Brief report: Hypoglycemia due to a monoclonal insulin-binding antibody in multiple myeloma

RECURRENT, severe hypoglycemia in the absence of exogenous insulin administration is uncommon. Reported causes include islet-cell adenomas or carcinomas, surreptitious use of insulin or sulfonylurea medications, stimulatory insulin-receptor antibodies, and various non—islet-cell tumors.^{1 2 3 4} The autoimmune insulin syndrome is another rare cause of hypoglycemia.^5,6 This syndrome is characterized by late postprandial hypoglycemia and the presence of polyclonal insulin-binding autoantibodies, typically occurring in a patient with other autoimmune disease. Excess insulin is released in response to a meal because of binding to antibodies. Later, as the bound insulin is released, it causes hypoglycemia. We describe a patient who presented with a hypoglycemic.