Cardiovascular Effects of Physiological and Standard Sex Steroid Replacement Regimens in Premature Ovarian Failure

Methods

Results

Given the intensive nature of the protocol, 18 patients (52%) completed the study (Figure 1). Women were young (19 to 39 years of age), and their premature ovarian failure was principally idiopathic or surgically induced, or attributed to Turner syndrome (Table). Both treatments were generally well tolerated, although some women reported adverse reactions to the patch adhesive when taking physiological treatment (see online data supplement, available at http://hyper.ahajournals.org) and were withdrawn from the study. No women withdrew because of unacceptable hormonal symptoms during their treatment (Figure S1). In general, more women withdrew during the first treatment phase (14 vs 1), suggesting a lack of tolerance of the research protocol rather than the intervention. The suppression of plasma luteinizing hormone and follicle-stimulating hormone concentrations for both treatments was similar (P>0.05 for both), suggesting equivalent sex steroid replacement (Figure 1).

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Figure 1. Mean (±SEM) values for serum (A) luteinizing hormone (LH; P=0.1435), (B) follicle-stimulating hormone (FSH; P=0.3548), (C) estradiol (P<0.0001), and (D) progesterone (P=0.007) concentrations with physiological sex steroid (▪) and standard () regimens. Data are from 2-way ANOVA with repeated measures.

Blood Pressure and Arterial Stiffness

Although none of the women were clinically hypertensive, in comparison with the standard regimen, physiological sex-steroid therapy was associated with a lower blood pressure (P<0.0001 for both systolic and diastolic blood pressures; Figure 2) and differed from the standard regimen at 3 (P<0.05), 6 (P<0.05), and 12 months (P<0.01). The same was seen in derived central arterial blood pressures (P<0.0001 for both systolic and diastolic pressures; data not shown) and clinic blood pressures, although the magnitude of effect was greater (Figure 2). At 12 months, there was an overall 7.3 mm Hg (95% CI: 2.5 to 12.0 mm Hg) 24-hour mean systolic and 7.4 mm Hg (95% CI: 3.9 to 11.0 mm Hg) 24-hour mean diastolic blood pressure benefit with physiological sex-steroid therapy. There were no differences in carotid-radial pulse wave velocity (P=0.411) or 24-hour mean heart rate (P=0.511) through the study period (data not shown).

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Figure 2. Changes in mean 24-hour ambulatory systolic (A) and diastolic (C) and clinic systolic (B) and diastolic (D) blood pressures with physiological sex steroid (▪) and standard () regimens (mean±SEM). P<0.0001 for treatment effect for all 4 measurements (2-way ANOVA with repeated measures; N=17 for all).

Renal and Humoral Factors

Compared with the standard regimen, physiological sex-steroid therapy reduced plasma Ang II (P=0.007) and serum creatinine concentrations (P=0.015), without affecting plasma aldosterone concentrations (Figure 3). There was an apparent reduction in PRA, but this did not reach statistical significance (P=0.180). Body mass index (P=0.146), serum urea nitrogen (P=0.063), sodium (P=0.402), and potassium (P=0.895) concentrations did not change during the study (data not shown).

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Figure 3. Changes in (A) serum creatinine (P=0.015), (B) PRA (P=0.180), (C) plasma Ang II (P=0.007), and (D) plasma aldosterone (P=0.784) concentrations after treatment with physiological sex steroid (▪) and standard () regimens (mean±SEM; N=13 for all; 2-way ANOVA with repeated measures).

Discussion

In comparison with a 12-month standard regimen, physiological sex steroid replacement therapy resulted in lower blood pressure, better renal function, and less activation of the renin-angiotensin system in women with premature ovarian failure. These differences are likely to have major consequences for the future long-term cardiovascular risk of these women.

Major randomized, controlled trials of primary prevention using HRT in older postmenopausal women have failed to demonstrate cardiovascular benefits¹⁸ and have even suggested harm.^19,20 Indeed, postmenopausal women maintained on HRT have an increased risk of stroke.²¹ These surprising findings have generated much debate. Several factors have been highlighted as obscuring a potentially beneficial effect of the hormonal intervention, including the age of study participants²² and the preparations of HRT administered (these studies used a variety of nonhuman and conjugated estrogens, with and without progestins). Many patients were elderly (>70 years of age), and posthoc analyses restricted to younger patients (50 to 59 years of age) have suggested apparent benefit.²³ This latter observation awaits prospective confirmation in the ongoing Early Versus Late Intervention Trial With Estradiol and the Kronos Early Estrogen Protection Study due to report in 2010.

Young women with untreated premature ovarian failure have an increased in risk of osteoporosis, cardiovascular disease, and cognitive impairment.²⁴ They are frequently prescribed hormone replacement until the age of normal menopause in accordance with national guidelines.¹⁰ The median age of natural menopause is reported to range between 49 and 52 years,²⁵ and, thus, these young women with early loss of ovarian function may require ≤4 decades of sex hormone replacement.

The oral contraceptive pill is known to increase blood pressure in women with normal ovarian function⁷ and is linked to adverse outcomes associated with blood pressure, including ischemic stroke⁸ and subarachnoid hemorrhage.⁹ It is important to recognize that such hormonal intervention is deliberately targeted at producing supraphysiological concentrations of sex steroids to inhibit ovulation and produce the desired contraceptive effect. Moreover, oral contraceptive therapy may be intermittent and often interrupted for planned pregnancies. The needs and consequences for women with premature ovarian failure are very different from fertile women requiring effective contraception. Our data would suggest that, whereas the administration of hormonal therapies based on contraceptive regimens provides adequate symptom relief, longer-term continuous use may be associated with potentially harmful cardiovascular effects.

There have been no previous prospective studies assessing the use of hormone replacement regimens on cardiovascular outcomes in young women with premature ovarian failure. Although our study uses different hormone regimens from those used in the large HRT trials, we have presented the first data comparing 2 sex steroid replacement regimens and the potential consequences for cardiovascular health. In this group of young women, we have demonstrated substantial effects on blood pressure that are more marked than those reported previously in postmenopausal women. If these data are substantiated in a larger long-term study, there would be major implications for cardiovascular health.

We did not demonstrate any difference in pulse wave velocity between the treatment regimens, suggesting that the hypertensive effect is not mediated through an increase in arterial stiffness. We suggest that the competing influences of effective estrogen replacement (known to improve vascular endothelial function and reduce arterial stiffness)²⁶ and increased blood pressure (robustly associated with reduced arterial compliance)²⁷ on vascular tone cancel out any potential changes in arterial compliance resulting in unchanged pulse wave velocity through the study. However, we suggest that our findings may be explained by an effect on the kidney and the renin-angiotensin system. A direct hypertensive effect would be anticipated to cause reflex suppression of the renin-angiotensin system with downregulation of PRA and Ang II concentrations. In contrast, we report no suppression in PRA and an increase in plasma Ang II concentrations, suggesting a causal relationship with the activation of the renin-angiotensin system.

The profile and consequences of estrogens are highly dependent on their route of administration. Parenteral administration by estrogen patches leads to a lower peak plasma concentration, lower hepatic exposure, and a more stable steady-state profile. In contrast, oral estrogen administration leads to wide plasma variations with high concentrations demonstrable within an hour of ingestion.²⁸ Moreover, to achieve adequate systemic effects, oral estrogen therapies are given at high doses because of extensive first-pass hepatic metabolism. Consequently, after oral administration, the liver is exposed to particularly high portal venous concentrations of estrogens, and this may underlie the stimulation of the renin-angiotensin system and elevation of blood pressure. In both preclinical²⁹ and clinical models,¹³ oral estradiol administration upregulates hepatic angiotensinogen mRNA expression and increases plasma angiotensinogen concentrations. Angiotensinogen is the substrate for renin, and plasma concentrations have been linked to clinical hypertension.^30,31 Upregulation of angiotensinogen production without suppression of PRA provides a clear explanation for the elevation in plasma Ang II concentrations. This, in turn, might account for the undoubted blood pressure changes seen in our study. Thus, we suggest that oral therapy causes high hepatic exposure to estrogens leading to excessive angiotensinogen production, activation of the renin-angiotensin system, and systemic hypertension: an effect avoided by transdermal estrogen preparations.³²

It is interesting to note the increase in serum creatinine in this study. This may be a consequence of alterations in renal blood flow secondary to renin-angiotensin system activation.³³ Alternatively, this may be because of changes in renal blood flow attributable directly to the effect of estrogen.³⁴ Finally, it may be attributable to the sustained changes in blood pressure. It is conceivable that hemodilution may have caused an apparent change in serum creatinine, although this variable was not measured in this study, and this may need to be addressed in future studies. Assuming that the change in creatinine is a real phenomenon, whatever the underlying mechanism, this does represent a clinically important change in renal function.

An important weakness of our study is the heterogeneous etiology of the women with premature ovarian failure. We predominantly included patients with idiopathic or surgically induced premature ovarian failure who are typical of the majority of women presenting with this condition. However, we also included patients with Turner syndrome and survivors of cancer who underwent treatment either premenarche or postmenarche. Patients with Turner syndrome have an increased incidence of cardiovascular abnormalities, including aortic coarctation and hypertension.³⁵ Patients who are survivors of radiotherapy and chemotherapy have had a toxic insult to the whole body that may influence the cardiovascular system.³⁶ Thus, the response to the intervention may vary according to etiology of ovarian failure. In our study, we observed no interaction of disease etiology with treatment effect, although our subgroup sizes are too small to draw any firm conclusions. However, we used a crossover design to enable each patient to act as his or her own control, as well as to maximize the power to detect differences in treatment regimens.

The other significant weakness of our study is the high drop out rate, with only 18 of 34 randomly assigned subjects (52%) completing the whole study, although more women withdrew during the first treatment phase, suggesting an intolerance of the research protocol rather than the intervention. Of the dropouts, only 4 women clearly withdrew because of intolerance of the treatment, and this was entirely attributed to adverse reactions to the patch adhesives. Improved adhesives may help to reduce these intolerances and make the treatment more acceptable.