Circulating insulin and insulin growth factor-1 are independent determinants of left ventricular mass and geometry in essential hypertension

Background-It is unclear whether insulin and insulin-like growth factor-1 (IGF-1) are independent determinants of left ventricular (LV) mass in essential hypertension. Methods and Results-We studied 101 never-treated nondiabetic subjects with essential hypertension. All had 24-hour noninvasive ambulatory blood pressure (ABP) monitoring and a 75-g oral glucose tolerance test. We determined fasting glucose, insulin, and IGF-1 and postload glucose and insulin 2 hours after glucose. Insulin resistance was estimated by the homeostasis model assessment (HOMA(IR)) formula. LV mass showed an association with body mass index (BMI) (r=0.47; P<0.01), postload insulin (r=0.54; P<0.01), HOMA(IR) (r=0.39; P<0.01), and IGF-1 (r=0.43; P<0.01) and a weaker association with average 24-hour systolic and diastolic ABPs (r=0.29 and r=0.26; P<0.05) and basal insulin (r=.0.31; P<0.05). Relative wall thickness was positively related to IGF-1 (r=0.39; P<0.01) but not to fasting or 2-hour postload insulin, HOMA(IR), and glucose. In a multiple regression analysis, the final LV mass model (R-2=0.64) included LGF-1, postload insulin, average 24-hour systolic ABP, sex: and BMI. IGF-1 and postload insulin accounted for >40% of variability of LV mass. The final model (R-2=0.36) for relative wall thickness included IGF-1 (16% total explained variability), average 24-hour systolic ABP, sex, BMI, and age but not insulin and HOMA(IR). Conclusions-These data indicate that insulin and IGF-I are powerful independent determinants of LV mass and geometry in untreated subjects with essential hypertension and normal glucose tolerance.