Abstract:ObjectiveTo explore the diagnostic features of insulin autoimmune syndrome (IAS). MethodsA retrospective analysis was performed in one patient diagnosed as IAS in Department of Endocrinology of the Third Affiliated Hospital of Sun Yatsen University. Then the relevant literatures were reviewed. ResultsA 19-year female patient with Graves disease suffered from serious hypoglycemia after she had taken Methimazole for more than ten days. The insulin releasing index was 4.13 when her blood glucose was 2.73mmol/L. The ratios of fasting insulin/fasting C-peptide were within 8.20-15.12. The insulin autoantibody (IAA) was positive. The patient′s pancreas was normal in abdomen enhanced MR. ConclusionIAS should be considered when a patient with autoimmune disease suffers from hypoglycemia, especially while the patient is taking sulfhydryl-containing drugs.