Somatostatinoma syndrome: does a clinical entity exist?

We report here 2 patients with somatostatin-secreting tumours and hypersomatostatinaemia. One subject, a 36 year old woman with diabetes, flushing, labile blood pressure and diarrhea, had elevated basal plasma levels of somatostatin-like immunoreactivity (SLIR) and calcitonin. Plasma SLIR increased further following tolbutamide administration. Plasma levels of prostaglandin E2 (PGE2) and pancreatic polypeptide (PP), normal in the basal state, showed exaggerated responses to pentagastrin and secretin, respectively. Immunocytochemistry of the tumour tissue revealed cells containing somatostatin-, calcitonin-, PGE2- and PP-like immunoreactivity. The other patient, a 52 year old male, had an SLIR-secreting tumour of the proximal duodenum and elevated basal and post-tolbutamide SLIR levels but no signs or symptoms suggestive of increased SLIR production. Tumour tissue revealed cells containing somatostatin- and calcitonin-like immunoreactivity. We conclude that patients with somatostatinomas do not always exhibit a predictable syndrome. Patients with these tumours may exhibit a range of clinical, biochemical and immunocytochemical features typical of endocrine tumours of mixed-cell origin, such that the dominant signs and symptoms associated with these neoplasms cannot readily be ascribed to overproduction of any single hormone.