Family study of serum carcinoembryonic antigen in inherited medullary carcinoma of the thyroid.

Serum carcinoembryonic antigen (CEA) and calcitonin were assayed in 8 patients with medullary carcinoma of the thyroid (MCT) and 14 unaffected family members, from 4 pedigrees of Sipple's syndrome and one pedigree with inherited MCT. Serum CEA ranged from 5.4 to 44.5 ng/ml in the patients, but less than 2.5 ng/ml in the unaffected. This is in contrast with retinoblastoma and cancer family syndrome, where not only the patients but also unaffected family members show high serum CEA, and cytoplasmic or selective maternal inheritance of serum CEA level is presumed. In inheritable MCT, serum CEA increases in association with the development of MCT, and serum CEA level per se is not inherited.