Endocrine Abstracts

Background: We previously demonstrated that elderly patients with GHD have increased and young GHD patients have reduced cardiac sympathovagal balance. Therefore we decided to investigate whether the relationship between age and cardiac sympathovagal balance is altered in GHD compared to healthy controls.

Method: HRV, which indirectly measures cardiac sympathovagal balance, was measured in 22 untreated GHD patients (13 F; mean age 47.4 yrs; range 19-73 yrs, average duration GHD 10.1 yrs). They were compared with 28 age and BMI matched healthy controls (14 F; mean age 48.5 yrs; range 19-79 yrs). HRV was analysed by power spectral analysis. Using this technique 2 frequency bands: low frequency (LF: 0.04-0.15 Hz, a measure of cardiac sympathetic activity) and high frequency (HF: 0.15-0.4 Hz, a measure of cardiac parasympathetic activity) were identified and the LF/HF ratio (a measure of cardiac sympathovagal tone) were obtained. The power within each band was also normalised (expressed as a percentage of total power). Total power (TP) is the sum of LF and HF.

Results: There were no significant differences in age, BMI, BP and any measurements of HRV between GHD patients and controls. TP correlated negatively with age in healthy controls and GHD subjects (p=0.04 and 0.006 respectively). However, LF/HF ratio (r=0.6, p=0.003) and normalised LF (r=0.69, p=0.0003) increased and normalised HF (r=-0.69, p=0.0003) reduced significantly with age in GHD patients. No significant changes in LF/HF ratio, normalised LF or HF were seen in healthy controls with age.

Conclusions: Cardiac sympathovagal balance increases with age in patients with GHD but not in healthy controls. This could contribute to the increased cardiac morbidity and mortality seen in adults with GHD.