['Left ventricular hypertrophy (LVH) in patients with arterial hypertension is closely related to the levels of blood pressure (BP), catecholamines, angiotensin II and other mitogenic peptides. Pheochromocytoma (pheo) is a type of hypertension caused by excessive production of catecholamines. The aim of this study was to determinate if left ventricular hypertrophy in patients with pheochromocytoma is related to catecholamines and neuropeptide Y (NPY).', '29 patients with pheochromocytoma (22 F, age 40 +/- 13 years), plasma concentration of neuropeptide Y immunoreactivity, noradrenaline (NA), and adrenaline (A) were determined. Twenty-four hour urine collection for determination of noradrenaline and adrenaline were performed. Every patient had echocardiographic examination and 24 h ambulatory blood pressure monitoring.', 'Left ventricular hypertrophy was diagnosed in 14 patients. No differences in systolic and diastolic blood pressure in patients with and without left ventricular hypertrophy were found. Plasma noradrenaline and adrenaline levels did not differ between both groups, while plasma neuropeptide Y immunoreactivity was higher in patients with left ventricular hypertrophy than in patients without left ventricular hypertrophy (18.46 +/- 13.26 vs. 9.3 +/- 5.9 fmol/ml (p = 0.02)). Left ventricular mass index (LVMI) correlated with plasma neuropeptide Y-immunoreactivity (r = 0.42 p = 0.023), however, no relationship between left ventricular mass index and plasma or urine noradrenaline and adrenaline levels were found.'] Does plasma neuropeptide Y immunoreactivity influence left ventricular mass in pheochromocytoma?