To determine the relationships between the circadian blood pressure profile and left ventricular mass, hormonal pattern and insulin sensitivity indices in patients with active acromegaly, ambulatory 24-h blood pressure monitoring (ABPM) was recorded in 25 subjects (47.0 ؎ 15.1 years, range 23-72). Serum growth hormone (GH) and insulin-like growth factor-1, fasting and mean plasma glucose and insulin during oral glucose tolerance test (OGTT), insulinogenic index, the sum of the plasma insulin levels and the homeostasis model insulin resistance index (Homa's index) were determined. Left ventricular mass index (LVMI) was calculated from two-dimensional guided M-mode echocardiogram. The prevalence of hypertension was 56% (n ؍ 14) and 40% (n ؍ 10) according to sphygmomanometric measurements and ABPM, respectively. Non-dipping profile was observed in six of 10 hypertensives and in