Spontaneous hypoglycaemia in a patient with Graves' disease

A 23-year-old man, on treatment for Graves' disease, presented to the emergency department, with 2 separate episodes of loss of consciousness. During the first episode, the initial serum glucose was 19 mg/mL, and 44 mg/dL during the second episode. The patient was non-diabetic, and had elevated blood insulin, C peptide and insulin antibody levels. His abdominal radiographic findings were normal. He was diagnosed with Hirata disease, and put on propylthiouracil as a replacement for carbimazole. Hypoglycaemia was managed with dextrose infusions and frequent meals. The patient's condition improved and he had no further episodes of hypoglycaemia during the follow-up period.