Insulin is a hormone secreted by the pancreatic beta cells in response to an elevation in blood glucose, or sugar. When a large amount of glucose enters the blood stream, insulin promotes uptake of glucose by the liver, which converts the glucose into its storage form, glycogen. The presence of insulin antibodies in the blood stream indicates that the body is mounting an immune response either to external, injected insulin or to its own insulin. Insulin antibodies bind to insulin, preventing the insulin from interacting with its normal sites of action. Consequently, the blood and urine glucose levels rise, leading to the classic symptoms of Type 1 diabetes mellitus, such as increased thirst, frequent urination, and increased appetite.
Type 1 diabetes occurs when the body attacks its own insulin-making beta cells in the pancreas. Although Type 1 diabetes has been called juvenile diabetes due to its frequent occurrence in childhood, scientific testing for insulin antibodies has resulted in the discovery of an adult-onset form of Type 1 diabetes, called latent autoimmune diabetes of adults (LADA). As many as 20 percent of adult diabetic patients, presumably with Type 2 diabetes, may in reality have LADA. Physicians may distinguish between these two entities by testing for insulin antibodies, with LADA patients typically testing positive for these antibodies. Type 2 diabetics have high circulating insulin levels, and they rarely test positive for insulin antibodies.
Insulin resistance is a condition characterized by the patient’s need for more than 200 units per day of insulin to control his blood sugar levels. This insulin resistance is most often related to the production of circulating immunoglobulin G (IgG) antibodies to insulin in almost every diabetic who injects insulin. The antibody levels may rise to levels as much as 1000 times the normal amounts in nearly 0.1 percent of insulin users. Changing from one form of insulin to another rarely helps, as the antibodies bind strongly to pork, beef, and human insulin. Insulin resistance persists for less than a year, with the antibody levels gradually declining to normal.
Two possible treatments for insulin antibodies exist in the United States. Steroids, such as prednisone, mitigate insulin resistance, possibly by suppressing the immune response. Additionally, lispro insulin is resistant to antibody binding, due to its altered shape These two treatments are useful during the period of insulin insensitivity. Reactivity to insulin can return suddenly, making the possibility of hypoglycemia a serious concern in these patients.