Insulin resistance (IR) (5) is a pathophysiological state characterized by a subnormal physiological response to insulin concentrations within reference intervals. Experimental and epidemiological studies have demonstrated a strong association of IR with many diseases or metabolic abnormalities, including coronary heart disease, stroke, type 2 diabetes, hypertension, dyslipidemia, systemic inflammation, and atherogenesis (1, 2). It is estimated that approximately 20.6 million adults aged 20 years or older in the US have diabetes, with the majority of these having type 2 diabetes in 2005 (3). The prevalence of hyperinsulinemia has increased by 35% among nondiabetic adults in the US in the past decade (4). It is believed that IR and subsequently compensatory hyperinsulinemia develop much earlier than ([beta]-cell dysfunction and may exist and progress years before even prediabetes would be diagnosed by the detection of impaired fasting glucose or impaired glucose tolerance. Several studies have demonstrated that early interventions, including lifestyle modification and pharmacological treatment, can effectively delay the onset of diabetes in prediabetic individuals and therefore decrease the incidence of cardiovascular disease and other diabetes-related chronic illnesses (5, 6). Thus, early identification of individuals who have developed IR is particularly important in clinical practice, but diagnosis is challenging.
