Malignant somatostatinoma presenting with diabetic ketoacidosis and inhibitory syndrome: pathophysiologic considerations.

Objective: To describe a patient with diabetic ketoacidosis secondary to a malignant somatostatinoma.

Methods: We present the clinical, laboratory, radiologic, and pathologic findings of a patient with diabetic ketoacidosis secondary to a malignant somatostatinoma. We also review the potential effects of somatostatin on glucose homeostasis and discuss the underlying pathophysiologic mechanisms.

Results: A 30-year-old woman presented with diabetic ketoacidosis and had a malignant somatostatinoma with hepatic, bone, and lymph node metastasis. She exhibited features of somatostatinoma "inhibitory syndrome" characterized by mild nonketotic hyperglycemia, hypochlorhydria, cholelithiasis, steatorrhea, anemia, and weight loss. In these tumors, the absence of ketoacidosis is thought to arise from the somatostatin-induced simultaneous suppression of the secretion of insulin and glucagon. The patient's primary tumor could not be located.

Conclusions: Diabetic ketoacidosis may occur in somatostatinomas. The secretion of larger molecular weight forms of somatostatin from the tumor may contribute to the ketogenesis.