Climacteric vasomotor symptoms do not imply autonomic dysfunction

To study whether oestrogen replacement therapy has an effect on autonomic haemodynamic control in postmenopausal women.

A placebo-controlled, prospective, randomised, double-blind cross-over trial.

Fourteen healthy postmenopausal women who had had a hysterectomy, of whom 12 were double-blind.

At the end of each treatment period we conducted autonomic nervous system tests: the Valsalva manoeuvre, the deep breathing test, study at rest and the active orthostatic test. Baroreflex sensitivity was evaluated non-invasively from the Valsalva manoeuvre. Heart rate variability was assessed in time and frequency domains during supine rest and standing. Serum oestradiol was also measured and the previous two weeks' symptoms were assessed.

Autonomic nervous function was mostly normal for age and unchanged by oestrogen. Vasomotor symptoms were not associated with autonomic dysfunction. Baroreflex sensitivity was 13.3 ms/mmHg (SD 7.4 ms/mmHg) with placebo and 10.5 ms/mmHg (SD 5.4 ms/mmHg) with oestrogen (P = 0.052). This was mostly due to a fall in three of the highest indices. In the orthostatic test the 30 s blood pressure overshoot in two women exceeded the normal 90% confidence interval upper limit, making the mean response strong, especially in the symptomatic group (n = 7). Oestrogen attenuated this overshoot.

Oestrogen did not have a consistent effect on the autonomic nervous system. Oestrogen attenuated a highly sensitive baroreflex and a strong 30 s blood pressure rise in the orthostatic test. This minor effect of oestrogen could be due to the fact that, in general, women with menopausal symptoms do not have impaired autonomic haemodynamic control. The effect of oestrogen in women with autonomic nervous system dysfunction remains to be studied.