Natural history of familial medullary thyroid carcinoma: effect of a program for early diagnosis.

To detect familial medullary thyroid carcinoma in a premetastatic stage, we administered tests provocative of calcitonin secretion (infusion of calcium or pentagastrin or both) each year for seven years to members of a pedigree now numbering 107. Since 1970, 21 patients converted from normal to abnormal secretory responses (two separate tests in which calcitonin levels exceeded 0.58 ng per milliliter). Twenty of 21 glands removed showed C-cell hyperplasia, and eight of the 20 also showed foci of carcinoma. As compared to the 12 patients with tumors detected during the first year of screening, all of whom had bilateral carcinoma (seven of 12 with local metastases), later carcinomas were smaller (mean diameter of 0.2 vs. 0.8 cm), were unilateral (in all but two cases) and occurred in younger patients (mean age of 14.9 vs. 36.4 years), and none had detectable metastases.