Insulin autoimmune syndrome (IAS)

Abstract

We report the case of a 54 year old man with a symptomatic hypoglycemia (tremor; sweating) since six weeks. Habitus and medical history conformed the criteria for metabolic syndrome (arterial hypertension, obesity, BMI 40.1 kg/m2, hyperlipidemia). Neither diabetes nor neuroendocrine tumors in the family history. The laboratory analysis revealed after an abrosia period of 72 hours the lowest plasma glucose at 68 mg/dl. The insulin secretion showed a decreasing tendency starting at 891 mU/l and falling down to 391 mU/l within a 72 hours fasting period. Glucose tolerance test detected extreme high insulin levels over 1000 mg/dl before glucose intake and throughout the whole testing. 180 Minutes after the glucose intake broke the patient into a sweat and reported nausea and indisposition. We detected a hypoglycemia (22 mg/dl). Non corresponding proinsulin and C-peptide levels were measured. Anti-insulin antibodies showed a non mensurable high titer (> 100 U/ml). Endoscopic ultrasound substantiated a small lesion (6 mm) without any reasonable suspicion of being an insulinoma. Insulin autoimmune syndrome (IAS) is an extremely rare cause of hypoglycemia, particularly in non-Asian populations. In patients presenting with hypoglycemia and excessively high insulin levels, consideration should be given to autoimmune hypoglycemia due to anti-insulin antibodies as a cause.