Effects of Hormone Replacement Therapy on Systemic Arterial Properties in Post-Menopausal Women

ABSTRACTEFFECTS OF HORMONE REPLACEMENT THERAPY ON SYSTEMIC ARTERIAL PROPERTIES IN POST-MENOPAUSAL WOMENEric Alps Chen, B.S.University of Pittsburgh, 2002Vascular stiffness properties contribute significantly to the arterial system hydraulic load. There is evidence that vascular stiffness plays a role in cardiovascular remodeling and may be an independent cardiovascular risk factor. Menopause accelerates age-associated increase in arterial stiffness and estrogen administration, which has vasodilating properties, can potentially mitigate this post-menopausal increase in stiffness. The present study examined the effects of chronic hormone replacement therapy (HRT) on systemic arterial mechanical properties in 35 post-menopausal women, divided into two groups: those receiving no HRT (Control, n = 25) and those receiving HRT (HRT-all, n = 10). The HRT-all group consisted of two subgroups: estrogen alone (HRT-E, n = 5) and a combination of estrogen and progesterone (HRT-EP, n = 5). Noninvasive data were collected serially at five times: once at the baseline during the first visit and during four subsequent visits after the initiation of the study at 19±1, 108±5, 193±4, and 388±8 days, respectively. Heart rate (HR), stroke volume (SV), and cardiac output (CO) did not change significantly in the control group throughout the study. This was also true for both HRT groups, except for a small decrease in HR at Visits 3 and 4 for the HRT-E group and an increase in CO at Visit 3 in the HRT-EP group. Mean arterial pressure decreased over time in control and both HRT groups, reaching statistical significance at later times (fifth visit). Systemic vascular resistance did not change significantly in control and both HRT groups. Global arterial compliance (AC) was unchanged for the control group but tended to increase in the HRT-all group, although no statistical significance was reached. In contrast, the subgroup analysis revealed that AC increased for the HRT-E subgroup, reaching statistical significance at the fifth visit. Similarly, significant decrements in pulse wave velocity (PWV), an index of regional vascular stiffness, were observed only for the HRT-E group. In conclusion, AC increased (vascular stiffness decreased) in subjects receiving chronic estrogen therapy only. The inclusion of progesterone seems to counteract the estrogen-mediated decrease in vascular stiffness, indicating that the vascular stiffness-associated cardio-protective effects of HRT, if any, may be limited to estrogen administration alone