Effects of hormonal replacement therapy on lipid and haemostatic factors in post-menopausal ESRD patients

Jung Sik Park, Hae Hyuk Jung, Won Seok Yang, Soon Bae Kim, Won Ki Min and Hyun Sook Chi

Departments of Internal Medicine and Clinical Pathology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea



   Abstract
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 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Background. Hormone replacement therapy (HRT) has been known to have beneficial effects on various atherosclerotic parameters in the general population of post-menopausal women. To evaluate the effects of HRT on those factors in end-stage renal disease (ESRD) patients, we evaluated the changes of lipid profile, coagulation and fibrinolysis markers, and plasma homocysteine levels after treatment.

Methods. Sixty-five post-menopausal women on maintenance haemodialysis were randomly assigned to either an HRT group (n=33) or a control group (n=32). Median age (range) and duration of haemodialysis (range) were 57 years (40–73) and 42 months (6–150) in the HRT group and 61 years (44–78) and 54 months (8–174) in the control group respectively. Oral conjugated oestrogen (0.625 mg) combined with medroxyprogesterone acetate (2.5 mg) was given daily for 12 weeks to the HRT group. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), lipoprotein (a) (Lp(a)), fibrinogen, plasminogen activator type 1 antigen (PAI-1), tissue plasminogen antigen (t-PA), von Willebrand factor (vWF), and plasma total homocysteine (tHcy) were measured before and 12 weeks after the start of the study in both groups.

Results. There was no difference in baseline values between the control and HRT groups. At 12 weeks, HRT increased HDL-C by 12% (P<0.01) and TG by 20% (P<0.01). HRT decreased LDL-C by 9% (P<0.01), and Lp(a) by 36% (P<0.01). PAI-1 and t-PA concentrations were also reduced by 21% (P<0.01) and 9% (P<0.05) respectively. The mean values of TC, fibrinogen, vWF, and tHcy levels did not change significantly after HRT.

Conclusions. The above results suggest that HRT has favourable effects on atherosclerosis risk parameters in post-menopausal women with ESRD as in the general population of post-menopausal women.

Keywords: haemostatic factors; homocysteine; hormone; lipid



   Introduction
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Cardiovascular disease is the major cause of death in patients with end-stage renal disease (ESRD) [1]. There are several risk factors for accelerated atherosclerosis in ESRD patients. These include lipid abnormalities (diminished high-density lipoprotein cholesterol (HDL-C), elevated low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and increased lipoprotein (a) (Lp(a)) ) [2,3], disturbances in haemostatic factors (increased fibrinogen, plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (t-PA), von-Willebrand factor (vWF)) [4,5], and hyperhomocysteinaemia [6].

Post-menopausal women, as compared with pre-menopausal women, are placed at an increased risk of developing coronary artery disease [7]. Post-menopausal women have higher LDL-C and Lp(a), and lower HDL-C than pre-menopausal women [8,9]. The deleterious lipid profile and cardiovascular outcome has been ascribed to menopausal loss of oestrogen [10]. In the general population of post-menopausal women, hormone replacement therapy (HRT) reduces cardiovascular risk by up to 50% [11]. Approximately 25–50% of this reduction in risk has been attributed to changes in the levels of lipoproteins [12]. Oral oestrogen administration decreases LDL-C and increases HDL-C and TG in normal menopausal women [8,13].

Haemostatic abnormalities such as high concentrations of t-PA and PAI-1 were noted in post-menopausal women [14], which may in part account for the higher risk of atherosclerosis after the menopause. Recently there have been many reports that oestrogen affects the haemostatic profile [1517].

Hyperhomocysteinaemia is an independent cardiovascular risk factor in the general population and ESRD patients [6]. Homocysteine is cytotoxic to the endothelial wall and promotes the oxidation of LDL-C. In several studies, homocysteine was also found to be lowered by oestrogen [18].

In cases of postmenopausal women on longterm maintenance haemodialysis, the risk of atheroslerotic cardiovascular disease is further increased due to lack of oestrogen. Oestrogen therapy in post-menopausal women with ESRD on haemodialysis has only been investigated in a recent study of a small number of patients [19]. We performed a prospective randomized controlled study to evaluate the effect of HRT on the atherogenic lipids, haemostatic factors, and homocysteine in post-menopausal women with ESRD on haemodialysis.



   Subjects and methods
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 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Patients
Seventy patients were eligible for entry into this study after providing informed consent. All patients had been on haemodialysis for at least 6 months, had had no menstrual period for more than 1 year, had serum oestradiol less than 25 pg/ml, normal liver function, and haematocrit greater than 25%. Patients with a history of previous hormone replacement therapy, cardiovascular accident, coronary artery disease, or a family history of breast cancer were excluded. The patients were haemodialysed three times weekly, using a dialyser of cellulosynthetic membrane (Hemophan®, Kawasumi Laboratories, Japan).

Study protocol
After randomization, the patients in the HRT group received oral conjugated equine oestrogen 0.625 mg with medroxyprogesterone acetate 2.5 mg daily for 12 weeks. Lipoproteins, haemostatic factors, and homocysteine were measured before and after 12 weeks of HRT. The same parameters were measured in the control group without HRT. All the patients enrolled in this study discontinued aspirin, antiplatelet drugs, and lipid-lowering agent beginning 2 months before and throughout the study periods. Thirty of 33 control group patients and 31 of 33 HRT group patients were treated with erythropoietin (Epo) to maintain a haemoglobin of 10 g/dl. The total dose of Epo was not different (P>0.1) between the control group (3920±2310 units/week) and the HRT group (4170±2170 units/week). Antihypertensive medications, phosphate binders, and vitamins were maintained during the study period at the same dosage as prior to the study.

The demographic characteristics of the patients and changes of oestradiol level are shown in Table 1Go. There was no significant difference in age, body mass index, the presence of diabetes mellitus, duration of haemodialysis, duration of amenorrhoea and baseline oestradiol level between the two groups. Oestradiol levels increased significantly in the HRT group (6.4 (4.8–8.3) pg/ml 47.9 (20.1–70.7 pg/ml), median (interquartile range), P<0.01) and did not change in the control group (5.2 (4.1–10.1) pg/ml vs 6.6 (4.4–7.8) pg/ml). Oestradiol levels increased both in DM subjects (5.5 (3.9–10.4) pg/ml vs 33.2 (15.9–62.1) pg/ml) and non-DM subjects (6.5 (4.9–8.1) pg/ml vs 53.2 (24.6–80.3) pg/ml) after HRT.


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Table 1. Comparison of demographic profile and oestradiol level

 

Biochemical analysis
Blood samples were drawn through the vascular access after overnight fasting before initiation of the haemodialysis session, prior to heparinization. All samples were centrifuged immediately at 3000 g for 30 min at 4°C and divided aliquots were stored at -70°C until assay. Serum total cholesterol and TG were measured by enzymatic methods using a Hitachi 747–200 chemical autoanalyser (Hitachi Ltd., Tokyo, Japan). HDL-C was analysed enzymatically after precipitation of other lipoproteins with heparin and MnCl2. LDL-C concentration was calculated by the Friedewald formula (LDL-C=total cholesterol–HDL-C–TG/5). Lp(a) was measured by one-step sandwich enzyme-linked immunosorbent assay using two monospecific polyclonal anti- apo(a) antibody (Immunozyme Lp(a)R, ImmunoGMBH, Saarbroeken, Germany). The intra-assay and inter-assay coefficients of variation were 5.8 and 9.8% respectively. Total L-homocysteine was measured by polarization immunoassay with IMX analyser (IMX Homocysteine, Axis Biochemicals ASA, Germany). Fibrinogen was measured by the thrombin time method. PAI-1 level was determined by enzyme-linked immunosorbent assay (TintElitze PAI-1, Biopool, Umea, Sweden). t-PA antigen concentration was measured by enzyme-linked immunosorbent assay (TintElitze tPA, Biopool). vWF was measured by the enzyme-linked immunosorbent assay (Asserachrom® vWF, Diagnostica Stago, Asnieres-sur-seine, France). Oestradiol was measured by radioimmunoassay (Estradiol MAIA®, Biodata, Italy).

Statistical analysis
Statistical analysis was performed using SPSS Windows version 6.0 (SPSS Inc, Chicago, IL, USA). All data except Lp(a) are expressed as mean±SD. Lp(a) concentration is expressed as median (interquartile range). The Student t-test was used to compare the values before and after treatment. Wilcoxon signed–rank test was used in the analysis of Lp(a) data because its distribution is skewed. Comparison was considered statistically significant at P<0.05.



   Results
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 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Among the 70 patients initially enrolled, 65 patients completed the study. Three patients of the control group refused final sampling of the blood and two of the HRT group were excluded because of poor compliance. Twenty-three of 33 (70%) patients allocated to the HRT group had transient episodes of vaginal bleeding. Four patients on HRT and one patient of the control group complained of breast tenderness. Though these symptoms were present, no patient stopped the medication. Obstruction of vascular access developed in three cases of the control group and one patient of the HRT group during the study period, but no other thromboembolic event occurred.

No significant difference was present in the baseline values of all lipid, haemostatic parameters and homocysteine between the HRT and control groups (Table 2Go). In the control group, all parameters were unchanged at 12 weeks. In the HRT group, however, there were significant reductions of LDL-C and Lp(a) after 12 weeks of HRT. LDL-C and Lp(a) decreased from 112±34 mg/dl to 102±39 mg/dl (P<0.01) and from 46.2 mg/dl to 29.7 mg/dl (P<0.01) respectively (Figure 1Go). In the case of HDL-C, a 12% increment was present. Serum TG were elevated by 20%. Of the haemostatic parameters, tPA and PAI-1 were decreased after HRT by 8 and 21% respectively. Fibrinogen and vWF concentrations were not changed significantly compared with baseline values. Plasma total homocysteine (tHcy) concentration was not changed in either the control group (20.8±6.3 vs 22.0±7.3 µmol/l) or the HRT group (23.4±6.7 vs 22.2±7.3 µmol/l).


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Table 2. Comparison of lipid and haemostatic profiles and homocysteine with 12 weeks of therapy

 


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Fig. 1. The individual changes in plasma Lp(a) in patients with and without HRT.

 
When we separated the data according to the presence of DM in the HRT group, the above changes were still present in non-DM patients (Table 3Go). In DM patients, however, the significance of the changes in HDL-C, LDL-C, PAI-1, and t-PA seen in the total HRT group were lost.


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Table 3. Comparison of lipid and haemostatic profiles and homocysteine in non-DM and DM patients in HRT group

 



   Discussion
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
This study showed that HRT had a favourable effect on lipoproteins, by increasing HDL-C as well as by decreasing both LDL-C and Lp(a) in post-menopausal ESRD patients on haemodialysis, though there was some increase in serum TG after HRT. In a previous study by Ginsburg et al. [19] HDL-C was elevated by 16% after oestradiol treatment for 8 weeks in 11 post-menopausal women with ESRD. This was also seen in the present study. In addition, we found a significant reduction of LDL-C after HRT. This finding is in agreement with the results in post-menopausal women in the general population. The reduction of LDL-C by oestrogen is thought to be caused by the up-regulation of LDL receptors or increased activity of the LDL receptor-related protein [16].

High plasma Lp(a) is known to be an independent risk factor for cardiovascular disease [3,20]. Lp(a) concentration has been reported to be stable and influenced little by diet, physical activity, and most drugs (including lipid-lowering agents) except niacin. In the general population oestrogen consistently decreases serum Lp(a). The post-menopausal Estrogen/Progestin Intervention Study of more than 300 patients has demonstrated that conjugated equine oestrogen therapy at 0.625 mg daily, with or without concomitant progestin, resulted in approximately 20% reduction in plasma Lp(a) concentrations [9]. In contrast to the report by Ginsburg et al. [19] that showed no change in Lp(a) after 8 weeks of oestradiol treatment in haemodialysis patients, Lp(a) was reduced by 36% after 12 weeks of HRT in our patients. The reasons for different responses to the HRT in ESRD patients are not clear. Since apo(a) phenotype was not performed in this study, the reduction of serum Lp(a) by oestrogen might be different depending on the apo(a) phenotype, which determines the level of serum Lp(a).

Haemostatic factors including PAI-1, t-PA antigen [14], vWF, and fibrinogen [21] are independent risk factors for coronary artery disease. An increased level of PAI-1 is associated with high incidence of coronary artery disease due to impaired fibrinolysis. Both t-PA and vWF are released from vascular endothelium and thus are markers for the endothelial damage. As in the study of the general population showing that oestradiol treatment for 6 months did not have an effect on vWF [15], the level of vWF was not affected by HRT in our patients. In the general population of post-menopausal women a 29–50% reduction of PAI-1 was reported after hormone replacement [16,17]. Significant reduction of PAI-1 by 21% was also observed in our patients after HRT. In addition, t-PA concentration decreased by 8% after HRT in our patients. Decrease in t-PA antigen could be a consequence of low levels of PAI-1 and inactive t-PA/PAI-1 complex rather than improvement of endothelial injury in view of no change in vWF, another marker of endothelial cell injury [15]. Fibrinogen is the major determinant of plasma viscosity and induces platelet aggregation. High plasma fibrinogen may precipitate the event of cardiovascular disease. In cross-sectional studies [21], there was a negative association between oestrogen and the plasma concentration of fibrinogen. In a longitudinal study, however, HRT for 6 months did not reduce the level of plasma fibrinogen [15]. In this study we did not see a reduction in the level of fibrinogen after 12 weeks of HRT.

Growing evidence suggests that hyperhomocysteinaemia is an independent risk factor for cardiovascular disease in ESRD patients as well as in the general population [6]. The level of plasma tHcy appears to be affected by oestrogen. Homocysteine is lower in pre-menopausal women than in post-menopausal women or men. In addition, plasma homocysteine concentration has been reported to decrease with pregnancy in young women and HRT in post-menopausal women [22]. The magnitude of reduction in homocysteine was 13.5% of baseline value in 135 post-menopausal women who had HRT for 3 months [18]. The homocysteine-lowering effect of oestrogen was explained by the transamination of methionine [23]. In this study, plasma homocysteine concentration was not changed by HRT. In post-menopausal ESRD patients, decreased catabolism in the kidney may be the additional factor in elevating the plasma homocysteine level [6]. Thus, the effects of oestrogen on homocysteine level in post-menopausal ESRD patients may not be the same as in the general population.

The effect of oestrogen on lipoproteins was reported to be smaller in diabetic patients [24]. This study showed similar results in lipid and haemostatic profiles. When we analysed our data according to the presence of DM, the significance of changes in HDL-C, LDL-C, PAI-1, and t-PA in total HRT group was lost in the DM HRT patients, whereas all these were still significant in non-DM HRT patients. This might be explained by a combination of the following two reasons. First, the smaller sample size in DM patients might have resulted in an insufficient power to detect statistically significant changes with HRT. Second, patients with DM showed a smaller increase in oestradiol levels with therapy than non-DM patients (change of the median levels from 5.5 to 33.2 pg/ml and 6.5 to 53.2 pg/ml respectively). These 40% lower oestradiol levels in DM patients could have contributed to the non-significant changes in lipid and haemostatic parameters in DM patients. The data presented here indicate that oestrogen replacement therapy in ESRD patients has comparable effects on atherogenic lipoprotein profile and coagulation factors as in healthy post-menopausal women. However, this study was performed with limited numbers of patients and with a limited treatment duration. The long-term side-effects of oestrogen replacement in ESRD patients could not be evaluated. Furthermore, this study has not addressed the ultimate question of whether improvement in measured parameters can lead to comparable reduction in cardiovascular mortality. This preliminary study, however, indicates the need for long-term prospective trials of large numbers of patients to answer these questions and to determine whether oestrogen replacement should be routinely prescribed in post-menopausal ESRD patients.



   Acknowledgments
 
This work was supported in part by grant no. HMP-97-M-2–0028 of the 1997 Good Health R & D Project, Ministry of Health and Welfare, ROK.



   Notes
 
Correspondence and offprint requests to: Jung Sik Park MD, Department of Internal Medicine, University of Ulsan, College of Medicine, Song-Pa, PO Box 145, Seoul 138–736, Korea. Back



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 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 

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Received for publication: 17.12.99
Revision received 22. 5.00.



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