Background: Insulin Autoimmune Syndrome, also known as Hirata disease, is a rare cause of spontaneous late postprandial hypoglycemia characterised by elevated insulin levels and insulin autoantibodies in the absence of prior exposure to exogenous insulin. Drug-induced Insulin Autoimmune Syndrome, particularly with alpha-lipoic acid, is emerging as a significant etiology.
Case Report: A middle aged patient presented with recurrent symptomatic late postprandial hypoglycaemia (plasma glucose: 62 mg/dL) relieved on taking fruit juice. Her oral hypoglycaemic medications were recently titrated in view of poor glycaemic control. There was no history of insulin or sulfonylurea use, organ failure, critical illness or skipping of meals. She was on vitamin supplements containing alpha lipoic acid in the last 2 months for diabetic peripheral neuropathy. Investigations showed no features of pituitary or adrenal insufficiency. For further evaluation of probable endogenous hyperinsulinism, she was subjected to an extended oral glucose tolerance test. Inappropriately elevated insulin and C-peptide levels were detected at a plasma glucose nadir of 55 mg/dL at 240 minutes. The molar ratio of insulin/C-peptide was more than 1 and insulin autoantibodies were grossly elevated. She was managed conservatively with dietary measures including low-carbohydrate frequent small meals and withdrawal of the vitamin supplement with alpha lipoic acid. There was a good response in 3 months.
Conclusion: Insulin Autoimmune Syndrome should be considered in patients with hyper insulinemic hypoglycaemia without insulin therapy, particularly when there is an exposure to alpha-lipoic acid. This awareness prevents unnecessary invasive interventions.
