Single dose nasal 17beta-estradiol administration reduces sympathovagal balance to the heart in postmenopausal women.

ABSTRACT

AIM: Long-term estrogen replacement therapy has favorable results on autonomic cardiovascular functions in postmenopausal women. Although acute estrogen administration has beneficial modulations on autonomic tone in animal studies, there are still controversies about the effects of acute estrogen on autonomic modulation to the heart in humans. The aim of this double-blind study was to investigate the acute effects of intranasal 17beta-estradiol administration on autonomic control of heart rate. METHODS: Nineteen postmenopausal women with typical hormone profiles were crossover randomized to 300 micro g nasal 17beta-estradiol (Aerodiol, Servier, Chambray-les-Tours, France) or an identical placebo at least 5 days apart. Both time domain and frequency domain heart rate variability (HRV) parameters were obtained during controlled respiration (CR) and handgrip exercise (HGE), before and 45 min after 17beta-estradiol or placebo administration. RESULTS: Baseline HRV parameters were similar for each occasion. Time domain indices obtained after 17beta-estradiol administration were not significantly different from results obtained with the placebo. In frequency domain parameters, 17beta-estradiol administration resulted in a reduced low frequency to high frequency ratio (LF/HF ratio) when compared with the placebo during CR (0.72 +/- 0.09 vs 1.00 +/- 0.15, P < 0.05) but not during HGE (3.03 +/- 0.37 vs 2.86 +/- 0.30, P > 0.05). CONCLUSION: A single intranasal 17beta-estradiol administration acutely reduced sympathovagal balance to the heart during the course of parasympathetic maneuver in healthy postmenopausal women.