Impaired Glucose Intolerance (IGT) and PCOS Impaired glucose tolerance, or insulin resistance, are defined as decreased insulin-mediated glucose utilization. It has long been recognized as a major risk factor for diabetes. Moreover, it was shown that lifestyle intervention or metformin in patients with IGT, may reduce the prevalence of T2D. Several dynamic invasive tests and calculated indices are currently available for detecting IGT. While the euglycemic clamp technique is considered the most accurate test for the assessment of insulin resistance, this cumbersome test is frequently replaced by the simple measurement of the ratio of fasting glucose to fasting insulin, or the 2-hour glucose level after a 75-g oral glucose tolerance test (OGTT) (WHO criteria, impaired glucose tolerance [IGT] >140 mg/dL to 199 mg/dL). As a result, reports of the prevalence on IGT in women with PCOS vary depending on the sensitivity and specificity of the tests employed and the heterogenic phenotypes of PCOS.