Medullary Carcinoma of the Thyroid, Pancreatic Nesidioblastosis and Microadenosis, and Pancreatic Polypeptide Hypersecretion: A New Association and Clinical and Hormonal Responses to Long-Acting Somatostatin Analog SMS 201-995*

We describe a 63-yr-old man with disseminated medullary carcinoma of the thyroid and pancreatic nesidioblastosis and microadenosis with pancreatic polypeptide (PP) hypersecretion. His major symptoms were watery diarrhea, flushing, and abdominal bloating; these and the elevated plasma PP levels did not change after resection of the distal two thirds of the pancreas, which contained a 2-cm mass of nesidioblastotic tissue. Postoperatively, a long-acting somatostatin analog, SMS 201-995 (100 micrograms/day), normalized PP secretion acutely and chronically (7 months) and ameliorated his symptoms. The analog had no side-effects and did not alter glucose tolerance, calcitonin hypersecretion, or growth of the medullary carcinoma, but it did inhibit GH secretion. After withdrawal from therapy for 1 month, PP hypersecretion and all symptoms except diarrhea recurred. The coexistence of medullary carcinoma of the thyroid and PP cell nesidioblastosis represents a new variant of the overlap syndromes between multiple endocrine neoplasia types I and II. Patients with medullary carcinoma and unexplained watery diarrhea should have fasting gastroenteropancreatic hormone assays done to screen for a potential gastrointestinal or pancreatic origin for the diarrhea.