Screening for medullary carcinoma of the thyroid in families with Sipple's syndrome: evaluation of new stimulation tests.

In search of new practical diagnostic methods for the early diagnosis of hereditary medullary carcinoma of the thyroid (MCT) calcitonin release has been studied following induction by pentagastrin, cholecystokinin-pancreozymin (the C-terminal octapeptide, C8-CCK, and the native swine extract), and ethanol in eighteen cases of MCT (all but one clinically occult), three 'borderline cases', seven first degree relatives of patients with hereditary MCT and thirty-five healthy controls. Pentagastrin, subcutaneous (s.c.) or intravenous (i.v.), induced a pronounced and rapid increase of serum calcitonin within 2-5 min. The elevation was roughly proportional to the tumour mass as estimated at operation. Seventeen out of eighteen MCT patients responded to s.c. pentagastrin with a significant increase in serum calcitonin and the response correlated well with that induced by calcium infusion test. Only two blood samples, at times 0 and 5 min, were necessary for diagnosis. In the MCT patients, i.v. pentagastrin produced more pronounced elevations of serum calcitonin than did s.c. pentagastrin, whereas no increase was seen in the control group. The subjective discomfort caused by i.v. pentagastrin was somewhat more intense but lasted shorter than that induced by s.c. administration. No serious complications were seen. All of nine MCT patients responded to C8-CCK with increments in serum calcitonin exceeding those of the control group and both of two responded similarly to the native cholecystokinin-pancreozymin extract. Generally the serum calcitonin response was lower and more variable after C8-CCK than after s.c. or i.v. pentagastrin, and the subjective discomfort was also more pronounced with abdominal cramps during the injection. Ethanol in the dose used was the least effective stimulator for serum calcitonin release. Clinically suspected MCT carriers with palpable tumours can be diagnosed by determination of the basal, i.e. non-stimulated serum calcitonin levels. Other possible Sipple genome carriers, who are at the time clinically healthy with normal basal serum calcitonin, should be subjected to a s.c. or i.v. pentagastrin stimulation test at each examination. These tests are much simpler to perform than a calcium infusion, test, but seem to have about the same sensitivity.