Methimazole-Induced Insulin Autoimmune Syndrome in a Korean Patient with Graves’ Disease Treated with Propylthiouracil: a Case Report and Literature Review

Insulin autoimmune syndrome (IAS) is rare. Herein, we report a case of methimazole-induced IAS successfully treated with propylthiouracil (PTU) and review related literature on Korean cases. A 48-year-old woman visited our hospital due to a hypoglycemic mental alteration. She had been taking medications for Graves’ disease including methimazole. Laboratory tests revealed a low serum glucose, high insulin, C-peptide, and anti-insulin antibody titer level. Abdominal computed tomography was negative for pancreatic tumors. Therefore, the patient was diagnosed with methimazole-induced IAS. After methimazole discontinuation and frequent diet, her hypoglycemic symptoms improved. She was treated with PTU for Graves’ disease. Previously, six cases of methimazole-induced IAS have been reported in Korea. Our case was the first in Korea to respond well to medical therapy (PTU) without other hypoglycemic treatments, such as steroids. PTU, which does not contain a sulfhydryl group, can be an option for the treatment of Graves’ disease and methimazole-induced IAS. KCI Citation Count: 0