of mechanisms of secretion of CT in normal man and in certain disease states. The secretion of CT is increased by induced hypercalcaemia and decreased by hypocalcaemia following EDTA. We have found elevated levels in patients with primary or secondary hyperparathyroidism or pernicious anaemia and in one patient with Zollinger‐Ellison syndrome. The correlations between CT, serum calcium, phosphate, urea, magnesium, parathyroid hormone and gastrin were investigated.