Study of the rate of early glucose disappearance following insulin injection: insulin sensitivity index

The euglycaemic hyperinsulinaemic glucose clamp is usually considered as the reference technique to evaluate insulin sensitivity. As it is an-expensive and time-consuming tool, we therefore tried to validate a simple insulin tolerance test (ITT) (IV bolus of 0.1 IU/kg of regular insulin, with glucose sampling at −5, 0, 3, 5, 7, 10 and 15 min) and to demonstrate its usefulness. Insulin sensitivity was measured by DG/G0 ratio (G0 = initial glycaemia, DG is the variation between G0 and the glycaemia obtained at 15 min by the calculation of the regression plot). We confirmed the existence of a correlation between the glucose uptake (mg/kg per min) evaluated by glucose clamp and the DG/G0 index (r = 0.9, P < 0.01). There was no stimulation of hormonal counter regulation during the test. The ITT was significantly correlated both with fasting insulin (r = −0.43, P < 0.01), and post-glucose load insulin concentration (r = −0.67, P < 0.01); each measurement expressing insulin sensitivity. Four groups of patients with different insulin sensitivity; controls, NIDDM, gynoid and android obese subjects, were clearly separated by ITT. We showed that fasting glycaemia and DG/G0 were correlated (y = 2.63/x − 0.093; r = 0.82, P < 0.01). These results suggest that ITT could be an easy, quick and low cost method to evaluate insulin resistance in clinical practice and epidemiological studies.