Hormone replacement therapy and stroke: are the results surprising?

Controversies Regarding Postmenopausal Hormone Replacement Therapy for Primary Cardiovascular Disease Prevention in Women

The debate over the safety and benefit of hormone replacement therapy (HRT) in postmenopausal women for primary prevention of cardiovascular disease (CVD) has been ongoing for the past several decades. Observational trials in the 1980s suggested a benefit of HRT for primary CVD prevention. However, randomized controlled trials in the 1990s suggested potential harm. Because of these discrepancies, recommendations from authorities on the usage of postmenopausal HRT have fluctuated. Many believed that the timing of HRT initiation relative to the onset of menopause, also known as the "timing hypothesis," was the factor that could explain the differences among these studies. Some recent investigations have concluded that HRT initiated in postmenopausal women near the onset of menopause confers a cardioprotective benefit, while others simply showed that HRT does not cause harm. Research has expanded to evaluate alternative doses, preparations, routes, and formulations, including selective estrogen receptor modulators, to demonstrate their suitability for this purpose. This article is a review of the major research studies of HRT in postmenopausal women with respect to its safety and efficacy for the primary prevention of CVD.

The effect of estradiol valerate and dienogest combination on serum homocysteine levels in postmenopausal women: a clinical trial

Several studies have verified that hormone replacement therapy (HRT) has protective effects on postmenopausal women's cardiovascular condition. However, highly significant recent studies have reported that women treated with HRT have more cardiovascular events than untreated women. An elevated homocysteine level is one important risk factor for cardiovascular disease (CVD). As a good indicator of CVD risk, we examined the changes in plasma homocysteine levels of postmenopausal women treated with HRT. In our study, we administered estradiol valerate (2 mg) and dionegest (2 mg) to 34 postmenopausal women recruited randomly from our menopause clinic, and measured plasma homocysteine levels of patients at baseline and after 3 and 6 months of therapy. The changes in plasma homocysteine levels of treated patients were not statistically significant (p = 0.241). Our results indicate that 6 months of estradiol valerate and dionegest therapy does not change homocysteine levels in postmenopausal women.

Hyper-reactivity of cerebral arteries from ovariectomized rats: therapeutic benefit of tamoxifen

1. An increased incidence of systemic hypertension has been documented in postmenopausal women and identified as an independent risk factor in the development of cerebrovascular stroke. The present study examined whether cerebrovascular reactivity was increased in the hypertensive ovariectomized rat, and explored the potential therapeutic benefit of the partial estrogen receptor agonist tamoxifen. 2. Female Sprague-Dawley rats were subjected to bilateral ovariectomy (OVX, n=16) or a sham operation (n=8). At 6-week postsurgery, rats were anesthetized to assess ventricular contractility and blood pressure. In a second series of experiments, OVX rats (n=8) were given tamoxifen starting 3 weeks postsurgery, and continued for 3 weeks. At the end of each protocol, the middle cerebral artery was harvested and rings were mounted in wire-myographs to measure isometric tension. 3. Systolic arterial pressure (SAP) was significantly increased (P<0.05) in the OVX rat (174+/-8 mmHg), as compared to sham (135+/-6 mmHg). The resting tension of isolated cerebral arteries from OVX rats (186+/-15 mg) was significantly elevated (P<0.05), as compared to sham (129+/-9 mg). Phenylephrine treatment did not elicit a constriction of cerebral arteries isolated from sham rats, whereas a potent response (P<0.05) was observed in OVX rats. Nitric oxide (NO) synthase inhibition with L-NNA led to a limited contraction in sham rats (8+/-3% of Emax), whereas a significant (P<0.05) increase was observed in OVX rats (34+/-12% of Emax). Lastly, vascular sensitivity (pD2) to sodium nitroprusside was significantly increased (P<0.05) in OVX rats, as compared to sham. 4. Tamoxifen therapy normalized the resting tension of isolated cerebral arteries from OVX rats, abrogated phenylephrine-mediated contraction, and modestly reduced SAP. By contrast, tamoxifen treatment of OVX rats did not attenuate L-NNA-mediated contractile response of cerebral arteries. 5. These data demonstrate that the cerebral artery isolated from the OVX rat was associated with an exaggerated vasoconstrictor response to phenylephrine, and altered NO-dependent vascular reactivity. The administration of tamoxifen to OVX rats normalized cerebral artery reactivity to phenylephrine. These findings provide the impetus to examine the potential therapeutic benefit of the partial estrogen receptor agonist tamoxifen to reduce the incidence of cerebrovascular stroke in postmenopausal women.