Effects of tibolone on serum concentrations of lipoprotein(a) in postmenopausal women

The effect of tibolone treatment on fasting blood sugar, insulin, insulin resistance and endothelial function in postmenopausal women: A meta-analysis of randomized controlled trials

BACKGROUND AND AIM

The menopause is associated in females with the presence of dysglycemia, insulin resistance and with the development of endothelial dysfunction. Tibolone (TIB) is a synthetic steroid compound with selective oestrogenic and, to a lesser extent, progestogenic and androgenic properties prescribed to postmenopausal women to alleviate the symptoms of the climaterium and to prevent the development of osteoporosis. However, the impact of TIB on fasting blood sugar (FBS), insulin, Homeostatic Model Assessment-Insulin Resistance (HOMA-IR) index and flow-mediated dilation (FMD) in women has not been evaluated so far. Thus, to investigate this research question, we conducted the present systematic review and meta-analysis.

METHODS

Two independent reviewers searched the Scopus, Web of Science, PubMed/Medline and Embase databases up to 20 December 2020. The weighted mean differences (WMDs) and the 95% confidence intervals (CI) were calculated using the DerSimonian and Laird random effects models between the TIB and control groups and included in the forest plot.

RESULTS

The overall findings were generated from 12 eligible randomized controlled trials. As compared to controls, TIB administration resulted in a significant reduction of FBS (WMD: -3.06 mg/dL, 95% CI: -5.30 to -0.82, P = 0.007), and of the HOMA-IR index (WMD: -0.61, 95% CI: -1.11 to -0.11, P = 0.01). However, treatment with TIB did not lead to significant changes of the FMD (WMD: 0.78%, 95% CI: -0.20 to 1.77, P = 0.12) or of insulin levels (WMD: -0.10 mIU/L, 95% CI: -2.04 to 1.83, P = 0.91).

CONCLUSION

TIB administration can decrease FBS and the HOMA-IR index in postmenopausal women. However, the use of TIB does not influence insulin levels or FMD.

The effect of tibolone treatment on lipid profile in women: A systematic review and dose-response meta-analysis of randomized controlled trials

Inconsistencies exist with regard to influence of tibolone treatment on the lipid profile. The reasons for these inconsistencies might derive from several factors, i.e., differences in baseline variables, intervention duration, participants' health status or baseline body mass index (BMI). To address these inconsistencies, based on a systematic search in Scopus, PubMed/Medline, Web of Science, and Embase for papers published until 21 December 2020, we conducted the current dose-response meta-analysis of randomized controlled trials (RCTs) to determine the impact of tibolone treatment on the lipid profile. The overall findings were derived from 26 RCTs. Tibolone administration decreased total cholesterol (TC) (weighted mean difference, WMD: -18.55 mg/dL, CI: -25.95 to -11.16, P < 0.001), high-density lipoprotein-cholesterol (HDL-C) (WMD: -9.42 mg/dL, CI: -11.83 to -7.01, P < 0.001) and triglyceride (TG) (WMD: -21.43 mg/dL, CI: -27.15 to -15.70, P < 0.001) levels. A significant reduction in LDL-C occurred when tibolone was prescribed for ≤ 26 weeks (WMD: -7.64 mg/dL, 95% CI: -14.58 to -0.70, P = 0.031) versus > 26 weeks (WMD: -8.84 mg/dL, 95% CI: -29.98, 12.29, P = 0.412). The decrease in TG (WMD: -22.64 mg/dL) and TC (-18.55 mg/dL) concentrations was more pronounced in patients with BMI ≥ 25 kg/m²versus BMI < 25 kg/m². This systematic review and meta-analysis discovered that tibolone decreases TC, HDL-C and TG levels. LDL-C concentrations are significantly reduced when tibolone administration lasts for ≤ 26 weeks.

Lipoprotein(a) in postmenopausal women: assessment of cardiovascular risk and therapeutic options

INTRODUCTION

Lipoprotein(a) [Lp(a)], a low-density lipoprotein (LDL)-like particle, has been independently associated with increased cardiovascular disease (CVD) risk in various populations, such as postmenopausal women. The purpose of this narrative review is to present current data on the role of Lp(a) in augmenting CVD risk in postmenopausal women and focus on the available therapeutic strategies.

METHODS

PubMed was searched for English language publications until November 2015 under the following terms: "therapy" OR "treatment" AND ["lipoprotein (a)" OR "Lp(a)"] AND ("postmenopausal women" OR "menopausal women" OR "menopause").

RESULTS

Only hormone replacement therapy (mainly oral estrogens) and tibolone have been specifically studied in postmenopausal women and can reduce Lp(a) concentrations by up to 44%, although evidence indicating a concomitant reduction in CVD risk associated with Lp(a) is lacking. As alternative treatments for women who cannot, or will not, take hormonal therapies, niacin and the upcoming proprotein convertase subtilisin / kexin type 9 (PCSK-9) inhibitors are effective in reducing Lp(a) concentrations by up to 30%. Statins have minimal or no effect on Lp(a). However, data for these and other promising Lp(a)-lowering therapies including mipomersen, lomitapide, cholesterol-ester-transfer protein inhibitors and eprotirome are derived from studies in the general, mainly high CVD risk, population, and include only subpopulations of postmenopausal women.

CONCLUSIONS

Past, present and emerging therapies can reduce Lp(a) concentrations to a varying extent. Overall, it remains to be proven whether the aforementioned reductions in Lp(a) by these therapeutic options are translated into CVD risk reduction in postmenopausal women.

Effects of tibolone or continuous combined oestradiol/norethisterone acetate on glucose and insulin metabolism

OBJECTIVE

To determine the effects of tibolone or oestradiol (E(2) )/norethisterone acetate (NETA) hormone replacement therapy on glucose and insulin metabolism in postmenopausal women.

DESIGN

Single-centre double-blind placebo-controlled randomized clinical trial.

SUBJECTS/METHODS

We randomized 105 healthy postmenopausal women to tibolone 2·5 mg daily, continuous combined oral E(2) 2 mg/NETA 1 mg daily or placebo over a 2-year study. We performed intravenous glucose tolerance tests (IVGTT) with measurements of plasma glucose, insulin and C-peptide concentrations and the IVGTT glucose elimination rate, k. Mathematical modelling was performed to determine measures of insulin sensitivity, S(i) , pancreatic insulin secretion and hepatic and plasma insulin elimination.

RESULTS

Tibolone decreased S(i) to 53-63% and k to 72-79% of baseline values but increased IVGTT phase 2 C-peptide concentrations 1·6-1·8-fold and pancreatic insulin secretion 2·2-2·4-fold, so overall IVGTT glucose concentrations were unaffected. Similar, but for k, significantly smaller changes in insulin and C-peptide secretion were seen with E(2) /NETA, also with no effect on overall IVGTT glucose concentrations.

CONCLUSIONS

Tibolone reduces insulin sensitivity. Healthy postmenopausal women seem able to compensate for this and maintain normal postload glucose concentrations, but it may not be advisable to prescribe tibolone to women with, or at increased risk for, diabetes.

Enigmatic role of lipoprotein(a) in cardiovascular disease

Lipoprotein (a), [Lp(a)] has many properties in common with low-density lipoprotein, (LDL) but contains a unique protein apolipoprotein(a), linked to apolipoprotein B-100 by a single disulfide bond. There is a substantial size heterogeneity of apo(a), and generally smaller apo(a) sizes tend to correspond to higher plasma Lp(a) levels, but this relation is far from linear, underscoring the importance to assess allele-specific apo(a) levels. The presence of apo(a), a highly charged, carbohydrate-rich, hydrophilic protein may obscure key features of the LDL moiety and offer opportunities for binding to vessel wall elements. Recently, interest in Lp(a) has increased because studies over the past decade have confirmed and more robustly demonstrated a risk factor role of Lp(a) for cardiovascular disease. In particular, levels of Lp(a) carried in particles with smaller size apo(a) isoforms are associated with coronary artery disease (CAD). Other studies suggest that proinflammatory conditions may modulate risk factor properties of Lp(a). Further, Lp(a) may act as a preferential acceptor for proinflammatory oxidized phospholipids transferred from tissues or from other lipoproteins. However, at present only a limited number of agents (e.g., nicotinic acid and estrogen) has proven efficacy in lowering Lp(a) levels. Although Lp(a) has not been definitely established as a cardiovascular risk factor and no guidelines presently recommend intervention, Lp(a)-lowering therapy might offer benefits in subgroups of patients with high Lp(a) levels.

Lipoprotein(a): A Unique Risk Factor for Cardiovascular Disease

Lipoprotein(a) (Lp(a)) is present in humans and primates. It has many properties in common with low-density lipoprotein, but contains a unique protein moiety designated apo(a), which is linked to apolipoprotein B-100 by a single disulfide bond. International standards for Lp(a) measurement and optimized Lp(a) assays insensitive to isoform size are not yet widely available. Lp(a) is a risk factor for coronary artery disease, and smaller size apo(a) is associated with coronary artery disease. The physiologic role of Lp(a) is unknown.

Hormone replacement therapy, selective estrogen receptor modulators, and tissue-specific compounds: cardiovascular effects and clinical implications

In industrialized countries, coronary heart disease (CHD) is not only the leading cause of death in women but of disability as well. Menopause, regardless of age at onset, is associated with a marked increase in CHD risk. Based on epidemiologic studies demonstrating mainly positive biologic effects of hormone replacement therapy (HRT) on CHD risk factors and outcomes, earlier recommendations decreed that most, if not all, postmenopausal women should be treated with long-term HRT. Recent randomized controlled trials with clinical CHD endpoints have shown that previously held dicta may not be accurate. Selective estrogen receptor modulators (SERMs) such as tamoxifen and raloxifene are alternatives to HRT. SERMs represent a growing class of compounds that act as either estrogen receptor agonists or antagonists in a tissue-selective manner. This pharmacologic profile may offer the opportunity to dissociate favorable cardiovascular effects of estrogen from unfavorable stimulatory effects on the breast and endometrium. The only data available regarding the effects of tamoxifen on cardiovascular events in postmenopausal women are from breast cancer trials. They showed fewer fatal myocardial events in women randomly assigned to tamoxifen compared with women assigned to placebo. Raloxifene is a so-called second-generation SERM. It seems clear that raloxifene increases bone mineral density, has no effect on the endometrium, and holds high promise for the prevention of breast cancer. The effect of raloxifene on cardiovascular disease is uncertain. On the basis of the Multiple Outcomes of Raloxifene Evaluation (MORE) trial, raloxifene may offer some protection to women with cardiovascular disease or to those who are at high risk. Proof that raloxifene reduces the risk of CHD requires a clinical trial with hard clinical endpoints. Such a study is currently underway. Clinical trials have demonstrated that the synthetic 19-nortestosterone derivative tibolone reduces climacteric complaints and prevent osteoporosis without causing menstrual bleeding. Tibolone lowers lipoprotein(a), fibrinogen, and plasminogen activator inhibitor-1 levels and improves glucose tolerance, insulin sensitivity, and endothelial function; however, it also lowers high-density lipoprotein cholesterol by >20%. The long-term impact of tibolone on the risk of CHD is not known and needs to be studied.

Effect of tibolone on markers of cardiovascular disease risk in postmenopausal women undergoing hemodialysis: a pilot study

OBJECTIVE

To assess the effect of tibolone on markers of vascular risk in postmenopausal women who were receiving hemodialysis.

DESIGN

One-year open-label study.

SETTING

"Zvezdara" University Medical Center, Belgrade, Serbia.

PATIENT(S)

Twenty-eight postmenopausal women undergoing chronic hemodialysis.

INTERVENTION(S)

Fifteen women received tibolone 2.5 mg three times per week; 13 other women served as controls.

MAIN OUTCOME MEASURE(S)

Mean arterial pressure and weight were measured at baseline and at 6 and 12 months, and blood was collected for insulin, total cholesterol, low-density lipoprotein, high-density lipoprotein, triglycerides, lipoprotein(a), high-sensitivity C-reactive protein (hs-CRP), endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), and markers of renal function.

RESULT(S)

Mean arterial pressure fell in the tibolone but not in the control group at 6 and 12 months versus baseline (mean [SD]: 93 [15] vs. 105 [11] mmHg and 94 [10] vs. 105 [11] mmHg, respectively). Weight, insulin, lipids, lipoprotein(a), hs-CRP, ET-1, VEGF, and renal function remained unchanged within each group, but high-density lipoprotein concentrations fell in the tibolone group after 12 months (1.2 [0.3] vs. 1.6 [0.6] mmol/L).

CONCLUSION(S)

The effects of tibolone on markers of vascular risk in postmenopausal women who are receiving hemodialysis and healthy women appear to differ. This should be taken into account when tailoring menopausal therapies to the specific requirements of each individual.

Hormone replacement therapy and the breast

Increasing numbers of women are using hormone replacement therapy (HRT) in their 50s and 60s. Oestrogen alone or oestrogen and progestogen combined given in this age group increase breast density and this has the effect of reducing both the sensitivity and specificity of breast screening in HRT users. HRT significantly increases the risk of developing breast cancer with combinations of oestrogen and progestogens increasing the risk to a greater degree than oestrogen alone. The longer HRT is used the greater the risk with 5 years use being associated with risks of 1.05-1.16 for oestrogen alone and 1.24-1.45 for oestrogen and progestogen combined. No consistent effect of HRT on breast cancer mortality has been demonstrated. Two studies have reported that more than 5 years HRT use is associated with an increased risk of death from breast cancer. A variety of non-oestrogenic agents are available to control menopausal symptoms and these may be of particular value in breast cancer survivors. HRT has been used in breast cancer survivors and although published data are reassuring, none have included sufficient patient numbers to detect small effects of HRT on breast cancer outcome. Prospective randomised trials are underway but are unlikely to include sufficient numbers to exclude a small adverse influence of HRT on breast cancer mortality. Tibolone, a gonadomemetic agent which has been used to control menopausal symptoms, appears to have less direct effects on the breast and is being evaluated as an alternative to oestrogen in breast cancer survivors who develop significant menopausal symptoms resistant to non-hormonal therapies. There is clear evidence that HRT causes breast cancer and the challenge for the physician is to control the menopausal symptoms using HRT or alternatives while at the same time limiting the risks associated with this treatment.

Effects of tibolone and conventional hormone replacement therapies on arterial and hepatic cholesterol accumulation and on circulating endothelin-1, vascular cell adhesion molecule-1, and E-selectin in surgically menopausal monkeys

OBJECTIVE

Menopause and aging are associated with a marked increase in the incidence of coronary heart disease as well as reductions in circulating estrogen, progestogen, and androgen levels. The synthetic compound tibolone and its metabolites have estrogenic, progestogenic, and androgenic characteristics. In the present study, we compared the effects of tibolone, estrogen replacement therapy, and estrogen plus progestogen replacement therapy on arterial and hepatic lipid accumulation and on circulating soluble adhesion molecule and endothelin-1 concentrations in surgically postmenopausal cynomolgus monkeys.

DESIGN

Animals were fed an atherogenic diet for 2 years while receiving either no hormone treatment (control, n = 31) or the following treatments at doses designed to mimic the human dose on a daily caloric intake basis: tibolone at 2.5 mg/day (HiTib, n = 31), tibolone at 0.625 mg/day (LoTib, n = 29), conjugated equine estrogens (CEE) alone at 0.625 mg/day (CEE, n = 29), or CEE plus continuous medroxyprogesterone acetate (MPA) at 2.5 mg MPA/day (CEE + MPA, n = 30).

RESULTS

Relative to the control group, iliac artery total cholesterol content was not different in the HiTib, LoTib, and CEE + MPA groups but was significantly lower in the group receiving CEE only (P < 0.05). In contrast, hepatic free cholesterol content was reduced in all treatment groups [HiTib (P < 0.01), LoTib (P < 0.05), CEE (P < 0.01), and CEE + MPA (P < 0.05)], whereas hepatic total and esterified cholesterol content were reduced in the HiTib, CEE, and CEE + MPA groups (all P < 0.05). HiTib and CEE groups had lower hepatic triglyceride levels per milligram of protein (P < 0.05). Iliac arterial cholesterol content was highly correlated with hepatic cholesterol content and with previously published histomorphometrically determined coronary artery atherosclerosis, supporting the use of the iliac artery as a surrogate for the coronary artery in the monkey. Circulating levels of soluble vascular cell adhesion molecule-1 were significantly reduced in the HiTib (P < 0.02) and CEE (P < 0.05) groups, whereas soluble E-selectin was reduced in the CEE group only (P < 0.01). Plasma endothelin-1 was significantly reduced in the LoTib (P < 0.05), CEE (P < 0.01), and CEE + MPA (P < 0.01) groups.

CONCLUSIONS

These results suggest that while tibolone caused marked depression of high-density lipoprotein cholesterol and a resultant twofold increase in the total plasma cholesterol/high-density lipoprotein cholesterol ratio, those effects did not result in exacerbation of iliac artery atherosclerosis, perhaps because of beneficial effects on vascular biology or hepatic metabolism.

Comparison of tibolone and conjugated equine estrogens effects on carotid artery atherosclerosis of postmenopausal monkeys

BACKGROUND AND PURPOSE

Tibolone is a tissue-specific compound that has favorable effects on bone and menopausal symptoms without stimulating endometrium or breast, but lowers concentrations of plasma high-density lipoprotein (HDL) cholesterol (HDLC). This study was designed to determine whether the HDL lowering with tibolone exacerbated common or internal carotid artery atherosclerosis and to evaluate tibolone treatment relative to conjugated equine estrogens (CEE) alone or in combination with medroxyprogesterone acetate (MPA).

METHODS

Carotid artery atherosclerosis was compared in groups of surgically postmenopausal cynomolgus monkeys treated with CEE, CEE+MPA, or either of 2 doses of tibolone versus untreated monkeys.

RESULTS

Despite a 30% to 52% lowering of HDLC with tibolone, there was no significant effect on carotid artery atherosclerosis. CEE and CEE+MPA, however, inhibited carotid artery atherosclerosis by approximately 60%.

CONCLUSIONS

In surgically postmenopausal cynomolgus monkeys, CEE and CEE+MPA inhibited common and internal carotid artery atherosclerosis. Despite the potentially adverse effects of tibolone on HDLC, tibolone did not exacerbate atherosclerosis.

Interaction of oestrogen and peroxisome proliferator-activated receptors with apolipoprotein(a) gene enhancers

A high plasma concentration of lipoprotein(a) [Lp(a)] confers an increased risk for the development of coronary heart disease. Hormones, such as oestrogen, are some of the few compounds known to reduce plasma Lp(a) levels. A putative enhancer region, located at the DHII DNase I hypersensitive site approx. 28 kb upstream of the apolipoprotein(a) [apo(a)] gene, contains a number of sequences similar to the binding half-sites for nuclear hormone receptors, such as the oestrogen receptor and the peroxisome proliferator-activated receptor (PPAR). The 180 bp core DHII enhancer increased the activity of the apo(a) promoter by over 7-fold in reporter-gene assays in HepG2 cells in vitro. Almost 60% of this increase was lost in the presence of co-transfected oestrogen receptor and oestrogen. In contrast, co-transfection with PPARalpha increased the effect of the DHII enhancer on apo(a) transcriptional activity by approx. 70% and could overcome the inhibitory effect of the oestrogen receptor on apo(a) transcription. Gel mobility-shift assays showed that oestrogen receptor protein bound to one half of a sequence corresponding to a predicted oestrogen receptor response element. PPARalpha also bound to this site and competed with oestrogen receptors for binding. In addition, PPARalpha bound to a separate site that comprised part of a direct repeat of nuclear hormone receptor half-sites. The results suggest that nuclear hormones affect plasma Lp(a) concentrations by binding to the sequences within the DHII enhancer, thereby altering the amount by which the enhancer increases the transcription of the apo(a) gene.

Effects of postmenopausal hormone replacement therapy on lipid, lipoprotein, and apolipoprotein (a) concentrations: analysis of studies published from 1974-2000

OBJECTIVE

To establish reference estimates of the effects of different hormone replacement therapy (HRT) regimens on lipid and lipoprotein levels.

DESIGN

Review and pooled analysis of prospective studies published up until the year 2000.

SETTING

Clinical trials centers, hospitals, menopause clinics.

PATIENT(S)

Healthy postmenopausal women.

INTERVENTION(S)

Estrogen alone, estrogen plus progestogen, tibolone, or raloxifene in the treatment of menopausal symptoms.

MAIN OUTCOME MEASURE(S)

Serum high- and low-density lipoprotein (HDL and LDL) cholesterol, total cholesterol, triglycerides, and lipoprotein (a).

RESULT(S)

Two-hundred forty-eight studies provided information on the effects of 42 different HRT regimens. All estrogen alone regimens raised HDL cholesterol and lowered LDL and total cholesterol. Oral estrogens raised triglycerides. Transdermal estradiol 17-beta lowered triglycerides. Progestogens had little effect on estrogen-induced reductions in LDL and total cholesterol. Estrogen-induced increases in HDL and triglycerides were opposed according to type of progestogen, in the order from least to greatest effect: dydrogesterone and medrogestone, progesterone, cyproterone acetate, medroxyprogesterone acetate, transdermal norethindrone acetate, norgestrel, and oral norethindrone acetate. Tibolone decreased HDL cholesterol and triglyceride levels. Raloxifene reduced LDL cholesterol levels. In 41 studies of 20 different formulations, HRT generally lowered lipoprotein (a).

CONCLUSION(S)

Route of estrogen administration and type of progestogen determined differential effects of HRT on lipid and lipoprotein levels. Future work will focus on the interpretation of the clinical significance of these changes.

Hormone replacement therapy and fractures in older adults

Estrogen deficiency in women is associated with accelerated bone loss, and estrogen replacement therapy has been proven to be effective in preventing osteoporosis and fractures in postmenopausal women. The introduction of selective estrogen receptor modulators that have an estrogen-like effect on the skeleton but have a different pattern of effects on other tissues may have an important role in the management of osteoporosis in women in the near future. In men, androgen deficiency has been shown to be associated with osteoporosis. Although androgen replacement in hypogonadal men may decrease bone resorption and increase bone mass, long-term placebo-controlled trials are needed to better define the benefits and risks of such therapy before it can be recommended. Sex hormone deficiency is linked to the development of osteoporosis in both women and men. In women, hormonal replacement by estrogen or the newly developed selective estrogen receptor modulators may prevent the development of osteoporosis and its related fractures. In men, there is early evidence that testosterone replacement therapy may enhance bone mass in hypogonadal men.

Lipid effects, effectiveness and acceptability of tibolone versus transdermic 17 beta-estradiol for hormonal replacement therapy in women with surgical menopause

OBJECTIVE

To compare the effectiveness of tibolone and 17 beta-estradiol on climacteric symptoms, lipid and biochemical parameters in women with surgical menopause.

METHODS

In a prospective randomised clinical trial group comparative study, the effects on the aforementioned parameters, as well as treatment compliance and side effects were studied with oral tibolone 2.5 mg per day and with transdermic 17 beta-estradiol at 50 microg per day for a period of 12 months. Statistical analysis was carried out using the Fisher-test, analysis of the variance (ANOVA) for the two factors and the Bouferoni test.

RESULTS

Lipid metabolism analysis showed lower levels of HDL and triglycerides in the tibolone group. Other biochemical parameters were not affected. Similar reductions in climacteric symptoms were found in both the groups, but the tibolone group revealed a greater improvement in psychological problems and in sexual behaviour. No differences were observed with respect to compliance and side effects.

CONCLUSIONS

Tibolone is as effective or more than 17 beta-estradiol in reducing climacteric symptoms, and shows greater triglyceride and total cholesterol improvements. Tibolone is a good alternative to estrogens in women with surgical menopause.

The role of megestrol acetate as an alternative to conventional hormone replacement therapy

OBJECTIVE

To investigate the effect of megestrol acetate on menopausal symptoms, lipid metabolism, bone metabolism and coagulation.

METHODS

In a prospective observational study, 71 postmenopausal women, for whom conventional hormone replacement therapy (HRT) was unsuitable, were treated with megestrol acetate 40 mg per day. At 0, 3, 6 and 12 months, fasting lipoproteins, bone biochemistry and thrombophilia profiles were measured and symptom score cards (Greene climacteric scale) completed. Bone mineral density measurement was performed at 0 and 12 months.

RESULTS

Forty-one women completed the study. Treatment produced significant decreases in psychological (p < 0.001), vasomotor (p < 0.001) and somatic (p < 0.01) symptoms. There were significant reductions in triglycerides (p < 0.001), total cholesterol (p < 0.001), very-low-density lipoprotein (VLDL) (p < 0.05), low-density lipoprotein (LDL) (p < 0.001), high-density lipoprotein (HDL) cholesterol (p < 0.001) and lipoprotein(a) (p < 0.001). Levels of protein C were reduced (p < 0.05) and fibrinogen increased (p < 0.05). Protein S, plasminogen and antithrombin III levels showed an upward trend, which did not reach statistical significance. Biochemical markers of bone turnover did not change, apart from a significant decrease in alkaline phosphatase. Spinal bone density decreased significantly after 12 months, while femoral neck density remained unchanged.

CONCLUSIONS

Megestrol acetate controls menopausal symptoms, has equivocal effects on cardiovascular risk markers and does not increase bone density. It is useful where estrogen is contraindicated.

A randomized study of the effects of tibolone and transdermal estrogen replacement therapy in postmenopausal women with uterine myomas

OBJECTIVE

To evaluate the effects of two types of hormone replacement therapy, an estrogen-progestin combination and tibolone, on uterine myomas in menopausal women.

STUDY DESIGN

Thirty-eight menopausal women with one or more uterine myomas were randomized to treatment with a transdermal system continuously releasing estradiol 50 microg/day combined with oral medroxyprogesterone acetate (MPA) 10 mg/day for 12 days/month or tibolone tablets 2.5 mg/day. The scheduled duration of both treatments was 12 months. Physical examination and abdominal/transvaginal ultrasonography were performed before entering the study and at 3, 6 and 12 months of treatment. At each ultrasonography the overall uterine volume was determined as well as the size of each myoma and the endometrial thickness and characteristics.

RESULTS

No statistically significant difference was detected between the two groups at any time during treatment. However, within-group analysis showed a significant increase of uterine volume and of myoma number and size in the estrogen-progestin group, whereas no such increase occurred in the patients treated with tibolone. Also, the mean endometrium width increased significantly from baseline to the end of treatment in the estrogen-progestin group, but not in the tibolone group.

CONCLUSIONS

Tibolone seems a valid alternative in menopausal patients with uterine myomas as it provides adequate relief from menopausal symptoms and avoids volume increase of the uterus and myomas.

Effects of misoprostol on lipoprotein (a) levels of ovariectomized rats

OBJECTIVE

To determine the effects of misoprostol on plasma lipoprotein (a) concentrations of ovariectomized rats.

DESIGN

Controlled prospective study.

SETTING

Animal research laboratory.

ANIMAL(S)

Four-month-old female Sprague-Dawley rats.

INTERVENTION(S)

Blood samples were obtained before and 60 days after ovariectomy, and the rats were divided into three groups. Group I (five rats) was treated with vehicle (water); groups II and III (nine and eight rats, respectively) were treated with oral misoprostol at 100 and 200 microg/kg/d, respectively, for 60 days, after which blood was drawn again.

MAIN OUTCOME MEASURE(S)

Serum lipoprotein (a) levels.

RESULT(S)

The median lipoprotein (a) level before ovariectomy was 10.8 mg/dL (range, 10.6-46.5 mg/dL). Sixty days after ovariectomy, the level increased significantly to 15.9 mg/dL (range, 10.6-36.9 mg/dL). After treatment, there was no change in lipoprotein (a) levels in the vehicle-treated group (range, 16.3-21.1 mg/dL); however, the lipoprotein (a) levels decreased significantly in the group treated with 100 microg/kg/d of misoprostol, from 15.4 mg/dL to 10.8 mg/dL, and in the group treated with 200 microg/kg/d of misoprostol, from 17.1 mg/dL to 10.6 mg/dL.

CONCLUSION(S)

Misoprostol caused a significant decrease in lipoprotein (a) levels.

Comparison of transdermal estradiol and tibolone for the treatment of oophorectomized women with deep residual endometriosis

STUDY OBJECTIVE

To compare the effect of HRT with transdermal estradiol and that of treatment with tibolone in post-menopausal women with residual endometriosis.

MATERIALS AND METHODS

21 women with residual pelvic endometriosis after bilateral oophorectomy with or without hysterectomy were enrolled in the study and were randomized to HRT with transdermal estradiol 50 mg twice weekly (n = 10) associated with cyclic medroxyprogesterone acetate 10 mg daily in women who preserved uterus, and to treatment with tibolone 2.5 mg administered orally once a day (n = 11). The duration of both treatments was scheduled to last at least 12 months. Residual endometriosis was located in the bowel wall in four patients, in the rectovaginal septum in six and deeply in the retroperitoneal pelvic space in six. All women were symptomatic before oophorectomy.

RESULTS

All the women were followed for 12 months. No patient suspended therapy because of side effects. Four patients of the estradiol group experienced moderate pelvic pain during treatment compared with only one patient in the tibolone group. One patient in the estradiol group reported severe dyspareunia.

CONCLUSION

Although our series is very small, it seems that tibolone may be a safe hormonal treatment for post-menopausal women with residual endometriosis.

Prevention of postmenopausal bone loss at lumbar spine and upper femur with tibolone: a two-year randomised controlled trial

OBJECTIVE

To examine the effects of tibolone on bone mineral density and its concurrent safety and subject acceptability.

DESIGN

Prospective randomised controlled study.

SETTING

Centre for Metabolic Bone Disease, Hull.

POPULATION

Forty-seven healthy post-menopausal women aged 50-57 years with normal bone mineral density at lumbar spine.

METHODS

Bone mineral density was assessed every 24 weeks at lumbar spine and proximal femur using dual energy X-ray absorptiometry.

RESULTS

The bone mineral density of the tibolone treated subjects tended to increase while those of the controls tended to fall. The higher densities in the tibolone group were significant at lumbar spine from week 24 (P = 0.002) and at the trochanter from week 72 (P = 0.014). The lower bone densities in the controls were significant at Ward's Triangle and femoral neck at week 96 (P < 0.0001), and at lumbar spine from week 24 onwards (P < 0.05). Between-treatment analysis indicated that, by the 96th week, the bone densities at all sites in the tibolone group were significantly different from those in the control group. At the lumbar spine the differences were highly significant throughout the study (P < 0.0004). Four women receiving tibolone withdrew from the study due to unacceptable adverse events. Two women withdrew from the control group. There was no significant difference between the groups in the number of subjects suffering adverse experiences. Vaginal bleeding occurred in seven women, all from the tibolone treated group, resulting in one withdrawal from the study.

CONCLUSION

Tibolone is thus an effective and well-tolerated alternative to oestrogen in the prevention of osteoporosis with its beneficial effects being most apparent at the lumbar spine.

Estrogen modulation of apolipoprotein(a) expression. Identification of a regulatory element

Elevated plasma levels of the lipoprotein particle Lp(a) are a major risk factor for cardiovascular disease. Lp(a) plasma levels are determined by the level of expression of its characteristic protein component, apo(a). Apo(a) expression is modulated by several hormones, of which estrogens are the best known. The chromosomal region responsible for estrogen response was identified within an apo(a) enhancer located at approximately 26 kilobases from the apo(a) promoter. Although the estrogen-responsive unit contains a potential estrogen response element, binding of estrogen receptor-alpha to DNA was not necessary. The receptor, activated by bound estradiol, interacts through its transactivation domains with a transcription factor necessary for the function of the enhancer, preventing its binding to DNA.

Postmenopausal hormone replacement, risk estimators for coronary artery disease and cardiovascular protection

Menopause, regardless of age at onset, is associated with a marked increase in coronary artery disease (CAD) risk. A large body of observational clinical studies repeatedly demonstrated favorable associations between postmenopausal hormone replacement therapy (HRT) and cardiovascular morbidity, mortality, and risk 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 nitric oxide (NO) and other vasodilators, and by inhibiting the synthesis and release of vasoconstricting agents, thus favoring vasodilation. Menopause-related changes in metabolic cardiovascular risk factors are identifiable, as are HRT-related changes in these factors. The metabolic effects include changes in lipoprotein (a), coagulation and fibrinolysis as well as homocysteine metabolism. The various actions of estrogen alone and combined with progestogen on the vascular system are reviewed. Furthermore, the outcome of the recently published Heart and estrogen/progestin replacement study (HERS) data are put in perspective. In addition, we outline the present data on the effects of raloxifene, a new second generation selective estrogen receptor modulator (SERM), which has been shown to favorably alter several markers of cardiovascular risk in postmenopausal women.

High resolution ultrasound assessment of the carotid artery: its relevance in postmenopausal women and the effects of tibolone on carotid artery ultrastructure

OBJECTIVES

Hormone replacement therapy protects from cardiovascular disease at the menopause in part by reduction of menopausal pro-atherogenic serum lipid changes. Tibolone has beneficial effects on lipids, although serum high density lipoprotein levels decrease. This study aimed primarily to establish the effects of long-term administration of tibolone on a new surrogate marker for cardiovascular disease risk, the measurement of carotid artery intima-media thickness (CIMT) using high-resolution ultrasound.

METHODS

Measurement of CIMT and assessment of carotid atherosclerotic plaques were undertaken in 31 women on tibolone and 30 voluntary controls from an ongoing open-label study of tibolone.

RESULTS

The two groups were comparable, except for mean age and prevalence of current smokers. Repeatability of CIMT measurements was acceptable (CV, 10.0%). CIMT was significantly thicker in those with atherosclerotic plaques and increased systolic blood pressure. Prevalence of plaques was raised in those who had ever smoked, and those with elevated systolic blood pressure. There was no influence of tibolone on CIMT, whether plaques were present or not.

CONCLUSIONS

This reliable technique demonstrates associations between CIMT and established risk factors. CIMT was significantly thicker in those with existing plaques. We did not demonstrate an effect of long-term tibolone use on either CIMT or prevalence of plaques.

Hormone replacement therapy in postmenopausal women with specific risk factors for coronary artery disease

Hormone replacement therapy (HRT) in postmenopausal women is associated with a reduction in the risk of developing coronary artery disease (CAD) of about 50%. Women with an elevated risk for CAD appear to benefit most by HRT. The HRT-associated cardiovascular protection may be related to favourable changes in several important cardiovascular risk estimators, such as circulating blood concentrations of cholesterol, lipoprotein(a) (Lp(a)) and homocysteine. This paper reviews the literature presently available on the effects of HRT on cholesterol, Lp(a) and homocysteine concentrations, and special attention will be given to the effects on their elevated concentrations. The effect of HRT in women with hypertension is reviewed as well. From this overview it can be concluded that risk factors such as cholesterol, Lp(a), and homocysteine can be favourably modulated by HRT, and especially, that the strongest reductions can be achieved in those women with the highest concentrations. Although clinical trials still need to demonstrate the impact of lowering concentrations of Lp(a) and homocysteine, HRT appears to be a promising risk reduction strategy in this respect.

The effects of tibolone

Tibolone is a non-bleeding form of hormone replacement therapy (HRT). When ingested, it is broken down into metabolites, of which the progestogenic metabolite predominates at the level of the endometrium, so that an atrophic endometrium is produced. For the postmenopausal woman, the availability of non-bleeding HRT has great appeal, and compliance is substantially improved. Other clinical situations in which tibolone is particularly useful include: women who have had hormone-dependent tumors in the past, women who have had endometriosis and women taking gonadotropin-releasing hormone agonists.

Effects of tibolone (Org OD14) treatment for 3 months on ovariectomy-induced osteopenia in 8-month-old rats on a low-calcium diet: preventive testing for 3 months

Tibolone (Org OD14), (7alpha, 17alpha)-17-hydroxy-7-methyl-19-norpregn-5(10)-en-20-yn++ +-3-one, is a synthetic steroid with weak estrogenic, progestational, and androgenic properties. We investigated the prophylactic effects of tibolone on bone loss, bone strength, and plasma and urinary parameters in 8-month-old ovariectomized rats on a low-Ca diet. Oral administration of tibolone (0.03-3 mg/kg/day) was started immediately after ovariectomy (ovx) and continued for 3 months. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. Oral administration of tibolone (1 or 3 mg/kg/day) significantly prevented a decrease in BMD and bone ash density (bone ash weight/volume) of the global femur, and BMDs in the femoral distal and proximal regions. Also in the lumbar vertebrae, the ovx-induced reduction in BMD was prevented by tibolone (1 and 3 mg/kg/ day) treatment, resulting in a significantly higher lumbar vertebral (L-2) bone compression strength compared to the ovx control group. Neither ovx alone nor supplemented with tibolone affected the BMD or bending strength of the femoral mid-diaphysial region. Tibolone (0.03-3 mg/kg/day) significantly reduced the ovx-induced increases in serum osteocalcin level. Furthermore, tibolone inhibited an increase in the urinary hydroxyproline/creatinine, pyridinoline/creatinine, and deoxypyridinoline/creatinine ratios induced by ovx. Tibolone also reduced body weight gain and serum cholesterol level, as has been reported for estrogen. These findings indicate that tibolone prevents reduction in bone mass associated with osteopenia by reducing increased trabecular bone resorption induced by a combination of ovx and a low-Ca diet.

Metabolic effects of tibolone in postmenopausal women with non-insulin dependent diabetes mellitus

OBJECTIVE

Postmenopausal women with non-insulin dependent diabetes (NIDDM) are frequently obese, hypertensive and hyperlipidaemic and hence at particular risk of coronary heart disease (CHD). They might therefore benefit from menopausal therapy. In view of the improvement in insulin sensitivity and the reduction in triglyceride levels induced by tibolone in healthy postmenopausal women we evaluated the effects of 12 months of tibolone on glycaemic control, serum insulin and lipid levels in postmenopausal women with NIDDM.

DESIGN

A prospective 12 months before/after intervention study.

PATIENTS

Fourteen postmenopausal women (mean age 58.14 +/- 1.25 years; mean duration of menopause 121.21 +/- 13.42 months; mean BMI: 26.55 +/- 0.97) with NIDDM (mean duration of diabetes 113.79 +/- 13.89 months).

MEASUREMENTS

Fasting and postprandial blood glucose levels were assessed monthly, serum fructosamine, fasting and postprandial insulin every 3 months and serum lipids (total cholesterol, triglyceride, HDL-cholesterol and LDL-cholesterol) every 6 months.

RESULTS

Changes in blood glucose, both fasting and postprandial, were not statistically significant during the treatment period. Serum fructosamine concentration increased significantly after 9 months. A significant decrease in fasting and postprandial insulin concentrations was observed after 9 months. A non-significant decrease was observed in total cholesterol, LDL cholesterol and triglyceride but no change in HDL cholesterol. Body weight did not change during the period of observation.

CONCLUSION

A slight deterioration in glycaemic control, a fall in insulin concentration and no change in serum lipids were observed in women with NIDDM during 12 months treatment with tibolone.

Effects of estrus cycle, ovariectomy, and treatment with estrogen, tamoxifen, and progesterone on apolipoprotein(a) gene expression in transgenic mice

Plasma levels of lipoprotein(a) (Lp(a)), are regulated by the synthetic rate of apolipoprotein(a) (apo(a)), a major protein component of this atherogenic lipoprotein. Exogenously administered sex steroid hormones are potent regulators of plasma Lp(a) concentrations. We utilized a recently developed apo(a) yeast artificial chromosome (YAC) transgenic mouse model to study the effects of ovariectomy, estrus cycle, and exogenous administration of ethinyl-estradiol, the partial estrogen receptor agonist, tamoxifen, and progesterone on circulating apo(a) plasma levels. Analysis of liver RNA revealed that estrogen and tamoxifen exerts their plasma apo(a) lowering effect at the level of apo(a) mRNA. This action of estrogen and tamoxifen may contribute to their antiatherosclerotic and cardiovascular protective effect.

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.

Long-term influence of different postmenopausal hormone replacement regimens on serum lipids and lipoprotein(a): a randomised study

OBJECTIVE

To assess the influence of three different postmenopausal hormone replacement therapies on levels of serum lipids and lipoprotein(a) [Lp(a)].

DESIGN

Open, randomised, controlled study.

PARTICIPANTS

One hundred and forty healthy, early postmenopausal women.

INTERVENTIONS

The women were randomised to receive continuous 17 beta-oestradiol, either orally (2 mg daily; n = 35) or transdermally (50 micrograms daily; n = 35), plus 10 mg dydrogesterone daily for 14 days of each 28-day cycle; or 2.5 mg tibolone daily (n = 35). Thirty-five untreated women acted as controls.

MAIN OUTCOME MEASURES

Fasting blood samples were analysed at baseline, 6, 12 and 24 months for low-density lipoprotein (LDL)-cholesterol, high-density lipoprotein (HDL)-cholesterol, very low density lipoprotein (VLDL), total cholesterol, triglycerides, lipoprotein(a)[Lp(a)], apolipoproteins A-1, A-2 and B, fibrinogen, and antithrombin factor III.

RESULTS

At 24 months oral oestradiol increased mean HDL cholesterol (7%; 95% CI 1-14), compared with no change in the transdermal group and a decrease of 26.8% in the tibolone group (95% CI 22.9-30.5); oral oestradiol decreased mean LDL cholesterol (11.8%; 95% CI 6.3-19), compared with no change in the tibolone group. Changes in apolipoprotein A-1 and B showed a similar pattern to HDL and LDL cholesterol, respectively. Oral oestradiol increased serum triglycerides (30%; 95% CI 18-42) after 24 months, compared with no change in the tibolone and transdermal oestradiol groups. Tibolone decreased serum Lp(a) by 36.6% after 24 months (95% CI 8.3-56.2), oral oestradiol decreased levels by 29.4% (95% CI 2-51.1), compared with no change in the transdermal oestradiol group.

CONCLUSIONS

Oral and to a lesser extent transdermal oestradiol when sequentially combined with dydrogesterone, showed a beneficial influence on serum lipids regarding the cardiovascular disease risk, which was not seen with tibolone. The significance of Lp(a) levels on cardiovascular disease risk remains to be determined.

Effects of postmenopausal hormone replacement therapy on lipoproteins including lipoprotein(a) and LDL subfractions

The purpose of this study was to examine the effects on lipoprotein risk markers for CHD of oestradiol given alone and in combination with the androgenic progestogen, norethisterone. Eighty postmenopausal women were randomly allocated to receive oestradiol (2 mg/day) alone or with continuous norethisterone (1 mg/day). Serum lipoprotein levels, including lipoprotein(a), were monitored during 12 months on treatment in all the women, and in a sub-set of 32 patients cholesterol was measured in the two major density subfractions of LDL. Oestradiol caused a transient rise in triglycerides, a small decrease in LDL cholesterol (significant only at 3 and 6 months, P < 0.05) and a consistent significant increase in HDL cholesterol (16%, P < 0.01). There was a downward trend in lipoprotein(a) levels which did not achieve statistical significance. The combined preparation caused significant, sustained decreases in triglycerides (31%, P < 0.01), total cholesterol (15%, P < 0.001), VLDL (42%, P < 0.01), LDL (9%, P < 0.05) and HDL (11%, P < 0.001). Lipoprotein(a) was also reduced (39%, P < 0.05). In the sub-set of patients in which LDL subfractions were measured, the reduction in LDL induced by oestradiol monotherapy was significant only at the 3-month visit (6%, P < 0.05). This was due to a decrease in the 'light' (1.025 < d < 1.044 g/ml) subfraction (10%, P < 0.05) and resulted in an apparent shift in subfraction distribution towards the 'heavy' (1.044 < d < 1.060 g/ml) subfraction, although there was no absolute increase in the latter. None of these changes was statistically significant at 12 months. Oestradiol/norethisterone caused sustained decreases in both 'light' (15%, P < 0.05) and 'heavy' (29%, P < 0.05) subfractions, with no significant change in the relative amounts. The changes in 'light' and 'heavy' LDL in this group were highly correlated with changes in triglyceride levels (r = -0.57, P < 0.05 and r = 0.82, P < 0.01 respectively). Therefore, at the end of 1 year's treatment with unopposed oestradiol the only statistically significant change was an increase in HDL cholesterol. Addition of norethisterone to the preparation reversed this potentially beneficial change, but favourably influenced triglycerides, VLDL, LDL subfraction profile and lipoprotein(a), which may counteract the adverse effect on HDL.

Metabolic effects of the menopause and oestrogen replacement

There is little doubt that the metabolic disturbances seen following the loss of ovarian function are most important in the development of cardiovascular disease in women. The loss of hormones at the menopause appears to reduce both insulin secretion and elimination, but increasing insulin resistance thereafter brings about an increase in circulating insulin concentrations. Changes in lipids and lipoproteins are in an adverse direction, as are changes in body fat distribution, and changes in haemostatic factors would tend to favour coagulation rather than fibrinolysis. HRT with oestrogen appears to improve most of the metabolic abnormalities related to the menopause, but this is in part dependent on the type of oestrogen used and the route of administration. The addition of progestogen may influence the metabolic changes induced by oestrogens, and this will vary according to the type of the progestogen. Overall, the metabolic effects of any of the current HRT regimens would seem likely to be beneficial for CHD. Nevertheless, future HRT regimens should ideally be tailored to produce the most favourable changes in CHD metabolic risk factors, particularly in the case of the regimens which attempt to avoid cyclical bleeding.

Effects of androgens on haemostasis

Androgen deficiency is associated with an increased incidence of cardiovascular disease. There is evidence that thromboembolic disease as well as myocardial ifarction in hypogonadic males are mediated by low baseline fibrinolytic activity. Hypogonadism in males is associated with an enhancement of fibrinolytic inhibition via increased synthesis of the plasminogen activator inhibitor PAI 1. On the other hand, stanozolol and danazol reduce PAI 1 and are associated with increased fibrinolytic activity. However, in male abusers of anabolic steroids the net effect on the haemostatic system may change from anti- to prothrombotic; there appears to be an individual threshold dose above which thrombogenic effects on platelets and vasomotion may overcome the profibrinolytic effects on PAI 1. There are numerous reports on weight-lifters dying of atherothrombotic ischemic heart disease while abusing anabolic steroids. Androgens are known to have profound effects on carbohydrate and lipid metabolism. In fact, much of the individual inconsistency of the effects of androgens on fibrinolytic and haemostatic activity appears to be based on the close interrelationship of these metabolic systems. Androgens may have unfavourable effects on the HDL/LDL cholesterol ratio, on triglyceride levels and on the insulin/insulin-like growth factor 1 (IGF 1) system. Hypertriglyceridemia as well as insulin resistance are both associated with low fibrinolytic activity and increased PAI 1 levels. On the other hand, lipoprotein(a), a recently acknowledged independent risk factor of CVD was shown to respond favourable to androgen treatment, in men as well as in women. In women, agonistic as well as antagonistic effects of estrogens and progestins need to be taken into account. In fact, estradiol may modulate testosterone effects on haemostasis. Androgen medication in premenopausal women, such as danazol, was found to reduce PAI 1 suggesting an improvement of the fibrinolytic activity. Also, in hormone replacement therapy (HRT) androgenic progestins or complex compounds with androgenic effects are associated with a marked reduction of PAI 1 and an improvement of fibrinolytic activity. Further improvement of fibrinolytic activity may be associated with the marked decrease of lipoprotein (a) (Lp(a)) in women on androgenic HRT. However, little is known on the interrelationship of estrogens, 19-nortestosterone or progesterone derivatives and testosterone. an interrelationship that may have substantial impact on the metabolic and particularly haemostatic net effects of a preparation. In summary, information on the effects of androgens on haemostasis is limited and may be particularly incomplete due to the fact that interaction with other sex steroids appears to be an important confounder. In any case, there are numerous effects of synthetic androgens on the synthesis and release of haemostatic factors, namely an increase of the inhibitors of coagulation and a decrease of the inhibitor of the fibrinolytic system. However, the use of androgens in patients with congenital deficiencies of these coagulation factors or previous events of cardiovascular disease has yielded disappointing results. On the other hand, particularly the reduction of fibrinolytic inhibition (PAI 1) and Lp(a) were considered favourable effects of androgens with regard to the risk of cardiovascular disease. Differences between preparations with pronounced androgenic versus antiandrogenic effects and the effect of combined preparations need to be studied in much more detail. The profibrinolytic effects of androgens may be of particular interest with regard to favourable effects of HRT on cardiovascular disease.

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.

The effect of add-back treatment with tibolone (Livial) on patients treated with the gonadotropin-releasing hormone agonist triptorelin (Decapeptyl)

OBJECTIVE

To assess whether tibolone can prevent the bone loss and symptomatic side effects normally associated with GnRH agonist (GnRH-a) use and whether tibolone modifies the effect of GnRH-a on endometriosis.

DESIGN

Prospective, double-blind, placebo-controlled, group comparative study.

SETTING

Gynecological research unit in a London teaching hospital.

PATIENTS

Twenty-nine patients with endometriosis and two with fibroids.

INTERVENTIONS

Six months of treatment with 3.75 mg/mo IM triptorelin combined with daily tablets of either placebo or 2.5 mg tibolone.

MAIN OUTCOME MEASURES

Daily symptom diary for hot flushes and bleeding episodes, laparoscopic scoring of endometriosis, endocrine and biochemical changes, and bone mineral density scans.

RESULTS

Lumbar spine bone mineral density decreased significantly from baseline in the placebo group (-5.1%) but not in the tibolone group (-1.1%). The frequency of hot flushes and sweating episodes was reduced significantly by tibolone. There was no difference between the two treatment groups with regard to the endometriosis scores.

CONCLUSIONS

The addition of tibolone to GnRH-a treatment reduces the bone loss and vasomotor symptoms that normally occur with GnRH-a, thus making long-term treatment with GnRH-a safer and more acceptable. It does not negate the therapeutic effect of GnRH-a on endometriosis.

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.

An examination of the effect of combined cyclical hormone replacement therapy on lipoprotein(a) and other lipoproteins

Lipoprotein(a) (Lp(a)) is an independent marker of cardiovascular disease which is relatively unresponsive to treatment with most of the commonly prescribed lipid lowering drugs. Concentrations of Lp(a) increase after the menopause, and the primary aim of this study was to determine whether combined hormone replacement therapy was effective in lowering levels of Lp(a) in postmenopausal women. An open longitudinal study was conducted among 42 women who had undergone a spontaneous menopause and were attending the outpatient clinic of the Prince of Wales Hospital, Hong Kong. All subjects were treated with 2 mg oral estradiol daily and 5 mg medroxyprogesterone acetate for 12 days each calendar month. Fasting blood samples for lipoprotein measurement were taken before the commencement of treatment and at 6 and 12 months. Lp(a) levels showed a skewed distribution with a median value before treatment of 9.45 mg/dl (range 1.47-95.62 mg/dl). After 6 months, there was a reduction to 7.70 mg/dl (1.12-72.59 mg/dl) (P < 0.01), and after 12 months the median concentration was 7.14 mg/dl (0.63-69.23 mg/dl) (P < 0.001 0-12 months). There were also significant reductions in the concentrations of apo B from 116.13 to 111.62 mg/dl and LDL-C from 3.02 to 2.74 mmol/l (P < 0.05), plus a lowering of TC of borderline significance. Apo A-I increased from 162.56 to 173.35 mg/dl (P < 0.01), but there were no significant changes in HDL-C or the HDL-C subfractions. TC, LDL-C, apo B and TG concentrations were higher and HDL-C and HDL2-C concentrations were lower when blood was sampled during combined treatment with estrogen and progesterone than when estrogen was being taken alone. Levels of Lp(a) were also lower during the estrogen only phase of treatment, but none of these differences were statistically significant. This study demonstrates that combined cyclical hormone replacement therapy is effective in reducing concentrations of Lp(a). The trend towards a more atherogenic lipid profile during the combined phase of treatment suggests that attention should be given to the timing of blood sampling in future studies of this nature.

Method-dependent increase in lipoprotein(a) in insulin-dependent diabetes mellitus during pregnancy

The current prevalent view is that plasma lipoprotein(a) [Lp(a)] concentrations are under strong genetic control. Most dietary and drug interventions seem to have little or no effect on plasma Lp(a) levels. However, evidence for a possible regulatory rol e of hormones is accumulating, for instance, fluctuations of Lp(a) levels during pregnancy have been reported. Also, in insulin-dependent diabetes mellitus (IDDM) patients, elevated Lp(a) levels have been reported. In the present longitudinal study, plasma lipid concentrations, including Lp(a), were determined in IDDM women before pregnancy, during pregnancy, and 3 months postpartum. In our study population, Lp(a) concentration was not significantly correlated with either hemoglobin A1c (HbA1c) levels of apolipoprotein(a) [apo(a)] phenotype. Changes in other lipid parameters observed during pregnancy in our IDDM population were similar to those reported during normal pregnancy. Lp(a) concentrations were quantified using two different immunochemical methods that possess different sensitivities and specificities: an immunoradiometric assay (IRMA) using two different anti-apo(a) antibodies, and an enzyme-linked immunosorbent assay (ELISA) using an anti-apo(a) and an anti-apo B antibody. Median prepregnancy Lp(a) concentrations were 118 mg/L (range, 15 to 672) as determined with the IRMA and 107 mg/L (range, 21 to 451) as determined with the ELISA. Women with IDDM showed, in general, no significant change in Lp(a) concentration during pregnancy when it was assayed with the IRMA, although a tendency to increased values was observed. When Lp(a) concentrations were determined with the ELISA, a strong and significant increase in Lp(a) from weeks 17 to 24 of pregnancy onward was found. The latter results confirm the prevalent view that during pregnancy Lp(a) levels are increased. However, the present results and those of others and Lp(a) in normal pregnancy strongly emphasize the importance of method selection when determining Lp(a) concentrations.

A comparative study of two hormone replacement therapy regimens on safety and efficacy variables

OBJECTIVE

To assess the effect of tibolone on endometrial safety, plasma estradiol concentrations, lipid metabolism and climacteric symptoms in comparison to sequential conjugated equine estrogens and medroxyprogesterone acetate in postmenopausal women.

METHODS

In a randomised, open-label, 6-cycle, group-comparative study, the effects on the aforementioned parameters were studied with tibolone 2.5 mg/day (N = 13) continuously, and with conjugated equine estrogens 0.625 mg/day continuously, combined with medroxyprogesterone acetate 5 mg/day (N = 11) (CEE/MPA) sequentially, during 12 days of each 28-day cycle. Within-group statistical analysis was performed with Student's t-test for paired samples, whereas between-group statistics were performed using the Student's t-test for independent groups.

RESULTS

Cytological evaluation revealed no endometrial stimulation in either group. In the tibolone group, there were no effects on estradiol levels, whereas in the CEE/MPA group, an increase in total and non-SHBG-bound estradiol plasma levels was reported. In the tibolone group, there were significant decreases in plasma total cholesterol, triglycerides, HDL-cholesterol and VLDL-cholesterol, whereas no significant changes in LDL-cholesterol and IDL-cholesterol were reported. In the CEE/MPA group there were significant decreases in plasma total cholesterol, HDL-cholesterol and LDL-cholesterol, whereas there were no significant changes in triglycerides, IDL-cholesterol and VLDL-cholesterol. Climacteric symptoms, particularly vasomotor episodes, decreased similarly in both groups.

CONCLUSIONS

Both tibolone and CEE/MPA were safe with respect to effects on the endometrium and both treatments induced changes in the plasma profiles of certain lipid and lipoprotein parameters. However, the overall clinical implications of these changes are unknown. Finally, both regimens were equally effective in the treatment of climacteric symptoms.

Androgens and women's health: genetic and epidemiologic aspects of lipid metabolism

Lipoprotein metabolism may be viewed as a process whereby large, triglyceride-carrying particles from the intestine and liver are broken down into smaller cholesterol-enriched lipoprotein particles. In the process, triglyceride is transported from the intestine and liver to adipose and other storage tissues. Androgen appears to affect lipoprotein metabolism in a number of ways. These include: increasing the activity of lipoprotein lipase and hepatic triglyceride lipase, resulting in higher levels of triglyceride in adipose tissue and a drop in total circulating high-density lipoprotein levels, respectively, and decreasing catabolic removal of low-density lipoproteins from circulating plasma. In pre- and postmenopausal women, androgen progestins in some oral contraceptives, especially the older 19-nortestosterone derivatives such as norgestrel, lower high-density lipoprotein and raise low-density lipoprotein levels. Newer 19-nortestosterone derivatives, such as desogestrel and norgestimate, have a lesser effect on circulating lipoproteins. Nonoral androgenic progestins (e.g., subcutaneous norgestrel) have little effect on circulating lipids, however, which indicates the significance of the "first pass" through the liver for oral agents. The effects of androgens on atherogenesis are largely unexplored, although preliminary studies indicate that they may promote the atherogenic process.

Effects of tibolone on lipoprotein(a) and HDL subfractions

OBJECTIVE

To determine the effects of tibolone, a synthetic steroid used to alleviate climacteric symptoms and prevent osteoporosis, on lipoprotein metabolism, with particular reference to lipoprotein(a) levels and HDL subfraction profiles.

DESIGN

Thirty nine postmenopausal women were treated with tibolone (Livial) 2.5 mg/day for 6 months and fasting serum lipoprotein levels were estimated at 0, 2, 4 and 6 months.

RESULTS

Lipoprotein(a) levels were reduced significantly over the 6 months from a median level of 245 (range < 60-780) mg/l to 152 (range < 60-530) mg/l, a reduction of 39% in the median level. A decrease was observed in approximately two thirds of the women. Reductions were noted in all 6 subjects whose pretreatment levels were high, although concentrations remained at a level associated with increased risk in all but one. There were significant decreases in triglycerides and VLDL cholesterol and no significant change in LDL cholesterol. There was a significant reduction of 18% in HDL cholesterol and a 26% reduction in the HDL2-HDL3 ratio.

CONCLUSION

The reduction in lipoprotein(a) levels may have a beneficial effect on cardiovascular risk, which could go some way towards balancing the potentially adverse effect on the cardiovascular system caused by the reduction in HDL cholesterol.