Somatostatinoma Syndrome: Biochemical, Morphologic and Clinical Features

Diabetes mellitus, steatorrhea, cholelithiasis and a tumor distorting the duodenum prompted a work-up for somatostatinoma in a 52-year-old man. The responses of pancreatic B-cells but not of A-cells to nutrient stimuli were inhibited, and growth-hormone release was suppressed, suggesting somatostatin resistance in some target tissues. Plasma somatostatin-like immunoreactivity ranged from 9000 to 13,000 pg per milliliter (normal: 88±8, mean ± S.E.M.) and was distributed in four molecular forms, including free somatostatin. The primary tumor contained 5 μg of somatostatin-like immunoreactivity per milligram of wet tissue, distributed in three of the molecular forms noted in plasma. Plasma calcitonin was also elevated (4650 pg per milliliter; normal: <120). Immunocytochemical studies showed that cells of the primary tumor contained somatostatin and calcitonin but no other peptide hormones. Only somatostatin was present in the metastases. Somatostatin was localized electron microscopically in all secretory granules, irrespective of size and shape, whereas calcitonin was present only within a single subpopulation of small granules in the same cells. (N Engl J Med 301:285–292, 1979) IN 1977, two cases of pancreatic somatostatinoma were reported by Larsson¹ and Ganda² and their colleagues. On the basis of these reports and the known pharmacologic effects of somatostatin, a tentative description of the somatostatinoma syndrome was proposed.³ However, in the first two patients the tumor was found incidentally at the time of cholecystectomy, and a complete preoperative work-up had not been performed. Three other patients with malignant islet-cell tumors that contained somatostatin have been described in brief communications.^{4 5 6} In addition to somatostatin, one of these tumors contained ACTH,⁴ and one calcitonin.⁶ In this case report, the diagnosis of somatostatinoma.