Endocrine Abstracts

Background: Insulin Autoimmune Syndrome is a rare condition characterized by hyperinsulinemic hypoglycemic episodes mediated by insulin autoantibodies (IAA). IAA form complexes with insulin leading to initial mild hyperglycemia and later hypoglycemia due to release of insulin. A comprehensive evaluation is necessary in all hyperinsulinemic hypoglycemia before a diagnosis of IAS is established. We present two cases of Hirata’s disease which presented with debilitating hypoglycemic episodes.

Case presentation: Two middle-aged women, presented with frequent episodes of sweating, palpitation and tremors for 3-4 weeks. One of them was hypertensive, diabetic on oral agents & the other one was prediabetic. Both had documented hypoglycemic episodes in fasting and postprandial state with blood glucose<45 mg/dl which relieved with food. They were subjected to a 72-hour fasting test. Our first case, who was earlier evaluated for fasting hypoglycemia and found to have fasting insulin of 89.8 μIU/ml in the presence of venous blood glucose of 41 mg/dl. After subjecting to 72-hour fasting, she developed hypoglycemia within 12 hours of fasting, with insulin levels being 12,912 μIU/ml. IAA was >100 mCU/ml (normal<5). Second case, on evaluation had postprandial insulin levels: >600 μIU/ml, fasting insulin: >300 μIU/ml, fasting C-peptide-8.17 ng/ml. She was subjected to OGTT as she did not develop hypoglycemia after 40 hours of fasting. At the end of the 4^th hour of OGTT, she developed hypoglycemia with RBS 40 mg/dl & corresponding insulin 117.7 μIU/ml. IAA was 90.4 mCU/ml. Imaging of the pancreas was normal in both cases. They became asymptomatic with a course of steroid.

Conclusion: It is important to note that Hirata’s disease can present as both fasting and postprandial hyperinsulinemic hypoglycemia. These cases highlight the importance of IAA and teach us that conventional imaging studies, fasting tests and OGTT alone may not be sufficient for a complete evaluation of hypoglycemia.