Correlation Between Insulin Suppression Test and Quantitative Insulin Sensitivity Check Index in Hypertensive and Normotensive Obese Patients

Insulin resistance plays a central role in the pathophysiology of diabetes and is associated with obesity and other cardiovascular risk factors (1). In the assessment of insulin resistance, several methods have been developed. The “gold standard” hyperinsulinemic-euglycemic clamp (2) and the insulin suppression test (IST) (3) are two established methods to quantify insulin sensitivity in vivo, but neither is easily applied in large populations. Thus, it is of interest to develop simple methods to estimate insulin sensitivity that are useful for large epidemiological studies. A mathematical model derived from the so-called homeostasis model assessment (HOMA) (4) has been described as a simple and reproducible method in clinical practice. Recently, Katz et al. (5) have described a novel quantitative insulin-sensitivity check index (QUICKI) that shows a high correlation with the hyperinsulinemic-euglycemic clamp. In the present report, we studied the correlation among IST, QUICKI, and HOMA in a population of normotensive-obese (NT-OB) and hypertensive-obese (HT-OB) patients in order to determine their accuracy.

We recruited 20 obese (BMI >30 kg/m²) male patients; 12 were NT-OB, and 8 were newly HT-OB and had never been treated before. None had previous history of metabolic disorders or were on medication with effects on insulin sensitivity. As the control group, 10 healthy (BMI <25 kg/m²) age- and sex-matched volunteers were included. To estimate the insulin sensitivity, we first performed an IST. This test acts by suppressing endogenous insulin secretion with a sustained infusion of somatostatin. Simultaneously, exogenous crystalline insulin is infused at a constant rate to achieve a steady state of plasma insulin (SSPI), and then the resultant steady state of plasma glucose (SSPG), in response to a constant glucose infusion is determined, as we have previously described (6). The insulin sensitivity index (ISI) was …