Insulin Autoimmune Syndrome (Hirata's Disease) Caused by Methimazole in a 47-Year-Old Man.

Insulin autoimmune syndrome (IAS), or Hirata's disease, is a rare disease characterized by episodes of hypoglycemia with elevated levels of insulin secondary to high concentrations of insulin autoantibodies. The use of methimazole is a risk factor for the development of Hirata's disease. We report a case of a 47-year-old man being treated for thyroid storm initially with methimazole and other agents.