Endocrine Abstracts

Somatostatinomas are rare neuroendocrine tumors diagnosed at a rather young age (mean age at diagnosis from 40 to 60 years). Non-auto-immune diabetes may associate with somatostatinoma as a result of abnormal somatostatin secretion, which inhibits insulin release. Steatorrhea and cholelithiasis are two other classical symptoms of these tumors. Here we report a case of somatostatinoma discovered while exploring a recently diagnosed diabetes, whose clinical and biological features were compatible with type 1 diabetes. A 43 year-old lean male, with no significant (personal or family) medical history presented with canonical symptoms of insulin deficiency and diarrhea since 2 months. HbA1c was 8.1%. Anti-GAD antibodies were positive at 5.1 UI/mL (N<1). Insulin treatment alleviated all the symptoms but the persisting diarrhea. The abdominal CT scan revealed a Vater ampulla mass. Pathological examinations of endoscopic ultrasonography-guided biopsies showed a 2 cm well-differentiated G2 neuroendocrine tumor (Ki-67 was 3%). Elevated values of serum somatostatin, i.e. 88 pmol/L (N<50) were consistent with somatostatinoma. The tumor was labelled by 18F-DG PET imaging but not by Somatostatin receptor scintigraphy. Pancreaticoduodenectomy was performed and pathological examination of the resected tumor disclosed a pT3 N1 M1a, grade G2 neuroendocrine carcinoma. Insulin therapy was maintained after surgery but with reduced doses. Hence we report a misleading initial presentation of type-1 diabetes with positive anti-GAD antibodies, which was, in fact, due to the underlying presence of a somatostatinoma. Diarrhea was the only atypical symptoms, which prompted us to broaden our initial investigations. The origin of antibody production in that context is discussed.