Somatostatinoma: causes, symptoms, diagnosis, treatment

Somatostatinoma (sigma-cell tumor of the islets of Langerhans) was first described relatively recently - in 1977, so the idea of the symptom complex characterizing this disease has not yet been formed. Tumors, in most cases carcinomas, originate from somatostatin-producing D-cells. Metastasis occurs mainly to the liver. Some authors believe that there is no clear clinical syndrome of somatostatinoma at all due to the heterogeneity of symptoms. At present, slightly more than 20 patients with somatostatin-secreting tumors of the pancreas and duodenum have been described in the literature. Undoubtedly, surgeons have encountered these neoplasms before during operations for cholelithiasis, but only now has it become clear that this is not a random combination. Along with cholelithiasis, somatostatinoma is accompanied by diabetes mellitus, diarrhea or steatorrhea, hypochlorhydria, anemia, and weight loss.

Apparently, many manifestations are the result of the blocking effect of somatostatin on the enzymatic function of the pancreas and the secretion of other hormones of the islets of Langerhans, which is why this symptom complex is sometimes called the “inhibitory syndrome”.

Most of the somatostatins described by the nature of secretion turned out to be polyhormonal. It is likely that this is one of the reasons for the heterogeneity of the clinical manifestations of the disease.

The symptoms that occur with somatostatinoma reflect the known effects of somatostatin. Pathological glucose tolerance is associated with inhibition of insulin release, which is not compensated by a simultaneous decrease in glucagon secretion. The increased incidence of cholelithiasis is largely due to the reduced contractility of the gallbladder under the influence of excess somatostatin (patients have a large atonic gallbladder). Steatorrhea is explained as a result of insufficient exocrine pancreatic function and impaired intestinal absorption. Gastric hypochlorhydria is a consequence of the inhibitory effect of somatostatin on acid-forming parietal cells and also on the release of gastrin by the mucous membrane of the antrum.

The diagnosis of somatostatinoma is based on evidence of elevated plasma peptide levels. In doubtful cases, a provocative test with tolbutamide, which stimulates the release of somatostatin, should be performed.

As a rule, after surgery, repeated courses of cytostatic therapy with streptozotocin and 5-fluorouracil are required.

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