Abstract
BACKGROUND: Hirata syndrome, or Insulin Autoimmune Syndrome (IAS), is a rare condition characterized by hyperinsulinemic hypoglycemia due to autoantibodies targeting endogenous insulin. Its rarity and unique presentation make diagnosis and management challenging. OBJECTIVE: To analyze the clinical presentation, diagnostic methods, and management of IAS based on a single-center experience. METHODOLOGY: This was a case series, conducted at a tertiary care center in northeast India, involving six cases diagnosed between January 2022 and April 2024. Clinical histories, including drug use and comorbidities, were reviewed. Laboratory analyses during hypoglycemic episodes assessed insulin, C-peptide, β-hydroxybutyrate, and cortisol levels. Extended OGTT and 72-hour fasting tests were used when spontaneous hypoglycemia was absent. Insulin autoantibodies (IAA) confirmed the diagnosis. RESULTS: Six IAS cases were identified, with most linked to α-lipoic acid in multivitamins and one to methimazole. Patients experienced recurrent postprandial hypoglycemia. Elevated insulin, C-peptide, and IAA levels confirmed the diagnosis. Management included discontinuation of causative drugs, dietary changes with frequent complex carbohydrate meals, and pharmacotherapy (acarbose or prednisolone). Follow-up showed resolution of hypoglycemia and normalization of IAA levels in all patients. CONCLUSION: IAS should be considered in patients with hypoglycemia and a history of sulfhydryl-containing medications. Early diagnosis using IAA measurement and appropriate management, including drug discontinuation, dietary adjustments, and pharmacotherapy, is essential. Further research is needed to refine treatment strategies and understand the pathogenesis of this rare syndrome.