Serum calcitonin response to induced hypercalcemia.

The rise in serum calcitonin (delta-CT240 min) has been measured during hypercalcemia induced by i.v. infusion of calcium gluconate. This calcium infusion test was used in a prospective screening for medullary carcinoma of the thyroid (MCT) in 4 families with Sipple's syndrome as well as in 3 sporadic cases of MCT. In 16 normal controls delta-CT240 was minus 0.2-+ 0.5 ng/ml (mean plus or minus 2 S.D.). Delta-CT240 was normal in 2 patients with chronic hypocalcemia. In all 14 MCT patients delta-CT240 was markedly higher (min-max 2.2-630 ng/ml), i.e. no false negatives were found. However, in these cases, the diagnosis was already evident from basal serum calcitonin (S-CT), which up to now has been our most sensitive diagnostic technique for MCT. 19 first-degree relatives of patients with Sipple's syndrome presented no signs of MCT. In 14 of these delta-CT240 was normal ("healthy relatives"), but in 5 it was slightly elevated, intermediate between the controls and the MCT patients. These 5 borderline cases were more sharply delineated from normal by delta-CT240 than by S-CT. Thus our calcium infusion test seems to be the most sensitive method for early diagnosis of occult MCT. We recommend the calcium infusion test for: (a) screening for MCT in all Sipple relatives with normal or only slightly elevated basal S-CT, (b) postoperative control in both sporadic and hereditary MCT, (c) investigation of supposed non-MCT tumours with calcitonin production.