THE AUTONOMIC NERVOUS SYSTEM AND CARDIOVASCULAR RISK ASSESSMENT DURING ONE YEAR OF GH REPLACEMENT THERAPY IN ADULTS WITH GH DEFICIENCY

Objective: This prospective study aims to evaluate the impact of Growth Hormone Deficiency (GHD) on cardiac autonomic tone, on cardiovascular risk and the changes after 12 months of GH replacement therapy (GHRT). GHD is associated with increased cardiovascular morbidity and mortality. This has been attributed to increased markers of cardiovascular risk and to abnormalities of the both cardiac and peripheral autonomic nervous system. Autonomic cardiac nervous system (ACNS) can be indirectly valued by analysis of heart rate variability (HRV) in clinostatism and orthostatism. Design: We compared 14 GHD patients at baseline and after 12 months of GHRT and 17 healthy controls. We analyzed some cardiovascular risk factors and we used analysis of HRV during Tilt Test that identified: HF (high frequency) and LF (low frequency) representing parasympathetic and sympathetic activity, respectively. Results: Compared with the control group, in either clinostatism or in orthostatism our patients showed a significantly lower value of LF (P<0.05; P<0.005), whereas HF was significantly reduced in orthostatism (P<0.05), but not in clinostatism (P=0.06). These values resulted unchanged after 12 months of GHRT. No statistically significant differences were found between LF/HF ratio in untreated or treated patients. In GHD patients there was a significant reduction of cardiovascular risk in 12 months of replacement therapy (P<0.002). Conclusions : Our study highlights the lack of sympathovagal imbalance in GHD patients; GHRT does not determine any change in the ACNS in the first year of treatment but reduces absolute cardiovascular risk in these patients.