Different Effects of Transdermal and Oral Hormone Replacement Therapy on the Renin-Angiotensin System, Plasma Bradykinin Level, and Blood Pressure of Normotensive Postmenopausal Women

Background This study compared the efficacy of transdermally administered estradiol with that of orally administered conjugated equine estrogens (CEE) on the renin–angiotensin system, plasma bradykinin level, and blood pressure (BP) in normotensive postmenopausal women (PMW). Methods A total of 38 normotensive PMW were randomly assigned to two groups. The transdermal hormone replacement therapy (HRT) group consisted of 19 women treated with a continuous transdermal estradiol patch (36 μg/day) plus cyclic oral medroxyprogesterone acetate (MPA; 2.5 mg/day for 12 days) for 12 months. The oral HRT group consisted of 19 women who received continuous oral CEE (0.625 mg/day) plus cyclic oral MPA (2.5 mg/day for 12 days) for 12 months. Plasma renin activity (PRA), serum angiotensin-converting enzyme (ACE) activity, plasma angiotensin (Ang) I, Ang II, and bradykinin concentrations, and BP were measured before and 12 months after the start of HRT. Results Transdermal HRT significantly decreased both diastolic and mean BP and concomitantly reduced bradykinin levels (all P< .05). However, no significant changes in PRA, ACE activity, Ang I, or Ang II levels were observed. The BP remained unchanged in the oral HRT group, but the PRA, Ang I, Ang II, and bradykinin levels had significantly increased and ACE activity had significantly decreased (all P< .05) at 12 months after the start of HRT. Conclusions Transdermal HRT decreased BP in normotensive PMW without influencing Ang II, whereas oral HRT increased Ang II without altering BP. Transdermal HRT may be more beneficial than oral HRT with regard to BP and Ang II levels.