Effects of hormone replacement therapy on the sympathetic nervous system and blood pressure

Abstract

Hypertension is a major health problem that significantly contributes to heart disease and stroke. While most studies of hypertension have focused on men, women also experience significant hypertension-related morbidity and mortality. However, the incidence of hypertension and cardiovascular disease is significantly lower in premenopausal women compared with men until the onset of menopause, at which time cardiovascular disease incidence increases dramatically in women and eventually approaches that in men. These observations indicate that the loss of estrogen contributes to menopause-related increases in blood pressure and cardiovascular disease, and suggest that the use of estrogen hormone replacement therapy could decrease the incidence of cardiovascular disease in postmenopausal women. However, new findings from the Women's Health Initiative study suggest that estrogen therapy has few positive benefits and some significant negative effects on the health of postmenopausal women, and these data have caused many to abandon long-term estrogen replacement therapy. Conversely, numerous clinical and basic research studies indicate that estrogen replacement therapy beneficially reduces blood pressure, thereby decreasing the incidence of hypertension and cardiovascular disease. Further, several of these studies suggest that one means by which estrogen lowers blood pressure is by decreasing sympathetic nervous system activity. This review examines the evidence supporting estrogen's ability to modulate sympathetic nervous system tone and thereby decrease arterial pressure.

Gender-Selective Interaction Between Aging, Blood Pressure, and Sympathetic Nerve Activity

“…However, our findings are consistent with experimental studies showing that estrogens may modulate sympathetic nervous system tone. 18,19 Third, subjects were recruited from 2 different white populations. In mitigation, the US and Polish subjects were comparable for age and body mass index.…”

Menopausal Complaints Are Associated With Cardiovascular Risk Factors

“…36 -39 Because a heightened sympathetic nervous system is thought to be involved in the occurrence of menopausal symptoms, as well as in the etiology of the cardiovascular risk profile, it is plausible that the favorable effects of estrogens on the cardiovascular system could derive from the inhibition of the sympathetic nervous system. 49,50 These findings should trigger further research.…”

Vascular Actions of Estrogens: Functional Implications

“…Depletion of estrogen with a concomitant increase in androgens would, therefore, reduce local inhibitory signals while increasing procontractile signals at the vascular wall, leading to increased peripheral resistance and blood pressure in the absence of concomitant decreases in sympathetic tone. In addition to these direct effects on the vascular wall, in general, withdrawal of estrogen increases sympathetic tone as measured by increases in peripheral sympathetic neuronal activity and circulating levels of norepinephrine resulting in increased blood pressure, especially in the presence of a stressor (Saab et al, 1989;Owens et al, 1993;Vongpatanasin et al, 2001;Wyss and Carlson, 2003;Fernander et al, 2004). Whether estrogen, when injected directly into the brain, increases or decreases sympathetic tone depends upon the specific nuclei that are stimulated (Saleh and Connell, 2007).…”