Diminished effectiveness of insulin in lowering plasma glucose levels, arbitrarily defined as a daily requirement of at least 200 units of insulin to prevent hyperglycemia or ketosis; usually due to binding of insulin or insulin receptor sites by antibodies; associated with obesity, ketoacidosis, and infection. See Also: metabolic syndrome.
Impairment of the normal response of muscle and other cells to endogenous or exogenous insulin often complicates the deficiency of endogenous insulin that is characteristic of Type 2 diabetes mellitus. It is a peripheral phenomenon and can occur even when the quality and quantity of insulin produced by the pancreas are normal. It apparently results from a decrease in the number of insulin receptor sites on cells, from a malfunction of the biochemical glucose transport system, or both. Insulin resistance is often associated with high levels of circulating antibody to insulin receptors. The phenomenon of insulin resistance explains why some patients with Type 2 diabetes have hyperinsulinemia in the fasting state, often coexisting with elevated plasma glucose levels. Insulin resistance correlates closely with obesity in diabetes. It occurs less frequently in lean patients with diabetes, whose principal problem is usually primary failure of insulin production. Insulin resistance is a prominent feature of the metabolic syndrome, which also includes obesity, dyslipidemias, hypertension, and hyperuricemia. Some women with polycystic ovaries, hirsutism, and anovulation also have insulin resistance and hyperinsulinemia. Thiazolidinediones (pioglitazone, rosiglitazone) improve insulin sensitivity in type 2 diabetes mellitus.
Reference: Stedman's Medical Dictionary