Post-menopausal hormone replacement therapy: effects of progestogens on serum lipids and lipoproteins. A review

Genetic, Molecular, and Cellular Determinants of Sex-Specific Cardiovascular Traits

Despite the well-known sex dimorphism in cardiovascular disease traits, the exact genetic, molecular, and cellular underpinnings of these differences are not well understood. A growing body of evidence currently points at the links between cardiovascular disease traits and the genome, epigenome, transcriptome, and metabolome. However, the sex-specific differences in these links remain largely unstudied due to challenges in bioinformatic methods, inadequate statistical power, analytic costs, and paucity of valid experimental models. This review article provides an overview of the literature on sex differences in genetic architecture, heritability, epigenetic changes, transcriptomic signatures, and metabolomic profiles in relation to cardiovascular disease traits. We also review the literature on the associations between sex hormones and cardiovascular disease traits and discuss the potential mechanisms underlying these associations, focusing on human studies.

Pharmacotherapeutic options for the treatment of menopausal symptoms

Introduction: Menopausal symptoms can be very overwhelming for women. Over the years, many pharmacotherapeutic options have been tested, and others are still being developed. Hormone therapy (HT) is the most efficient therapy for managing vasomotor symptoms and related disturbances. The term HT comprises estrogens and progestogens, androgens, tibolone, the tissue-selective estrogen complex (TSEC), a combination of bazedoxifene and conjugated estrogens, and the selective estrogen receptor modulators, such as ospemifene. Estrogens and progestogens and androgens may differ significantly for chemical structure and can be delivered through different routes, thereby displaying various pharmacological and clinical properties. Tibolone, TSEC and SERM also exhibit unique pharmacodynamics that can be exploited to obtain distinctive therapeutic effects. Non-hormonal options fall mainly into the selective serotonin reuptake inhibitor (SSRI) and selective noradrenergic reuptake inhibitor (SNRI), GABA-analogue drug classes.Areas covered: Herein, the authors describe the pharmacokinetics and pharmacodynamics of hormonal (androgens, estrogens, progestogens, tibolone, TSEC, SERMs) and non-hormonal (SSRIs, SNRIs, Gabapentin, Pregabalin, Oxybutynin, Neurokinin antagonists) treatments for menopausal symptoms and report essential clinical trial data in humans.Expert opinion: Patient tailoring of treatment is key to managing symptoms of menopause. Physicians must have in-depth knowledge of the pharmacology of compounds to tailor therapy to the individual patient's characteristics and needs.

Pharmacology of estrogens and progestogens: influence of different routes of administration

This review comprises the pharmacokinetics and pharmacodynamics of natural and synthetic estrogens and progestogens used in contraception and therapy, with special consideration of hormone replacement therapy. The paper describes the mechanisms of action, the relation between structure and hormonal activity, differences in hormonal pattern and potency, peculiarities in the properties of certain steroids, tissue-specific effects, and the metabolism of the available estrogens and progestogens. The influence of the route of administration on pharmacokinetics, hormonal activity and metabolism is presented, and the effects of oral and transdermal treatment with estrogens on tissues, clinical and serum parameters are compared. The effects of oral, transdermal (patch and gel), intranasal, sublingual, buccal, vaginal, subcutaneous and intramuscular administration of estrogens, as well as of oral, vaginal, transdermal, intranasal, buccal, intramuscular and intrauterine application of progestogens are discussed. The various types of progestogens, their receptor interaction, hormonal pattern and the hormonal activity of certain metabolites are described in detail. The structural formulae, serum concentrations, binding affinities to steroid receptors and serum binding globulins, and the relative potencies of the available estrogens and progestins are presented. Differences in the tissue-specific effects of the various compounds and regimens and their potential implications with the risks and benefits of hormone replacement therapy are discussed.

The effect of desogestrel for hormone replacement therapy on the blood lipid profiles of postmenopausal women

OBJECTIVE

To determine the effect of a hormone replacement protocol containing conjugated equine estrogens and desogestrel (which has a highly selective progestogenic and low androgenic effect) as the progestogen, on the plasma lipid profile, as compared with two other hormone replacement treatments (HRT).

METHOD

Eighty-nine healthy postmenopausal women were divided prospectively into four groups. A control group of 24 women did not receive HRT. Twenty-nine women received conjugated equine estrogen and medroxyprogesterone, and 13 women received a protocol containing estradiol, estriol and norethisterone acetate. Fasting blood lipid was taken at the end of each third cycle. The cumulative therapeutic response was calculated in each group as compared with initial values and between groups. Significance was analyzed by t-tests.

RESULTS

A protocol containing desogestrel significantly decreased low-density lipoprotein cholesterol (27%; P < 0.05) and increased high-density lipoprotein cholesterol (HDL-C) by 30% (P < 0.05%) after 9 months. The ratio of total cholesterol to HDL-C also decreased significantly (44%; P < 0.05).

CONCLUSION

The most beneficial effect on plasma lipid profile was obtained with an HRT protocol containing desogestrel as the progesterone.

Treatment with hormone replacement therapy lowers remnant lipoprotein particles in healthy postmenopausal women: results from a randomized trial

BACKGROUND

Recent evidence indicates that remnant lipoprotein particles (RLPs) may play a role in atherosclerosis. Remnant lipoprotein particles have been suggested to be the most atherogenic particles among the triglyceride-rich lipoproteins. In particular, these triglyceride-rich particles were identified as an independent risk factor for cardiovascular diseases (CVD) in women. Postmenopausal hormone replacement therapy (HRT) beneficially affects lipid profile, although total triglyceride levels often increase. Evidence on the effects of HRT on RLPs is limited. We determined whether 3 months' treatment of postmenopausal women with Tibolone or conjugated oestrogens combined with medroxyprogesterone acetate (CEE + MPA) affects RLP-cholesterol (RLP-C).

MATERIALS AND METHODS

One hundred and five healthy postmenopausal women were randomized to either 2.5 mg of Tibolone, 0.625 mg of CEE + 2.5 mg of MPA or placebo. At baseline and after 3 months the lipid profile was determined. For assessment of RLP-C we used an immunoseparation-based method.

RESULTS

Treatment with CEE + MPA significantly reduced RLP-C (-0.03 mmol L-1, P-value = 0.01) and appeared to increase triglycerides (0.15 mmol L-1, P-value = 0.20) compared with placebo. Tibolone did not significantly change RLP-C (-0.01 mmol L-1, P-value = 0.35) and significantly decreased triglycerides (-0.35 mmol L-1, P-value = 0.004).

CONCLUSIONS

Treatment of postmenopausal women with conjugated oestrogens and medroxyprogesterone acetate reduced RLP-C, without a reduction in total triglycerides, whereas Tibolone did affect triglyceride levels, but not RLP-C. These observations may be relevant for explaining the effect of HRT on cardiovascular risk in healthy postmenopausal women.

A novel concept to preserve the beneficial effects of hormone replacement therapy in bilaterally female ovariectomized rats: role of lovastatin therapy

Estrogen replacement therapy (ERT) is claimed to reduce cardiovascular mortality by about 50% in postmenopausal women. This improvement is caused by favorable changes in lipid and lipoproteins metabolism, however, it also increases the incidence of the endometrial hyperplasia. Addition of progestin to ERT, referred to as hormone replacement therapy (HRT), has been shown to successively reduce this risk to the endometrium. Unfortunately, it has an adverse effect on high-density lipoprotein cholesterol (HDLC) concentration, thus compromising the benefits of ERT. Therefore the issue here whether HRT given alone and/or concomitantly with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (lovastatin) could exert any significant additional favorable effect on the lipid profile in bilaterally ovariectomized female rats. Sixty female Wistar rats were ovariectomized and treated with ERT (0.625 mg kg (-1)estradiol, E (2), IM every 2 weeks), HRT (estradiol plus progesterone, E (2)+ P, 0.625 mg kg (-1)estradiol and 5 mg progesterone kg (-1) respectively, IM every 2 weeks), and lovastatin (20 mg kg (-1)day (-1)orally) plus HRT (L + HRT) for 6 weeks. Blood aliquots were collected for serum and plasma separation. Serum vitamin E and plasma levels of C-reactive protein (CRP), nitric oxide (NO), lipid profile, and the susceptibility of non-HDLC to oxidation were determined. Moreover, thoracic aortas were dissected and directed for measurement of its lipid peroxide and NO contents. Treatment of ovariectomized rats with HRT showed a significant decrease ( P< 0.0001) in HDLC concentration compared to the group treated alone with ERT and increase ( P< 0.0001) in CRP levels compared to ovariectomized rats. HDLC and CRP are two powerful and significant predictors for increased cardiovascular risk in postmenopausal women. Addition of lovastatin as a complementary therapy to HRT revealed a significant 27% increment in HDLC and 48% decrement in CRP concentrations. Moreover, it significantly increased vitamin E, each of plasma and tissue content of NO and decreased atherogenic indexes (TC/HDLC, LDLC/HDLC), aortic lipid peroxide and susceptibility of non-HDLC to oxidation. In conclusion, this current study demonstrated that lovastatin together with continuous combined HRT seems to be more effective in the secondary prevention of coronary heart disease not only due to lipid lowering properties but also related to several other additive effects such as modification of endothelial function and inflammatory responses.

How progestins influence the cardiovascular effect of hormone replacement therapy

Hormone replacement therapy aims to protect against osteoporosis and alleviate fastidious menopausal symptoms such as hot flushes, depression, sleep disturbances and vaginal dryness. In view of the acknowledgement of estrogen deficiency as a major trigger for the acceleration of cardiovascular risk after menopause, hormone replacement therapy may also be proposed as a substantial beneficial cardioprotective agent. The effects of progestins on lipoprotein profile and vasomotor tone are dependent on the chemical structure and the scheme of administration of progestins, with androgenic progestins and cyclical therapy having a potential detrimental effect. Prospective primary and secondary prevention studies, however, suggest that the adjunct of non-androgenic progestins to estrogen therapy is at least as effective as estrogen replacement therapy in reducing cardiovascular mortality and morbidity. Data from recent randomized secondary prevention studies have to be viewed with caution.

Comparison of the antiatherosclerotic effect of tibolone with that of estradiol and ethinyl estradiol in cholesterol-fed, ovariectomized rabbits

OBJECTIVE

Tibolone is a synthetic steroid with tissue-specific estrogenic, progestogenic, and androgenic properties. The drug relieves climacteric symptoms and prevents osteoporosis but does not stimulate the endometrium. We have previously shown that in laboratory animals tibolone inhibits the atherogenesis induced by a high-cholesterol diet. Therefore, we compared the antiatherosclerotic effect of oral tibolone at different dose levels with that of oral 17beta-estradiol (E2) and ethinyl estradiol (EE).

DESIGN

Atherosclerotic lesion formation (increase in vessel wall cholesterol deposition and fatty streak formation) was measured in ovariectomized rabbits after 20 weeks on an atherogenic diet (fed daily 80 g of a rabbit chow containing 0.4% cholesterol, 3.75% peanut oil, and 3.75% coconut oil) in eight groups: group 1, placebo (n = 35); group 2, control (n = 34) received normal rabbit chow; group 3, E2 group (E2 4 mg, n = 12); group 4, EE group (EE 60 microg, n = 10); and groups 5-8, tibolone (6 mg, n = 12; 2 mg, n = 13; 0.6 mg, n = 25; and 0.15 mg, n = 11, respectively). During the study, blood samples were obtained for the evaluation of plasma triglycerides, cholesterol, lipoproteins, and glutamate pyruvate transaminase. After 20 weeks, the animals were killed, and cholesterol concentration and the formation of fatty streaks in the wall of the aortic arch were evaluated.

RESULTS

In the placebo group, the atherogenic diet induced a mean increase in total plasma cholesterol concentration from 1.1+/-0.1 mmol/L (control group) to 34.1+/-1.8 mmol/L (mean +/- SE). This resulted in an accumulation of cholesterol in the aortic arch from 48+/-4 (control group) to 608+/-44 nmol/mg protein and in the formation of fatty streaks (41.8+/-3.2% of the surface of the aortic arch was covered with fatty streaks). Tibolone had strong dose-dependent antiatherosclerotic effects. It reduced the accumulation of cholesterol in the aortic arch at doses of 6 to 0.15 mg by 99, 97, 87, and 57% and the formation of fatty streaks by 98, 97, 81, and 38%, respectively. E2 had only a marginal antiatherosclerotic effect, whereas EE showed an effect comparable to that of tibolone at doses of 2 to 0.6 mg. With EE, the accumulation of cholesterol in the vessel wall was reduced by 93% and the formation of fatty streaks by 73%. Mean plasma cholesterol concentrations were also reduced by tibolone (64, 70, 61, and 47%) and EE (57%). This reduction was mainly mediated via a reduction in beta-very-low-density lipoprotein cholesterol. Analysis, however, indicated that the observed antiatherosclerotic effects of tibolone and EE, at least partly, are due to a direct effect on the vessel wall and independent of the changes in plasma cholesterol. At equipotent antiatherosclerotic doses, EE showed a stronger uterotropic effect (measured as the increase in uterine weight) than tibolone. EE increased uterine weight from 0.57 g/kg body weight (BW) (control group) to 3.5 g/kg BW; tibolone at doses of 6, 2, 0.6, and 0.15 mg increased uterine weight to 2.5, 2.8, 2.2, and 1.3 g/kg BW, respectively.

CONCLUSION

Tibolone can protect the arterial vessel wall against atherosclerotic lesions induced by a hypercholesterolemic diet. However, it has much less estrogenic effects on the uterus compared with EE at equipotent doses, indicating tissue selectivity for tibolone. The clinical implications of these findings require investigation.

Three-year study of estrogen alone versus combined with progestin in postmenopausal women with or without hypercholesterolemia

This study compares the effects of long-term hormone replacement therapy on the lipid profile of postmenopausal women with or without hypercholesterolemia, with a comparison of 2 different regimens over a 3-year period. A total of 209 women were enrolled in this prospective, nonrandomized trial. They were classified into 2 groups according to baseline serum levels of total cholesterol and low-density lipoprotein (LDL) cholesterol. The hypercholesterolemic group consisted of 83 subjects with a total cholesterol level of 220 mg/dL or higher and LDL cholesterol 140 mg/dL or higher. The normocholesterolemic group consisted of 126 subjects with normal total and LDL cholesterol levels. Therapy was assigned as follows: 44 subjects in the hypercholesterolemic group and 67 in the normal cholesterol group with a total hysterectomy received conjugated equine estrogen (CEE) 0.625 mg/d, while 39 subjects in the hypercholesterolemic group and 59 in the normal cholesterol group with a physiological menopause received CEE 0.625 mg/d plus medroxyprogesterone acetate 2.5 mg/d. Fasting blood samples were monitored periodically for 3 years. Nine women withdrew from the study. Hormone replacement therapy had a more favorable effect in the hypercholesterolemic group versus the normal cholesterol group by decreasing total and LDL cholesterol, 7.0% and 16.6%, versus the normal cholesterol group, 0.8% and 3.9%. Serum levels of high-density lipoprotein (HDL) cholesterol were increased in both groups (hypercholesterolemic, 14.4%; normal cholesterol group, 26.5%), with the increase being larger in the normal cholesterol group. These changes were similar with both treatments and were maintained over 3 years. Serum levels of triglyceride were also increased in both groups, with the increase being statistically significant only in the group with normal cholesterol levels at baseline. There were no consistently reported side effects of therapy. The effects of postmenopausal hormone replacement therapy, estrogen with or without progestin, on the lipid profile appear to be related to the subject's baseline lipid values. Thus, such therapy may have a more favorable effect on LDL cholesterol in postmenopausal women with hypercholesterolemia, with the beneficial effect being maintained over 3 years.

The effect of hormone replacement therapy on metabolism of lipoprotein remnants in postmenopausal women

OBJECTIVE

The measurement of remnant-like particles reflects chylomicron and very low density lipoprotein remnants which are most likely atherogenic particles. We investigated the effects of menopausal status and postmenopausal hormone replacement on metabolism of remnant lipoprotein-cholesterol.

METHODS

We measured remnant lipoprotein-cholesterol by an immunoseparation assay in 20 premenopausal, 40 postmenopausal, and 30 bilaterally oophorectomized women. Of 70 postmenopausal subjects, 21 surgically menopausal women (with total hysterectomy) were started on hormone replacement with conjugated equine estrogen, 0.625 mg/day, and 36 naturally postmenopausal women were begun on a combination of conjugated equine estrogen 0.625 mg/day, plus medroxyprogesterone acetate, 2.5 mg/day. Plasma levels of remnant lipoprotein-cholesterol and other common lipids were measured after 6 and 12 months of treatment.

RESULTS

Plasma remnant lipoprotein-cholesterol levels in postmenopausal and surgically menopausal women were significantly higher than in premenopausal women (P < 0.005). Plasma total and low-density lipoprotein cholesterol levels decreased and high-density lipoprotein cholesterol increased significantly (P < 0.01) in both treatment groups, respectively. Plasma triglyceride levels were not changed by treatment; however, remnant lipoprotein-cholesterol levels decreased in both treatment groups (estrogen group; P = 0.07, estrogen-progestin group; P < 0.05). No side effects of therapy were consistently reported.

CONCLUSIONS

We confirmed that remnant lipoprotein-cholesterol increases after menopause. Hormone replacement therapy improves disordered lipoprotein metabolism and exerts a favorable effect on lipoprotein remnant metabolism in postmenopausal women.

Micronized progesterone: clinical indications and comparison with current treatments

OBJECTIVE

To integrate and evaluate the pharmacokinetic, endocrine, and clinical effects of micronized progesterone formulations.

DESIGN

Published articles concerning the pharmacokinetics of orally administered progesterone and the potential clinical uses of oral micronized progesterone were reviewed. Results concerning their use for secondary amenorrhea, premenopausal bleeding disorders, luteal phase dysfunction, termination of premature labor, hormone replacement therapy, and premenopausal syndrome are summarized. Critical issues to be resolved through ongoing preclinical and clinical research are highlighted.

RESULT(S)

Because of the enhanced bioavailability of oral micronized progesterone, the compound may be useful for a variety of therapeutic indications. Oral micronized progesterone is available in France, and a formulation recently has been approved in the United States for the treatment of secondary amenorrhea and postmenopausal hormone replacement therapy. A large body of evidence, including the Postmenopausal Estrogen/Progestin Interventions study, suggests that the use of a combination of estrogen and oral micronized progesterone is optimal for long-term hormone replacement therapy. There also are data indicating that oral micronized progesterone could be of potential use for the treatment of premenopausal bleeding disorders, luteal phase disorders, and premature labor.

CONCLUSION(S)

Oral micronized progesterone has widespread clinical potential, particularly for the treatment of secondary amenorrhea and dysfunctional premenopausal bleeding, and as a component of postmenopausal hormone replacement therapy.

Tibolone prevents atherosclerotic lesion formation in cholesterol-fed, ovariectomized rabbits

Tibolone (Org OD14), a synthetic steroid with estrogenic and progestogenic/androgenic properties, is clinically effective for the treatment of climacteric symptoms and the prevention and treatment of osteoporosis in postmenopausal women. The effect on atherogenesis, however, is not known. In the current study, we investigated the effect of tibolone in comparison with that of estradiol and norethisterone acetate on atherogenesis in 140 ovariectomized New Zealand White rabbits that had been induced by an atherogenic diet (0.4% cholesterol, 20 weeks). Tibolone at 18, 6, or 2 mg/d orally completely prevented cholesterol accumulation and fatty streak formation in the aorta; the impairment of endothelium-dependent smooth muscle relaxation of the aorta; and complex lesion formation after endothelial denudation in the carotid artery. Tibolone also reduced the increased postovariectomy plasma lipid concentrations. Analysis of the results, however, indicated that a substantial part of the strong, beneficial effects were plasma lipid independent. Compared with subcutaneous estradiol decanoate (150 microgram once weekly) and oral 17beta-estradiol (4 mg/d), the effects of tibolone were more pronounced at equipotent uterotropic activity. Norethisterone acetate (1 mg/d) did not affect atherosclerotic lesion formation. There are no indications that the progestogenic/androgenic properties of tibolone counteracted its atheroprotective effect on the vessel wall. Therefore, tibolone has the intrinsic potential to be a compound that protects the arterial vessel wall against atherosclerotic processes.

Effects of Continuous and Cyclic Hormone Replacement Therapy on the Lipoprotein Profile in Postmenopausal Women

Objective:

To provide an overview of the information concerning cyclic and continuous hormone replacement therapy (HRT) and the effects of the various regimens on the lipid profile.

Data Sources:

MEDLINE (January 1966–December 1996) and Index Medicus (January 1995-December 1996) searches were conducted to identify relevant studies and review articles. Bibliographies of selected articles also were reviewed.

Study Selection:

Studies addressing continuous and cyclic use of a progesterone formulation along with daily conjugated equine estrogen (CEE) and their effects on the lipid profiles of postmenopausal women were selected for review.

Data Extraction:

Applicable data were selected and used in a review format.

Data Synthesis:

CEE has been shown to increase high-density-lipoprotein cholesterol, which may decrease the risk of cardiovascular heart disease. Medroxyprogesterone acetate (MPA) has been added to CEE for postmenopausal HRT to prevent endometrial hyperplasia and cancer. However, MPA negates the beneficial effects of CEE on the lipid profile. Many different HRT regimens, both continuous and cyclic, are being used to increase compliance and to decrease adverse effects. Which regimen offers the best lipid profile results is evaluated in this article.

Conclusions:

The lipid profile effects of HRT using continuous MPA are not significantly different from those obtained with cyclic MPA. Use of a continuous MPA regimen may also offer the long-term advantages of less vaginal bleeding and increased compliance.

Neuroendocrine effects of different estradiol-progestin regimens in postmenopausal women

OBJECTIVE

New regimens and routes of administration of hormonal replacement therapy (HRT) in climateric women are becoming available. Since there is no information on the neuroendocrine effects of sequential combined treatment with 17 beta-estradiol and a progestin, the present study evaluated the neuroendocrine, clinical vasomotor and psychological changes before and after different sequential combined HRT regimens (17 beta-estradiol plus nomegestrol acetate, or cyproterone acetate, or vaginal progesterone). Vasomotor and behavioral effects were evaluated by using the Kupperman score, while changes in plasma endorphin (beta-END) levels were used as marker of neuroendocrine effects.

METHODS

Postmenopausal women (n = 30) were randomly divided into three groups (ten women for each group); all women received continuous 17 beta-estradiol (50 mg, transdermal) and each group was sequentially treated with different progestins for 12 days/month: group A, cyproterone acetate (5 mg p.o.); group B, nomegestrol acetate (5 mg p.o.); and group C, progesterone (100 mg, vaginal cream). A group of healthy fertile women (n = 8) served as control. Before and after 6 months of HRT, postmenopausal women underwent an evaluation of subjective Kupperman score and two neuroendocrine tests: (a) naloxone (4 mg i.v.) and (b) clonidine (1.25 mg i.v.). Plasma beta-END levels were measured before and at 15, 30, 45, 60 and 90 min after drug injection. Control women were studied by administering the two neuroendocrine tests only once.

RESULTS

Postmenopausal women before HRT showed a pathological Kupperman and no changes of plasma beta-END levels in response to the clonidine and naloxone tests score. On the contrary the increase was significant in healthy women. In each of the three groups of treated women both naloxone and clonidine tests induced a significant increase in plasma beta-END levels (P < 0.01). After 6 months of HRT, an improvement of vasomotor and psychological symptoms was shown by a decrease of Kupperman score.

CONCLUSIONS

The present study indicates that sequential treatment with transdermal 17 beta-estradiol and progestin, no matter which progestin was used, restores the beta-END release, improves vasomotor and psychological symptoms.

Metabolic effect of two hormonal preparations in postmenopausal women

OBJECTIVES

To compare the metabolic and endocrinological effects of estradiol valerate/cyproterone acetate (EV/CPA) to a regimen of conjugated estrogens/medroxyprogesterone acetate (CE/MPA) in postmenopausal women.

METHODS

Lipid profile, endocrinological parameters, coagulation factors, renin and angiotensinogen were followed in postmenopausal women randomized to EV/CPA or CE/MPA during 12 cycles.

RESULTS

Following 12 cycles of treatment, total plasma cholesterol decreased more with EV/CPA than with CE/MPA. Low-density cholesterol decreased with EV/CPA while it increased with CE/MPA. High-density cholesterol remained fairly unchanged, and triglycerides increased significantly in both groups. Estradiol and estrone levels increased significantly more with EV/CPA than with CE/MPA while the sex-hormone-binding globulin increased more with CE/MPA. Follicle stimulating and luteinizing hormone levels also decreased significantly. Total testosterone and dihydroepiandrosterone sulfate remained stable. Total levothyroxine serum levels increased significantly, but thyroid stimulating hormone and triiodothyronine levels remained stable. Coagulation parameters also remained stable. Angiotensinogen increased, while plasma renin activity and blood pressure remained unchanged.

CONCLUSION

It is concluded that both EV/CPA and CE/MPA produce favourable metabolic effects. A better lipid profile, compatible with decreased cardiovascular risk, is observed with the EV/CPA regimen. Higher circulating estrogen levels may explain in part this observation.

Medroxyprogesterone attenuates estrogen-mediated inhibition of neointima formation after balloon injury of the rat carotid artery

BACKGROUND

Estrogen blunts the neointimal proliferative response to balloon injury of the carotid artery in intact female rats and gonadectomized rats of both sexes. This study tested whether, in gonadectomized rats of both sexes. (1) progestin (medroxyprogesterone acetate, MPA) alters neointima formation in injured carotid arteries, (2) addition of MPA alters the antiproliferative effects of estrogen, and (3) an interaction between MPA and estrogen can be accounted for by MPA-induced alterations in serum 17 beta-estradiol levels.

METHODS AND RESULTS

Male and female Sprague-Dawley rats were subjected to gonadectomy, then were randomly divided into four subgroups and treated with either (1) 17 beta-estradiol, (2) MPA, (3) 17 beta-estradiol + MPA, or (4) vehicle, and balloon injury of the right common carotid artery was carried out. Two weeks later, rats were killed by overdose of pentobarbital, and the carotid arteries were subjected to morphometric analysis for evaluation of myointimal thickening. Estradiol inhibited myointimal proliferation after vascular injury in gonadectomized rats of both sexes (P < .05). MPA alone did not alter neointima formation, but addition of MPA to estradiol completely blocked the antiproliferative effects of estrogen without altering serum 17 beta-estradiol levels.

CONCLUSIONS

These data indicate that exogenous progestin given alone does not alter the vascular injury response in the rat carotid injury model but that addition of a progestin blocks the antiproliferative effects of estrogen in this model. These effects are seen in gonadectomized rats of both sexes. These findings have direct implications for postmenopausal hormone replacement therapy in humans.

Changes in plasma lipids and lipoproteins associated with starting or stopping postmenopausal hormone replacement therapy. Atherosclerosis Risk in Communities Study

The Atherosclerosis Risk in Communities Study investigators examined nearly 4000 postmenopausal women from 1987 through 1989 and 3 years later to determine changes in plasma lipids occurring with the starting or stopping of hormone replacement therapy. Women who started estrogen plus progestin therapy (n = 74) had decreases of 9.8 mg/dl in low-density lipoprotein (LDL) cholesterol and 5.8 mg/dl in apolipoprotein B and increases of 1.2 mg/dl in high-density lipoprotein (HDL) cholesterol (HDL change not significant), 13.5 mg/dl in apolipoprotein A-I, and 14.0 mg/dl in triglycerides. Women who started estrogen alone (n = 149) had similar changes, except for a much larger increase in HDL cholesterol (5.8 mg/dl), principally in HDL-2. Women who stopped hormone therapy (n = 138) had lipid changes opposite to those who started therapy, but smaller in magnitude. These results confirm those of the Postmenopausal Estrogen/Progestin Interventions Trial in a community-based longitudinal cohort: women initiating estrogen plus progestin therapy have decreases in LDL cholesterol, but the increase in HDL cholesterol is less than that for starting estrogen alone. In addition, the current study extends findings to apolipoproteins and HDL subfractions.

The menopause and the cardiovascular system

Combining the wealth of epidemiological, metabolic and recent mechanistic data, it would appear biologically plausible that HRT, either oestrogen alone or in combination with progestogen, is cardioprotective. Further research is required, as information is lacking on cardiovascular effects of HRT instigated at an older age. There is a need to identify cardiovascular benefit, indirect and/or direct, of combined oestrogen/progestogen therapy using randomized trials. The various progestogen types and doses also need to be investigated. Studies are also required to investigate the effect of HRT use in higher risk patients with established CVD. There is scant information on the effect of HRT on blood pressure of patients with hypertension. Cardiovascular risk factor profiles and incidence surveys need to be conducted in developing countries to characterize their female population and to identify the prevalence of CVD; this needs to be undertaken before widespread recommendations on CVD prevention and the role of HRT can be made. If HRT is to be used effectively in the future treatment of heart disease in women these questions need to be addressed. At present HRT is indicated for the relief of menopausal symptoms and the prevention of osteoporosis. In women without these indications, ORT may be recommended in those who have had a premature menopause, and possibly in those who have established CHD or who are at high risk of developing CHD. It is too early to suggest a blanket recommendation for the use of HRT in the treatment of the symptoms of women with established CVD, but HRT after the menopause may at least be safely used in the secondary prevention of CHD.

Current estrogen-progestin and estrogen replacement therapy in elderly women: association with carotid atherosclerosis. CHS Collaborative Research Group. Cardiovascular Health Study

The cardioprotective effects of combined estrogen/progestin replacement therapy have been questioned. Therefore, we have compared carotid arterial wall thickening and the prevalence of carotid stenosis in elderly women (> or = 65 years old) currently using replacement estrogen/progestins (E + P) with arterial pathology and its prevalence in women using unopposed estrogens (E). This cross-sectional study used baseline data from all 2962 women participating in the Cardiovascular Health Study, a population-based study of coronary heart disease and stroke in elderly adults. Users of hormone replacement therapy (HRT) were categorized as never (n = 1726), past (n = 787), current E (n = 280), or current E + P (n = 73). Maximal intimal-medial thicknesses of the internal and common carotid arteries and stenosis of the internal carotid arteries were measured by ultrasonography. Current E + P users resembled current E users in most respects, although some lifestyle factors were more favorable among E + P users. Current E + P use and current E use (as compared with no use) were associated with smaller internal carotid wall thicknesses (-0.22 mm; P = 0.003; and -0.09 mm; P = 0.05, respectively) and smaller common carotid wall thicknesses (-0.05 mm; P = 0.03; and -0.02 mm; P = 0.1, respectively) and lower odds ratios (OR) for carotid stenosis (> or = 1% vs. 0%); OR = 0.61; 95% confidence interval [CI]: 0.36 to 1.01; and OR = 0.91, 95% CI: 0.67 to 1.24, respectively), after adjustment for current lifestyle and risk factors. When both groups of current HRT users were compared, there were no significant differences in carotid wall thicknesses or prevalence of carotid stenosis. For this sample of elderly women, both current E + P therapy and current E therapy were associated with decreased measures of carotid atherosclerosis. These measures did not differ significantly between the two groups of HRT users.

Estrogens, progestins and lipid metabolism

OBJECTIVES

To review some aspects in the recent literature related to the effects of postmenopausal estrogen and progestin use on major plasma lipoprotein risk factors for coronary heart disease (CHD).

METHODS

Collection of relevant information from medical journals, and by the use of Medline and Current Contents.

RESULTS

The beneficial effects of estrogen (LDL cholesterol reduction and HDL cholesterol elevation) are well established. The effects on HDL are modified to different degrees by progestins, depending on the androgenic properties of the latter: the 'sex steroid sensitive' HDL2 subfraction is decreased by nortestosterone derived progestins with androgenic activity. Recently developed methodology employing stable isotopes has helped to clarify underlying mechanisms. Progestins alone, as well as estrogen-progestin combinations have been shown to reduce the plasma levels of Lp(a), another lipoprotein risk factor for CHD. According to one study, estrogen administered alone had a similar effect.

CONCLUSIONS

The effects of hormone replacement therapies on lipid metabolism have been partly established and investigations on the underlying mechanisms are being published. This information will be useful for developing new replacement regimens with more protection against CHD and less adverse effects.

Pathogenesis of atherosclerosis

Atherosclerosis is a disease which affects large and medium-sized arteries. Typical features of atherosclerosis are accumulation of intra- and extracellular lipids, foam cell formation, proliferation of smooth muscle cells and accumulation of connective tissue. Plasma lipids and lipoproteins play an important role in the formation of atherosclerotic lesions. Recent evidence suggests that oxidation of low-density lipoprotein (LDL) may play an important role in the pathogenesis of atherosclerosis. Incidence of cardiovascular disease increase significantly after menopause. Part of the increase is due to atherogenic changes in plasma lipoproteins, i.e. increase in LDL and decrease in high density lipoprotein (HDL). Clinical endpoints of cardiovascular diseases are usually caused by atherosclerosis and thrombosis, both of which can be influenced after menopause by sex steroids. Hormone replacement therapy has anti-atherogenic effects on plasma lipoprotein fractions. Recent evidence also suggests that estrogens may have several protective effects on the vascular wall, including direct inhibition of LDL degradation, oxidation and smooth muscle cell proliferation.

The menopause and hormone replacement therapy: lipids, lipoproteins, coagulation and fibrinolytic factors

OBJECTIVES

To review the recent literature concerning the effects of the menopause and hormone replacement therapy (HRT) on the plasma lipoprotein and hemostatic system, as well as on the interaction between these two coronary heart disease (CHD) risk factor systems. METHODS. Collection of information from relevant scientific journals, and by the use of Medline and Current Contents.

RESULTS

The mainly beneficial effects of unopposed oral estrogen replacement on the plasma lipoprotein pattern are preserved to different degrees after addition of progestin to the regimen. Nortestostorone-derived progestins tend to lower HDL cholesterol levels more than progesterone derivatives. The slight triglyceride-elevating effect on conjugated equine estrogens was in a large study not significantly counteracted by progesterone derivatives but can, according to other studies, be reversed by nortestosterone-derived progestins. A limited number of studies on transdermal administration of estradiol has suggested that the effects on plasma lipoproteins are smaller than during oral administration. There is no convincing evidence that currently used HRT regimens would significantly increase the risk of thrombosis. Nevertheless, the finding in some studies that plasma triglyceride elevations could in theory be associated with impaired fibrinolysis and enhanced coagulation merit further attention as some HRT regimens tend to increase plasma triglyceride levels. From a theoretical point of view, transdermal estrogen delivery would be preferable in women at risk for thrombosis, as they have less pronounced effects on liver functions, including production of hemostatic factors and very-low-density lipoprotein triglycerides.

CONCLUSIONS

While the numerous existing HRT regimens provide many alternative and useful possibilities, further studies are needed concerning (a) novel progestins with minimal HDL cholesterol lowering effects, (b) transdermal and other non-oral routes for HRT, (c) possible antioxidative properties of estrogen and (d) metabolic links between the lipoprotein and hemostatic risk factor systems.

Effect of postmenopausal estrogen replacement therapy on lipoproteins

OBJECTIVES

To investigate the association between menopause and lipoproteins and the effect of hormone replacement therapy (HRT).

METHODS

Total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides were estimated in 50 postmenopausal women and 25 ovulating women who served as controls. The lipoprotein estimations were repeated after 1 year of therapy with natural estrogen-norgestrel combination.

RESULTS

More postmenopausal women than younger women had lipoprotein values in the high-risk status (P <0.001). There were no significant changes in lipoprotein levels (P >0.05) after HRT. Women with a body mass index below 26 kg/m2 had a significant reduction in their lipoprotein risk status (P <0.01).

CONCLUSION

There was no demonstrably clear effect of the estrogen-progestin combination on lipoprotein levels, probably because of other compounding variables such as obesity, lack of exercise and the type of progestin used.

Cardiovascular risk factors and combined estrogen-progestin replacement therapy: a placebo-controlled study with nomegestrol acetate and estradiol

OBJECTIVE

To assess the effects of oral E2 replacement therapy combined with nomegestrol acetate, a 19-norprogesterone derivative, on cardiovascular risk factors.

DESIGN

A double-blind randomized prospective study comparing the effect of a placebo and two oral E2-nomegestrol acetate combinations (1 mg-2.5 mg and 1.5 mg-3.75 mg) over a three-cycle trial.

SETTING

Department of Internal Medicine and Nutrition, Hotel-Dieu, Paris, France.

PATIENTS

Fifty-seven nonhysterectomized women with natural menopause.

MAIN OUTCOME MEASURES

Blood pressure, renin substrate, glucose, total cholesterol, high-density and low-density lipoprotein cholesterol, triglycerides, apoproteins A1 and B, lipoprotein(a), antithrombin III, fibrinogen, plasminogen, prothrombin fragment 1 + 2, protein C, and total and free protein S.

RESULTS

Both treatments significantly reduced menopausal complaints, total cholesterol, low-density lipoprotein cholesterol and lipoprotein(a). Treatment with the 1.5 mg-3.75 mg combination resulted in a significant increase in apolipoprotein A1. No significant change were observed in other parameters.

CONCLUSIONS

Sequentially combined with oral E2 in hormone replacement therapy, nomegestrol acetate had favorable effects on plasma lipids and lipoproteins. This nonandrogenic progestin decreased lipoprotein(a) levels as observed previously with medroxyprogesterone acetate combined with conjugated equine estrogens.

Hormone replacement therapy and cardiovascular risk: the cardiovascular physicians' viewpoint

Sufficient evidence has accumulated showing that hormone replacement therapy (HRT) does protect against cardiovascular disease in women, although data regarding the true magnitude of that protection remains incomplete. There is no evidence that HRT increases the risk of hypertension or thromboembolism, and beneficial effects have been found for plasma lipids, clotting factors and cardiovascular haemodynamics. However, the evidence is not convincing of any beneficial effect of HRT in preventing strokes, and concerns about the risk of cancer with HRT remain. Despite this, considerable uncertainty continues to exist amongst clinicians as to the balance of beneficial and harmful effects from administering HRT. Overall, HRT seems to do no harm and may be protective. A much greater awareness of the long-term consequences of the menopause and the potential benefits of HRT should be encouraged so that women (and their doctors) can make informed decisions about their requirements.

A prospective two-year study of progestin given alone in postmenopausal women: effect on lipid and metabolic parameters

OBJECTIVE

A controlled study was conducted to assess the long-term effect of a progestin with very low androgenic potency given alone on serum lipoprotein profile, serum renin substrate, sex hormone-binding globulin levels, and serum antithrombin III activity in early postmenopausal women.

STUDY DESIGN

Thirty-five early postmenopausal women who had not received any form of hormonal treatment after menopause were randomly assigned to a 2-year regimen of 500 micrograms of a progestin derived from 19-norprogesterone (promegestone) or a placebo for 21 days of a 28-day treatment cycle. Serum lipid and lipoprotein levels and other biochemical parameters were measured in the two groups, and differences were sought by statistical analysis.

RESULTS

After 2 years of treatment the women in the two groups showed no statistically significant variation from baseline values in the concentrations of any of the biochemical parameters studied.

CONCLUSIONS

The results show that a progestin with very low androgenic activity given alone has no influence on lipid profile and hepatic synthesis of several proteins in early postmenopausal women.

Postmenopausal hormone therapy and atherosclerotic disease

Several lines of evidence suggest that estrogen is an important determinant of cardiovascular risk in women. Epidemiologic data document low rates of coronary heart disease (CHD) in premenopausal women, a narrowing of the gender gap in CHD mortality after menopause, and elevated risk of CHD among young women with bilateral oophorectomy not treated with estrogen. Nearly all of the more than 30 observational studies of exogenous estrogen replacement therapy have indicated a reduced risk of CHD among women receiving estrogen therapy. In a meta-analysis comparing estrogen users and nonusers, the estimated reduction of CHD among users was 44%. In angiographic studies, women taking estrogen were less likely to have coronary artery stenosis. Estrogen is known to affect a wide range of physiologic processes that may have an impact on CHD risk. Use of oral estrogen has favorable effects on serum lipid profiles; it increases high-density lipoprotein cholesterol levels by 10% to 15% and decreases low-density lipoprotein cholesterol levels by a similar magnitude. Other proposed mechanisms include inhibition of endothelial hyperplasia, reduced arterial impedance, enhanced production of prostacyclin, increased insulin sensitivity, and inhibition of oxidation of low-density lipoprotein. Nevertheless, the role of hormone replacement therapy in preventing clinical atherosclerotic events in women remains inconclusive because of the absence of randomized trial data. The benefit-to-risk ratio must be reliably assessed, because estrogen has complex actions, including postulated benefits (CHD, osteoporosis, and menopausal symptoms) and postulated risks (endometrial cancer, breast cancer, and gallstones.(ABSTRACT TRUNCATED AT 250 WORDS)

Sex steroids and lipoprotein metabolism

Lipoprotein metabolism is involved in atherogenesis. Female sex-hormones have substantial effects on both lipoprotein metabolism and the vessel wall. Cholesterol, one of the major lipids in lipoproteins, is both the substrate for, and the target of, the steroidal sex hormones.

The prevention of cardiovascular disease. Emphasis on secondary prevention

Atherosclerosis is a progressive disease affecting all major arteries. Clinical evidence of atherosclerosis increases the risk of subsequent morbid and mortal events fivefold to sevenfold over the next 5 to 10 years. The same risk factors contribute to the initial development of CVD events as to their recurrence. Both coronary and noncoronary events, such as stroke or PAD, reflect the severity of the underlying atherosclerotic process and strongly predict future excess CVD morbidity and mortality. Short-term and long-term survival depends on modifying the risk factors that contribute to CVD events. Although absolute proof of benefit for secondary prevention does not exist for all risk factors, the data from primary prevention trials and the secondary prevention trials that have been done argue strongly for aggressive intervention. Benefit has been demonstrated for smoking cessation, cholesterol reduction, and blood pressure control. Selected patients may benefit from additional medical, procedural, or surgical interventions to prolong life, such as beta-blocking agents, aspirin, or carotid endarterectomy. Many secondary prevention measures are a cost-effective way to reduce the substantial morbidity and mortality due to CVD. Contrary to primary prevention, even modest treatment effects from secondary prevention efforts can benefit large numbers of patients. Finally, secondary prevention may be more successful because patients with clinical evidence of CVD may be more highly motivated than their healthy counterparts to make and maintain lifestyle changes.

Association of hormone-replacement therapy with various cardiovascular risk factors in postmenopausal women. The Atherosclerosis Risk in Communities Study Investigators

BACKGROUND

Most epidemiologic studies of cardiovascular disease in postmenopausal women suggest that estrogen-replacement therapy has a protective effect. The effects of the use of estrogen combined with progestin are less well studied.

METHODS

To examine the associations of hormone-replacement therapy with concentrations of plasma lipids and hemostatic factors, fasting serum concentrations of glucose and insulin, and blood pressure, we studied 4958 postmenopausal women participating in a population-based investigation. Using cross-sectional data, we classified the women into four groups according to their use of hormone-replacement therapy: current users of estrogen alone, current users of estrogen with progestin, nonusers who had formerly used these hormones, nonusers who had never used them.

RESULTS

Current users had higher mean levels of high-density lipoprotein cholesterol, its subfractions high-density lipoprotein2 and high-density lipoprotein3, and apolipoprotein A-I than nonusers and lower mean levels of low-density lipoprotein cholesterol, apolipoprotein B, lipoprotein(a), fibrinogen, antithrombin III, and fasting serum glucose and insulin. However, current users of estrogen alone had higher triglyceride, factor VII, and protein C levels than either nonusers or current users of estrogen with progestin. After making certain assumptions, we estimated that the findings, if causal, would translate into a reduction of 42 percent in the risk of coronary heart disease in users of hormones as compared with nonusers. Women using estrogen with progestin would have an even greater estimated benefit.

CONCLUSIONS

A randomized trial is needed to eliminate possible selection biases in our observational study that are related to the prescription of replacement hormones. Nevertheless, hormone-replacement therapy appears to be associated with a favorable physiologic profile, which probably mediates its protective effects on cardiovascular disease. The use of estrogen combined with progestin appears to be associated with a better profile than the use of estrogen alone.

Oestrogens and atherosclerotic vascular disease--lipid factors

Cardiovascular disease remains the major cause of death for postmenopausal women in Western societies. The majority of epidemiological studies indicate that postmenopausal oestrogen replacement therapy is associated with a 50% reduction in the risk of cardiovascular disease, with much of the reduction being mediated by changes in the plasma concentration of cholesterol within high and low density lipoproteins. In addition to favourably influencing the plasma concentration of lipoproteins, oestrogens also influence the complex metabolism of lipoproteins in the arterial wall, helping to impede the formation of the atherosclerotic plaque. Whilst oestrogens alter endothelial function, vascular reactivity and fibrinolysis, these changes are also seen with reduction of LDL cholesterol and may partly reflect the altered concentration of plasma lipoproteins induced by oestrogens. Oral oestrogens have substantially greater favourable effects on LDL and HDL cholesterol than their transdermal counterparts but also result in greater hypertriglyceridaemia. Most progestogens antagonize the beneficial effects of oestrogens on lipoproteins in a dose-dependent manner; however, cyclical use of low doses of progestogens with an oral oestrogen generally retains a net beneficial effect. Lipoprotein levels fluctuate during cyclical therapy, the most adverse changes being noted at the end of the progestogen phase. Lipoprotein concentrations are constant during continuous combined regimens which have the potential for more prolonged exposure to an adverse progestational effect. Despite adverse effects on the lipoprotein profile, animal studies suggest that progestogens do not substantially reverse the beneficial effects of oestrogens on the development of atherosclerosis. Finally, oestrogen therapy may be useful in the management of postmenopausal women with hyperlipidaemia, and also in the secondary prevention of clinical sequelae in women with established atherosclerosis.

Putative apolipoprotein B-100 in the freshwater turtle Chrysemys picta: effects of estrogen and progesterone

1. The isolation and purification of a putative apolipoprotein B-100 in the plasma of the freshwater turtle Chrysemys picta is described. 2. The protein was purified through differential ultracentrifugation and subsequent Sepharose 6B column chromatography. 3. The molecular weight of the protein determined by electrophoresis was approximately 350 kDa. 4. An antibody to chicken apolipoprotein B-100 specifically recognizes this 350 kDa protein in Western blots, suggesting its identity with apolipoprotein B-100. 5. An antibody to the putative Chrysemys apolipoprotein B-100-like protein was developed and used in an ELISA to quantitate protein levels in plasma. 6. Acute estrogen treatment increased levels of apolipoprotein B-100 (7.64 +/- 0.79 mg/ml plasma) over that of control animals (5.07 +/- 1.74 mg/ml plasma). 7. In contrast, chronic estrogen treatment reduced apolipoprotein B-100 significantly to 2.94 +/- 0.53 mg/ml plasma (P < 0.05).

The effects of two fixed hormonal replacement therapy protocols on blood lipid profile

Hormonal Replacement Therapy (HRT) is known to be accompanied by changes in blood lipid profile. The present prospective cohort study compared the blood lipid profile of healthy postmenopausal women treated with either (a) a preparation containing a fixed regimen of estradiol, estriol and norethisterone acetate (EENA, marketed under the trade name Trisequens); (b) a fixed protocol of conjugated equine estrogen and medroxyprogesterone acetate (CEEMPA, marketed under the trade name Premaril Plus); or with (c) a concurrent group which underwent no treatment. Blood lipid profiles (total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C), and triglycerides (TG)) were performed at the beginning of the study and at 3-month intervals, for 9 months. The EENA-treated women showed a significant and profound decrease in TC and LDL-C when compared with their initial values, with the control group, and with the CEEMPA group. The CEEMPA group showed an increase in HDL-C values and a decrease in LDL-C values when compared with their initial values and with the control group, but no increase was shown when compared with an EENA group. There was a favorable decrease in the TC/HDL-C and LDL-C/HDL-C ratios in both treatment protocols. As the primary goal of prevention of coronary artery disease is total cholesterol reduction, the EENA protocol seems to be preferred.

Effects of sex steroids on serum lipids and lipoproteins

Cardiovascular disease is the leading cause of death in women but manifests itself primarily in the postmenopausal years. Menopause appears to increase the cardiovascular risk, at least when surgically induced, whereas the effects of the natural menopause are still a matter of debate. Why postmenopausal women apparently lose their natural cardioprotection is not established, but oestrogen deficiency seems to play an important role. Loss of ovarian hormone production at the menopause significantly alters serum lipids and lipoproteins, giving rise to more atherogenic lipid profiles throughout the postmenopausal years, and these changes may in part be responsible for the alleged cardiovascular risk. Postmenopausal hormone replacement therapy, using oral unopposed oestrogens, induces potential favourable effects on lipids and lipoproteins, and epidemiological evidence has established that the risk of cardiovascular mortality is reduced by 40-60% in women receiving postmenopausal oestrogen therapy. Part of this reduction seems to be explained by changes in lipids and lipoproteins. Parenteral administration of oestrogens induces comparable, although less pronounced effects on lipids and lipoproteins, and the possible cardioprotective role of parenteral administration remains obscure. The addition of progestogens to postmenopausal oestrogen therapy is essential for endometrial protection, but progestogens apparently antagonize some of the actions of oestrogens on lipid metabolism. However, the type, the dose, the duration and the route of administration, as well as the potency balance between the oestrogen and the progestogen employed, are important determinants for the ultimate effect on lipid metabolism. With the use of cyclic administration and the lowest possible doses of progestogens, the oestrogenic actions on lipids and lipoproteins can be largely preserved, but the cardioprotective potential of combined oestrogen-progestogen therapy is as yet unknown.

Effects of post-menopausal oestrogen-progestogen replacement therapy on serum lipids and lipoproteins: a review

There are strong indications that post-menopausal oestrogen replacement therapy has a protective effect on the cardiovascular system, due to changes in the lipid profile. There are also indications that the addition of progestogens to oestrogen therapy may negatively influence these effects on the lipid metabolism. The present survey was undertaken to provide a comprehensive summary of all the available data on the effect of combined oestrogen-progestogen treatment on the post-menopausal lipid profile published from 1984 onwards. It appears that many progestogens are capable of diminishing the beneficial changes induced by oestrogens. The ultimate effect depends on the type and daily dose of both the oestrogen and the progestogen component. Oestradiol or oestradiol valerate administered cyclically with progesterone or cyproterone acetate appear to have the most favourable impact on lipids and lipoproteins.

Role of plasma lipoproteins in the pathogenesis of atherosclerotic disease, with special reference to sex hormone effects

Plasma lipoproteins constitute a complex lipid transport system. Very low-density lipoproteins transport triglycerides to peripheral tissues, whereas low-density lipoproteins are the main carriers of cholesterol. Cholesterol transport in low-density lipoprotein enters body cells by way of "low-density lipoprotein receptor pathway" but may also be taken up by macrophages by way of the "scavenger pathway." Excessive influx of cholesterol by way of the "scavenger pathway" may result in deposition of cholesterol in arterial walls and atheroma formation. In a yet incompletely known process of "reverse cholesterol transport," cholesterol is carried away from the tissues to the liver by high-density lipoproteins. The above-mentioned transport processes are regulated by a well-synchronized system that involves several enzymes and lipid transport proteins. Under normal conditions, the lipoprotein system is able to balance the flow of cholesterol and other lipids in both directions between the liver and peripheral tissues. This delicate balance may be disturbed by many factors, including contraceptive steroids. The metabolic steps influenced by administration of contraceptive steroids are summarized.

Regulation of hepatic lipase and serum lipoproteins by sex steroids

The influence of sex steroids on the serum lipoprotein pattern was recognized more than 30 years ago, and it still remains among the areas of major interest. This is because of the compatible sex difference in plasma lipoprotein pattern and in coronary heart disease risk. Recent discoveries of the role of hepatic lipase in lipoprotein metabolism have elucidated mechanisms behind sex steroid-induced changes in lipoproteins. These steroids regulate the activity of hepatic lipase, an enzyme bound to the endothelial cells of liver sinusoids. Hepatic lipase has a central role in the removal of phospholipids and triglycerides from subfractions of high-density lipoprotein (HDL2) particles, but it may also function in the lipolysis of triglyceride-rich particles. Some older and more recent developments in this area will be reviewed.