Objective       To investigate the etiology

manifestations

diagnosis and treatment of insulin autoimmune syndrome (IAS).      Methods        One adult male patient

suffered from frequent hypoglycemia was admitted in our department on March 4

2012. He was finally diagnosed as IAS. The clinical features of the case was analyzed in combination with literature review.       Results        After taking methimazole for a month for the treatment of Graves’ disease

the patients manifested clinical symptoms of Whipple’s triad. The results of 75 g OGTT test showed that serum glucose was increased

both fasting and postprandial serum insulin were increased

and the postprandial serum insulin level was higher than 1 000 mU/L. The result of Insulin autoantibody (IAA) was positive. After methimazole was stopped

prednisone 30 mg/d was used

with the dosage gradually reduced. The symptoms of hypoglycemia diminished

with the recovery of plasma glucose and insulin levels and negative IAA.       Conclusion        IAS is a rare disease which may result in repeated episode of hypoglycemia. It may be caused by methimazole. To assay serum insulin and insulin autoantibody are greatly helpful to distinguish IAS.