The effect of tamoxifen and transdermal 17beta-estradiol on cerebral arterial vessels: a randomized controlled study

A Systematic Review and Meta-Analysis Examining Whether Changing Ovarian Sex Steroid Hormone Levels Influence Cerebrovascular Function

Sex differences in cerebrovascular disease rates indicate a possible role for ovarian sex steroid hormones in cerebrovascular function. To synthesise and identify knowledge gaps, a systematic review and meta-analysis was conducted to assess how ovarian sex steroid hormone changes across the lifespan affect cerebrovascular function in women. Three databases (EMBASE, MEDLINE and Web of Science) were systematically searched for studies on adult cerebrovascular function and ovarian sex steroid hormones. Forty-five studies met pre-defined inclusion criteria. Studied hormone groups included hormone replacement therapy (HRT; n = 17), pregnancy (n = 12), menstrual cycle (n = 7), menopause (n = 5), oral contraception (n = 2), and ovarian hyperstimulation (n = 2). Outcome measures included pulsatility index (PI), cerebral blood flow/velocity (CBF), resistance index (RI), cerebral autoregulation, and cerebrovascular reactivity. Meta-analysis was carried out on HRT studies. PI significantly decreased [−0.05, 95% CI: (−0.10, −0.01); p = 0.01] in post-menopausal women undergoing HRT compared to post-menopausal women who were not, though there was considerable heterogeneity (I² = 96.8%). No effects of HRT were seen in CBF (p = 0.24) or RI (p = 0.77). This review indicates that HRT improves PI in post-menopausal women. However, there remains insufficient evidence to determine how changing ovarian sex steroid hormone levels affects cerebrovascular function in women during other hormonal phases (e.g., pregnancy, oral contraception).

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.

The cerebrovascular risks associated with tamoxifen use

Tamoxifen, a selective oestrogen receptor modulator with oestrogen antagonistic effects in the breast, is an effective treatment for breast cancer. Although tamoxifen has been shown to have favourable effects on cardiovascular risk factors, several studies have shown an increased risk of venous thrombosis and stroke. The mechanisms of increased risk of both venous and arterial thrombosis remain unclear based on measurement of markers of thrombosis in women using tamoxifen. In addition, the aetiology of stroke, emphasising the distinction between cerebral venous thrombosis and ischaemic or haemorrhagic stroke, as well as paradoxical embolism, needs to be determined before the issue of stroke risk can be clarified. Future studies of women with breast cancer using tamoxifen should be designed to determine the stroke etiologies that are most common in women using tamoxifen, the role of additional chemotherapy and existing stroke risk factors, and the potential mechanisms of venous and arterial thrombosis.

Effects of transdermal and oral postmenopausal hormone therapy on vascular function: a randomized, placebo-controlled study in healthy postmenopausal women

OBJECTIVE

To compare the effect of transdermal and oral estrogen therapy, the latter with or without the addition of gestodene, on plasma concentrations of markers of endothelial function and on ultrasonographic parameters of vascular function in healthy postmenopausal women.

DESIGN

In a 15-month, randomized, double-blind, placebo-controlled study, 152 healthy hysterectomized postmenopausal women received daily doses of placebo (n = 49), 50 microg of transdermal 17ss-estradiol (tE2, n = 33), 1 mg of oral E2 (oE2, n = 37), or 1 mg of oral estradiol combined with 25 microg of gestodene (oE2+ G, n = 33) for 13 cycles of 28 days, followed by four washout cycles with placebo in each group. At baseline and in cycles 4, 13, and 17, we measured plasma levels of endothelial markers and ultrasonographic markers of vascular function (pulsatility index [PI] and, at baseline and cycle 13, arterial stiffness).

RESULTS

Compared with placebo, we found reductions in soluble vascular cell adhesion molecule (oE2, P < 0.01; oE2+ G, P < 0.001), sE-selectin (oE2 + G, P < 0.05), von Willebrand factor (tE2, P < 0.05), and divergent effects in PI and stiffness parameters in the carotid artery. We found no effect on PI in the retinal and femoral arteries, or on stiffness parameters in the femoral and brachial artery.

CONCLUSIONS

Oral hormone therapy reduced plasma levels of adhesion molecules, whereas transdermal estrogen therapy reduced von Willebrand factor. Effects on ultrasonographic parameters of vascular function in the carotid artery were inconclusive.

Effects of estradiol alone or in combination with cyproterone acetate on carotid artery pulsatility index in postmenopausal women

OBJECTIVES

The incidence of cardiovascular disease (CVD) increases dramatically with the loss of ovarian function. Observational studies indicate that the risk of CVD may be reduced by up to 50% in postmenopausal women who take estrogen replacement therapy. Estrogen therapy reduces internal carotid artery pulsatility index (PI). The improvement in carotid PI following HRT has been proposed as a marker of the cardioprotective effect of estrogen therapy. Cyclical progesterone addition to ERT partially antagonizes the reduction on the carotid artery PI. As progesterone, androgens has been shown to decreases arterial vasodilatation and carotid PI. To our knowledge no information is available regarding the effect of CPA addition on the carotid artery PI in women taking estrogen replacement therapy.

METHODS

We recruited a total of 30 women in postmenopause for at least 12 months and were in good health. Fifteen women were postmenopausal following surgical bilateral oophorectomy for benign condition. Fifteen postmenopausal women received estradiol valerate for 21 days and CPA (1 mg) for 10 days for 3 months (Group E/CPA). Ovarectomized women (n=15) received estradiol hemihydrate (2 mg) for 3 months (Group E). The main factor investigated was PI, an indicator of impedence to blood flow down stream. Doppler US were performed before the start and at the end of the therapy.

RESULTS

The mean reductions respect to basal values were 11.5% in women treated with E and 10.8% in women treated with E/CPA. No significant difference was found between treatment values.

CONCLUSIONS

The results of the present study demonstrate that cyproterone acetate addition to E do non-antagonize the effect of estrogen on carotid artery PI. The present study demonstrate that both estradiol hemihydrate and estradiol valerate plus cyproterone acetate lead to similar improvement in carotid artery; through this mechanism both treatments could potentially reduce the incidence of cerebrovascular disease in postmenopausal women.

Effects of raloxifene on carotid blood flow resistance and endothelium-dependent vasodilation in postmenopausal women

Raloxifene is one of the most important selective estrogen receptor modulators currently employed for the treatment of postmenopausal osteoporosis. However, it has also been suggested that this compound affects the vascular system. We evaluated both carotid blood flow resistance and endothelium-dependent vasodilation in 50 healthy postmenopausal women randomly assigned to receive, in a double blind design, either raloxifene (60 mg per day; N=25 subjects) or placebo (N=25 subjects) for 4 months. Indices of carotid blood flow resistance, such as the pulsatility index (PI) and resistance index (RI), as well as the flow-mediated brachial artery dilation were measured both at baseline and at the end of treatment. Changes in PI were -1.86+/-2.24 and -2.15+/-2.22% after placebo and raloxifene treatment, respectively, with no significant differences between groups. Changes in RI were -0.77+/-1.72 and -1.81+/-1.54% after placebo and raloxifene treatment, respectively, with no significant differences between groups. At the end of the treatment period, the increments in artery diameter measured after the flow stimulus were 10.79+/-2.39 and 6.70+/-1.23% for placebo and raloxifene, respectively, with no significant differences between groups. These results demonstrate no significant effects of raloxifene on either carotid blood flow resistance or brachial artery flow-mediated dilation in postmenopausal women.

The role of reproductive hormones in maintaining cognition

This article briefly reviews the impact of hormones on cognition. Estrogen has the most profound impact on brain functioning. Testosterone also seems to have significant brain-related benefits, whereas progesterone seems to have minor or possibly even adverse effects. As the field of neuroscience progresses, more definitive conclusions will follow. As the focus is shifted, however, from extending life to improving the quality of life, the existing data are very compelling. The brain is a target for the sex steroid hormones. Clearly, this is an exciting and dynamic area for further study. Although skeptics may believe that more definitive proof is necessary before recommending hormone replacement for their patients to preserve their cognitive health, it seems prudent to discuss the evidence available to empower the patient further to guide their own treatment options and validate their symptoms. For those who still subscribe to the menopause-is-natural philosophy this question is posed, "why does the brain naturally have sex hormone receptors if they are not necessary?"

Effect of raloxifene on the ovarian circulation in women after menopause

OBJECTIVE

We sought to determine whether raloxifene effects the ovarian circulation in women after menopause.

STUDY DESIGN

The resistance indices of the ovarian blood flow were assessed in 130 women after menopause who were randomly assigned to receive either 60 mg of raloxifene, a continuous combined estrogen-progestin tablet daily, or neither treatment for 24 months.

RESULTS

The women who received raloxifene or hormonal replacement therapy had a significant time-related decrease in the resistance index of the ovarian artery blood flow compared to baseline values (resistance index, 0.91) starting after 12 and 18 months of treatment (resistance index, 0.88 and 0.89, respectively; P <.002 and.001, respectively). Whereas significant increases in the resistance index respective to the prestudy values were observed in the nontreated women at 24 months (resistance index, 0.93; P <.0001). The mean (+/-SD) resistance index of the ovarian blood flow at the end of the study (resistance index, 0.89) was significantly lower in the women who were treated with raloxifene than in the women who were treated with hormone replacement therapy (P <.002). No changes in the ovarian dimensions or appearance were noticed during the entire study.

CONCLUSION

Daily therapy with raloxifene has significant ovarian vascular-relaxing effect in women after menopause. This potentially important direct vasculoprotective long-term effect of raloxifene on cardiovascular disease deserves further investigation.

Estrogen and cerebrovascular physiology and pathophysiology

Numerous studies have uncovered a wide variety of estrogen effects with apparent cardiovascular benefits, the most recognized ones being vasodilation, anti-atherogenesis, diminished post-ischemic inflammation and anti-oxidant effects. This article provides an overview of the influence of estrogen on the cerebral vasculature, under physiologic and pathophysiologic conditions, and covers both acute and chronic effects. The discussion is primarily focused on the vasodilatory and anti-inflammatory actions of estrogen, since those particular estrogen influences have received the greatest attention in studies published to date. With respect to vasodilation, although some consideration is given to the role of other vasodilating mechanisms and factors, the emphasis is mostly placed on the endothelial isoform of nitric oxide synthase, eNOS, which has emerged as a clear target of estrogen. Some consideration is given to recent findings that suggest that estrogen can stimulate eNOS activity by decreasing the expression of the eNOS inhibitor caveolin-1. With regard to the ability of estrogen to counteract inflammation, potential mechanisms by which estrogen limits the post-ischemic leukocyte adhesion, and the expression of the inducible NOS, are discussed.

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.

Estrogens, progestins, selective estrogen receptor modulators, and the arterial tree

We reviewed studies of the effects of different estrogens, progestins, and selective estrogen receptor modulators at the coronary and carotid arterial sites to help determine their likely effects on cardiovascular morbidity and mortality. All English-language studies published between 1997 and 2000 on MEDLINE, Current Contents, and Best Evidence were reviewed, including in vitro, other animal, human physiologic, and clinical trial studies. We synthesize, assess limitations, and integrate across systems with the in vivo experience in humans to evaluate the clinical context. Estrogens have favorable direct effects in most circumstances, progestins oppose these effects, and early studies suggest that selective estrogen receptor modulators are protective. In some systems the dosage, route of delivery, and type of progestin may be important and risk factors may modulate hormone effects. The evaluation of endothelial dysfunction gives a unique in vivo opportunity to assess the vascular properties of hormones, although the relationship between the in vivo physiologic effects of hormones and clinical outcomes remains to be determined.

Preliminary assessment of cognitive function in breast cancer patients treated with tamoxifen

BACKGROUND

Tamoxifen is an anti-estrogen used in the treatment of breast cancer and to reduce the incidence of breast cancer in high risk women. Although the brain is an estrogen target organ and several studies have found a beneficial effect of estrogen on cognitive function, the effect of tamoxifen on cognition has not been reported. Therefore, we initiated a follow-up study of women who had participated in a study of breast cancer to assess the effect of tamoxifen treatment on cognitive function.

METHODS

We recruited previously interviewed patients who were cases in a population-based case-control study of 2,653 women with primary breast cancer diagnosed between 1987 and 1996 at ages 55-72 years in Los Angeles County, California, USA. In November 1997, each case was mailed a follow-up questionnaire. Cognitive function was assessed by (1) clock drawing. (2) copying a box drawing, and (3) narrative writing to describe a pictured scene. Women reporting treatment with tamoxifen were categorized as standard-term users (4-5 years), short-term users (< 4 years) or long-term users (6 + years) and compared to never users. Tamoxifen users were also classified as past or current users. Differences in the mean cognitive test scores were tested after adjusting for age, age at diagnosis, stage of disease, radiation therapy, chemotherapy, race, education, marital status, previous use of oral contraceptives, type of menopause, age at last menstrual period, previous use of hormone replacement therapy, and depressive symptoms using analysis of covariance. All p-values for differences in the proportion of women who had errors on the tests are 2-sided and adjusted for age, stage of disease at diagnosis, and chemotherapy.

FINDINGS

Information from 1,163 women aged 57-75 years of age was analyzed; 710 had taken tamoxifen. There was little difference between women who had used tamoxifen for the standard five years and never users on the three cognitive tests. However, more women who had used tamoxifen for the standard term reported seeing their physician for memory problems than non-users (3.8% vs 1.5%, p = 0.04). This was especially true for current users of standard-term (8.0%, p = 0.003). Current users also had a significantly lower mean complexity score (p = 0.03) on the narrative writing task. No differences were seen between past users and non-users.

INTERPRETATION

Our study suggests that current use of tamoxifen may adversely effect cognition. Further study of tamoxifen and cognition is needed so that healthy women considering tamoxifen for the primary prevention of breast cancer have comprehensive information about the side effects of the treatment.

Acute effects of smoking on human cerebral blood flow: a transcranial Doppler ultrasonography study

Middle cerebral artery (MCA) flow velocity was continuously monitored during smoking in an observational study (n = 14) using transcranial Doppler (TCD) ultrasonography. Cerebral autoregulatory vasodilator capacitance under inspired CO2 challenge was also measured before smoking and at peak smoking effect. Several puffs on a single lighted cigarette over a period of five minutes acutely increased MCA mean flow velocity in every subject (group mean increase: 19%, individual increases ranged 2-64%) with a response onset and offset detectable within several seconds of beginning and ending smoking. The mechanism for the increase in MCA flow velocities appeared to be independent of the CO2 autoregulatory mechanism. Gender subgroup analysis showed smoking acutely suppressed the CO2 vasodilator capacitance by 56% in men but only by 5% in women (p = 0.05). The magnitude of the acute smoking-induced increases in MCA flow velocities appeared to be independent of the estimated cigarette yields for nicotine, carbon monoxide, and "tar." Smoking in healthy subjects acutely increased MCA mean flow velocity, which may reflect a global increase in cerebral blood flow via complex influences on the cerebral autoregulation.

Resistance of pelvic arteries and plasma lipids in postmenopausal women: comparative study of tibolone and continuous combined estradiol and norethindrone acetate replacement therapy

OBJECTIVE

We sought to compare vascular resistance and plasma lipids in postmenopausal women assigned to tibolone (a synthetic estrogen replacement steroid) therapy or continuous combined hormone replacement therapy.

STUDY DESIGN

Pulsatility and resistance indexes in pelvic arteries (color Doppler transvaginal ultrasonography) and lipids were monitored in this double-blind 1-year trial of 100 women randomized to either 2.5 mg tibolone or 2 mg 17beta-estradiol plus 1 mg norethindrone acetate daily.

RESULTS

Both indexes of the arcuate arteries (uterine arteries) were significantly reduced beyond 3 and 6 months (12 months) from baseline, respectively, by the combined regimen compared with tibolone alone. Tibolone increased the resistance index of arcuate arteries but did not affect uterine arteries. There was no effect of either regimen on the internal iliac arteries. The medians of the percentage changes from baseline of high-density lipoprotein cholesterol (triglycerides) were significant between groups after 1 year, as follows: -17% (-16%) in the tibolone group and -4% (+15%) in the combined group, respectively. Both regimens similarly reduced total and low-density lipoprotein cholesterol and lipoprotein Lp(a).

CONCLUSION

Hormone replacement therapy may induce different or opposite changes of both vascular resistance and lipids. It is unknown whether these findings may modify cardiovascular risk.

Oestrogen and progestogen hormone replacement therapy for peri-menopausal and post-menopausal women: weight and body fat distribution

BACKGROUND

Hormone replacement therapy (HRT) is commonly prescribed to treat menopausal symptoms and to prevent post-menopausal bone loss. However, many women are concerned about hormonal replacement therapy because they believe that such treatment will result in weight gain. The effect of HRT on weight and body fat distribution has not yet been examined in systematic reviews. It is an important topic since many women decline oestrogen therapy due to their concerns about resultant weight gain, and thus forego its potential therapeutic benefits.

OBJECTIVES

To evaluate the effect of unopposed oestrogen or combined oestrogen and progestogen hormone replacement therapy (HRT) upon the weight and body fat distribution of perimenopausal and postmenopausal women.

SEARCH STRATEGY

The search strategy of the Menstrual Disorders and Subfertility Group was used for the identification of randomised controlled trials (RCTs). Computerised searches of MEDLINE, EMBASE, Current Contents, Biological Abstracts and CINAHL were performed. Attempts were made to identify trials from citation lists of review articles and relevant papers already obtained. In most cases, first authors of each eligible trial were contacted for additional information. All those trials that had been located as at August 1998 were examined for eligibility.

SELECTION CRITERIA

All randomised, placebo or no treatment controlled trials that detailed the effect of HRT on weight or body fat distribution, including studies where HRT was combined with other therapy such as diet, supplements or exercise. Studies were eligible for consideration even though the main focus of the trial may have been on another aspect of HRT. Previous HRT use should have ceased at least one month (in the case of patches, cream or gel) or three months (for oral preparations or subcutaneous pellets) before commencement of the study.

DATA COLLECTION AND ANALYSIS

Twenty two RCTs were identified that fulfilled the inclusion criteria for this review. The results of one trial were not available in a form that allowed it to be included in the meta-analysis; however, it has been included in the text of the review for discussion. Twenty four RCTs are awaiting assessment pending additional information from first authors. Two reviewers extracted the data independently, and the weighted mean differences for continuous outcomes were estimated from the data. Results for unopposed oestrogen and combined oestrogen were analysed separately, and the effect of each treatment regimen on body weight, BMI, waist-hip ratio, fat mass and skinfold measurement was examined where available. The effect of differing dosage levels on these parameters was also examined.

MAIN RESULTS

Outcomes were evaluated separately for unopposed oestrogen and oestrogen/progestogen regimens. Statistical analysis was performed using the weighted mean difference for continuous outcomes as recommended by the Cochrane Menstrual Disorders and Subfertility Group. No statistically significant difference was found in mean weight gain between those using unopposed oestrogen and non-HRT users (0.66 kg, 95% CI -0.62, 1.93). No significant difference was found in mean weight gain between those using oestrogen/progestogen therapy and non-HRT users (-0.47 kg, 95% CI -1.63, 0.69). Insufficient data exist to enable meta-analysis of the effect of unopposed oestrogen on BMI. The reviewers found no statistically significant difference in mean BMI increase between those using oestrogen/progestogen and non-HRT users (-0.50, 95% CI -1.06, 0.06). Insufficient data exist to enable meta-analysis of the effect of HRT on waist-hip ratio, fat mass or skinfold thickness.

REVIEWER'S CONCLUSIONS

There is evidence of no effect of unopposed oestrogen or combined oestrogen on body weight, indicating that these regimens do not cause extra weight gain in addition to that normally gained at menopause. (ABSTRACT TRUNCATED)

Monitoring of hormone replacement therapy in postmenopausal women by transvaginal sonography and color flow doppler: study in different phases of sequential therapy

OBJECTIVE

To assess uterine artery blood flow and endometrial thickness in postmenopausal patients receiving sequential hormone replacement therapy (HRT) at different phases of the treatment.

DESIGN

Prospective controlled study.

SETTING

Ultrasound and menopause units of the obstetrics and gynecology department of the University of Tor Vergata, Rome, Italy.

PATIENT(S)

Forty postmenopausal women were treated with cyclic sequential HRT (transdermal E2, 50 microg/d, days 1-21; and dydrogesterone, 10 mg/d, days 12-24).

INTERVENTION(S)

All patients underwent transvaginal color Doppler sonography in the estrogen (phase E) and progestogen (phase E/P) phases and after uterine bleeding when no hormone was administered (phase 0).

MAIN OUTCOME MEASURE(S)

Endometrial thickness; systolic, diastolic, and mean velocities; and pulsatility and resistance indices of the uterine arteries.

RESULT(S)

No statistically significant difference in endometrial thickness between phase E (6.5+/-1.6 mm) and phase E/P (6.0+/-1.7 mm) was observed. In phase 0, compared with phases E and E/P, a statistically significant decrease in endometrial thickness was found (4.1+/-1.2 mm). Doppler flow impedance parameters of uterine arteries during the different phases of the HRT cycle showed no differences between the phases considered.

CONCLUSION(S)

The decrease in endometrial thickness in phase 0 suggests a protective effect of our cyclic sequential regimen on the endometrium. Dydrogesterone does not interfere markedly with the vasodilatory effect of estrogen on uterine arteries.

Estrogens and atherosclerosis: phytoestrogens and selective estrogen receptor modulators

The development of atherosclerosis in animal models and the incidence of coronary heart disease in postmenopausal women are markedly reduced by estrogen treatment. Estrogen have acute beneficial effects on vascular reactivity and longer-term effects on critical steps in the pathogenesis of atherosclerosis. Phytoestrogens present in soybeans and other plant products are weak estrogens but appear to have potent beneficial effects on the arterial wall. The phytoestrogens have certain similarities to 'designer hormones' which are being developed to retain their beneficial effects on the cardiovascular system and the skeleton without having cancer promoting effects on the breast and endometrium.