Circulating Insulin and Insulin Growth Factor-1 Are Independent Determinants of Left Ventricular Mass and Geometry in Essential Hypertension

Abstract

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 IGF-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-1 are powerful independent determinants of LV mass and geometry in untreated subjects with essential hypertension and normal glucose tolerance.