Evidence of a role of endogenous estrogen in the modulation of autonomic nervous system

The role of ovarian hormones, mainly estrogen, in the modulation of autonom ic nervous control of the cardiovascular system is poorly understood. Menop ause is associated with an altered control of the cardiovascular system wit h a shift toward increased sympathetic activity. Natural menopause, however , is the consequence of a process of ovarian senescence and of a slow but g radual decrease in plasma levels of ovarian hormones. To evaluate the physi ologic role of estradiol-17 beta in the modulation of the nervous autonomic control of the cardiovascular system, we evaluated the effect of acute wit hdrawal of ovarian hormones on the balance of vagal and sympathetic influen ces on the cardiovascular system. For this purpose analysis of heart rate v ariability (HRV) was performed on the 24-hour electrocardiographic recordin gs of a group of fertile women at basal conditions and during the 5 weeks i mmediately subsequent to bilateral oophorectomy. Data obtained were compare d with those from a group of age-matched women who had undergone hysterecto my with conservation of the ovaries. Observations were repeated in oophorec tomized persons after 3 months of estrogen replacement therapy (ERT).