Abstract
A 74-year-old man, with no history of insulin or antithyroid drug use experienced abrupt-onset hypoglycemia at the age of 48 and was diagnosed with insulin autoimmune syndrome. Despite having taken voglibose since the age of 61 in addition to carbohydrate intake, he experienced hypoglycemic symptoms at midnight, early morning, and before each meal every few days. At the age of 72, he was administered 30 mg/day of prednisolone (PSL), which was tapered to 10 mg/day as hypoglycemia frequency decreased. After one year of continuous PSL administration, he experienced hypoglycemic symptoms only in early morning about twice a month, his fasting immunoreactive insulin (IRI) decreased from 116.0 μU/ml to 77.7 μU/ml, and his insulin autoantibody binding capacity decreased from 75.4% to 69.0%. Scatchard analysis showed a monoclonal antibody indicating low affinity and high binding capacity for his insulin autoantibodies. Due to the PSL dose, no significant effect was seen on insulin affinity, although the number of autoantibody binding sites decreased. For HLA, no DR4 was found but DRB1*0901 was observed.
