Hypoglycaemia and fits in a thyrotoxic man.

We report prolonged severe hypoglycaemia with raised serum insulin levels in a Sri Lankan man with recently diagnosed Graves disease being treated with carbimazole. We diagnosed insulin autoimmune syndrome on the basis of raised anti-insulin antibody levels, and this diagnosis was supported by the subsequent course of the illness. The patient recovered completely after carbimazole was replaced with propylthiouracil and he was treated with dextrose infusions, frequent high-carbohydrate meals and a course of prednisolone.