Values of fasting glucose levels, glucose tolerance tests, and glucose-insulin ratios as predictors of glucose tolerance

Objective: To examine the ability to use parameters obtainable from an oral glucose tolerance test to predict insulin action as determined under hyperinsulinemic, hyperglycemic conditions. Design: Prospective clinical investigation. Setting: University medical center clinical research unit. Patient(s): Healthy male volunteers. Intervention(s): Oral glucose tolerance test and hyperglycemic (+125 mg/dL) clamp studies. Main outcome measure(s) Glucose and insulin (I) levels, rate of glucose uptake (M) under hyperglycemic conditions, and M/I ratios. Result(s): Among individuals with normal glucose tolerance, as assessed by an oral glucose tolerance test, the fasting insulin level is the glucose tolerance test parameter that correlates best with insulin action during a hyperglycemic clamp. Conclusion(s): Measurement of fasting serum insulin levels in conjunction with an oral glucose tolerance test improves the ability to assess insulin action. Such combinations may improve the ability to diagnose insulin-resistant states.