A Short Calcium Infusion in the Diagnosis of Medullary Thyroid Carcinoma

Abstract

A brief calcium infusion has been utilized as a provocative test for calcitonin secretion in patients with medullary thyroid carcinoma. One hundred and fifty mg calcium was infused over 5–10 min and plasma samples collected at intervals up to 1 hr for calcitonin measurements. Seven infusions in 4 patients with medullary tumor produced a significant increase of plasma calcitonin over basal concentrations. In one patient with normal (nondiagnostic) basal calcitonin, the calcium infusion produced a diagnostic increase in hormone concentration. The infusions were well tolerated and the plasma calcium increase was less than one milligram. Our results suggest that this short calcium infusion, with calcitonin measurements made before and 10–30 min after the beginning of infusion provides a reliable, convenient, and safe provocative procedure for calcitonin secretion in medullary thyroid carcinoma suspects.