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

Diagnosis, Treatment, and Prevention of Stroke in Transgender Adults

Purpose of Review

To identify the current state of science on stroke in transgender adults and highlight gaps in need of further research. We will review current research on cerebrovascular risk and disease, hormone therapy, and stroke in transgender individuals. Finally, we will provide a framework for healthcare providers to prevent and reduce disparities through inclusive care practices.

Recent Findings

Transgender people experience unique stroke risk factors, secondary to both psychosocial stress and health-related behaviors. These include higher rates of HIV, tobacco use, stimulant use, and hepatitis C. The use of gender-affirming hormone therapy may lead to an increased risk for ischemic stroke, but the data are limited and require further research.

Summary

Recent research has highlighted the numerous healthcare disparities faced by transgender individuals. Regarding stroke disparities, these are multifactorial and include contributions from health-related behaviors, inadequate access to care, the use of hormonal therapy, and minority stress. Further research is needed to increase access to care and reduce the substantial gap in outcomes for these individuals.

Oral Contraceptives, Hormone Replacement Therapy, and Stroke Risk

BACKGROUND

Millions of women worldwide use exogenous hormones as oral contraceptives or hormone replacement therapy. Still, time-dependent and long-term consequences of exogenous hormones on stroke risk remains unclear.

METHODS

We examined the association between self-reported oral contraceptive and hormone replacement therapy use and stroke risk in 257 194 women from the UK Biobank, born between 1939 and 1970. Outcomes included any type of stroke, ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. Exposures were analyzed as time-varying variables in Cox regression models.

RESULTS

During first year of oral contraceptive use, an increased event rate of any stroke was observed (hazard ratio [HR], 2.49 [95% CI, 1.44-4.30]), while the hazards were found to be comparable during remaining years of use (HR, 1.00 [95% CI, 0.86-1.14]), compared with nonusers. Similarly, first year of hormone replacement therapy use was associated with higher hazard rates of any stroke (HR, 2.12 [95% CI, 1.66-2.70]), as well as cause-specific stroke, including ischemic stroke (HR, 1.93 [95% CI, 1.05-3.57]) and subarachnoid hemorrhage (HR, 2.17 [95% CI, 1.25-3.78]), which remained increased for any stroke during remaining years of use (HR, 1.18 [95% CI, 1.05-1.31]), and after discontinuation (HR, 1.16 [95% CI, 1.02-1.32]).

CONCLUSIONS

Oral contraceptive use and hormone replacement therapy were associated with an increased risk of stroke, especially during the first year of use, possibly due to immediate changes in hemostatic balance. This study provides new insights on the effects of hormone exposure on stroke risk and provide evidence of not only an overall risk but also a pronounced effects seen in the beginning of treatment.

Associations between Aquaglyceroporin Gene Polymorphisms and Risk of Stroke among Patients with Hypertension

Background

Dysregulations of AQP7 and AQP9 were found to be related to lipid metabolism abnormality, which had been proven to be one of the mechanisms of stroke. However, limited epidemiological studies explore the associations between AQP7 and AQP9 and the risk of stroke among patients with hypertension in China.

Aims

We aimed to investigate the associations between genetic variants in AQP7 and AQP9 and the risk of stroke among patients with hypertension, as well as to explore gene-gene and gene-environment interactions.

Methods

Baseline blood samples were drawn from 211 cases with stroke and 633 matched controls. Genomic DNA was extracted by a commercially available kit. Genotyping of 5 single nucleotide polymorphisms (SNPs) in AQP7 (rs2989924, rs3758269, and rs2542743) and AQP9 (rs57139208, rs16939881) was performed by the polymerase chain reaction assay with TaqMan probes.

Results

Participants with the rs2989924 GG genotype were found to be with a 1.74-fold increased risk of stroke compared to those with the AA+AG genotype, and this association remained significant after adjustment for potential confounders (odds ratio (OR): 1.74, 95% confidence interval (CI): 1.23-2.46). The SNP rs3758269 CC+TT genotype was found to be with a 33% decreased risk of stroke after multivariate adjustment (OR: 0.67, 95% CI: 0.45-0.99) compared to the rs3758269 CC genotype. The significantly increased risk of stroke was prominent among males, patients aged 60 or above, and participants who were overweight and with a harbored genetic variant in SNP rs2989924. After adjusting potential confounders, the SNP rs3758269 CT+TT genotype was found to be significantly associated with a decreased risk of stroke compared to the CC genotype among participants younger than 60 years old or overweight. No statistically significant associations were observed between genotypes of rs2542743, rs57139208, or rs16939881 with the risk of stroke. Neither interactions nor linkage disequilibrium had been observed in this study.

Conclusions

This study suggests that SNPs rs2989924 and rs3758269 are associated with the risk of stroke among patients with hypertension, while there were no statistically significant associations between rs2542743, rs57139208, and rs16939881 and the risk of stroke being observed.

The effect of age, sex and strains on the performance and outcome in animal models of stroke

Stroke is one of the leading causes of death worldwide, and the majority of cerebral stroke is caused by occlusion of cerebral circulation, which eventually leads to brain infarction. Although stroke occurs mainly in the aged population, most animal models for experimental stroke in vivo almost universally rely on young-adult rodents for the evaluation of neuropathological, neurological, or behavioral outcomes after stroke due to their greater availability, lower cost, and fewer health problems. However, it is well established that aged animals differ from young animals in terms of physiology, neurochemistry, and behavior. Stroke-induced changes are more pronounced with advancing age. Therefore, the overlooked role of age in animal models of stroke could have an impact on data quality and hinder the translation of rodent models to humans. In addition to aging, other factors also influence functional performance after ischemic stroke. In this article, we summarize the differences between young and aged animals, the impact of age, sex and animal strains on performance and outcome in animal models of stroke and emphasize age as a key factor in preclinical stroke studies.

Postmenopausal hormone therapy and risk of stroke: A pooled analysis of data from population-based cohort studies

BACKGROUND

Recent research indicates a favourable influence of postmenopausal hormone therapy (HT) if initiated early, but not late, on subclinical atherosclerosis. However, the clinical relevance of timing of HT initiation for hard end points such as stroke remains to be determined. Further, no previous research has considered the timing of initiation of HT in relation to haemorrhagic stroke risk. The importance of the route of administration, type, active ingredient, and duration of HT for stroke risk is also unclear. We aimed to assess the association between HT and risk of stroke, considering the timing of initiation, route of administration, type, active ingredient, and duration of HT.

METHODS AND FINDINGS

Data on HT use reported by the participants in 5 population-based Swedish cohort studies, with baseline investigations performed during the period 1987-2002, were combined in this observational study. In total, 88,914 postmenopausal women who reported data on HT use and had no previous cardiovascular disease diagnosis were included. Incident events of stroke (ischaemic, haemorrhagic, or unspecified) and haemorrhagic stroke were identified from national population registers. Laplace regression was employed to assess crude and multivariable-adjusted associations between HT and stroke risk by estimating percentile differences (PDs) with 95% confidence intervals (CIs). The fifth and first PDs were calculated for stroke and haemorrhagic stroke, respectively. Crude models were adjusted for age at baseline only. The final adjusted models included age at baseline, level of education, smoking status, body mass index, level of physical activity, and age at menopause onset. Additional variables evaluated for potential confounding were type of menopause, parity, use of oral contraceptives, alcohol consumption, hypertension, dyslipidaemia, diabetes, family history of cardiovascular disease, and cohort. During a median follow-up of 14.3 years, 6,371 first-time stroke events were recorded; of these, 1,080 were haemorrhagic. Following multivariable adjustment, early initiation (<5 years since menopause onset) of HT was associated with a longer stroke-free period than never use (fifth PD, 1.00 years; 95% CI 0.42 to 1.57), but there was no significant extension to the time period free of haemorrhagic stroke (first PD, 1.52 years; 95% CI -0.32 to 3.37). When considering timing as a continuous variable, the stroke-free and the haemorrhagic stroke-free periods were maximal if HT was initiated approximately 0-5 years from the onset of menopause. If single conjugated equine oestrogen HT was used, late initiation of HT was associated with a shorter stroke-free (fifth PD, -4.41 years; 95% CI -7.14 to -1.68) and haemorrhagic stroke-free (first PD, -9.51 years; 95% CI -12.77 to -6.24) period than never use. Combined HT when initiated late was significantly associated with a shorter haemorrhagic stroke-free period (first PD, -1.97 years; 95% CI -3.81 to -0.13), but not with a shorter stroke-free period (fifth PD, -1.21 years; 95% CI -3.11 to 0.68) than never use. Given the observational nature of this study, the possibility of uncontrolled confounding cannot be excluded. Further, immortal time bias, also related to the observational design, cannot be ruled out.

CONCLUSIONS

When initiated early in relation to menopause onset, HT was not associated with increased risk of incident stroke, regardless of the route of administration, type of HT, active ingredient, and duration. Generally, these findings held also for haemorrhagic stroke. Our results suggest that the initiation of HT 0-5 years after menopause onset, as compared to never use, is associated with a decreased risk of stroke and haemorrhagic stroke. Late initiation was associated with elevated risks of stroke and haemorrhagic stroke when conjugated equine oestrogen was used as single therapy. Late initiation of combined HT was associated with haemorrhagic stroke risk.

Estrogens as neuroprotectants: Estrogenic actions in the context of cognitive aging and brain injury

There is ample empirical evidence to support the notion that the biological impacts of estrogen extend beyond the gonads to other bodily systems, including the brain and behavior. Converging preclinical findings have indicated a neuroprotective role for estrogen in a variety of experimental models of cognitive function and brain insult. However, the surprising null or even detrimental findings of several large clinical trials evaluating the ability of estrogen-containing hormone treatments to protect against age-related brain changes and insults, including cognitive aging and brain injury, led to hesitation by both clinicians and patients in the use of exogenous estrogenic treatments for nervous system outcomes. That estrogen-containing therapies are used by tens of millions of women for a variety of health-related applications across the lifespan has made identifying conditions under which benefits with estrogen treatment will be realized an important public health issue. Here we provide a summary of the biological actions of estrogen and estrogen-containing formulations in the context of aging, cognition, stroke, and traumatic brain injury. We have devoted special attention to highlighting the notion that estrogen appears to be a conditional neuroprotectant whose efficacy is modulated by several interacting factors. By developing criteria standards for desired beneficial peripheral and neuroprotective outcomes among unique patient populations, we can optimize estrogen treatments for attenuating the consequences of, and perhaps even preventing, cognitive aging and brain injury.

Hormone therapy for preventing cardiovascular disease in post-menopausal women

BACKGROUND

Evidence from systematic reviews of observational studies suggests that hormone therapy may have beneficial effects in reducing the incidence of cardiovascular disease events in post-menopausal women, however the results of randomised controlled trials (RCTs) have had mixed results. This is an updated version of a Cochrane review published in 2013.

OBJECTIVES

To assess the effects of hormone therapy for the prevention of cardiovascular disease in post-menopausal women, and whether there are differential effects between use in primary or secondary prevention. Secondary aims were to undertake exploratory analyses to (i) assess the impact of time since menopause that treatment was commenced (≥ 10 years versus < 10 years), and where these data were not available, use age of trial participants at baseline as a proxy (≥ 60 years of age versus < 60 years of age); and (ii) assess the effects of length of time on treatment.

SEARCH METHODS

We searched the following databases on 25 February 2014: Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE and LILACS. We also searched research and trials registers, and conducted reference checking of relevant studies and related systematic reviews to identify additional studies.

SELECTION CRITERIA

RCTs of women comparing orally administered hormone therapy with placebo or a no treatment control, with a minimum of six months follow-up.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. We calculated risk ratios (RRs) with 95% confidence intervals (CIs) for each outcome. We combined results using random effects meta-analyses, and undertook further analyses to assess the effects of treatment as primary or secondary prevention, and whether treatment was commenced more than or less than 10 years after menopause.

MAIN RESULTS

We identified six new trials through this update. Therefore the review includes 19 trials with a total of 40,410 post-menopausal women. On the whole, study quality was good and generally at low risk of bias; the findings are dominated by the three largest trials. We found high quality evidence that hormone therapy in both primary and secondary prevention conferred no protective effects for all-cause mortality, cardiovascular death, non-fatal myocardial infarction, angina, or revascularisation. However, there was an increased risk of stroke in those in the hormone therapy arm for combined primary and secondary prevention (RR 1.24, 95% CI 1.10 to 1.41). Venous thromboembolic events were increased (RR 1.92, 95% CI 1.36 to 2.69), as were pulmonary emboli (RR 1.81, 95% CI 1.32 to 2.48) on hormone therapy relative to placebo.The absolute risk increase for stroke was 6 per 1000 women (number needed to treat for an additional harmful outcome (NNTH) = 165; mean length of follow-up: 4.21 years (range: 2.0 to 7.1)); for venous thromboembolism 8 per 1000 women (NNTH = 118; mean length of follow-up: 5.95 years (range: 1.0 to 7.1)); and for pulmonary embolism 4 per 1000 (NNTH = 242; mean length of follow-up: 3.13 years (range: 1.0 to 7.1)).We performed subgroup analyses according to when treatment was started in relation to the menopause. Those who started hormone therapy less than 10 years after the menopause had lower mortality (RR 0.70, 95% CI 0.52 to 0.95, moderate quality evidence) and coronary heart disease (composite of death from cardiovascular causes and non-fatal myocardial infarction) (RR 0.52, 95% CI 0.29 to 0.96; moderate quality evidence), though they were still at increased risk of venous thromboembolism (RR 1.74, 95% CI 1.11 to 2.73, high quality evidence) compared to placebo or no treatment. There was no strong evidence of effect on risk of stroke in this group. In those who started treatment more than 10 years after the menopause there was high quality evidence that it had little effect on death or coronary heart disease between groups but there was an increased risk of stroke (RR 1.21, 95% CI 1.06 to 1.38, high quality evidence) and venous thromboembolism (RR 1.96, 95% CI 1.37 to 2.80, high quality evidence).

AUTHORS' CONCLUSIONS

Our review findings provide strong evidence that treatment with hormone therapy in post-menopausal women overall, for either primary or secondary prevention of cardiovascular disease events has little if any benefit and causes an increase in the risk of stroke and venous thromboembolic events.

Sex differences in stroke: the contribution of coagulation

Stroke is now the leading cause of adult disability in the United States. Women are disproportionately affected by stroke. Women increasingly outnumber men in the elderly population, the period of highest risk for stroke. However, there is also a growing recognition that fundamental sex differences are present that contribute to differential ischemic sensitivity. In addition, gonadal hormone exposure can impact coagulation and fibrinolysis, key factors in the initiation of thrombosis. In this review we will discuss sex differences in stroke, with a focus on platelets, vascular reactivity and coagulation.

Hormone replacement therapy and the association with coronary heart disease and overall mortality: clinical application of the timing hypothesis

Conclusions from randomized controlled trial (RCT) data over the past 10 years has spanned from presumed harm to consistency with observational data that hormone replacement therapy (HRT) decreases the risk for coronary heart disease (CHD) as well as overall mortality in women who are recently postmenopausal. Multiple clinical studies including randomized trials and observational studies converge with animal experimentation to show a consistency that HRT decreases CHD risk and overall mortality in primary prevention when HRT is started at the time of or soon after menopause. The totality of data supports the "timing" hypothesis that posits that HRT effects are dependent on when HRT is started in relation to age and/or time-since-menopause. The totality of data shows that HRT decreases CHD and overall morality when started in women who are less than 60 years old and/or less than 10 years postmenopausal, providing a "window-of-opportunity". Further evidence shows that women who start HRT when in their 50s and continued for 5-30 years that there is an increase of 1.5 quality-adjusted life-years (QALYs). Additionally, HRT is highly cost-effective at $2438 per QALY gained. The totality of data converges to show a consistency between randomized trials and observational studies that when started in women at or near menopause and continued long-term, HRT decreases CHD and overall mortality compared with women who do not use HRT. This article is part of a Special Issue entitled 'Menopause'.

Guidelines for the prevention of stroke in women: a statement for healthcare professionals from the American Heart Association/American Stroke Association

PURPOSE

The aim of this statement is to summarize data on stroke risk factors that are unique to and more common in women than men and to expand on the data provided in prior stroke guidelines and cardiovascular prevention guidelines for women. This guideline focuses on the risk factors unique to women, such as reproductive factors, and those that are more common in women, including migraine with aura, obesity, metabolic syndrome, and atrial fibrillation.

METHODS

Writing group members were nominated by the committee chair on the basis of their previous work in relevant topic areas and were approved by the American Heart Association (AHA) Stroke Council's Scientific Statement Oversight Committee and the AHA's Manuscript Oversight Committee. The panel reviewed relevant articles on adults using computerized searches of the medical literature through May 15, 2013. The evidence is organized within the context of the AHA framework and is classified according to the joint AHA/American College of Cardiology and supplementary AHA Stroke Council methods of classifying the level of certainty and the class and level of evidence. The document underwent extensive AHA internal peer review, Stroke Council Leadership review, and Scientific Statements Oversight Committee review before consideration and approval by the AHA Science Advisory and Coordinating Committee.

RESULTS

We provide current evidence, research gaps, and recommendations on risk of stroke related to preeclampsia, oral contraceptives, menopause, and hormone replacement, as well as those risk factors more common in women, such as obesity/metabolic syndrome, atrial fibrillation, and migraine with aura.

CONCLUSIONS

To more accurately reflect the risk of stroke in women across the lifespan, as well as the clear gaps in current risk scores, we believe a female-specific stroke risk score is warranted.

ESTROGEN REPLACEMENT THERAPY FOR STROKE

Stroke is the third most common cause of death and severe disability among Western populations. Overall, the incidence of stroke is uniformly higher in men than in women. Stroke is rare in women during the reproductive years, and rapidly increases after menopause, strongly suggesting that estrogen (E2) plays an important role in the prevention of stroke. Ongoing studies are currently evaluating both the benefits and risks associated with E2 replacement therapy and hormone replacement therapy in stroke. Equally important is the role of E2 receptor (ER), as studies indicate that ER populations in several tissue sites may significantly change during stress and aging. Such changes may affect the patient's susceptibility to neurological disorders including stroke, and greatly affect the response to selective E2 receptor modulators (SERMs). Replacement therapies may be inefficient with low ER levels. The goal of this review paper is to discuss an animal model that will allow investigations of the potential therapeutic effects of E2 and its derivatives in stroke. We hypothesize that E2 neuroprotection is, in part, receptor mediated. This hypothesis is a proof of principle approach to demonstrate a role for specific ER subtypes in E2 neuroprotection. To accomplish this, we use a retroviral mediated gene transfer strategy that express subtypes of the ER gene in regions of the rat brain most susceptible to neuronal damage, namely the striatum and cortex. The animal model is exposed to experimental stroke conditions involving middle cerebral artery occlusion (MCAo) method, and eventually the extent of neuronal damage will be evaluated. A reduction in neuronal damage is expected when E2 is administered with specific ER subtypes. From this animal model, an optimal E2 dose and treatment regimen can be determined. The animal model can help identify potential E2-like therapeutics in stroke, and screen for beneficial or toxic additives present in commercial E2 preparations that are currently available. Such studies will be informative in designing drug therapies for stroke.

PPARγ activation rescues mitochondrial function from inhibition of complex I and loss of PINK1

Parkinson's disease has long been associated with impaired mitochondrial complex I activity, while several gene defects associated with familial Parkinson's involve defects in mitochondrial function or 'quality control' pathways, causing an imbalance between mitochondrial biogenesis and removal of dysfunctional mitochondria by autophagy. Amongst these are mutations of the gene for PTEN-induced kinase 1 (PINK1) in which mitochondrial function is abnormal. Peroxisome proliferator-activated receptor gamma (PPARγ), a nuclear receptor and ligand-dependent transcription factor, regulates pathways of inflammation, lipid and carbohydrate metabolism, antioxidant defences and mitochondrial biogenesis. We have found that inhibition of complex I in human differentiated SHSY-5Y cells by the complex I inhibitor rotenone irreversibly decrease mitochondrial mass, membrane potential and oxygen consumption, while increasing free radical generation and autophagy. Similar changes are seen in PINK1 knockdown cells, in which potential, oxygen consumption and mitochondrial mass are all decreased. In both models, all these changes were reversed by pre-treatment of the cells with the PPARγ agonist, rosiglitazone, which increased mitochondrial biogenesis, increased oxygen consumption and suppressed free radical generation and autophagy. Thus, rosiglitazone is neuroprotective in two different models of mitochondrial dysfunction associated with Parkinson's disease through a direct impact on mitochondrial function.

Hormone therapy for preventing cardiovascular disease in post-menopausal women

BACKGROUND

Evidence from systematic reviews of observational studies suggest that hormone replacement therapy (HT) may have beneficial effects in reducing the incidence of cardiovascular disease (CVD) events in post-menopausal women. This is an updated version of a Cochrane review first published in 2005 (Gabriel-Sanchez 2005).

OBJECTIVES

To assess the effects of HT for the prevention of CVD in post-menopausal women, and whether there are differential effects between use of single therapy alone compared to combination HT and use in primary or secondary prevention.

SEARCH METHODS

We searched the following databases to April 2010: Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library, MEDLINE, EMBASE and LILACS.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of women comparing orally administered HT with placebo with a minimum of six-months follow-up.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. Risk Ratios (RR) with 95% confidence intervals were calculated for each outcome. Results were combined using fixed-effect meta-analyses, and where possible, further stratified analyses conducted to assess the effect of time on treatment. Additionally, univariate meta-regression analyses were undertaken to assess whether length of trial follow-up, single or combination treatment, or whether treatment for primary or secondary prevention were potential predictors for a number of CVD outcomes in the trials.

MAIN RESULTS

Four new trials were identified through the update; one trial included in the previous review was excluded. Therefore the review included 13 trials with a total of 38,171 post-menopausal women. Overall, single and combination HT in both primary and secondary prevention conferred no protective effects for all cause mortality, CVD death, non-fatal MI, or angina. There were no significant differences in the number of coronary artery by-pass procedures or angioplasties performed between the trial arms. However there was an increased risk of stroke for both primary and secondary prevention when combination and single HT was combined, RR 1.26 (95% CI 1.11 to 1.43), in venous thromboembolic events, RR 1.89 (95% CI 1.58 to 2.26) and in pulmonary embolism RR 1.84 (95% CI 1.42 to 2.37) relative to placebo. The associated numbers needed-to-harm (NNH) were 164, 109 and 243 for stroke, venous thromboembolism and pulmonary embolism respectively.

AUTHORS' CONCLUSIONS

Treatment with HT in post-menopausal women for either primary or secondary prevention of CVD events is not effective, and causes an increase in the risk of stroke, and venous thromboembolic events. HT should therefore only be considered for women seeking relief from menopausal symptoms. Short-term HT treatment should be at the lowest effective dose, and used with caution in women with predisposing risk factors for CVD events.

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 and the risk of stroke: perspectives 10 years after the Women's Health Initiative trials

Principal findings on stroke from the Women's Health Initiative (WHI) clinical trials of hormone therapy indicate that estrogen, alone or with a progestogen, increases a woman's risk of stroke. These results were not unexpected, and research during the past decade has tended to support these findings. Consistent evidence from clinical trials and observational research indicates that standard-dose hormone therapy increases stroke risk for postmenopausal women by about one-third; increased risk may be limited to ischemic stroke. Risk is not modified by age of hormone initiation or use, or by temporal proximity to menopause, and risk is similar for estrogen plus progestogen and for unopposed estrogen. Limited evidence implies that lower doses of transdermal estradiol (≤50 μg/day) may not alter stroke risk. For women less than 60 years of age, the absolute risk of stroke from standard-dose hormone therapy is rare, about two additional strokes per 10 000 person-years of use; the absolute risk is considerably greater for older women. Other hormonally active compounds - including raloxifene, tamoxifen, and tibolone - can also affect stroke risk.

Stroke in women: disparities and outcomes

Stroke is the leading cause of disability in the United States and affects 15 million people worldwide. Studies performed in various parts of the world have found differences between sexes in stroke incidence, prevalence, mortality, and outcomes. Although men are at higher risk of stroke for most age groups below age 85 years, after this age the incidence reverses dramatically, with women being much more at risk. Furthermore, recent studies suggest that women have worse recovery than men post-stroke. Many aspects of recovery may influence this outcome, including sex-specific comorbidities, aggressiveness of acute treatment, prevention therapies, and varying degrees of social support and rates of depression. It is important to further define and investigate sex differences in stroke incidence, care, treatment, and outcomes to improve functional recovery in women.

Neuroprotective effects of genistein in VSC4.1 motoneurons exposed to activated microglial cytokines

Pro-inflammatory cytokines released from activated microglia may be responsible for neuronal damage and resulting motor deficits associated with CNS disorders such as spinal cord injury, Parkinson's disease, and multiple sclerosis. Estrogen (17β-estradiol) is capable of ameliorating motoneuron death following spinal cord injury, but has a number of deleterious side effects. Genistein (GEN), an estrogen receptor beta agonist and potent antioxidant, may represent an alternative to estrogen in treating neurodegenerative disorders. However, little is known about the neuroprotective effects of GEN. We therefore tested whether GEN would prevent apoptosis in cultured motoneurons following exposure to pro-inflammatory cytokines released from IFN-γ activated microglia. Exposure of ventral spinal cord 4.1 motoneurons to microglial cytokine supernatant in vitro caused significant apoptosis and reduced mitochondrial membrane potential. An increase in reactive oxygen species, intracellular Ca(2+), calpain, caspases, cytochrome c, and the bax:bcl-2 ratio were also noted. GEN treatment reversed apoptotic death and cellular changes following cytokine exposure and was associated with increased expression of estrogen receptor β suggesting that GEN may promote neuroprotection via receptor-mediated pathways. The addition of ICI 182, 780, an estrogen receptor antagonist following GEN treatment attenuated neuroprotection, suggesting that GEN may act mainly via estrogen receptor β to protect VSC4.1 motoneurons. We conclude that GEN protects cultured ventral spinal cord 4.1 cells from inflammatory insult and thus may represent a potential beneficial therapy in the treatment of neurodegenerative disorders.

Middle cerebral artery occlusion model in rodents: methods and potential pitfalls

A variety of animal models have been developed for modeling ischemic stroke. The middle cerebral artery occlusion (MCAO) model has been utilized extensively, especially in rodents. While the MCAO model provides stroke researchers with an excellent platform to investigate the disease, controversial or even paradoxical results are occasionally seen in the literature utilizing this model. Various factors exert important effects on the outcome in this stroke model, including the age and sex of the animal examined. This paper discusses emerging information on the effects of age and sex on ischemic outcomes after MCAO, with an emphasis on mouse models of stroke.

Prospective study of endogenous circulating estradiol and risk of stroke in older women

OBJECTIVE

To test the hypothesis that circulating endogenous estradiol is associated with stroke risk in older postmenopausal women. Stroke incidence increases after menopause, when endogenous estrogen levels fall, yet exogenous estrogen increases strokes in older postmenopausal women. The relation between endogenous estrogen and stroke is unclear.

DESIGN

Prospective case-control study.

SETTING

Study of Osteoporotic Fractures.

PATIENTS OR OTHER PARTICIPANTS

Women at least age 65 years (99% follow-up) who were not taking estrogen at baseline.

MAIN OUTCOME MEASURES

Free estradiol index (FEI) was calculated by dividing total estradiol by sex hormone-binding globulin concentrations measured in banked baseline serum. Using logistic regression, odds ratios were estimated for a first-ever atherothrombotic stroke associated with endogenous FEI in 196 women who had a subsequent validated stroke (median follow-up, 8 years) compared with 219 randomly selected women who did not. Potential mediators were assessed in multivariable models.

RESULTS

The age-adjusted odds of atherothrombotic stroke increased with increasing FEI quartiles (P(trend) = .007). Women in the highest FEI quartile had an age-adjusted 2.31-fold (odds ratio, 2.31; 95% confidence interval, 1.28-4.17) higher odds than women in the lowest quartile. Women with greater central adiposity had a suggestively stronger association (P = .08). Atherogenic dyslipidemia, type 2 diabetes mellitus, and C-reactive protein level were potential mediators of this relation.

CONCLUSIONS

Endogenous estradiol level is an indicator of stroke risk in older postmenopausal women, especially in those with greater central adiposity. Potential mediators, including atherogenic dyslipidemia, insulin resistance, and inflammation, might underlie this association. Whether estradiol, independent of atherogenic adiposity, influences such mediators and stroke risk needs to be determined. Estrogen-altering agents might be harmful or beneficial depending on endogenous estradiol levels, especially in women with greater central adiposity.

Sex-specific responses to stroke

Stroke is a sexually dimorphic disease, with differences between males and females observed both clinically and in the laboratory. While males have a higher incidence of stroke throughout much of the lifespan, aged females have a higher burden of stroke. Sex differences in stroke result from a combination of factors, including elements intrinsic to the sex chromosomes as well as the effects of sex hormone exposure throughout the lifespan. Research investigating the sexual dimorphism of stroke is only in the beginning stages, but early findings suggest that different cell death pathways are activated in males and females after ischemic stroke. A greater understanding of the mechanisms underlying sex differences in stroke will lead to more appropriate treatment strategies for patients of both sexes.

Postmenopausal hormone therapy and the risk of cardiovascular disease

BACKGROUND

Risks and benefits of postmenopausal hormone therapy remain highly controversial. After publication of the Women's Health Initiative hormone trials and several other major trials, the American Heart Association designated postmenopausal hormone therapy as 'Class III', if initiated for the purpose of cardiovascular disease prevention. Subsequent post hoc analyses of the Women's Health Initiative data have renewed enthusiasm for hormone therapy among younger postmenopausal women.

OBJECTIVE

To review data from randomized clinical trials that have assessed cardiovascular outcomes of hormone therapy including coronary heart disease, stroke, peripheral arterial disease, and venous thromboembolism.

METHODS

The review focuses on cardiovascular effects of hormone therapy only and does not attempt to integrate potential risks and benefits related to symptoms, cancer, osteoporosis or other noncardiovascular effects of postmenopausal hormone therapy. The literature search included original trial publications, post hoc analyses, and aggregate data from meta-analyses published in English and accessible to the author in full-text format for detailed analysis.

RESULTS/CONCLUSION

Risks of hormone therapy seem to predominate among older postmenopausal women. Data among younger women close to menopause are insufficient to recommend such therapy for cardiovascular disease prevention.

Neuroprotective effects of estrogens following ischemic stroke

Our laboratory has investigated whether and how 17beta-estradiol (E(2)) protects the brain against neurodegeneration associated with cerebrovascular stroke. We have discovered that low, physiological concentrations of E(2), which are strikingly similar to low-basal circulating levels found in cycling mice, dramatically protect the brain against stroke injury, and consequently revealed multiple signaling pathways and key genes that mediate protective action of E(2). Here we will review the discoveries comprising our current understanding of neuroprotective actions of estrogens against ischemic stroke. These findings may carry far reaching implications for improving the quality of life in aging populations.

Estradiol is a potent protective, restorative, and trophic factor after brain injury

Estrogens are a group of pleiotropic steroid hormones that exhibit diverse mechanisms of action in multiple physiologic systems. Over the past 30 years, biomedical science has begun to appreciate that endogenous estrogens and their receptors display important roles beyond the reproductive system. Our growing appreciation of novel, nonreproductive functions for estrogens has fundamentally contributed to our knowledge of their role in human health and disease. Recent findings from the Women's Health Initiative have caused clinicians and scientists to question whether estrogens are protective factors or risk factors. In light of the dichotomy between basic science and clinical studies, this review will attempt to reconcile differences between them. We will focus on studies from our laboratory and others highlighting the beneficial properties of the most abundant endogenous estrogen, 17beta-estradiol, using in vivo and in vitro models of cerebral ischemia and neuronal injury. These studies demonstrate that 17beta-estradiol powerfully protects the brain using multiple molecular mechanisms that promote: (1) decreased cell death, (2) increased neurogenesis, (3) an enhancement of neurotrophic support, and (4) the suppression of proinflammatory pathways.

Hormone replacement therapy to maintain cognitive function in women with dementia

BACKGROUND

As estrogens have been shown to have several potentially beneficial effects on the central nervous system, it is biologically plausible that maintaining high levels of estrogens in postmenopausal women by means of estrogen replacement therapy (ERT) could be protective against cognitive decline in women with Alzheimer's disease (AD) or other dementia syndromes.

OBJECTIVES

To investigate the effects of ERT (estrogens only) or HRT (estrogens combined with a progestagen) compared with placebo in randomized controlled trials (RCTs) on cognitive function of postmenopausal women with dementia.

SEARCH STRATEGY

The Cochrane Dementia and Cognitive Improvement Group Specialized Register, which contains records from many medical databases, The Cochrane Library, EMBASE, MEDLINE, CINAHL, PsycINFO and LILACS were searched on 7 November 2007 using the terms ORT, PORT, ERT, HRT, estrogen*, oestrogen* and progesterone*.

SELECTION CRITERIA

All double-blind randomized controlled trials (RCTs) into the effect of ERT or HRT for cognitive function with a treatment period of at least two weeks in postmenopausal women with AD or other types of dementia.

DATA COLLECTION AND ANALYSIS

Abstracts of the references retrieved by the searches were read by two reviewers (EH and KY) independently in order to discard those that were clearly not eligible for inclusion. The two reviewers studied the full text of the remaining references and independently selected studies for inclusion. Any disparity in the ensuing lists was resolved by discussion with all reviewers in order to arrive at the final list of included studies. The selection criteria ensured that the blinding and randomization of the included studies was adequate. The two reviewers also assessed the quality of other aspects of the included trials. One reviewer (EH) extracted the data from the studies, but was aided and checked by JB from Cochrane.

MAIN RESULTS

A total of seven trials including 351 women with AD were analysed. Because different drugs were used at different studies it was not possible to combine more than two studies in any analysis.On a clinical global rating, clinicians scored patients taking CEE as significantly worse compared with the placebo group on the Clinical Dementia Rating scale after 12 months (overall WMD = 0.35, 95% CI = 0.01 to 0.69, z = 1.99, P < 0.05).Patients taking CEE had a worse performance on the delayed recall of the Paragraph Test (overall WMD = -0.45, 95% CI = -0.79 to -0.11, z = 2.60, P < 0.01) after one month than those taking placebo. They had a worse performance on Finger Tapping after 12 months (WMD = -3.90, 95% CI = -7.85 to 0.05, z = 1.93, P < 0.05).Limited positive effects were found for the lower dosage of CEE (0.625 mg/day) which showed a significant improvement in MMSE score only when assessed at two months, and disappeared after correction for multiple testing. No significant effects for MMSE were found at longer end points (3, 6 and 12 months of treatment). With a dosage of 1.25 mg/d CEE, short-term significant effects were found for Trial-Making test B at one month and Digit Span backward at four months. After two months of transdermal diestradiol (E2) treatment, a highly significant effect was observed for the word recall test (WMD = 6.50, 95% CI = 4.04 to 8.96, z = 5.19, P < 0.0001). No other significant effects were found for other outcomes measured.

AUTHORS' CONCLUSIONS

Currently, HRT or ERT for cognitive improvement or maintenance is not indicated for women with AD.

Estrogen and progestogen therapy in postmenopausal women

This Educational Bulletin discusses the effectiveness of hormone therapy (HT) for relieving vasomotor and urogenital symptoms and the side effects associated with such treatment; considers the evidence concerning the effects of HT on the risk of osteoporosis and related fractures and on the risks of coronary artery disease, dementia, and colorectal cancer; and considers the longer term effects of HT on the risks of stroke, venous thromboembolism, and cancer of the breast, endometrium, and ovary.

Sex differences in stroke

Increasing evidence suggests that sex differences exist in the etiology, presentation, treatment, and outcome from stroke. The reasons for these sex disparities are becoming increasingly explored, but large gaps still exist in our knowledge. Experimental studies over the past several years have demonstrated intrinsic sex differences both in vivo and in animal models which may have relevance to our understanding of stroke in clinical populations. A greater understanding of the differences and similarities between males and females with respect to the risk factors, pathophysiology, and response to stroke will facilitate the design of future clinical trials and enhance the development of treatment strategies to improve stroke care in both sexes. This article reviews the current literature on sex differences in stroke with an emphasis on the clinical data, incorporating an analysis of bench research as it pertains to the bedside.

The effects of raloxifene and tibolone on homocysteine and vascular histopathological changes

The aim of the present study was to examine the effects of raloxifene (RLX) and tibolone (TBN) on plasma homocysteine (Hcy) levels and their relationship with atherosclerotic changes in the walls of the carotid artery in ovariectomised rats. Thirty surgically ovariectomised Wistar albino rats after a menopausal period of 6 cycles were randomly assigned to receive RLX 0.01 mg/kg/day (n=10), TBN 0.04 mg/kg/day (n=10) and the same dose of placebo (n=10) for 6 cycles. Serum levels of vitamin B12, folate and Hcy were measured and carotid arteries were examined histopathologically following the termination of treatment. Hcy levels were 3.27+/-0.97, 2.57+/-0.32 and 2.28+/-0.12 micromol/l, Vitamin B12 levels were 901.90+/-239.76, 694.70+/-112.20 and 631+/-309.44 pg/ml and folate levels were 73.80+/-12.71, 72.51+/-7.05 and 84.79+/-20.82 ng/ml in receiving RLX, TBN and placebo respectively. Hcy levels were increased by RLX vs. placebo (P=0.006) but not by TBN vs. placebo (P=0.070). Vitamin B12 levels were found to be elevated by TBN vs. the control group (P=0.041) but not by RLX vs. placebo (P=0.059). Histopathological examination of carotid arteries from rats receiving both RLX and TBN revealed no difference vs. placebo. Data obtained from the study support the view that neither RLX nor TBN appears to have a primary protective effect on vascular disease by effecting the metabolism of Hcy at menopause.

Traitement hormonal substitutif de la ménopause et risque vasculaire

Although experimental data and results of observational studies suggest that hormone replacement therapy (HRT) was associated with a reduction in the risk of heart disease, the results for stroke have been far less clear. Several recent randomized secondary prevention studies have found that HRT is not protective against the risk of coronary heart disease, stroke or progression of atherosclerosis. Moreover, an increased risk of stroke and first coronary event with hormone therapy has been found in low-risk healthy post menopausal women. In light of these findings, although the absolute risk of vascular event associated with HRT is low, most organizations recommend caution in using HRT. Hormone therapy should not be initiated to prevent vascular disease among postmenopausal women. There are numerous plausible explanations for the divergent findings from observational and randomized clinical trials of hormone therapy. Some discrepancies are certainly the result of methodological differences between the study designs. They also suggest other biological effects of hormone therapy than modification of classic vascular risk factors. Further studies should focus on identifying the mechanisms of risk and determining whether and how different regimens of hormone therapy influence vascular risk.

Timing of estrogen therapy after ovariectomy dictates the efficacy of its neuroprotective and antiinflammatory actions

Recent studies describing the seemingly contradictory actions of estrogens in ischemic stroke injury have led us to reevaluate the circumstances under which estrogen therapy (ET) provides benefits against cerebral stroke and decipher its mechanisms of action. One prominent feature that follows stroke injury is massive central and peripheral inflammatory responses. Evidence now suggests that postischemic inflammatory responses strongly contribute to the extent of brain injury, and 17beta-estradiol (E(2)) may protect the ischemic brain by exerting antiinflammatory actions. In an attempt to explain recently reported dichotomous effects of E(2) in stroke injury, we tested the hypothesis that an extended period of hypoestrogenicity both prevents E(2) from protecting the brain against ischemia and simultaneously suppresses its antiinflammatory actions. We report that E(2) exerts profound neuroprotective action when administered immediately upon ovariectomy, but not when administered after 10 weeks of hypoestrogenicity. Consistently, E(2) treatment given immediately at the time of ovariectomy attenuated central and peripheral production of proinflammatory cytokines after ischemic stroke. In contrast, E(2) did not suppress production of proinflammatory molecules when it was administered after 10 weeks postovariectomy. These results demonstrate that a prolonged period of hypoestrogenicity disrupts both neuroprotective and antiinflammatory actions of E(2). Our findings may help to explain the results of the Women's Health initiative that reported no beneficial effect of ET against stroke because the majority of the subjects initiated ET after an extended period of hypoestrogenicity.

Differences in brain volumes among males and female hormone-therapy users and nonusers

Numerous studies have shown gender differences in the brain volumes of elderly adults. Some evidence shows that higher estrogen levels may be neuroprotective, suggesting that hormone therapy (HT) may in part be responsible for these gender differences; however, few studies have examined the relation between HT and brain volumes. Brain volumes of caudate, putamen, hippocampus, gray matter, white matter, white-matter lesions, and cerebrospinal fluid were measured on magnetic resonance imaging scans. A comprehensive neuropsychological battery was administered. Women were separated into two groups based on HT use, and we used multiple regression analyses to compare these groups with one another and with men. Results of brain-volume measurements showed that HT users had significantly less gray matter and more cerebrospinal fluid than nonusers. Results of the neuropsychological testing showed that HT users performed better on the Shipley Vocabulary Test than males did.

Complex actions of sex steroids in adipose tissue, the cardiovascular system, and brain: Insights from basic science and clinical studies

Recent publications describing the results of the Women's Health Initiative (WHI) and other studies reporting the impact of hormone therapy on aging women have spurred reexamination of the broad use of estrogens and progestins during the postmenopausal years. Here, we review the complex pharmacology of these hormones, the diverse and sometimes opposite effects that result from the use of different estrogenic and progestinic compounds, given via different delivery routes in different concentrations and treatment sequence, and to women of different ages and health status. We examine our new and growing appreciation of the role of estrogens in the immune system and the inflammatory response, and we pose the concept that estrogen's interface with this system may be at the core of some of the effects on multiple physiological systems, such as the adipose/metabolic system, the cardiovascular system, and the central nervous system. We compare and contrast clinical and basic science studies as we focus on the actions of estrogens in these systems because the untoward effects of hormone therapy reported in the WHI were not expected. The broad interpretation and publicity of the results of the WHI have resulted in a general condemnation of all hormone replacement in postmenopausal women. In fact, careful review of the extensive literature suggests that data resulting from the WHI and other recent studies should be interpreted within the narrow context of the study design. We argue that these results should encourage us to perform new studies that take advantage of a dialogue between basic scientists and clinician scientists to ensure appropriate design, incorporation of current knowledge, and proper interpretation of results. Only then will we have a better understanding of what hormonal compounds should be used in which populations of women and at what stages of menopausal/postmenopausal life.

Risk of stroke and hormone replacement therapy. A prospective cohort study

OBJECTIVE

The purpose of this study was to examine the risk of first-ever stroke in relation to use of hormone replacement therapy (HRT) among middle-aged and older Swedish women.

MATERIALS

A total of 16,906 women, 45-73 years old, from the 'Diet and Cancer' study in Malmö, Sweden were examined. Women were considered as HRT users if they took systemic hormone therapy regularly. Incidence of stroke was followed for a mean period of 10.5 years.

RESULTS

In all, 2148 (12.7%) women used HRT. A total of 461 stroke cases occurred during follow-up, 48 of them in HRT users. Incidence of total stroke and ischemic subtype had no significant relation to HRT use. However, an increased risk of hemorrhagic stroke was found in women taking unopposed estrogen (RR=2.55, 95%CI: 1.03-6.35) or un-native estrogen regimens (RR=4.27, 95%CI: 1.71-10.66). Although not significantly, the risk of stroke was 33% lower in women who started their treatment before menopause. Among HRT users, the risk of stroke was associated with advancing age, smoking, excess body weight and hypertension.

CONCLUSIONS

There is no significant association between hormone therapy and risk of total stroke in women during 10.5 years follow-up. Preparations of estrogen and time for initiation of treatment may affect the risk of stroke.

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.

Estrogen and phytoestrogens: Effect on eNOS expression and in vitro vasodilation in cerebral arteries in ovariectomized Watanabe heritable hyperlipidemic rabbits

OBJECTIVES

To evaluate the effect of estrogen replacement therapy or soy isoflavones supplement on endothelium-dependent relaxation in vitro and gene expression of endothelial nitric oxide synthase (eNOS) in cerebral arteries in a rabbit model of human hypercholesterolemia.

STUDY DESIGN

Thirty-six female ovariectomized Watanabe heritable hyperlipidemic (WHHL) rabbits were randomised to treatment with 17beta-estradiol (17beta-E(2)), SoyLife 150 or control for 16 weeks. Ring segments of basilar artery (BA) and posterior cerebral artery (PCA) were mounted in myographs for isometric tension recordings. Concentration response curves to carbamylcholine chloride, sodium nitroprusside (SNP) and l-NAME were evaluated after precontraction with potassium. Total RNA was extracted, reverse transcribed and eNOS quantitated by real-time polymerase chain reaction (real-time PCR).

RESULTS

Plasma cholesterol was significantly higher at termination in the SoyLife group (P<0.0001), whereas low-density lipoprotein (LDL) cholesterol was comparable in all treatment groups. Neither treatment influenced the endothelium-dependent responses to carbamylcholine chloride or l-NAME or the endothelium-independent response to SNP in any of the arteries. Correspondingly, eNOS mRNA was similarly expressed in all treatment groups in both arteries.

CONCLUSIONS

Improvement of cerebral endothelial function by estrogen or soy isoflavones in ovariectomized WHHL rabbits is not supported by the present data. The findings may be unique to the WHHL rabbit in which the hypocholesterolemic effect of estrogens mediated by upregulation of liver LDL receptors is excluded.

Where are we with postmenopausal hormone therapy in 2005?

Recently, two large randomized placebo-controlled studies on long-term postmenopausal hormone replacement therapy, the Heart and Estrogen/progestin Replacement Study (HERS) and the Women's Health Initiative (WHI), have raise a lot of controversies, especially on the cardiovascular aspects. We briefly review these two trials and discuss what we know and do not know about postmenopausal hormone therapy, including the evidence on novel choices such as raloxifene and tibolone.

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.

Estrogens and Cerebrovascular Stroke: What Do Animal Models Teach Us?

Recent findings from the Women's Health Initiative (WHI) suggest that hormone therapy (HT) and estrogen therapy (ET) increase the risk of stroke in postmenopausal women. These results were unexpected based upon many previous clinical, observational, and epidemiological studies and a large body of evidence that come from studies performed in animal models. Before we assume that these results are widely applicable to other hormone preparations and to all older postmenopausal women, we should consider whether the particular hormone preparations, the doses that were used, the age of the women, the length of time that they were postmenopausal prior to the initiation of treatment, and/or their health status may have been important factors in the results of this clinical trial. We believe that results of studies using animal models provide insights into why the result of the WHI should have been expected. Furthermore, results of basic science studies provide a strong rationale for the design of future clinical studies that will more accurately test the effects of ET/HT on the risk and outcomes of cerebrovascular stroke in middle-aged perimenopausal and early postmenopausal women. We will review data, predominantly from our laboratory, gathered over the past six years that lead us to this conclusion.

Association between hormone replacement therapy and subsequent stroke: a meta-analysis

OBJECTIVES

To review completed trials assessing effect of hormone replacement therapy on subsequent risk of stroke, assessing stroke by pathological type, severity, and outcome.

DESIGN

Systematic review of randomised controlled trials identified from the Cochrane Library, Embase, and Medline; reviews; and reference lists of relevant papers.

STUDIES REVIEWED

28 trials, with 39 769 subjects, were identified. REVIEW MEASURES: Rates for cerebrovascular events analysed with a random effects model. Sensitivity analyses for heterogeneity included phase of prevention (primary or secondary), type of hormone replacement therapy (oestrogen alone or combined with progesterone), type of oestrogen (estradiol or conjugated equine oestrogen), size of trial (< 5000 or > 5000 patients), length of follow up ( pound 3 years or > 3 years), sex (women only or men only), and trial quality (high or low).

RESULTS

Hormone replacement therapy was associated with significant increases in total stroke (odds ratio 1.29 (95% confidence interval 1.13 to 1.47), n = 28), non-fatal stroke (1.23 (1.06 to 1.44), n = 21), stroke leading to death or disability (1.56 (1.11 to 2.20), n = 14), ischaemic stroke (1.29 (1.06 to 1.56), n = 16), and a trend to more fatal stroke (1.28 (0.87 to 1.88), n = 22). It was not associated with haemorrhagic stroke (1.07 (0.65 to 1.75), n = 17) or transient ischaemic attack (1.02 (0.78 to 1.34), n = 22). Statistical heterogeneity was not present in any analysis.

CONCLUSIONS

Hormone replacement therapy was associated with an increased risk of stroke, particularly of ischaemic type. Among subjects who had a stroke, those taking hormone replacement therapy seemed to have a worse outcome. Hormone replacement therapy cannot be recommended for the primary or secondary prevention of stroke.

Glia-neuron crosstalk in the neuroprotective mechanisms of sex steroid hormones

Proteins involved in the intramitochondrial trafficking of cholesterol, the first step in steroidogenesis, such as the steroidogenic acute regulatory protein (StAR) and the peripheral-type benzodiazepine receptor (PBR), are upregulated in the nervous system after injury. Accordingly, a local increase in the levels of steroids, such as pregnenolone and progesterone, is observed following traumatic injury in the brain and spinal cord. The expression and activity of aromatase, the enzyme that synthesizes estradiol, is also increased in injured brain areas and its inhibition results in an increased neurodegeneration. These findings suggest that an increase in steroidogenesis is part of an overall mechanism used by the nervous tissue to cope with neurodegenerative conditions. Neural steroidogenesis is the result of a coordinated interaction of neurons and glia. For example, after neural injury, there is an upregulation of StAR in neurons and of PBR in microglia and astroglia. Aromatase is expressed in neurons under basal conditions and is upregulated in reactive astrocytes after injury. Some of the steroids produced by glia are neuroprotective. Progesterone and progesterone derivatives produced by Schwann cells, promote myelin formation and the remyelination and regeneration of injured nerves. In the central nervous system, the steroids produced by glia regulate synaptic function, affect anxiety, cognition, sleep and behavior, and exert neuroprotective and reparative roles. In addition, glial cells are targets for steroids and mediate some of the effects of these molecules on neurons, including the regulation of survival and regeneration.

Selective estrogen receptor modulators protect hippocampal neurons from kainic acid excitotoxicity: differences with the effect of estradiol

Neuroprotective effects of estradiol are well characterized in animal experimental models. However, in humans, the outcome of estrogen treatment for cognitive function and neurological diseases is very controversial. Selective estrogen receptor modulators (SERMs) may represent an alternative to estrogen for the treatment or the prevention of neurodegenerative disorders. SERMs interact with the estrogen receptors and have tissue-specific effects distinct from those of estradiol, acting as estrogen agonists in some tissues and as antagonists in others. In this study we have assessed the effect of tamoxifen, raloxifene, lasofoxifene (CP-336,156), bazedoxifene (TSE-424), and 17beta-estradiol on the hippocampus of adult ovariectomized rats, after the administration of the excitotoxin kainic acid. Administration of kainic acid induced the expression of vimentin in reactive astroglia and a significant neuronal loss in the hilus. SERMs did not affect vimentin immunoreactivity in the hilus, while 17beta-estradiol significantly reduced the surface density of vimentin immunoreactive profiles. Estradiol, tamoxifen (0.4-2 mg/kg), raloxifene (0.4-2 mg/kg), and bazedoxifene (2 mg/kg) prevented neuronal loss in the hilus after the administration of kainic acid. Lasofoxifene (0.4-2 mg/kg) was not neuroprotective. These findings indicate that SERMs present different dose-dependent neuroprotective effects. Furthermore, the mechanisms of neuroprotection by SERMs and estradiol are not identical, because SERMs do not significantly affect reactive gliosis while neuroprotection by estradiol is associated with a strong down-regulation of reactive astroglia.

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.