Insulin resistance is a strong predictor of the development of type 2 diabetes mellitus and cardiovascular disease. Girls with premature adrenarche (PA) or obesity may be at an increased risk for the development of insulin resistance. Recently, in prepubertal girls with PA, a fasting glucose to insulin ratio (FGIR) of less than 7 was found to be predictive of insulin resistance as determined by the frequently sampled iv glucose tolerance test. We sought to compare the FGIR with 2 insulin sensitivity measures, SiM (an adjusted mean measure of insulin sensitivity based on fasting and 2 h post glucose load insulin sensitivity measures) and the composite whole body insulin sensitivity index, ISI(comp), both derived from the 2-h oral glucose tolerance test in 2 groups of children at risk: girls with PA and obese girls. We studied 25 prepubertal girls with PA and/or obesity and further classified them as insulin resistant (IR) or insulin sensitive (IS) based on the FGIR. Four simple measures of insulin sensitiv...