Effects of estrogen replacement therapy on serum lipid values and angiographically defined coronary artery disease in postmenopausal women

Effect of gender differences and estrogen replacement therapy on vascular reactivity

The incidence of cardiovascular disease is lower in premenopausal women compared with men; following menopause, the risk of mortality from cardiovascular disease increases in females. Postischemic dilatation of the brachial artery has been used previously as an index of endothelium-mediated vasodilation. Using this index, we examined a group of premenopausal and postmenopausal women, some of whom were on estrogen replacement therapy (ERT). All subjects were normotensive (blood pressure [BP] <140/90 mm Hg) and normoglycemic (blood glucose, <100 mg/dL). Fourteen healthy women (mean age, 27 +/- 0.8 years; mean total cholesterol, 174 +/- 6.7 mg/dL) and fourteen healthy men (mean age, 26 +/- 1.4 years; mean total cholesterol, 181 +/- 7.2 mg/dL) were investigated. Nineteen postmenopausal women were also examined; 11 were on ERT (mean age, 55 +/- 2.1 years; mean total cholesterol, 213 +/- 6.6 mg/dL) and eight were not on ERT (mean age, 60 +/- 3.6 years; mean total cholesterol, 222 +/- 14.4 mg/dL). Ischemia was induced by inflating a cuff over the forearm to a pressure of 40 mm Hg above systolic for 5 minutes. Doppler ultrasonography (Acuson [Mountain View, CA] 128XP/10c ultrasonograph with a 7.5-MHz linear array transducer) was used to measure the brachial artery diameter before inflation and 15 seconds and 45 to 60 seconds following cuff deflation. Flow-mediated dilatation (FMD%) and hyperemia were defined as the percentage increase over basal diameter and basal flow, respectively. Postischemic median dilatation in men was 4.20% (interquartile range, 2.13% to 5.56%) and 11.48% (interquartile range, 8.70% to 14.29%) in age-matched premenopausal women (P < .01). For women on ERT, the postischemic median dilatation was 8.11% (interquartile range, 6.01% to 11.60%), as compared with 2.82% (interquartile range, 1.32% to 3.28%) for women without ERT (P < .01). Premenopausal women showed significantly greater dilatation after ischemia than postmenopausal women without ERT (P < .0001). Hyperemia was similar in all groups. These findings show that postischemic vasodilation of the brachial artery is greater in premenopausal women versus age-matched men; it is decreased in postmenopausal women, and ERT restores it toward normal. The pathophysiology underlying the diminution in postischemic dilatation may be relevant to atherogenesis and coronary artery disease (CAD).

Effects of hormone replacement therapy on hemostatic cardiovascular risk factors

OBJECTIVES

From observational studies, there is evidence that hormone replacement therapy in postmenopausal women causes a decrease in cardiovascular events. It remains unknown, however, precisely by which mechanisms this reduction is achieved. The primary aim of this work was to study the effects of hormone replacement therapy on established hemostatic risk factors during 1-year treatment of healthy postmenopausal women. The secondary aim was to investigate whether there was any significant difference in these risk factors between hormone replacement therapy administered as a cyclic estrogen/sequential progestogen or continuous estrogen/sequential progestogen regimen.

STUDY DESIGN

Sixty postmenopausal women were randomized to treatment with estradiol valerate 2 mg/day either continuously or cyclic (days 1 to 21; placebo on days 21 to 28). Both groups received cyproterone acetate 1 mg/day on days 12 to 21. Blood samples were collected before treatment and on cycle days 17 to 22 in cycles 3, 6, and 12. Thirty women with basic characteristics identical to the women included in the treatment group were included as a reference group. Blood samples were collected after 0, 6, and 12 months of observation.

RESULTS

Hormone replacement therapy during 1 year caused a marginal but significant increase in plasma concentration of factor VIIc after 12 months of treatment (P <.05), a significant decrease in fibrinogen, and a significant decrease in the protein concentrations of tissue-type plasminogen activator, plasminogen activator inhibitor-1, and lipoprotein(a) after 3, 6, and 12 months of treatment (P <.05). Possible differences in the integrated response between the reference group and the hormone replacement therapy group were evaluated by comparison of the area under the curve as estimated in each individual on the basis of each analyte in the sampling periods. The area under the curve of fibrinogen was significantly lower in the hormone replacement therapy group than in the reference group (P <.03), whereas other variables did not deviate significantly between the groups. The areas under the curve did not deviate significantly between the group that received cyclic estrogen/sequential progestogen and the group that received continuous estrogen/sequential progestogen.

CONCLUSIONS

One-year treatment with hormone replacement therapy influenced favorably a number of prognostic cardiovascular risk factors in healthy women. The most important effect was the lowering of fibrinogen. Furthermore, in this study the effect of hormone replacement therapy on hemostasis did not deviate between a cyclic estrogen/sequential progestogen regimen and a continuous estrogen/sequential progestogen regimen.

Arthur C. Corcoran Memorial Lecture. Hormones and vasoprotection

There is a strong link between menopause and increased cardiovascular disease incidence in women, and observational studies suggest that postmenopausal hormone replacement therapy reduces cardiovascular disease risk by about half. Observational studies suffer from important limitations, however, and the only published prospective controlled trial of the effects of hormone replacement therapy on cardiovascular outcomes, the Heart Estrogen-Progestin Replacement Study (HERS), showed no net benefit of continuous estrogen plus synthetic progestin treatment in women with established coronary disease. Fundamental mechanistic studies of the cellular and molecular events by which hormones protect (or fail to protect) blood vessels from damage are needed to define the role of postmenopausal hormone replacement therapy in cardiovascular disease prevention. Most studies suggest that estrogen inhibits the neointimal response to acute injury in normal blood vessels, but this vasoprotective effect was not seen in vessels with preexisting atherosclerosis. Studies from our laboratory in the rat carotid injury model have shown that estrogen inhibits neointima formation via effects on all 3 layers of the vascular wall, including inhibition of medial smooth muscle cell migration and proliferation, stimulation of regrowth of endothelium, and inhibition of adventitial cell migration into neointima. Our laboratory is currently using transduced (lacZ) syngeneic fibroblasts as 'reporter' cells to delineate the factors that stimulate migration of adventitial cells into neointima after vascular injury and their modulation by estrogen and the other sex hormones. These fundamental studies will establish more rational strategies for therapeutic intervention in vascular diseases, including the basis for future gene therapy.

Electrocardiogram pattern in hypercholesterolemic women: the influence of hormone replacement therapy

OBJECTIVE

The aim of this study was to delineate electrocardiogram (ECG) patterns in postmenopausal women with hypercholesterolemia and to assess the possible influence of female sex hormones.

STUDY DESIGN

A total of 72 postmenopausal women with moderately elevated total cholesterol levels constituted the case group, of which 48 came from a clinical trial and 24 from a cohort study. Some 236 women aged 50-59 years with normal levels of cholesterol were participants in the same cohort study in the local area. These 236 women had been subdivided into three groups: premenopausal, postmenopausal and postmenopausal with hormone replacement therapy (HRT). Of the 48 women in the clinical study group, 12 patients showed pathological ECG changes. Six of these patients were treated with HRT for 2 years (transdermal estradiol 50 micrograms/day and a daily dose of 5 mg medroxyprogesterone acetate, MPA) and the rest were non-users of HRT.

RESULTS

In the women with hypercholesterolemia, 16 of 72 patients (22%) showed ischemic ECG changes, compared to nine of 88 (10%) with normal cholesterol levels (p = 0.04). We found no significant difference in the prevalence of ECG changes between postmenopausal women with and without HRT in the groups with normal levels of cholesterol. In the hormone treatment group, four of six patients showed an improvement in ECG pattern, in contrast to two of six non-users of HRT.

CONCLUSIONS

This preliminary study revealed a higher prevalence of pathological ECG changes in postmenopausal women who had hypercholesterolemia than in normocholesterolemic women. These findings support the idea that hyperlipidemia contributes to the overall increase in cardiovascular disease, as this is also associated with ECG changes. Transdermal estradiol combined with MPA has a beneficial effect in reversing the process of atherosclerosis, as well as improving the ECG pattern. The prevalence of pathological ECG patterns was similar for HRT users and non-users. This outcome may be affected by several factors. Hence, further research is warranted.

Cardiovascular disease in postmenopausal women

With many risk factors for cardiovascular disease, myocardial infarction in particular now being well defined, it becomes increasingly clear that a majority of these factors are not only age, but also gender specific. Confidential risk factors such as smoking, hypertension, diabetes mellitus, overweight and hyperlipaemia, might have a different impact in women than in men. Moreover, there are substantial clinical differences between male and female ischaemic heart disease, both as to presentation, as well as to diagnosis, therapy and prognosis. In addition to a discussion to the risk factors mentioned above, the cardioprotective actions of oestrogens will be reviewed.

Wellness in women after 40 years of age: the role of sex hormones and pheromones

In the past twenty years hundreds of peer-reviewed studies have provided a significant body of information to guide the health care of women in the second halves of their lives. The harmonic nature of the fertile reproductive system forms the background against which hormonal replacement therapy can be understood to best serve women. In addition, the 1986 discovery of human pheromones and the subsequent 1998 confirmation of their existence increases certain sexual options for maturing women. Not all hormonal replacement therapies and wellness regimens serve women well. Some regimens have the potential to produce disease, especially over-the-counter remedies like dehydroepiandrosterone and the formulas that contain estrogen. Some regimens profoundly improve the quality of life of many women; some women do not need or want such regimens. All sex hormones affect physiologic systems including the cardiovascular system, bone metabolism, cognitive function, sexual response, and sexual attractiveness. The 7 years before menopause have recently been revealed to be an extremely complex era. During this period, some women increase their estrogen levels to new lifetime highs; others start an unequivocal decline, and still others vary from month to month. Coupled to this variability in estrogen is an equally variable set of changes in progesterone secretion by the ovary as androgen secretion patterns also change. Many women show increases in circulating androgens while many others show deficiencies. Both the adrenal and the ovarian sources of these hormones show age-related changes that alter a woman's capacity to attract sexual attention through both her physical appearance (and condition) and her pheromonal excretions. The complex contributions to the overall health of a woman may not always be understood. Often a hysterectomy can exacerbate--rather than ameliorate--the conditions that led to the surgery. One in 2 American women is offered a hysterectomy, a rate 5 times higher than that of the European countries for which data are available. Ninety percent of hysterectomies are not related to cancer; they are elective procedures. Avoidance of elective hysterectomy helps prevent its side effects: sexual deficits, acceleration of cardiovascular and bone disease, and more rapid aging. No efficacy data exist that suggest that elective hysterectomy works better than the alternative approaches that do not induce these side effects. The health and well-being of women who have already had hysterectomies, with or without ovariectomies, can be improved by a recognition of the cascade of difficulties that must addressed. Estrogen, progesterone, and androgens all tend to be compromised by hysterectomy; all should be considered for replacement. Because hormonal regimens can be prescribed to enhance the quality of life, the review of the available research can allow the medical art to greatly benefit mature women. Not surprisingly, the emerging conclusion reveals that structurally human hormones, prescribed appropriately, almost always best serve the patient.

Estrogen replacement therapy and outcome of coronary balloon angioplasty in postmenopausal women

Estrogen replacement therapy (ERT) in women after menopause is associated with prevention of clinical coronary artery disease. However, few studies have investigated possible benefits from ERT in postmenopausal women undergoing treatment for established coronary disease. We therefore retrospectively reviewed the clinical outcomes of 428 postmenopausal women undergoing percutaneous transluminal coronary balloon angioplasty (PTCA) to test the hypothesis that ERT has a beneficial effect in this setting. The women were divided into 2 groups based on ERT status at the time of the procedure. Estrogen users were younger (60 +/- 10 vs 68 +/- 9 years, p <0.001), more commonly had family histories of coronary heart disease (54% vs 41%, p = 0.04), had less incidence of hypertension (63% vs 76%, p = 0.02), and had slightly fewer diseased vessels per patient (1.3 +/- 0.5 vs 1.5 +/- 0.7, p = 0.03) compared with nonusers. No in-hospital deaths occurred in estrogen users compared with 5% hospital mortality in nonusers (p = 0.01). The combined outcome of death or myocardial infarction (MI) also was lower in estrogen users (4% vs 12%, p = 0.04). Of 348 women discharged after successful PTCA, 336 (97%) were able to be contacted at an average follow-up interval of 22 +/- 17 months (range 5 to 82). Estrogen users had superior event-free survival both for death as well as for death or nonfatal MI. Repeat revascularizations were similar in both groups (32% vs 24%, p = 0.15). In a Cox proportional-hazards model, nonusers had 4 times the likelihood of death after angioplasty compared with estrogen users (OR = 4.025, 95% CI = 1.3 to 13.4, p = 0.02). We conclude that estrogen replacement may offer protection against clinical coronary events in postmenopausal women who already have established coronary disease and are undergoing balloon angioplasty. The benefit was independent of age, smoking, presence of diabetes mellitus, or the number of diseased coronary vessels. However, it did not include a reduction in repeat revascularization procedures, suggesting no reduction in restenosis.

Apolipoprotein B and coronary artery disease in women: a cross-sectional study in women undergoing their first coronary angiography

The association between plasma apolipoprotein (apo) B concentrations and angiographically determined coronary artery disease (CAD) was investigated in women in a cross-sectional study. Stenosis of >60% in 1 or more coronary arteries was classified as CAD+. CAD- was defined as a maximum stenosis of 10% in any coronary artery. Fasting plasma concentrations of apoB, apoA-I, cholesterol (chol), low density lipoprotein cholesterol (LDL-chol), high density lipoprotein cholesterol (HDL-chol), and triglycerides (TGs) were determined. Information on nonlipid risk factors was obtained from questionnaires. CAD+ women (n=160) were older than CAD- women (n=129), 64.0+/-7.8 vs 57.8+/-11.1 years, respectively. CAD+ compared with CAD- women had higher frequencies of diabetes (14.7% vs 5.8%, P=0.05), hypertension (53% vs 37%, P=0.018), and ever-smoking (48% vs 35%, P<0.001). CAD+ women had higher plasma concentrations of apoB (1.48+/-0.32 vs 1.25+/-0.34 g/L, P<0.001), chol (7.01+/-1.19 vs 6.38+/-1.22 mmol/L, P=0.001), LDL-chol (4.74+/-1.09 vs 4.13+/-1.13 mmol/L, P<0.001), and TGs (1.98+/-0.84 vs 1.71+/-0.93 mmol/L, P=0.007) and lower levels of HDL-chol (1.28+/-0.28 vs 1.37+/-1.38 mmol/L, P=0.028). After correction for nonlipid risk factors, apoB, chol, LDL-chol, HDL-chol, and TG were independently related to CAD. In the lowest quartiles of chol, LDL-chol, and TG, CAD+ women had higher apoB concentrations than CAD- women. In contrast, chol, LDL-chol, TG, or HDL-chol levels were not different in any quartile of apoB. ApoB showed the most significant relation with the number of stenotic vessels, and apoB was associated with CAD in the normolipidemic subgroup. In conclusion, apoB was superior to chol, LDL-chol, HDL-chol, TG, and apoA-I in discriminating between CAD+ and CAD-.

Estrogen modulates AT1 receptor gene expression in vitro and in vivo

BACKGROUND

The AT1 receptor has been implicated in the pathogenesis of hypertension and atherosclerosis. Estrogen deficiency is also associated with cardiovascular diseases. Therefore, we examined the AT1 receptor gene expression in ovariectomized rats with and without estrogen replacement therapy and the influence of estrogen on AT1 receptor expression in cultured vascular smooth muscle cells.

METHODS AND RESULTS

Rat aortic tissue was examined 5 weeks after ovariectomy. In one group, estrogen (1.7 mg estradiol) was administered during the 5-week period. Functional experiments assessed angiotensin II-induced contraction of aortic rings. AT1 receptor mRNA levels were measured by quantitative polymerase chain reaction and Northern blotting. AT1 receptor density was assessed by radioligand binding assays. These techniques were also applied in cultured vascular smooth muscle cells. The efficacy of angiotensin II on vasoconstriction was significantly increased in aortas from ovariectomized rats. As assessed by radioligand binding assays, AT1 receptor density was increased to 160% without changes in receptor affinity during estrogen deficiency. AT1 receptor mRNA levels were consistently increased to 187% in ovariectomized rats compared with sham-operated animals. Estrogen substitution therapy in ovariectomized rats reversed this AT1 receptor overexpression. To explore the underlying mechanisms, the direct influence of estradiol on AT1 receptor expression was investigated in VSMCs. Estradiol (1 micromol/L) led to a time-dependent downregulation of AT1 receptor mRNA, with a maximum of 33.3% at 12 hours. There was a correlative decrease in AT1 receptor density.

CONCLUSIONS

This novel observation of estrogen-induced downregulation of AT1 receptor expression could explain the association of estrogen deficiency with hypertension and atherosclerosis, because activation of the AT1 receptor plays a key role in the regulation of blood pressure, fluid homeostasis, and vascular cell growth.

Conjugated equine estrogens inhibit progression of atherosclerosis but have no effect on intimal hyperplasia or arterial remodeling induced by balloon catheter injury in monkeys

OBJECTIVES

This study sought to determine the effects of estrogen treatment on atherosclerosis progression and the proliferative and structural responses of the atherosclerotic arteries to injury.

BACKGROUND

Estrogen treatment suppresses the intimal response to arterial injury in nonatherosclerotic rodents and rabbits and inhibits the in vitro proliferation of smooth muscle cells. However, the effect of estrogen on the response of atherosclerotic arteries to transmural injury, as occurs in balloon catheter angioplasty in humans, is unknown.

METHODS

Forty-six ovariectomized cynomolgus monkeys were fed an atherogenic diet for 30 months; 25 received 175 microg/day of conjugated equine estrogens, and 21 served as untreated control animals. All animals underwent balloon catheter injury of the left iliac artery. Subsets of animals underwent a necropsy study at 4, 7, 14 and 28 days after injury; injured and contralateral (uninjured) arteries were pressure-fixed and evaluated morphometrically.

RESULTS

Estrogen treatment resulted in a 37% decrease (p < 0.05) in atherosclerosis (plaque area) in the uninjured artery. In response to injury, arterial cell proliferation increased at days 4 and 7, and intimal area was increased two- to threefold at day 28 (p < 0.05). Although estrogen treatment resulted in a trend toward decreased arterial cell proliferation at day 4, there was evidence of increased cell proliferation in both media and intima at day 7 (p < 0.05). However, there was no effect of estrogen treatment on intimal area or indexes of arterial remodeling in the injured artery at day 28 (p > 0.4). CONCLUSIONS. In contrast to previous studies of nonatherosclerotic animals, the results indicate that in the circumstance of transmural injury to arteries of primates with preexisting atherosclerosis, estrogen does not suppress arterial neointimal or structural responses to injury.

Estrogen replacement therapy and cardiovascular protection: lipid mechanisms are the tip of an iceberg

Cardiovascular disease remains a major cause of mortality among postmenopausal women. After menopause, atherogenesis is promoted by a number of metabolic and vascular changes. A multitude of observational clinical studies have come to the conclusion that estrogen replacement therapy (ERT) reduces cardiovascular risk by approximately 50% and that estrogen's favorable effects on the lipid profile can explain only 25-50% of the overall observed reduction. Estrogens are now known to have potent anti-atherogenic properties through lipid and non-lipid mechanisms; both will be highlighted in view of the recent literature. Estrogens induce favorable changes on lipids and lipoproteins, partly by increasing HDL-cholesterol and decreasing both LDL-cholesterol and lipoprotein (a). Non-lipid mechanisms of estrogen action include decreasing insulin resistance, serum fibrinogen, factor VII and plasminogen activator inhibitor-1 (PAI-1). Moreover, estrogens maintain endothelial cell integrity, decrease expression of adhesion molecules, lower systemic blood pressure, promote vasodilatation, decrease platelet aggregability, inhibit vascular smooth muscle cell proliferation, possess potent antioxidant and calcium antagonist activities, inhibit adrenergic responses and downregulate platelet and monocyte reactivity. Also mentioned are recent reports linking estrogen to the renin-angiotensin system, relaxin, serotonin and homocysteine. What was once thought of as a simple action is now being increasingly appreciated as a complex, multifaceted mechanism, which serves to prove that estrogen is a powerful cardiovascular agent.

Postmenopausal hormone therapy. Is it useful for coronary prevention?

Contemporary interest in postmenopausal hormone therapy as a coronary preventive intervention in women derives from the increased prevalence of coronary disease in the postmenopausal years, the importance of estrogen status as a determinant of coronary risk for women, the less favorable outcomes of coronary events for women than for men, the biologically plausible mechanisms of estrogen benefit, and encouraging epidemiologic data suggesting that estrogen use may favorably affect coronary risk. Observational studies describe the greatest reduction in mortality risk with estrogen use in women at high risk for coronary disease or with documented coronary heart disease, with greater benefit currently accruing for those with angiographically severe rather than angiographically mild disease. Noncoronary risks of estrogen use warrant consideration; these include endometrial hyperplasia, breast cancer, and venous thromboembolism. Noncoronary benefits include a decrease in osteoporosis and osteoporotic fractures and in vasomotor symptoms of estrogen deficiency. Because about one of two U.S. women die from cardiovascular disease (heart disease and stroke), emphasis is warranted on available data, which suggest that the group of women likely to experience the greatest cardioprotection from hormone therapy are those with defined coronary disease or those at high risk for occurrence; the group of women least likely to benefit are those at increased risk for breast cancer.

Inhibition of LDL oxidation by a new estradiol receptor modulator compound LY-139478, comparative effect with other steroids

Oxidation of low-density lipoprotein (LDL) is postulated to be essential for the development of atherosclerosis. LY-139478 is a new non-steroidal potent estrogen analog, but its effects on in vitro LDL oxidation have not been completely elucidated. We investigated the ability of LY-139478 to inhibit in vitro copper sulfate-mediated LDL oxidation using several methods, including conjugated diene (CD) accumulation, relative electrophoretic mobility on agarose gel, thiobarbituric acid-reactive substances (TBARS) assay, and superoxide anions scavenging activity. The antioxidative potential of LY-139478 was compared to testosterone (T), 17-alpha-estradiol (17alphaE), 17-beta-estradiol (17betaE), dehydroepiandrosterone (D), and dehydroepiandrosterone-3-sulfate (DS). LY-139478 was superior to 17alphaE and 17betaE in prolonging the lag phase and decreasing the slope and peak concentration of the conjugated diene accumulation, decreasing the rate of migration of LDL on agarose gel electrophoresis, and inhibiting the production of melonyldialdehyde (MDA) in the TBARS assay. T, D and DS were ineffective in all three assays. It was previously shown that when native LDL is oxidized by previously oxidized LDL (secondary oxidation) the lag phase is lost (Schnitzer et al. Free Rad Res 1995;23:137). LY-139478 was at least 15-fold more effective than 17alphaE, and 17betaE in slowing the propagation phase and reducing CD accumulation in this secondary oxidation, with 50% inhibition at 10 microM and 98% inhibition at 100 microM. However, none restored the lag phase. T, D and DS were ineffective. Superoxide anion generation was inhibited only by DS at high doses (500 microM). These results demonstrate that LY-139478 is an effective inhibitor of LDL oxidation and is superior to natural steroidal hormones, including 17betaE, in protecting against primary and secondary LDL oxidation.

Modulation of cardiac hypertrophy by estrogens

Gender-specific differences in heart disease have long been known but it has only been since the advent of molecular biology that it has become possible to investigate the molecular mechanisms. Most biochemical work in the last 50 years has focused on the characterization of the steroid hormones involved in gender specificity. More recently, the cloning of the steroid receptors and characterization of the signaling pathways through these proteins has given new insights into the mechanisms underlying the mode of action of steroid hormones. It has also become clear that the steroid receptors can be classified into families (receptors for thyroid hormone, glucocorticoids, estrogens, androgens, retinoic acid, and so called orphan receptors of mostly unknown function). The structures of these receptors show very close resemblance and all are DNA-binding proteins acting as transcription factors. Some (if not all) act as repressors of transcription of some genes in the native state and are converted to activators (or perhaps repressors of other genes) upon binding of the cognate hormone. Naturally, classical target tissues for estrogens and androgens have been studied first and only in very recent years has it been recognized that estrogens and androgens act on a much wider spectrum of tissues. In the cardiovascular field, the beneficial effect of estrogen replacement therapy in postmenopausal women which reduces the incidence of cardiovascular disease by some 40% and the lower incidence of cardiovascular disease in premenopausal women have mostly been explained by the beneficial action of estrogens on the lipid profile (increase in HDL and decrease in LDL cholesterol). Recently, functional estrogen receptors have also been shown in vascular smooth muscle cells and in the endothelium. Our own group has characterized the presence of estrogen receptors in the myocardium and in cardiac fibroblasts. We have also shown that these receptors are transcriptionally active because they are able to drive a minigene composed of a triple estrogen responsive DNA regulatory element (promoter) coupled to the firefly luciferase gene which serves as a reporter by way of its ability to drive a light-emitting reaction. We are in the process of characterizing the target genes for estrogen in the myocardium. A specific series of immediate-early genes is induced by estradiol (the major premenopausal estrogen) and we have also characterized a number of tissue-specific genes whose expression is driven by estrogens in the myocardium. The ultimate goal of these investigations is to explore the use of estrogens in the treatment of cardiac hypertrophy (and failure) by way of their properties to counteract (at least some of) the pathological switches in gene expression in these disease entities.

Effect of naturally reduced ovarian function on plasma lipoprotein and 27-hydroxycholesterol levels in baboons (Papio sp.)

Female baboons over 15 years of age develop irregular menstrual cycles, an indication of declining ovarian function similar to that occurring in perimenopausal women. To determine the effect of declining ovarian function on plasma lipoprotein metabolism and plasma oxysterols, we measured plasma lipoprotein and 27-hydroxycholesterol levels in 86 female baboons from 15-28 years of age with regular (n = 51) and irregular (n = 35) menstrual cycles. We sampled blood and liver while they were consuming a basal diet and after consuming a high cholesterol and high fat diet for 7 weeks. On the basal diet, baboons with irregular cycles had higher VLDL + LDL/HDL cholesterol ratios (P = 0.034). After consuming the HCHF diet for 7 weeks, total plasma (P < 0.001) and VLDL + LDL (P < 0.001) cholesterol concentrations and VLDL + LDL/HDL sterol ratios (P < 0.001) increased in both cycle groups; whereas HDL cholesterol concentrations increased only in baboons with regular cycles (P = 0.009). As a result, HDL cholesterol concentrations (P = 0.006) were lower and VLDL + LDL/HDL cholesterol ratios (P = 0.002) were higher in baboons with irregular cycles on the HCHF diet. Plasma 27-hydroxycholesterol concentrations were higher in baboons with regular cycles than in those with irregular cycles on both basal (P = 0.018) and HCHF (P = 0.037) diets and were positively correlated (P < 0.001) with hepatic sterol 27-hydroxylase activities on both diets. Hepatic sterol 27-hydroxylase activities were negatively correlated with the VLDL + LDL/HDL cholesterol ratios on the HCHF diet (r = -0.342, P = 0.033). These results suggest that declining ovarian function changes the plasma lipoprotein pattern to one that is more atherogenic. Ovarian failure is also associated with decreased concentrations of plasma 27-hydroxycholesterol (the major oxysterol of plasma), and the decrease in plasma 27-hydroxycholesterol concentration was due to the decrease in hepatic sterol 27-hydroxylase activity. The effects of ovarian failure on plasma lipoprotein metabolism and plasma 27-hydroxycholesterol may be mediated by the decreased production of estrogen in perimenopausal baboons. Thus, the perimenopausal baboon is an excellent model for menopause and can be used for studies that cannot be conducted in women.

Androgen receptor-mediated antagonism of estrogen-dependent low density lipoprotein receptor transcription in cultured hepatocytes

Postmenopausal women receiving hormone replacement therapy have a lower risk of coronary heart disease than women who do not receive hormone treatment. Multiple mechanisms are likely to underlie estrogen's cardioprotective action, including lowering of plasma low density lipoprotein (LDL) cholesterol. Using an in vitro system exhibiting normal regulation of LDL receptor (LDLR) gene transcription, we show that 17beta-estradiol activates the LDLR promoter in transiently transfected HepG2 cells. LDLR activation by estrogen in HepG2 cells is dependent on the presence of exogenous estrogen receptor, and the estrogen-responsive region of the LDLR promoter colocalizes with the sterol response element previously identified. The estrogen response is concentration dependent, saturable, and sensitive to antagonism by estrogen receptor antagonists. Further, we show that compounds with androgen receptor agonist activity attenuate the estrogen-induced up-regulation of LDLR in our model system. Progestins with androgen receptor agonist activity, such as medroxyprogesterone acetate, also suppress estrogen's effects on LDLR expression through their androgenic properties. Characterization of the interplay between these hormone receptors on the LDLR in vitro system may allow a better understanding of the actions of sex steroids on LDLR gene expression and their roles in cardiovascular disease.

Menopause and post-menopause

From the endocrine point of view, menopause is considered a deficiency state and oestrogen therapy regarded as restoring the pre-menopausal endocrine milieu. Oestrogen therapy alleviates acute climacteric symptoms and also reduces the risk of cardiovascular disease, osteoporosis and Alzheimer's disease. Cardiovascular protection seems to be the major benefit of oestrogen replacement: it reduces morbidity and mortality from coronary heart disease by approximately 50%. The mechanisms are complex and not fully under-stood. In this review we discuss currently available data on the effects of hormone replacement therapy on serum lipids and lipoproteins, the vessel wall (endothelium dependent and endothelium independent), blood flow, cardiac function, blood pressure, haemostasis, insulin sensitivity and direct anti-atherosclerotic effect as possible mechanisms of cardioprotection. Oestrogen therapy reduces the rate of post-menopausal bone loss, increases bone mineral density (BMD) and decreases fracture rate. Recent evidence suggests that initiation of oestrogen therapy in older women produces larger increases in BMD which might provide a significant protective effect at the time when fracture is common. The incidence of Alzheimer's disease is reduced by 50% in post-menopausal women taking oestrogen replacement. Limited clinical trials of oestrogen treatment in women with this disease have documented beneficial effects on cognitive function. The results of epidemiological studies of the effects of oestrogens on breast cancer risk are conflicting but recent evidence suggests that the risk is increased in current users after 5 years of use and among older women. In contrast, increase in the risk of venous thromboembolism is most significant within the first 12 months of therapy, strongly suggesting the importance of individual susceptibility.

[Estrogens for prevention of coronary heart disease?]

In recent years, reports of favourable effects of estrogen therapy on cardiovascular morbidity and mortality have led to enthusiasm for widespread use of estrogens by postmenopausal women. Guidelines for estrogen therapy issued by the American College of Physicians include the statement "Women who have coronary heart disease are likely to benefit from hormone therapy". What evidence support this recommendation? More than 30 observation studies have examined the effect of estrogen replacement therapy on cardiovascular event and all cause mortality. In addition there have been 13 case controlled studies. The majority showed lower morbidity and mortality from coronary heart disease among users of postmenopausal estrogens than among non-users. Recently, 2 meta-analyses estimated the reduction in coronary heart disease associated with estrogen use to be in the range of 35 to 44%, respectively. All of these observational studies share a fatal flaw: Women who take estrogens are different from women who do not. Some differences have been measured, others have not. Women who take estrogens are on average better educated, healthier, have higher incomes and have better access to health care. These difference rather than the estrogens may account for much of the lower risk of heart disease. At this time we cannot tell from these observational studies what the real benefit of estrogens on coronary heart disease might be. Estrogen replacement therapy is not without risk. Estrogens increase the risk of endometrial carcinoma approximately 6-fold, an effect that is eliminated by the addition of progestins. Controversy continues over whether estrogen replacement increases the risk of breast cancer. A number of prospective randomized studies are now under way that will establish whether estrogen replacement therapy definitely reduces the risk of cardiovascular disease in women with and without coronary lesions and whether it increases the risk of breast cancer. Until the results of these trials are available claims on the definite usefulness of hormone supplementation to prevent coronary heart disease in postmenopausal women remain premature. In the light of the probable usefulness estrogen replacement therapy for the prevention of cardiovascular events should be recommended for women with increased risk for or definitively proven coronary heart disease.

Effect on survival of estrogen replacement therapy after coronary artery bypass grafting

We examined the relation between postmenopausal estrogen placement therapy (ERT) and survival in 1,098 women who underwent coronary artery bypass grafting (CABG). Patients were selected for the study if their age was > or = 55 years at the time of preoperative coronary angiography or if they had previously undergone bilateral oophorectomy. Life-table analysis was used to compare survival after surgery in 92 women who received ERT and 1,006 women who did not. Five-year survival was 98.8% in the estrogen users and 82.3% in the non-users. Ten-year survival was 81.4% in the users and 65.1% in the nonusers (p = 0.0001 by Lee Desu test). The women who did not take estrogen were significantly older (p < 0.001), had more vessels with significant stenosis (p = 0.033), lower ejection fractions (p = 0.051), and more prior myocardial infarctions (p = 0.054). However, a Cox proportional-hazards model selected the number of coronary arteries narrowed (RR 1.43, p < 0.0001), estrogen use (RR 0.38, p = 0.001), left main coronary stenosis (RR 1.83, p = 0.001), and diabetes mellitus (RR 1.57, p = 0.003) as the significant independent predictors of survival. These data suggest that ERT improves survival significantly after CABG in postmenopausal women with coronary artery disease.

Responses of HDL subclasses, Lp(A-I) and Lp(A-I:A-II) levels and lipolytic enzyme activities to continuous oral estrogen-progestin and transdermal estrogen with cyclic progestin regimens in postmenopausal women

Seventy postmenopausal women took part in the study. Subjects received either continuous oral 17 beta-estradiol 2 mg/day combined with norethisterone acetate 1 mg/day (E2/NETA, Kliogest) or transdermal treatment consisting of 28 day cycles with patches delivering 17 beta-estradiol 50 micrograms/day (Estraderm) combined with cyclic medroxyprogesterone acetate 10 mg/day (E2/MPA, Provera), on days 17-28. At baseline the serum lipid and lipoprotein concentrations, composition and concentrations of high density lipoprotein (HDL) subclasses, lipoprotein (Lp)(AI) and Lp(A-I:A-II) levels were comparable in the two groups. In the E2/NETA group, after 12 months hormone replacement therapy (HRT), the HDL2 cholesterol concentration decreased by 17% (P < 0.01) and the HDL3 cholesterol remained unchanged. The concentrations of HDL2b, HDL2a and HDL3a were reduced by 30, 26 and 15%, respectively, P < 0.001, and the cholesterol:triglyceride ratio decreased significantly in all HDL subclasses. Apolipoprotein (apo) A-I concentration decreased by 5% (P < 0.05), but apo A-II, Lp(A-I) and Lp(A-I:A-II) concentrations remained unchanged. In the E2/MPA group the HDL2 and HDL3 cholesterol levels were both reduced by 6% (P < 0.05) and the HDL3a, HDL3b and HDL3c concentrations decreased by 14, 12 and 17% during the E2/MPA phase compared with baseline (P < 0.01). No major changes in the composition of HDL subclasses occurred in the E2 MPA group during treatment. The apo A-I and Lp(A-I) levels were not changed, but apo A-II and Lp(A-I:A-II) concentrations decreased by 8 and 5%, P < 0.001 and P < 0.05, respectively. At 12 months the postheparin plasma hepatic lipase (HL) activity decreased only in the E2/NETA group (by 12%, P < 0.05). The cholesteryl ester transfer protein (CETP) activity was not affected by either HRT regimen. The results of our study show that the 2 HRT regimens have multiple effects on HDL particles and HRT induced changes in HDL are not associated with changes in activities of lipolytic enzymes or CETP.

Hormone replacement therapy and cardioprotection: basic concepts and clinical considerations

A large body of epidemiological evidence shows that estrogen use after the menopause reduces the incidence of cardiovascular disease up to 50%. The use of progestin as co-medication in HRT appears not to attenuate the cardioprotective effects of estrogen. Menopause-related changes in metabolic cardiovascular risk factors are identifiable, as are HRT-related changes in these factors. Estrogens may act in a gender-specific way on vascular endothelial cells and other components of the vessel wall enhancing the synthesis and release of NO and other vasodilators and by inhibiting the synthesis and release of vasoconstricting agents, thus favoring vasodilation. Angiographic studies demonstrated in postmenopausal women with ischemic heart disease a reduction in coronary stenosis by estrogen monotherapy. Several studies, including the PEPI-trial, failed to demonstrate any major effect of HRT on blood pressure. The information on HRT and cardioprotection which is available so far is very promising and merits recommending HRT not only in healthy women but also in women with cardiovascular disease as well as in women with increased risk for this disease.

The mythology of hormone replacement therapy

OBJECTIVE

To evaluate the literature on contraindications contained in pharmaceutical data sheets of five currently available oestrogen replacement preparations (HRT). These contraindications include cardiovascular disease, diabetes, liver diseases, otosclerosis, endometriosis, melanoma and hormone-dependent tumours.

DESIGN

Systematic review.

INTERVENTIONS

Oestrogen replacement regimens.

RESULTS

The contraindications to the five HRT preparations have been taken uncritically from the data sheets of oral contraceptives. In some of these conditions not only is HRT not contraindicated, it is indicated. The data sheets for the HRT preparations all state that cardiovascular disease is a contraindication, but systematic review shows that ischaemic heart disease, hypertension and hyperlipidaemia are not contraindications, and in ischaemic heart disease HRT may actually be indicated. Similarly, systematic review shows that diabetes, chronic liver disease, endometriosis, some cases of treated cancer of the endometrium and breast, melanoma and otosclerosis are not contraindications to HRT.

CONCLUSIONS

The information in the pharmaceutical data sheets of HRT regimens should be modified as more accurate information could influence how these preparations are prescribed by doctors as well as affect patient compliance.

Lipoprotein disorders in women: which women are the best candidates for hormone replacement therapy?

OBJECTIVE

To review the data examining hormone replacement therapy (HRT) in the treatment of lipoprotein disorders in women.

DATA SOURCE

A MEDLINE search (1975-1995) of the English-language literature was performed to identify pertinent primary literature and review articles. Articles were also identified through bibliographies of selected articles.

DATA EXTRACTION

Controlled and uncontrolled studies evaluating the effects of lipoprotein concentrations or coronary risk and the effects of estrogen and HRT on coronary heart disease and lipoprotein concentrations in women were evaluated. Trials pertaining to adverse effects of therapy were also examined. Emphasis was placed on recent clinical trials.

DATA SYNTHESIS

The National Cholesterol Education Program's (NCEP's) 1993 report recommends estrogen replacement therapy as a treatment option in postmenopausal women with hyperlipidemia. Recent trials suggesting that triglycerides and highly-density lipoproteins are more closely related to coronary risks in women necessitate an improved understanding of estrogen and progestin's effects of lipoprotein concentrations. A recent trial has clarified the lipoprotein effects of HRT in women with normal lipid concentrations and suggests that beneficial effects on low-density lipoproteins are maintained, although progestins attenuate beneficial changes in high-density lipoproteins and triglyceride elevations persist. The few trials evaluating estrogen use in women with hyperlipidemia suggest a beneficial effect as well.

CONCLUSIONS

In the absence of contraindications, postmenopausal women with hyperlipidemia should be offered estrogen replacement therapy as conjugated equine estrogen of 0.625 mg/D. Pending further information. NCEP's recommendations should be followed regarding goals of therapy.

Sex steroids and the cardiovascular system

HRT decreases significantly the risk of cardiovascular disease in postmenopausal women. More and more data indicate that this is true not only for unopposed oestrogen but also for combined oestrogen/progestin therapy. The latter point is of utmost importance since the global treatment strategy for women with an intact uterus includes a progestin.

Medroxyprogesterone acetate antagonizes inhibitory effects of conjugated equine estrogens on coronary artery atherosclerosis

Although estrogen replacement therapy is associated with reduced risk of coronary heart disease and reduced extent of coronary artery atherosclerosis, the effects of combined (estrogen plus progestin) hormone-replacement therapy are uncertain. Some observational data indicate that users of combined hormone replacement consisting of continuously administered oral conjugated equine estrogens (CEE) and oral sequentially administered (7 to 14 days per month) medroxyprogesterone acetate (MPA) experience a reduction in risk similar to that of users of CEE alone. However, the effects of combined, continuously administered CEE plus MPA (a prescribing pattern that has gained favor) on the risk of coronary heart disease or atherosclerosis are not known. We studied the effects of CEE (monkey equivalent of 0.625 mg/d) and MPA (monkey equivalent of 2.5 mg/d), administered separately or in combination, on the extent of coronary artery atherosclerosis (average plaque size) in surgically postmenopausal cynomolgus monkeys fed atherogenic diets and treated with these hormones for 30 months. Treatment with CEE alone resulted in atherosclerosis extent that was reduced 72% relative to untreated (estrogen-deficient) controls (P < .004). Atherosclerosis extent in animals treated with CEE plus MPA or MPA alone did not differ from that of untreated controls. Although treatment had marked effects on plasma lipoprotein patterns, statistical adjustment for variation in plasma lipoproteins did not alter the between-group relationships in atherosclerotic plaque size, suggesting that these factors do not explain substantially the atheroprotective effect of estrogen or the MPA-associated antagonism. Although the mechanism(s) remains unclear, we conclude that oral CEE inhibits the initiation and progression of coronary artery atherosclerosis and that continuously administered oral MPA antagonizes this atheroprotective effect.

Relation between estrogen replacement therapy and restenosis after percutaneous coronary interventions

OBJECTIVES

We attempted to determine the relation between estrogen replacement therapy and the rate of restenosis after coronary angioplasty and atherectomy.

BACKGROUND

Although estrogen replacement therapy in women has been associated with a reduction in cardiovascular events and improvement in endothelial function, no study has examined whether estrogen reduces restenosis rates after percutaneous coronary interventions.

METHODS

A total of 204 women enrolled in the Coronary Angioplasty Versus Excisional Atherectomy Trial with angiographic follow-up were contacted, and their menopausal and estrogen replacement status was determined. Late loss in minimal lumen diameter, late loss index, minimal lumen diameter, rate of restenosis > 50% and actual percent of stenosis were compared in estrogen users and nonusers by quantitative coronary angiography at 6-month follow-up.

RESULTS

Late loss in minimal lumen diameter was significantly less in women using estrogen than in nonusers (-0.13 vs. -0.46 mm, p = 0.01). A regression analysis of the determinants of late loss in minimal lumen diameter revealed that estrogen use was the single most important predictor of subsequent late loss (F = 13.38, p = 0.0006). Formal testing revealed a highly significant interaction between the use of estrogen and intervention (angioplasty or atherectomy). Women undergoing atherectomy who received estrogen had a significantly lower late loss index (0.06 vs. -0.63, p = 0.002), less late loss (0.06 vs. -0.61 mm, p = 0.0006), larger minimal lumen diameter (p = 0.044) and lower restenosis rates (p = 0.038 for > 50% stenosis) than those not using estrogen. In contrast, estrogen had minimal effects on restenosis end points after angioplasty.

CONCLUSIONS

This study demonstrates the potential for estrogen replacement therapy to reduce angiographic measures of restenosis in postmenopausal women after coronary intervention, particularly in those undergoing atherectomy.

No association of menopause and hormone replacement therapy with carotid artery intima-media thickness. Atherosclerosis Risk in Communities (ARIC) Study Investigators

BACKGROUND

Cardiovascular disease is the major cause of death in older women. Information on the relation of menopause and hormone replacement therapy with carotid atherosclerosis is limited.

METHODS AND RESULTS

We examined cross-sectionally the association of menopausal status, years since last menstruation, and hormone replacement therapy status with carotid artery intima-media thickness as determined by B-mode ultrasound. Female participants (n = 5436) in the Atherosclerosis Risk in Communities Study without a history of symptomatic cardiovascular disease were included in the analyses. Menopause status in 45- to 54-year-old women who had never used hormone replacement therapy was not strongly associated with carotid intima-media thickness (mean = 0.65 mm and 0.67 mm in premenopausal and postmenopausal women, respectively, adjusted for age, race, cigarette years of smoking, body mass index, sport index, systolic blood pressure, use of blood pressure medications, drinking status, diabetes, and education level). In postmenopausal women aged 55 to 64 years, women with < or = 5 years since last menstruation had an adjusted average intima-media thickness (0.74 mm) comparable to those with > 5 years since last menstruation (0.75 mm) (P > .05). Although hormone replacement therapy use was associated with a more favorable lipid and hemostasis profile than nonuse, its use was not associated with intima-media thickness in postmenopausal women aged 55 to 64 years (adjusted average = 0.74 mm for current users of estrogen alone and approximately 0.75 mm each for current users of estrogen plus progestin, former users, and never users).

CONCLUSIONS

The data suggest that the well-known associations of hormone replacement therapy with reductions in atherosclerotic cardiovascular disease may be attributable more to acute physiological effects, such as hemodynamic changes or reduced thrombosis, than to atherosclerosis itself.

Estrogen replacement therapy

For decades, observers have noted that women lose their natural resistance to coronary disease following menopause. It is now known that this increase in coronary risk is due to the loss of the protective effect of estrogen. Although still somewhat controversial, estrogen replacement therapy appears to offer significant cardioprotective benefits to postmenopausal women. These benefits extend to women with a history of coronary artery disease as well as to those without. The exact mechanism by which estrogen confers protection is not known, although the primary focus has been on estrogen's effect on serum lipids. Estrogen reduces total cholesterol levels and low-density-lipoprotein cholesterol levels and increases levels of high-density lipoproteins. Recent data suggest that estrogen may also have a beneficial effect on lipoprotein (a), a less studied lipid fraction, and may affect lipid metabolism in the blood-vessel wall. Numerous studies are under way to define better the risks and benefits of estrogen replacement therapy. Until more is known, the decision to recommend estrogen replacement therapy must be made on an individual basis.

Gender considerations in hypertension pathophysiology and treatment

Cardiovascular disease is the leading cause of death among women, yet clinical trials have not evaluated specific treatment strategies for women. Recently, there has been an expansion of scientific literature exploring differences between women and men with hypertension and cardiovascular disease. The cardioprotective effects of estrogen have been well demonstrated, and the loss of endogenous estrogens with aging contributes to the rapid increase in the incidence of coronary artery disease after menopause. Many of the adverse effects of estrogen deficiency are reversible with estrogen replacement. Estrogen improves lipoprotein profiles, has vasodilatory effects on the endothelium, and inhibits vascular smooth muscle cell growth and constriction. These effects likely all contribute to the reduction in coronary artery disease in the presence of estrogen, and the clinical benefits are not attenuated by concurrent progestins. There are gender-specific differences in the epidemiology of hypertension and coronary artery disease, as well as differences in the pathophysiology and clinical manifestations of disease. Given important experimental interactions between estrogens and the major classes of antihypertensive agents, as well as secondary benefits such as a possible reduction in bone loss with certain agents, a gender-specific approach to hypertension appears to be warranted. Future clinical trials will need to address gender-specific differences in treatment approaches.

Estrogen effects in the heart

Gender specific differences in cardiovascular disease are largely mediated by sex hormones. The use of estrogens significantly reduces the overall incidence of heart disease in postmenopausal women. Beneficial effects of estrogens on plasma lipoprotein levels are clearly established. However, these do not explain the magnitude of risk reduction seen in clinical studies. Thus additional and currently unknown functions of estrogens must be operative. Elucidation of the exact estrogen action in the heart will have important implications in the treatment of cardiovascular disease. It will probably enhance the therapeutic repertoire in treating heart disease, the most common cause of death in industrialized countries. We will review the current understanding of the function of estrogens in the heart and discuss potential strategies on how to apply these data to clinical practice.

Beneficial effect of treatment with transdermal estradiol-17-beta on exercise-induced angina and ST segment depression in syndrome X

We investigated the acute effect of transdermal estradiol-17-beta on exercise-induced ischemia in 15 postmenopausal women (mean age 58 +/- 6 years) with syndrome X (angina pectoris, positive exercise test and normal coronary angiogram) and eight healthy women (mean age 58 +/- 5 years) in a placebo-controlled, double-blind crossover trial. Two exercise tests were performed on separate days, separated by at least 1 week, after application of placebo or 100 micrograms/24 h estradiol-17-beta. In the control group there was no difference between estradiol and placebo. Patients with syndrome X, on the other hand, showed an increased time to angina (323 +/- 99 versus 233 +/- 67 s, P = 0.0044), time to 1 mm ST depression (257 +/- 142 versus 187 +/- 122 s, P = 0.039), total exercise time (363 +/- 104 versus 323 +/- 85 s, P = 0.038), and working capacity (93 +/- 17 versus 89 +/- 15 W, P = 0.0086) during active treatment. In conclusion, estradiol-17-beta has a beneficial effect on myocardial ischemia in postmenopausal women with syndrome X and may be a useful therapeutic agent in this disease.

Mechanisms whereby oestrogens influence arterial health

Coronary heart disease (CHD) is uncommon in premenopausal women compared with men of similar age, but its incidence increases after the menopause to reach that of men. There is now good population-based evidence that hormone replacement therapy (HRT) in postmenopausal women reduces the incidence of CHD, perhaps by up to 50%. Oestrogens have a beneficial effect on arterial health in many different ways. HRT may both reduce the risk of atheroma formation and improve arterial function. Depending on the formulation, HRT can lower LDL and triglycerides, and increase HDL. Oestrogen may also produce qualitative as well as quantitative improvements in lipoproteins. It can improve insulin resistance and hence carbohydrate metabolism, and may enhance fibrinolysis rather than coagulation. Thus these effects of HRT on risk factor for CHD will reduce the risk of atheroma development and progression. Oestrogen has direct effects on blood vessels and improves vascular function through various mechanisms including endothelium-dependent and calcium-dependent processes. HRT should therefore now be considered for use in postmenopausal women with established CHD risk.

Determination of 17 alpha-dihydroequilenin in rat, rabbit and monkey plasma by high-performance liquid chromatography with fluorimetric detection

A high-performance liquid chromatographic (HPLC) method with fluorescence detection for the determination of total (unconjugated and conjugated) 17 alpha-dihydroequilenin in male and female rat, female rabbit and male and female rhesus monkey plasma is described here. Plasma sample preparation involved hydrolysis with enzyme (Glusulase), addition of internal standard (14 beta-equilenin) and solvent extraction. The extracts were chromatographed on a C6, 5-microns reversed-phase HPLC column and detection was accomplished with a fluorescence detector operated at an excitation wavelength of 210 nm and an emission wavelength of 370 nm. The assay was linear over a range of 2.5 to 100 ng/ml in male and female rat plasma, and 5 to 500 ng/ml in female rabbit and male and female monkey plasma. The method was specific, accurate and reproducible (percent differences < 14.5; coefficients of variation < 9.5%) in all matrices examined. The applicability of this method was successfully tested by quantifying total plasma concentrations of 17 alpha-dihydroequilenin in ovariectomized female rats, ovariectomized female rabbits and a normal female rhesus monkey receiving 2.0, 8.3 and 0.1 mg/kg, respectively, of 17 alpha-dihydroequilenin sulfate intragastrically.

Hormone replacement therapy and cardiovascular disease

Coronary heart disease is the principal cause of death in postmenopausal women. Postmenopausal women have an elevated cardiovascular risk profile in the form of android obesity (increased waist/hip ratio), hyperinsulinemia, impaired glucose tolerance, increased insulin resistance and elevated plasma LDL, VLDL, serum triglyceride and lipoprotein (a). A significant decrease in the relative risk of cardiovascular disease is observed with estrogen replacement therapy. The addition of progestogens commonly used in hormone replacement regimes does not, based on present evidence, seem to affect cardiovascular protection adversely. The literature on this subject has been reviewed and recommendations made with implications for the future.

Estrogens, menopause, and coronary artery disease

The incidence of cardiovascular disease increases after menopause as women age. Estrogen-replacement therapy has been found to reduce cardiovascular risk by about 50% in over 30 observational studies. Part of the beneficial effect appears to be due to a reduction of LDL cholesterol and an increase in HDL cholesterol. Another important mechanism is related to the effect of estrogen on endothelial function. In making a decision to use estrogen-replacement therapy, the benefits must be weighed against the risks of endometrial and breast cancer.

Benefit/risk of estrogen therapy in cardiovascular disease: current knowledge and future challenges

In the United States, cardiovascular disease represents the leading cause of death among women. A majority of the deaths are due to coronary disease. In addition, the incidence of heart attacks increases with age. Among those who are 65 years of age or older, the estimated heart attack rate is 374,000 per year for women, compared with 440,000 per year for men. In the past three decades, a number of observational studies have suggested that estrogen therapy can reduce the risk of coronary disease in postmenopausal women. This protective effect appears to be much greater in women who have existing coronary disease. These observational data point to the potential usefulness of estrogen therapy in preventing cardiovascular death among women. Although large, well-controlled, clinical trials are needed to confirm the benefit of estrogen therapy, several important findings strongly support the cardioprotective effect of estrogen therapy. For example, in monkeys estrogen prevents the accumulation of low-density lipoprotein (LDL) cholesterol (a known risk factor for heart disease) in coronary arteries, and estrogen has also been shown to increase high-density lipoprotein (HDL) cholesterol (a known cardioprotective factor). Estrogen also possesses a vasodilating property, which can improve cardiac performance in ischemic heart disease. In addition, recent studies have demonstrated that estrogens (especially equilin) exhibit a high antioxidant effect, which may also be related to cardioprotectivity. Although estrogen therapy has been observed to decrease the risk of coronary disease, long-term estrogen therapy has also been found to increase the risk of uterine carcinoma; the addition of progesterone to estrogen therapy may lessen this undesirable risk, however. On the other hand the addition of progesterone to estrogen therapy may decrease estrogen's beneficial effect on HDL cholesterol. What should be the present position on estrogen therapy in postmenopausal women? What is the best dosage regimen? Should it be used alone or in combination with a progesterone? These important issues are discussed, as are several current clinical trials addressing the issue of estrogen therapy in postmenopausal women.

Clinical pharmacology of estrogens: cardiovascular actions and cardioprotective benefits of replacement therapy in postmenopausal women

The use of estrogens in postmenopausal women has been the subject of much controversy regarding hormone formulation, dosage, use in combination with progestins, duration of treatment, and contraindications. Estrogens have been prescribed to relieve menopausal symptoms for more than three decades. The hormones reduce the gynecologic and psychologic changes associated with menopause while inhibiting bone resorption and possibly reducing the risk of cardiovascular disease. Their use however has been complicated by an increased risk of endometrial cancer and possibly breast cancer. The use of estrogens as cardioprotective agents is discussed and the clinical experiences and the possible mechanisms of action are reviewed. The clinical pharmacology of estrogens and the various formulations that are available as monotherapy or in combination with progestins will also be reviewed.

Clinical pharmacology of estrogens: cardiovascular actions and cardioprotective benefits of replacement therapy in postmenopausal women

The use of estrogens in postmenopausal women has been the subject of much controversy regarding hormone formulation, dosage, use in combination with progestins, duration of treatment, and contraindications. Estrogens have been prescribed to relieve menopausal symptoms for more than three decades. The hormones reduce the gynecologic and psychologic changes associated with menopause while inhibiting bone resorption and possibly reducing the risk of cardiovascular disease. Their use however has been complicated by an increased risk of endometrial cancer and possibly breast cancer. The use of estrogens as cardioprotective agents is discussed and the clinical experiences and the possible mechanisms of action are reviewed. The clinical pharmacology of estrogens and the various formulations that are available as monotherapy or in combination with progestins will also be reviewed.