HOMA-IR

The HOMA-IR (Homeostasis Model Assessment of Insulin Resistance) test, also called the insulin resistance index, estimates insulin resistance from fasting plasma glucose and fasting insulin. It is used to identify evolving insulin resistance and to stratify cardiometabolic risk, including the likelihood of type 2 diabetes, atherosclerosis, and cardiovascular disease. The assay is also applied to contextualize metabolic risk in disorders associated with insulin resistance such as metabolic syndrome, polycystic ovary syndrome, chronic kidney disease, chronic hepatitis B or C, and hepatic steatosis.

Insulin resistance is a state in which insulin-responsive tissues display reduced sensitivity to insulin, leading to impaired cellular glucose uptake and altered glucose metabolism. It arises from a combination of metabolic and hemodynamic disturbances, low-grade inflammation, and genetic predisposition, and it is linked to increased risk of type 2 diabetes, cardiovascular disease, dysmetabolism, and the metabolic syndrome. Insulin is a peptide hormone generated from proinsulin by pancreatic beta cells. It promotes transport of glucose from blood into muscle and adipose tissue, stimulates glycolysis and the synthesis of glycogen and fatty acids in the liver, suppresses lipolysis and ketogenesis, and supports energy storage and utilization. With developing insulin resistance, circulating insulin concentrations rise and fasting glucose tends to increase, which is associated with higher risk of type 2 diabetes, atherosclerosis (including coronary disease), hypertension, ischemic heart disease, and ischemic stroke. HOMA-IR is calculated as: fasting insulin (μIU/mL) × fasting glucose (mmol/L) ÷ 22.5. Higher HOMA-IR values reflect increased fasting insulin and/or glucose and indicate greater tissue insulin resistance, correlating with elevated risk for type 2 diabetes and cardiovascular disease. Population-based thresholds for insulin resistance by HOMA-IR are commonly defined at approximately the 70th–75th percentiles of its cumulative distribution. As an adjunctive marker, the insulin resistance index assists in characterizing metabolic syndrome—a cluster of risk factors for cardiovascular disease, type 2 diabetes, atherosclerosis, hepatic steatosis, and some malignancies—in which obesity and insulin resistance drive interrelated metabolic, hormonal, and clinical abnormalities. The calculation is informative for detecting impaired glucose tolerance and diabetes when fasting glucose is below 7 mmol/L. Clinical contexts in which HOMA-IR is often applied include suspected insulin resistance in women with polycystic ovary syndrome, gestational diabetes, chronic kidney disease, chronic hepatitis B or C, and nonalcoholic fatty liver disease, as well as during infectious, oncologic, or autoimmune conditions and in patients receiving medications such as glucocorticoids or oral contraceptives.