Both left ventricular (LV) hypertrophy and insulin resistance (IR) have often been demonstrated in patients with essential hypertension (EH). Insulin may exert a direct growth promoting effect on cardiomyocytes rather than affecting the LV internal diameter. The purpose of this study was to examine the effect of IR on LV geometry. We enrolled 105 patients (71 females, mean age, 49.2 +/- 13.6 years) with recently diagnosed and untreated hypertension (blood pressure > 140 and/or 90 mmHg, fasting glucose < 110 mg/dL), and grouped them as normal (N) (39 patients, 26 females, mean age, 48.5 +/- 14.7 years) if all M-mode echocardiographic measurements were within normal limits, concentric remodeling (CR) (22 patients, 15 females, mean age, 50.5 +/- 14.8 years) if relative wall thickness was increased but left ventricular mass index (LVMI) was normal, concentric hypertrophy (CH) (13 patients, 9 females, mean age, 50.3 +/- 10.8 years) if both ventricular thicknesses and the LVMI were increased, and eccentric hypertrophy (EH) (31 patients, 21 females, mean age, 48.6 +/- 12.9 years) if ventricular thicknesses were normal, but LVMI was increased. Transthoracic echocardiography was performed in all subjects, and interventricular septal thickness (IVS), posterior wall thickness (PWT), sum of wall thickness (SWT), left ventricular end-diastolic internal diameter (LVED), relative wall thickness (RWT), and LVMI were recorded. Blood samples for routine biochemical examination and fasting insulin levels were obtained and then the homeostasis model assessment (HOMA) index was calculated by the formula: HOMA Index = Fasting Blood Glucose (mg/dL) x Immunoreactive Insulin (microU/mL)/405, for the assessment of IR. There were no significant differences among the groups with respect to age, blood pressure (BP) levels, fasting blood glucose (FBG), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), total cholesterol (TC), or triglyceride (TG) levels. Insulin levels were significantly higher in the CR and CH groups in comparison with the N group (P = 0.004), and the HOMA index was higher in the CH group compared to the N group (P = 0.024). In Pearson's correlation analysis, insulin was found to be directly correlated with IVS (r = 0.29, P = 0.002), SWT (r = 0.25, P = 0.009), and RWT (r = 0.33, P = 0.0001). The HOMA index was also directly correlated with IVS (r = 0.33, P = 0.001), SWT (r = 0.29, P = 0.002), and RWT (r = 0.29, P = 0.003). Cardiac changes in hypertensive patients include increased LVMI and altered LV geometry. The concentric LV geometry seen in hypertensive patients might be mediated, at least in part, by increased insulin levels and the HOMA index.