BACKGROUND: Growth hormone deficiency (GHD) is known to cause higher rates of cardiovascular mortality. The purpose of the study was to analyze the structural and functional changes in the heart and investigate their relation to autonomic function as assessed with heart rate variability (HRV). METHODS: Eleven untreated GHD patients (mean age 50.4 +/- 10.7 years, M/F: 3/8) and 15 age- and sex-matched healthy persons (mean age 45.3 +/- 10.4 years, M/F: 5/10) were compared. Both groups were examined with echocardiography, HRV, and exercise testing and findings were analyzed. RESULTS: The groups were similar in height, weight, body mass index, body surface area, systolic and diastolic blood pressure, heart rate. The GHD patients had lower exercise duration and metabolic equivalent (MET) compared to controls (7.94 +/- 1.26 vs. 9.8 +/- 1.9 min, P < 0.001, for MET 8.85 +/- 0.86 vs. 10.7 +/- 2.23, P = 0.03). On echocardiography, GHD patients had lower interventricular septum diastolic diameter (9 +/- 0.89 vs. 10.7 +/- 0.88 mm, P < 0.001) and posterior wall thickness (8.4 +/- 0.93 vs. 9.8 +/- 0.91 mm, P = 0.002), and lower left ventricle mass index (90.9 +/- 20 vs. 112 +/- 8 g/m2, P = 0.01). Left ventricular ejection fraction was lower in the GHD patients (57.4 +/- 5.12% vs. 65.5 +/- 4.1%, P < 0.001). Time and frequency domain heart rate variability parameters, SDNN, SDANN, VLF, LF ve LF/HF were lower in GHD patients compared to controls. There was a significant correlation between left ventricle diastolic diameter and LF (r = 0.62, P = 0.02). CONCLUSION: GHD seemed to cause decreased left ventricle mass and decreases in the sympathetic components of HRV that may have a bearing on the increased cardiovascular risk seen in these patients.