Ischemic stroke and use of estrogen and estrogen/progestogen as hormone replacement therapy

Sex hormones and stroke: Beyond estrogens

Stroke risk and poor stroke outcomes in postmenopausal women have usually beeen attributed to decreased levels of estrogen. However, two lines of evidence suggest that this hormone may not be solely responsible for elevated stroke risk in this population. First, the increased risk for CVD and stroke occurs much earlier than menopause at a time when estrogen levels are not yet reduced. Second, estrogen therapy has not successfully reduced stroke risk in all studies. Other sex hormones may therefore also contribute to stroke risk. Prior to menopause, levels of the gonadotrophin Follicle Stimulating Hormone (FSH) are elevated while levels of the gonadal peptide inhibin are lowered, indicating an overall decrease in ovarian reserve. Similarly, reduced estrogen levels at menopause significantly increase the ratio of androgens to estrogens. In view of the evidence that androgens may be unfavorable for CVD and stroke, this elevated ratio of testosterone to estrogen may also contribute to the postmenopause-associated stroke risk. This review synthesizes evidence from different clinical populations including natural menopause, surgical menopause, women on chemotherapy, and preclinical stroke models to dissect the role of ovarian hormones and stroke risk and outcomes.

Postmenopausal Hormone Therapy and Risk of Stroke: Impact of the Route of Estrogen Administration and Type of Progestogen

Supplemental Digital Content is available in the text.

Background and Purpose—

The benefit/risk analysis of hormone therapy in postmenopausal women is not straightforward and depends on cardiovascular disease. Evidence supports the safety of transdermal estrogens and the importance of progestogens for thrombotic risk. However, the differential association of oral and transdermal estrogens with stroke remains poorly investigated. Furthermore, there are no data regarding the impact of progestogens.

Methods—

We set up a nested case–control study of ischemic stroke (IS) within all French women aged 51 to 62 years between 2009 and 2011 without personal history of cardiovascular disease or contraindication to hormone therapy. Participants were identified using the French National Health Insurance database, which includes complete drug claims for the past 3 years and French National hospital data. We identified 3144 hospitalized IS cases who were matched for age and zip code to 12 158 controls. Conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI).

Results—

Compared with nonusers, the adjusted ORs of IS were1.58 (95% CI, 1.01–2.49) in oral estrogen users and 0.83 (0.56–1.24) in transdermal estrogens users (P<0.01). There was no association of IS with use of progesterone (OR, 0.78; 95% CI, 0.49–1.26), pregnanes (OR, 1.00; 95% CI, 0.60–1.67), and nortestosterones (OR, 1.26; 95% CI, 0.62–2.58), whereas norpregnanes increased IS risk (OR, 2.25; 95% CI, 1.05–4.81).

Conclusions—

Both route of estrogen administration and progestogens were important determinants of IS. Our findings suggest that transdermal estrogens might be the safest option for short-term hormone therapy use.

Estrogen Therapy and Ischemic Stroke in Women with Diabetes Aged Over 55 Years: A Nation-Wide Prospective Population-Based Study in Taiwan

This study explores the possible association between the risk of ischemic stroke and conjugated equine estrogen (CEE) use in women who are over 55 years old and have diabetes. Data from the National Health Insurance system of Taiwan were used to identify 428 women over 55 years old with diabetes who used CEE (0.625 mg daily) from 2003 to 2009. For comparison, 21026 women with diabetes who were from the same cohort and did not use estrogen were used as a control group, excluding patients with previous ischemic stroke at the baseline. The propensity score method was used to identify a 1:3 ratio for the matched cohort (n = 1284). Covariates used for propensity score-matching included age and comorbidities. Cox’s proportional hazard model was applied to estimate the relationship between CEE use and ischemic stroke. The overall incidence of ischemic stroke was significantly lower in patients using CEE than in the control group (0.9% compared with 3.0%, p = 0.016). Further analyses using Cox’s proportional hazard model revealed that after adjusting for age, comorbidities, socioeconomic status, urbanization, and other medications associated with ischemic stroke, a lower risk was present in patients with CEE use (hazard ratio: 0.34; 95% confidence interval: 0.12–0.97). Time of menopause could not be identified because of the nature of the database. CEE might decrease the risk of ischemic stroke in women with diabetes aged over 55 years, according to this population-based study.

Alphaxalone inhibits growth, migration and invasion of rat C6 malignant glioma cells

Malignant gliomas are the most devastating and aggressive brain tumors affecting the central nervous system. The insidious growth and infiltration are the most prominent characteristics of malignant gliomas, which render the current therapies for malignant gliomas including surgery, radiation and chemotherapy unsuccessful. Inhibition of infiltration as well as proliferation in combination with surgery might be more effective in the treatment of malignant gliomas. In the current study, we demonstrate the alphaxalone (3-hydroxypregnane-11,20-dione) could effectively inhibit the proliferation of C6 glioma cells in a concentration dependent manner. Moreover, this compound could also suppress the migration and invasion of C6 glioma cells at a concentration without causing significant cytotoxicity. Except the in vitro anti-glioma activity, alphaxalone effectively delayed the growth of rat C6 malignant glioma xenografts in vivo. Together, these findings suggest alphaxalone might be a promising candidate for the treatment of malignant gliomas and may also provide helpful clues for anti-glioma drugs development in future.

Revisiting the timing hypothesis: biomarkers that define the therapeutic window of estrogen for stroke

Significantly extended life expectancy coupled with contemporary sedentary lifestyles and poor nutrition has created a global epidemic of cardiovascular disease and stroke. For women, this issue is complicated by the discrepant outcomes of hormone therapy (HT) for stroke incidence and severity as well as the therapeutic complications for stroke associated with advancing age. Here we propose that the impact of estrogen therapy cannot be considered in isolation, but should include age-related changes in endocrine, immune, and nucleic acid mediators that collaborate with estrogen to produce neuroprotective effects commonly seen in younger, healthier demographics. Due to their role as modulators of ischemic cell death, the post-stroke inflammatory response, and neuronal survival and regeneration, this review proposes that Insulin-like Growth Factor (IGF)-1, Vitamin D, and discrete members of the family of non-coding RNA peptides called microRNAs (miRNAs) may be crucial biochemical markers that help determine the neuroprotective "window" of HT. Specifically, IGF-1 confers neuroprotection in concert with, and independently of, estrogen and failure of the insulin/IGF-1 axis is associated with metabolic disturbances that increase the risk for stroke. Vitamin D and miRNAs regulate and complement IGF-1 mediated function and neuroprotective efficacy via modulation of IGF-1 availability and neural stem cell and immune cell proliferation, differentiation and secretions. Together, age-related decline of these factors differentially affects stroke risk, severity, and outcome, and may provide a novel therapeutic adjunct to traditional HT practices.

Estrogen and neuroprotection: from clinical observations to molecular mechanisms

We now appreciate that estrogen is a pleiotropic gonadal steroid that exerts profound effects on the plasticity and cell survival of the adult brain. Over the past century, the life span of women has increased, but the age of the menopause remains constant. This means that women may now live over one third of their lives in a hypoestrogenic, postmenopausal state. The impact of prolonged hypoestrogenicity on the brain is now a critical health concern as we realize that these women may suffer an increased risk of cognitive dysfunction and neurodegeneration due to a variety of diseases. Accumulating evidence from both clinical and basic science studies indicates that estrogen exerts critical protective actions against neurodegenerative conditions such as Alzheimer's disease and stroke. Here, we review the discoveries that comprise our current understanding of estrogen action against neurodegeneration. These findings carry far-reaching possibilities for improving the quality of life in our aging population.

Hormone therapy administration in postmenopausal women and risk of stroke

HRT, consisting of estrogens alone, or in combination with a progestogen, is widely used for the relief of symptoms in postmenopausal women. Early observational studies have suggested that HRT might be associated with a reduced risk of cardio- and cerebro-vascular events. These encouraging results prompted randomized controlled trials assessing the risks and benefits of HRT in primary and secondary prevention of arterial vascular events. However, these clinical trials and further observational studies did not confirm the protective effect of HRT; it is now established that HRT increases the risk of stroke. This increased risk is mainly related to an increased risk of ischemic stroke. Oral estrogen alone and combined with progestogen are associated with a similar increased risk, which may be dose dependent. Conversely, a low dose of transdermal estrogens with or without a progestogen does not seem to be associated with such an increased risk of stroke, whereas the impact of tibolone, a synthetic steroid, remains uncertain. In summary, there is now a large amount of evidence demonstrating that HRT is associated with increased risk of stroke, in particular, ischemic subtype.

Hormone therapy and stroke: is it all about timing?

Although women have a lower incidence of stroke than men in most age groups, women have an overall increased lifetime risk of stroke. Women also have unique risk factors for stroke, including the menopausal transition, the existence of debilitating vasomotor symptoms for some women, and the issues related to hormonal treatment for those symptoms. Although the initial studies of hormone therapy (HT) use in postmenopausal women suggested significant protection against heart disease, there was no obvious protection against stroke. Randomized trials of HT for secondary prevention showed a lack of benefit for both heart disease and stroke, and the suggestion of some early risk after initiation. However, the Women's Health Initiative (WHI), a primary prevention study of the impact of HT on women aged 50 to 79 years, showed an increased risk of stroke, whether the HT was estrogen alone or estrogen combined with progestin. Therefore, HT is not recommended for stroke prevention, and it appears to cause harm. The reason for this increased stroke risk is not understood, but some have suggested that the initiation of HT closest to the time of menopausal transition should decrease the risk. Although there was a lower risk of heart disease when HT was initiated earlier, the risk appeared to be the same for stroke regardless of the timing. This was shown in both the WHI and the Nurses' Health Study cohorts. Therefore, more research is needed to understand the mechanisms for the increased stroke risk and to identify those who may be at risk because of HT for vasomotor symptoms, atrophic vaginitis, or osteoporosis, the three remaining indications for HT use in women. Trials are under way to assess the intermediate outcomes of HT on subclinical vascular disease in perimenopausal/early postmenopausal women.

Different cerebrovascular effects of medroxyprogesterone acetate and norethisterone acetate in the New Zealand White rabbit

OBJECTIVE

The lack of a cardioprotective effect of hormone replacement therapy (HRT), as suggested by the Heart and Estrogen/progestin Replacement Study (HERS) and Women's Health Initiative (WHI) may in part be explained by the progestin used. The aim of this study was to elucidate the effect of different progestins on cerebrovascular reactivity in an animal model.

METHODS

Fifty-six ovariectomized New Zealand White rabbits were randomized into seven groups receiving hormone treatment for 4 weeks: medroxyprogesterone acetate (MPA) (10 mg/day); norethisterone acetate (NETA) (3 mg/day); conjugated equine estrogens (CEE) (1.25 mg/day); 17beta-estradiol (E2) (4 mg/day); MPA + CEE (10 mg/day + 1.25 mg/day); NETA + E2 (3 mg/day + 4 mg/day); or placebo. Segments from the basilar and posterior cerebral arteries were mounted in myographs for tension recordings. Concentration-response curves to potassium, acetylcholine, sodium nitroprusside, L-NAME (N(omega)-nitro-L-arginine methyl ester), calcium and endothelin-1 were established.

RESULTS

Treatment with MPA caused a significant increase in vasoconstriction, expressed as E(max) (mN/mm, mean +/- SEM; p < 0.05), in response to potassium (3.18 +/- 0.19 vs. 2.47 +/- 0.19) and calcium (4.00 +/- 0.22 vs. 3.34 +/- 0.14) in the posterior cerebral artery, and to endothelin-1 (6.88 +/- 0.69 vs. 5.22 +/- 0.30) in the basilar artery, when compared with NETA. This difference was neutralized in the groups receiving the combined treatment of MPA + CEE and NETA + E2. No overall differences were seen between CEE and E2.

CONCLUSIONS

In rabbit cerebral arteries, MPA treatment causes a higher development in arterial tension compared with NETA, indicating that different progestins may display different cerebrovascular effects. However, when accompanied by estrogens, as in the case of HRT, this difference is eliminated.

Postmenopausal hormone therapy in clinical perspective

Although many of the risks and benefits of postmenopausal hormone therapy are known, only recently has the magnitude of these effects and their perspective to other therapies become more fully understood. Careful review of randomized controlled trials indicates that the risks of postmenopausal hormone therapy including breast cancer, stroke and venous thromboembolism are similar to other commonly used agents. Overall, these risks are rare (less than 1 event per 1,000 women) and even rarer when initiated in women less than 60 years of age or within 10 years of menopause. In addition, the literature indicates similar benefit of postmenopausal hormone therapy, in women who initiate hormone therapy in close proximity to menopause, to other medications used for the primary prevention of coronory heart disease in women.

Ischemic stroke in a man using estrogen

Ischemic cerebrovascular disease has been associated with oral contraceptives but not standard hormone replacement in women. It is unknown whether or not estrogen therapy in a male is associated with an increased risk of stroke. We report a single case of a genetic male taking high doses of estrogen and progesterone who suffered a stroke. A 46-year-old man was using high doses of estrogen and progesterone while awaiting surgical gender reassignment. He had suffered a deep venous thrombosis 1 year prior to presentation. He developed an acute left visual field cut, left neglect, and left hemiparesis. Neuroimaging disclosed a large right hemispheric stroke. A complete evaluation did not reveal an etiology. No identifiable cause could be found for this patient's stroke, except for his high-dose hormonal therapy. Physicians treating male-to-female transsexuals need to be aware of this rare complication of hormone therapy.

Hormone therapy and cerebrovascular events: a population-based nested case-control study

OBJECTIVE

The relationship between postmenopausal hormone therapy (HT) and cerebrovascular disease has been examined in several epidemiological studies and clinical trials with conflicting results. The authors aimed to evaluate the association between the use of HT and the incidence of first cerebrovascular event.

DESIGN

The study cohort comprised 158,031 women 50 to 69 years old registered in the U.K. General Practice Research Database between 1991 and 1997. The authors conducted a nested case-control analysis using all 920 confirmed cases of cerebrovascular events identified during the follow-up (536 of transient ischemic attack [TIA]; 259 of ischemic stroke; 125 of hemorrhagic stroke) and 10,000 controls.

RESULTS

The odds ratios of TIA, ischemic stroke, and hemorrhagic stroke among women currently using HT were 1.48 (95% CI, 1.17-1.87), 1.12 (95% CI, 0.78-1.59) and 1.21 (95% CI, 0.76-1.93), respectively, compared to never users. The overall risk estimate for having a cerebrovascular event was 1.34 (95% CI, 1.11-1.61). The risk of TIA was greater (1.96) among women using high doses of estrogen (95% CI, 1.34-2.87).

CONCLUSION

Overall, a small increased risk of stroke associated with HT use of comparable magnitude to the one observed in recent clinical trials was found. The increased risk was more apparent for TIA than for stroke and was greater at higher doses.

Estrogens and experimental ischemic stroke: a systematic review

Estrogens are believed to provide females with endogenous protection against cerebrovascular events although clinical trials studying long-term hormone replacement have yielded disappointing results. In contrast, estrogens might be neuroprotective after experimental ischemia. We performed a systematic review of controlled experimental studies that administered estrogens before, or after, cerebral ischemia and measured lesion volume. Relevant studies were found from searching PubMed, Embase and Web of Science. From 161 identified publications, 27 studies using 1,304 experimental subjects were analyzed using the Cochrane Review Manager software. Estrogens reduced lesion volume in a dose-dependent manner, after either transient (P<0.001) or permanent (P<0.001) ischemia and whether administered before or up to 4 h after ischemia onset; no studies assessed efficacy for later time periods. The effect size for estrogens decreased with increasing quality scores for studies of transient ischemia. Estrogens reduced lesion volume when administered to ovariectomized females and young adult males, but had no effect in intact females. Limited data were present for aged animals and the full dose-response relationship was not available in all experimental groups. On the basis of these data, estrogens are a candidate treatment for ischemic stroke, although further preclinical studies are also warranted.

Differential modulation of estrogen receptors (ERs) in ischemic brain injury: a role for ERalpha in estradiol-mediated protection against delayed cell death

Estradiol enhances plasticity and survival of the injured brain. Our previous work demonstrates that physiological levels of estradiol protect against cerebral ischemia in the young and aging brain through actions involving estrogen receptors (ERs) and alterations in gene expression. The major goal of this study was to establish mechanisms of neuroprotective actions induced by low levels of estradiol. We first examined effects of estradiol on the time-dependent evolution of ischemic brain injury. Because estradiol is known to influence apoptosis, we hypothesized that it acts to decrease the delayed phase of cell death observed after middle cerebral artery occlusion (MCAO). Furthermore, because ERs are pivotal to neuroprotection, we examined the temporal expression profiles of both ER subtypes, ERalpha and ERbeta, after MCAO and delineated potential roles for each receptor in estradiol-mediated neuroprotection. We quantified cell death in brains at various times after MCAO and analyzed ER expression by RT-PCR, in situ hybridization, and immunohistochemistry. We found that during the first 24 h, the mechanisms of estradiol-induced neuroprotection after MCAO are limited to attenuation of delayed cell death and do not influence immediate cell death. Furthermore, we discovered that ERs exhibit distinctly divergent profiles of expression over the evolution of injury, with ERalpha induction occurring early and ERbeta modulation occurring later. Finally, we provide evidence for a new and functional role for ERalpha in estradiol-mediated protection of the injured brain. These findings indicate that physiological levels of estradiol protect against delayed cell death after stroke-like injury through mechanisms requiring ERalpha.

Estrogens as neuroprotectants against ischemic stroke

Estrogens have proven vasoprotective properties against atherosclerosis that depend on the direct effect on vascular smooth muscle and endothelium and on systemic actions that imply serum lipids, coagulation and fibrinolytic cascades, vasoactive proteins and antioxidant systems. They also have neuroprotective effects against cerebral ischemia that include antioxidant and anti-inflammatory effects, modulation of protein synthesis, inhibition of apoptosis and trophic effects and preservation of microvascular blood flow in the ischemic area. Estrogenic actions depend on activation of specific estrogen receptors that modulate gene expression and produce long-term effects on vascular endothelial and smooth muscle cells, neurons and glia, on interaction with plasma membrane sites that produce rapid non-genomic actions and also on receptor-independent mechanisms. This paper reviews what it is known about the mechanisms underlying the vaso- and neuroprotective effects of estrogens. Experimental and clinical evidences of such protective effects are also discussed. Therapeutical implications for stroke prevention and treatment derived from the available evidence are considered.

Oestrogen and stroke in women: assessment of risk

The Women's Health Initiative reported an increased risk of stroke with hormone therapy, which has had a major effect on the use of these drugs. The increased risk was unexpected because research with animals showed that oestrogen reduces the extent of experimental strokes, and in human beings, oestrogen improves endothelial-dependent blood flow and lipid profiles. The mechanisms of risk might be related to oestrogen's proinflammatory and prothrombotic effects. However, the overall risk is still uncertain because of the complex actions of oestrogen at different doses, with or without progesterone, and the presence or absence of atherosclerotic risk factors. A similar debate about oral contraceptives and stroke risk in young women continues as data accumulate. Further studies are needed to identify the mechanisms of risk of stroke with oestrogen, as well as the risk factors that put women at particularly high risk of stroke with these hormones.

Combined postmenopausal hormone therapy and cardiovascular disease: toward resolving the discrepancy between observational studies and the Women's Health Initiative clinical trial

Observational research on postmenopausal hormone therapy suggests a 40-50% reduction in coronary heart disease incidence among women using these preparations. In contrast, the Women's Health Initiative clinical trial of estrogen plus progestin found an elevated incidence over a 5.6-year intervention period through July 7, 2002. Toward explaining this discrepancy, the authors analyzed data from this trial, which included 16,608 postmenopausal women aged 50-79 years, and corresponding data from 53,054 women in the Women's Health Initiative observational study, 33% of whom were estrogen-plus-progestin users at baseline. Estrogen-plus-progestin hazard ratio estimates for coronary heart disease, stroke, and venous thromboembolism in the observational study were 39-48% lower than those in the clinical trial following age adjustment. However, hazard ratios tended to decrease with increasing time from initiation of estrogen-plus-progestin use, and observational study hazard ratio estimates are heavily weighted by longer-term use while clinical trial hazard ratio estimates reflect shorter-term use. Following control for time from estrogen-plus-progestin initiation and confounding, hazard ratio estimates were rather similar for the two cohorts, although there was evidence of some remaining difference for stroke. These analyses have implications for both the design and the analysis of observational studies.

Modulatory effects of progesterone on inducible nitric oxide synthase expression in vivo and in vitro

Nitric oxide (NO) is produced in the CNS following injury-induced expression of inducible nitric oxide synthase (iNOS), yet its role as protective or damaging is unclear. Previous studies investigating the therapeutic potential of female sex steroids in stroke and trauma suggest that NO from this source is harmful, since oestradiol and progesterone decreased the level of iNOS expression in vitro and improved neurological outcome. We investigated the effects of progesterone on stroke-induced expression of iNOS in mice, as well as cytokine-induced expression of iNOS and its transcriptional activators in cells relevant to injury. We observed a significant reduction in stroke-induced iNOS transcript in progesterone-treated mice and in cultured macrophages. In contrast, progesterone significantly amplifed cytokine-induced iNOS mRNA in cultured primary astrocytes, although the expression of protein was decreased. We sequenced upstream of the 1.5 kb reported iNOS promoter region and identified a potential progesterone response element (PRE). Astrocytes transiently transfected with iNOS promoter/CAT reporter gene constructs containing the PRE displayed a significant increase in induction of CAT expression after progesterone treatment, and this was diminished in cells transfected with a construct containing a disrupted PRE. These observations suggest the involvement of iNOS in the neuroprotective effects of progesterone.

17 Beta-estradiol prevents focal cerebral ischemic damages via activation of Akt and CREB in association with reduced PTEN phosphorylation in rats

This study aimed to assess the signaling pathway of the neuroprotective action of estrogen in the cerebral ischemic injury evoked by subjecting rats to 2-h occlusion of the middle cerebral artery (MCA) followed by 24-h reperfusion. Rats received 17 beta-estradiol (1, 4 and 10 mg/kg, i.p.) 24 h before and 5 min after the completion of 2-h MCA occlusion. The cerebral infarct area was consistently observed in the cortex and striatum of the left hemisphere. Increased terminal deoxynucleotidyl transferase-mediated deoxyuridine-biotin nick-end labeling (TUNEL)-positive cells and DNA fragmentation in the penumbral zone were significantly reduced by 17 beta-estradiol. In line with these results, 17 beta-estradiol significantly increased Akt and cyclic AMP response element binding protein (CREB) with increased Bcl-2 protein in the ischemic area, whereas the elevated the phosphatase and tensin homolog deleted from chromosome10 (PTEN) phosphorylation was significantly reduced with decreased Bax protein and cytochrome c release. Inhibition of DNA fragmentation, PTEN phosphorylation, and Akt activation by 17 beta-estradiol were antagonized by iberiotoxin, a maxi-K channel blocker. Taken together, it is suggested that suppression of cerebral ischemic injury by 17 beta-estradiol may be ascribed to the maxi-K channel opening-coupled downregulation of PTEN phosphorylation and upregulation of Akt and CREB phosphorylation with resultant increase in Bcl-2 protein and decrease in Bax protein and cytochrome c release.

Progesterone enhances functional recovery after middle cerebral artery occlusion in male mice

Sex differences have been observed in the outcome after ischemia that are believed to be attributable to sex steroid hormones. The present study investigated the possible benefits of progesterone administration after focal cerebral ischemia. Male mice underwent 60-minute middle cerebral artery occlusion (MCAO) and received progesterone (8 mg/kg, intraperitoneally) or vehicle (dimethyl sulfoxide) 1, 6, and 24 hours after MCAO. The lesion volume at 48 hours after MCAO was significantly reduced (P < 0.05) in progesterone-treated mice compared with vehicle-treated mice. All other mice underwent tests of well being (survival rate and body weight recovery), motor ability (grid test and rotarod), and cognitive ability (water maze) for up to 21 days. MCAO significantly worsened outcome in all of these tests compared with shams. Progesterone treatment was beneficial in that compared with vehicle, it significantly improved survival rate, weight recovery, and motor ability. This improvement was most apparent during water maze testing, where progesterone-treated mice were indistinguishable from shams in terms of acquiring the task. These results indicate beneficial effects of progesterone administration after cerebral ischemia and illustrate the need to further investigate the mechanisms of progesterone action.

A comparative review of the risks and benefits of hormone replacement therapy regimens

The Women's Health Initiative (a large, randomized, placebo-controlled trial) investigated the effect of conjugated equine estrogens combined with medroxyprogesterone acetate on specific potential long-term benefits and risks. A review of the clinical studies that have investigated different types and regimens of estrogens combined with progestins was conducted to assess how applicable the results of the Women's Health Initiative are to hormone replacement therapy regimens in general. The studies that were reviewed were limited to randomized clinical trials and observational studies that have been published over the last 15 years (1987-2002) and to meta-analyses and reviews that may have included the literature before 1987. The increased risks for venous thromboembolism, stroke, coronary heart disease, and breast cancer that were identified in the Women's Health Initiative trial have also been reported with postmenopausal hormone therapies that contain a variety of estrogen and progestin products. The beneficial effects that were noted in the Women's Health Initiative, with respect to reductions in fractures and colorectal cancer, have not been evaluated in large, randomized controlled trials that use different estrogen/progestin combinations; however, observational trials that used a variety of estrogen or hormone replacement therapy products and randomized clinical studies that evaluated bone mineral density (an excellent predictor of fracture risk) with different estrogen/hormone replacement therapy regimens would suggest that results would be similar to those found in the Women's Health Initiative. Although the relief of menopausal symptoms, the primary reason women seek treatment, was not included in the overall benefit/risk analysis of the Women's Health Initiative, numerous trials suggest that all therapies are effective. Overall, these data indicate that the benefit/risk analysis that was reported in the Women's Health Initiative can be generalized to all postmenopausal hormone replacement therapy products.

[Hormonal replacement therapy and cardiovascular risk: contra-indication or non-indication?]

In the field of cardiovascular risk and treatment of menopause, only one instruction can be currently given to the prescribers: caution. Since the publication of heart and estrogen/progestin replacement study, the dogma of the cardioprotection induced by hormonal replacement therapy began to crumble. This paradigm had set up with observational studies, which for the majority had neglected in their retrospective analysis the socio-economic factor. Since shock caused by HERS, nine randomized studies are accumulated. All are negative, except for EPAT. At present, all confirms the prophetic recommendation of J.E. Rossow, in 1996: "Putting the brakes on the bandwagon". The last guidelines formally prohibit HRT in coronary women or with the aim of primary prevention of chronic conditions in healthy postmenopausal women.

Effect of hormone replacement therapy on cardiovascular disease: current opinion

Cardiovascular disease (CVD) is increasingly being recognised as having a profound effect on women, especially after menopause. Lack of oestrogen has been targeted as one of the reasons for increased incidence of CVD in postmenopausal women. Oestrogen has been found to have favourable effects on lipid profile, tone of vascular smooth muscle cells and fibrinogen levels. Several observational studies have supported these experimental findings, consistently demonstrating reduced cardiovascular risks in users of hormone replacement therapy (HRT). However, evidence from recent clinical trials has challenged this widespread belief. Heart and Estrogen/Progesterone Replacement Study II, Estrogen Replacement and Atherosclerosis trial and more recently, Women's Health Initiative, have shown that HRT has no role in primary and secondary prevention of CVD and most authorities currently do not advocate HRT for the prevention of CVD.

Estrogens: protective or risk factors in brain function?

Over the past century, the average lifespan of women has increased from 50 to over 80 years, but the age of the menopause has remained fixed at 51 years. This "change of life" is marked by a dramatic and permanent decrease in circulating levels of ovarian estrogens. Therefore, more women will live a greater proportion of their lives in a chronic hypoestrogenic state. Ovarian steroid hormones are pleiotropic and have multiple, diverse, and possibly opposing actions in different contexts. In light of recent reports of the possible health risks of hormone replacement therapy (HRT) on several different physiological systems, the question of whether estrogens are protective or risk factors must be carefully re-evaluated.

Loss of benefit from estrogen replacement therapy in diabetic ovariectomized female rats subjected to transient forebrain ischemia

In nondiabetic animals, estrogen has been shown to provide significant neuroprotection in focal and transient forebrain ischemia models. However, that neuroprotection may be diminished or lost in the diabetic. In this study, we compared the level of brain damage in intact, ovariectomized (OVX) and 17beta-estradiol (E(2))-treated OVX female rats rendered diabetic and chronically ( approximately 4 weeks) hyperglycemic via streptozotocin (STZ). Rats were subjected to 20 min of unilateral transient forebrain ischemia (reduction in cortical CBF to 20% of baseline). Neurologic function was analyzed daily and brain histopathology (in H&E-stained sections) was evaluated at 72 h of reperfusion. Supplemental histopathologic information was obtained from additional TUNEL-stained sections. When comparing neurologic outcome scores in the three groups, E(2)-treated OVX females displayed the highest degree of dysfunction and intact females the least (OVX rats not treated with E(2) were intermediate), with the difference between the intact and E(2)-treated groups being statistically significant. That same order was often observed with the regional histopathologic analyses of H&E-stained tissue. A significantly higher magnitude of neuronal loss in both OVX groups, when compared to intact females, was observed in the CA4 sector of the hippocampus and in the cortex. In addition, cell loss in the dorsal thalamus of the E(2)-treated group was significantly greater than in the intact females. Those results were generally corroborated by TUNEL-analysis, with 67% of the E(2)-treated, 33% of the control OVX, and only 17% of the intact females displaying TUNEL-positive cells in multiple regions. In conclusion, the present findings strongly suggest that the neuroprotective benefits of estrogen replacement therapy may be lost in the diabetic female rat.

Postmenopausal hormone therapy and the risk of cardiovascular disease: the epidemiologic evidence

The relation between hormone use in postmenopausal women and cardiovascular disease remains controversial. Whereas epidemiologic studies and clinical studies assessing several intermediate cardiovascular disease endpoints indicate a clear benefit for the primary prevention of coronary artery disease (CAD), secondary-prevention trials of relatively short duration do not support a benefit. More recent epidemiologic studies continue to supply evidence that long-term postmenopausal hormone therapy may reduce the risk for CAD in healthy women. Adding progestin to the regimen does not appear to attenuate the benefit. The Nurses' Health Study and studies from Europe, where estradiol is the commonly prescribed form of estrogen, suggest that estrogen at lower doses may confer similar benefit. However, remarkably consistent data from both epidemiologic studies and a secondary-prevention trial indicate a significantly increased risk of venous thromboembolism with hormone use. The data on stroke are inconclusive, but there is little evidence to suggest a benefit of hormone use on either ischemic or hemorrhagic stroke. Existing evidence indicates that the various potential benefits and risks should be weighed carefully when prescribing hormone therapy to a postmenopausal woman.

Maximizing health in menopausal women with disabilities

There are nearly 30 million women with disabilities in the United States. Of these, more than 16 million are over the age of 50. Years ago, women with disabilities did not commonly live to the age of menopause, and, if they did, they reached this stage of life in a very debilitated condition. Now, women with disabilities are entering their mature years as active members of society who can look forward to productive futures. Because the health needs of women with disabilities might differ from those of other women, special attention should be focused on how physiological changes of perimenopausal and menopausal states affect this population. In addition to functional changes that might affect menopausal women with disabilities, basic health maintenance issues may be adversely affected by environmental factors. Physical barriers can influence compliance with preventive health screening that is essential in aging populations. Treatment options might need to be tailored to the individual. The disabling condition itself may progress, resulting in secondary conditions requiring creative interventions. A comprehensive evaluation and the development of a suitable management plan, which takes into account the multifactorial nature of aging as a disabled woman, are essential in delivering optimal care to this population.

Conjugated estrogen administration improves common carotid artery elastic properties in normotensive postmenopausal women

BACKGROUND

Various vascular effects of estrogens have been proposed to explain further the beneficial effect of replacement therapy in cardiovascular events.

HYPOTHESIS

The study was undertaken to assess the effect of conjugated estrogen on the elastic properties of the large arteries in normotensive, healthy, postmenopausal women.

METHODS

Toward this end, we investigated the acute effect of conjugated estrogen on the elastic properties of the common carotid artery (CCA) in 20 normotensive, healthy, postmenopausal women (age 54+/-3 years) at baseline and 20 min after the intravenous administration of 1.25 mg conjugated estrogens. The CCA distensibility was derived by a combination of surface ultrasonographic data and simultaneous blood pressure measurements at the brachial artery. The carotid pulsatility index, a measure of brain impedance, was determined electronically by tracing the CCA Doppler waveform.

RESULTS

At baseline, CCA distensibility had a negative correlation with both patients' age and time since menopause (r = -0.57 and r = -0.48, p < 0.05 for both cases). After estrogen administration, estradiol and estrone plasma levels were restored to the range of usual premenopausal values. Estrogen induced a significant increase in CCA distensibility by 0.92+/-0.005 dyne(-1) x cm2 x 10(-6) (from 2.03 to 2.95 dyne(-1) x cm2 x 10(-6)) and a significant reduction in CCA pulsatility index by 0.24+/-0.06, (from 2.17 to 1.93) (p < 0.001 for both cases). The improvement in CCA distensibility had a negative correlation with both patients' age and time since menopause (r= -0.46 and r = -0.44, respectively, p < 0.05 for both cases).

CONCLUSIONS

Acute conjugated estrogen administration induced an improvement in CCA elasticity and a reduction in brain impedance in normotensive, postmenopausal women. As the age of women and the time since menopause increased, the improvement in carotid distensibility decreased in such selected subjects.

Estrogens modulate experimentally induced apoptosis of granule cells in the adult hippocampus

Estrogens are known to have broad effects on neuronal plasticity, but their specific role in neuronal cell death has not been determined. In the present study, we investigated the effects of beta-estradiol on an experimental model of apoptosis of granule cells of the dentate gyrus, i.e., apoptosis induced by intraventricular injection of the microtubule polymerization inhibitor colchicine. Cell death was characterized with multiple methods, including TUNEL and DNA electrophoresis. Nonrandom digestion of DNA was observed within 8-10 hours after colchicine injection, followed by condensation and fragmentation of granule cell nuclei and extensive anterograde degeneration of mossy fibers/terminals in 2 days. We compared the outcomes of the above-described manipulation in ovariectomized or sham-operated rats and animals treated daily with beta-estradiol or vehicle. Animals were lesioned with colchicine or vehicle 2 weeks after ovariectomy or sham operation. Beta-estradiol or vehicle was administered for 1 week prior to lesion and was continued for a further 2 weeks. Total numbers and densities of granule cells in different animal groups were counted by stereology in various anteroposterior levels of the hippocampus. Our results show that ovariectomy intensifies colchicine-induced granule cell apoptosis, which is ameliorated by exogenous beta-estradiol. In doses that ameliorate the adverse effect of ovariectomy, exogenous beta-estradiol appears to have no effect of preventing granule cell death in animals with intact ovaries; i.e., an estrogen excess is not more neuroprotective than physiological levels of these hormones. Taken together, our results indicate that estrogen deprivation increases the vulnerability of hippocampal neurons to injury and may predispose to neurological diseases occurring after menopause.

A clinical trial of estrogen-replacement therapy after ischemic stroke

BACKGROUND

Observational studies have suggested that estrogen-replacement therapy may reduce a woman's risk of stroke and death.

METHODS

We conducted a randomized, double-blind, placebo-controlled trial of estrogen therapy (1 mg of estradiol-17beta per day) in 664 postmenopausal women (mean age, 71 years) who had recently had an ischemic stroke or transient ischemic attack. Women were recruited from 21 hospitals in the United States and were followed for the occurrence of stroke or death.

RESULTS

During a mean follow-up period of 2.8 years, there were 99 strokes or deaths among the women in the estradiol group, and 93 among those in the placebo group (relative risk in the estradiol group, 1.1; 95 percent confidence interval, 0.8 to 1.4). Estrogen therapy did not reduce the risk of death alone (relative risk, 1.2; 95 percent confidence interval, 0.8 to 1.8) or the risk of nonfatal stroke (relative risk, 1.0; 95 percent confidence interval, 0.7 to 1.4). The women who were randomly assigned to receive estrogen therapy had a higher risk of fatal stroke (relative risk, 2.9; 95 percent confidence interval, 0.9 to 9.0), and their nonfatal strokes were associated with slightly worse neurologic and functional deficits.

CONCLUSIONS

Estradiol does not reduce mortality orthe recurrence of stroke in postmenopausal women with cerebrovascular disease. This therapy should not be prescribed for the secondary prevention of cerebrovascular disease.

Hormone replacement therapy and stroke: risk, protection or no effect?

Despite declining death rates due to stroke over the last several decades, stroke remains the third leading killer (after heart disease and cancer) of women in most developed countries. Because stroke not only kills but also leaves many survivors mentally and physically impaired, control of the disease must be through primary prevention. Several observations lead to the speculation that estrogen may reduce stroke risk. This paper reviews the epidemiologic studies that have evaluated the association of hormone replacement therapy (HRT) and stroke. In the past 25 years, 29 studies have produced no conclusive evidence of a beneficial effect. The lack of consistency in stroke endpoints, definition of HRT user, estrogen preparation, and influence of combined regimen might account in part for the unclear relationship. Nonetheless, the preponderance of evidence suggests that HRT does not increase stroke risk. Some data indicate that estrogen users have a moderately reduced risk of fatal stroke, but details about the optimal dose, duration and type of estrogen are insufficient. The apparent difference in the findings of studies of fatal and non-fatal stroke suggests that estrogen may prevent the most lethal form of stroke or may improve survival. Additional data from ongoing randomized clinical trials in the coming years may help resolve the question of the effect of HRT on stroke morbidity and mortality.

Evidence-based practice in women's health: hormone therapy for women at menopause

Women's health providers, especially midwives, must take into account the known benefits and risks, as well as the "unknown," when recommending the use of hormone therapy for menopausal women, especially as it relates to heart disease, breast cancer, impaired cognition, and osteoporosis. The most recent evidence available from various studies about the benefits and risks of estrogen and hormone therapy at menopause suggests that, although hormone therapy may be protective in some women against heart disease and osteoporosis, evidence is less certain about the benefits of hormone protection against impaired cognition and the risks of breast cancer with use. The clinical approach used by midwives in which individualizing care based on each woman's health status history as well as preferences is highly appropriate for women in the perimenopausal and menopausal period.

Relaxant effects of 17-beta-estradiol in cerebral arteries through Ca(2+) entry inhibition

Estrogens account for gender differences in the incidence and outcome of stroke, but it remains unclear to what extent neuroprotective effects of estrogens are because of parenchymal or vascular actions. Because reproductive steroids have vasoactive properties, the authors assessed the effects and mechanisms of action of 17-beta-estradiol in rabbit isolated basilar artery. Cumulative doses of 17-beta-estradiol (0.3 micromol/L to 0.1 mmol/L) induced concentration-dependent relaxation that was larger in basilar than carotid artery, in male than female basilar artery, and in KCl-precontracted than UTP-precontracted male basilar artery. Endothelium removal did not modify relaxation induced by 17-beta-estradiol in basilar artery, whereas relaxation induced by acetylcholine (1 nmol/L to 0.1 mmol/L) was almost abolished. Neither the estrogen receptor antagonist ICI 182,780 (1 micromol/L), nor the protein synthesis inhibitor cycloheximide (1 micromol/L) affected 17-beta-estradiol-induced relaxations. Relaxations induced by the K(+) channel openers NS1619 and pinacidil in the same concentration range were greater and lower, respectively, when compared with relaxation to 17-beta-estradiol, which was not significantly modified by incubation with the K(+) channel blockers charybdotoxin (1 nmol/L and 0.1 micromol/L) or glibenclamide (10 nmol/L and 1 micromol/L). Preincubation with 17-beta-estradiol (3 to 100 micromol/L) produced concentration-dependent inhibition of CaCl(2)-induced contraction, with less potency than the Ca(2+) entry blocker nicardipine (0.01 to 10 nmol/L). The authors conclude that 17-beta-estradiol induces endothelium-independent relaxation of cerebral arteries with tissue and gender selectivity. The relaxant effect is because of inhibition of extracellular Ca(2+) influx to vascular smooth muscle, but activation of estrogen receptors, protein synthesis, or K(+) efflux are not involved. Relatively high pharmacologic concentrations of 17-beta-estradiol causing relaxation preclude acute vascular effects of physiologic circulating levels on the cerebral circulation.

Association of serum estrogen level and ischemic neuroprotection in female rats

Estrogen-related ischemic neuroprotection has been documented in male and ovariectomized female rats. The precise molecular mechanism underlying estrogen's neuroprotective effect remains obscure. In the present study, we examined whether endogenous estrogen levels affect post-ischemic outcomes in normal cycling female rats. Occlusion of both the common carotid arteries and the right middle cerebral artery (1.5 h) followed by reperfusion (24 h) caused cortical infarction, increased neutrophil accumulation, and elevated antioxidant enzyme and lactate dehydrogenase activities. These post-ischemic changes varied in the female rats and were inversely correlated with circulating estrogen levels. More severe post-ischemic changes and injury accompanied the decline in circulating estrogen levels in normal cycling female rats, indicating that estrogen is probably the major hormonal player in female resistance to ischemia.

Estrogens: trophic and protective factors in the adult brain

Our appreciation that estrogens are important neurotrophic and neuroprotective factors has grown rapidly. Although a thorough understanding of the molecular and cellular mechanisms that underlie this effect requires further investigation, significant progress has been made due to the availability of animal models in which we can test potential candidates. It appears that estradiol can act via mechanisms that require classical intracellular receptors (estrogen receptor alpha or beta) that affect transcription, via mechanisms that include cross-talk between estrogen receptors and second messenger pathways, and/or via mechanisms that may involve membrane receptors or channels. This area of research demands attention since estradiol may be an important therapeutic agent in the maintenance of normal neural function during aging and after injury.

Neuroprotection by estradiol

This review highlights recent evidence from clinical and basic science studies supporting a role for estrogen in neuroprotection. Accumulated clinical evidence suggests that estrogen exposure decreases the risk and delays the onset and progression of Alzheimer's disease and schizophrenia, and may also enhance recovery from traumatic neurological injury such as stroke. Recent basic science studies show that not only does exogenous estradiol decrease the response to various forms of insult, but the brain itself upregulates both estrogen synthesis and estrogen receptor expression at sites of injury. Thus, our view of the role of estrogen in neural function must be broadened to include not only its function in neuroendocrine regulation and reproductive behaviors, but also to include a direct protective role in response to degenerative disease or injury. Estrogen may play this protective role through several routes. Key among these are estrogen dependent alterations in cell survival, axonal sprouting, regenerative responses, enhanced synaptic transmission and enhanced neurogenesis. Some of the mechanisms underlying these effects are independent of the classically defined nuclear estrogen receptors and involve unidentified membrane receptors, direct modulation of neurotransmitter receptor function, or the known anti-oxidant activities of estrogen. Other neuroprotective effects of estrogen do depend on the classical nuclear estrogen receptor, through which estrogen alters expression of estrogen responsive genes that play a role in apoptosis, axonal regeneration, or general trophic support. Yet another possibility is that estrogen receptors in the membrane or cytoplasm alter phosphorylation cascades through direct interactions with protein kinases or that estrogen receptor signaling may converge with signaling by other trophic molecules to confer resistance to injury. Although there is clear evidence that estradiol exposure can be deleterious to some neuronal populations, the potential clinical benefits of estrogen treatment for enhancing cognitive function may outweigh the associated central and peripheral risks. Exciting and important avenues for future investigation into the protective effects of estrogen include the optimal ligand and doses that can be used clinically to confer benefit without undue risk, modulation of neurotrophin and neurotrophin receptor expression, interaction of estrogen with regulated cofactors and coactivators that couple estrogen receptors to basal transcriptional machinery, interactions of estrogen with other survival and regeneration promoting factors, potential estrogenic effects on neuronal replenishment, and modulation of phenotypic choices by neural stem cells.

Primary stroke prevention

Stroke is one of the leading causes of death and disability worldwide. Although important advances in therapeutic approaches have been made, treatment is still far from satisfactory. Thus, major efforts should be made on stroke prevention. We present evidence-based recommendations for primary stroke prevention. Changes to modifiable risk factors, the role of drugs and surgery are discussed. New markers may help identification of subjects at high risk.

Gender differences and the effects of synthetic exogenous and non-synthetic estrogens in focal cerebral ischemia

The role of gender difference and estrogen in ischemic cerebrovascular events is controversial. Evidence is lacking as to whether or not there are significant gender differences in the incidence and outcome of stroke in the clinical setting. Recent clinical epidemiological studies have demonstrated that there is no significant association between the use of hormonal replacement therapy and the risk of stroke. However, several animal studies have shown that there are gender differences in stroke outcome and that exogenous administered estrogens are neuroprotective. In this study, the influence of gender differences and the effects of synthetic and non-synthetic estrogens were examined in a model of focal cerebral ischemia using 210 male, intact female, and ovariectomized female rats. All animals underwent 3 h of middle cerebral artery and bilateral common carotid artery occlusion. After 72 h, the rats were sacrificed and stained for histological assessment of infarction. There were no gender differences in infarction volume. Intravenous administration of either low or high dose 17 beta-estradiol or tibolone did not alter infarct volume. Subcutaneous administration of low and high dose 17beta-estradiol using 7-day release pellets did not alter infarct volume. Low dose tibolone using implanted 7-day release pellets did not alter infarct volume. However, high dose tibolone using implanted 7-day release pellets significantly (P<0.05) reduced infarct volume only in ovariectomized female rats. These results demonstrate that estrogen therapy has no effect on infarction volume following severe focal cerebral ischemia.

Risk of hormone replacement therapy in stroke patients

Hormone replacement therapy (HRT) (oestrogen with or without progestin) is often initiated with the onset of menopause to decrease symptoms of oestrogen deficiency, such as vasomotor instability (hot flashes) and urogenital effects (1-3). HRT can also prevent long-term consequences of oestrogen deficiency, such as osteoporosis and cardiovascular disease (1-3). The decision to start HRT in peri- and postmenopausal women is complicated by concerns of increased risk for thromboembolic events, uterine cancer and breast cancer (2-4). Thromboembolic stroke is a particular concern due to its association with the use of oral contraceptives with high oestrogen content (3, 4). However, for older women it has been suggested that HRT use decreases or has no effect on stroke risk (5-9). Should these findings apply to a women with a history of thromboembolism, in this case ischemic stroke?

Estrogen reduces mouse cerebral artery tone through endothelial NOS- and cyclooxygenase-dependent mechanisms

Gender and estrogen status are known to influence the incidence and severity of cerebrovascular disease. The vasoprotective effects of estrogen are thought to include both nitric oxide-dependent and independent mechanisms. Therefore, using small, resistance-sized arteries pressurized in vitro, the present study determined the effect of gender and estrogen status on myogenic reactivity of mouse cerebral arteries. Luminal diameter was measured in middle cerebral artery segments from males and from females that were either untreated, ovariectomized (OVX), or OVX with estrogen replacement (OVX + EST). The maximal passive diameters of arteries from all four groups were similar. In response to increases in transmural pressure, diameters of arteries from males and OVX females were smaller compared with diameters of arteries from either untreated or OVX + EST females. In the presence of N(G)-nitro-L-arginine methyl ester, artery diameters decreased in all groups, but diameters remained significantly smaller in arteries from males and OVX females compared with untreated and OVX + EST females. After endothelium removal or when inhibition of nitric oxide synthase and cyclooxygenase were combined, differences in diameters of arteries from OVX and OVX + EST were abolished. These data suggest that chronic estrogen treatment modulates myogenic reactivity of mouse cerebral arteries through both endothelium-derived cyclooxygenase- and nitric oxide synthase-dependent mechanisms.

Estrogen as a neuroprotectant in stroke

Recent evidence suggests that reproductive steroids are important players in shaping stroke outcome and cerebrovascular pathophysiologic features. Although women are at lower risk for stroke than men, this native protection is lost in the postmenopausal years. Therefore, aging women sustain a large burden for stroke, contrary to a popular misconception that cancer is the main killer of women. Further, the value of hormone replacement therapy in stroke prevention or in improving outcome remains controversial. Estrogen has been the best studied of the sex steroids in both laboratory and clinical settings and is considered increasingly to be an endogenous neuroprotective agent. A growing number of studies demonstrate that exogenous estradiol reduces tissue damage resulting from experimental ischemic stroke in both sexes. This new concept suggests that dissecting interactions between estrogen and cerebral ischemia will yield novel insights into generalized cellular mechanisms of injury. Less is known about estrogen's undesirable effects in brain, for example, the potential for increasing seizure susceptibility and migraine. This review summarizes gender-specific aspects of clinical and experimental stroke and results of estrogen treatment on outcome in animal models of cerebral ischemia, and briefly discusses potential vascular and parenchymal mechanisms by which estrogen salvages brain.