Hypoglycemia: A tale of three causes

A 52-year old male with a history of insulin treated T2DM complicated by end stage renal disease (ESRD requiring hemodialysis and prior gastric bypass surgery presented with severe recurrent hypoglycemia with seizures. A 72 hour fast demonstrated hyperinsulinemic hypoglycemia. Abdominal CT scan and endoscopic ultrasound guided biopsy demonstrated a pancreatic neuroendocrine tumor (pNET). Symptoms persisted despite pNET resection and on further testing he was found to have a highly specific insulin antibody resulting in insulin autoimmune syndrome. He responded well to prednisone therapy with resolution of hypoglycemia and decline in the insulin autoantibody titers. This study concludes that autoimmune forms of hypoglycemia are uncommon and interpretation of tests can be challenging. However, insulin autoimmune syndrome (IAS) should be considered in a patient with both fasting and postprandial hypoglycemia in setting of very high insulin levels with associated anti-insulin antibodies and elevated insulin to C peptide molar ratio.