EVALUATION OF 2 INSULIN ASSAYS IN INSULIN-RESISTANCE-SYNDROME (SYNDROME-X)

Recent data suggest that proinsulin is associated with cardiovascular risk factors in nondiabetic and diabetic subjects. Since most conventi onal insulin assays cross-react with proinsulin, it has been suggested that the associations of insulin concentrations with dyslipidemia and hypertension could actually reflect associations with proinsulin. We examined these associations by using both a conventional immunoreactiv e insulin assay and a specific Linco insulin assay that does not cross -react with proinsulin in 623 nondiabetic and in 180 non-insulin-depen dent diabetic subjects who participated in the San Antonio Heart Study , a population-based study of diabetes and cardiovascular disease. Bot h the immunoreactive insulin assay and the specific Linco insulin assa y were equally correlated with cardiovascular risk factors in nondiabe tic subjects. Insulin concentrations were moderately correlated with h igh triglyceride and low high-density lipoprotein cholesterol levels a nd were weakly correlated with increased blood pressure. In diabetic s ubjects there were only weak associations between insulin and cardiova scular risk factors using either assay. We conclude that the associati on of insulin concentrations with cardiovascular risk factors is not a function of using insulin assays that cross-react with proinsulin and that for epidemiological studies of cardiovascular risk factors, conv entional immunoreactive insulin assays are as good as the newer specif ic insulin assays.