Insulin Autoimmune Syndrome in a Patient with Hashimoto's Thyroiditis / 대한갑상선학회지

ABSTRACT

Insulin autoimmune syndrome (IAS) is characterized by fasting hypoglycemia, endogenous hyperinsulinemia, and the presence of autoantibodies to insulin or insulin receptor in patients that have never been exposed to exogenous insulin. This syndrome is occasionally accompanied by several autoimmune disorders. There is no reported case of concurrent IAS with Hashimoto's thyroiditis. A 52-year-old female was diagnosed with Hashimoto's thyroiditis and was treated with 25 microg/d levothyroxine for 3 years. Recently, she experienced recurrent fasting hypoglycemic symptoms that disappeared rapidly with a carbohydrate-rich diet, although she had no history of diabetes or insulin use. Blood analysis showed hypoglycemia and elevated serum levels of insulin and C-peptide. Imaging studies did not reveal a mass lesion in the pancreas, and selective calcium-stimulated venous sampling also gave a negative result. However, anti-insulin antibody titer was high and assay for anti-insulin receptor antibody was positive. Here, we report a case of IAS concomitant with Hashimoto's thyroiditis.