Menopausal hormone therapy and coronary heart disease: the roller-coaster history.

In the USA it is estimated that more than one million women become menopausal each year. Coronary heart disease (CHD) is the leading cause of mortality in menopausal woman globally. The majority of perimenopausal to postmenopausal women experience bothersome symptoms including hot flashes, night sweats, mood liability, sleep disturbances, irregular bleeding and sexual dysfunction. While menopausal hormone therapy (HT) effectively treats most of these symptoms, use of HT has become confusing, especially related to CHD risk. Despite years of observational and retrospective studies supporting a CHD benefit and improved survival among HT users, the Heart and Estrogen/Progestin Replacement Study (HERS) and the Women's Health Initiative (WHI) raised doubts about this long-held premise. The timing hypothesis has since emerged and states that when HT is initiated in younger women, soon after menopause onset, there may be cardiovascular benefit. The following review discusses the roller-coaster history of HT use as it pertains to CHD in postmenopausal women. Studies that highlight HT's CHD benefit are reviewed and provide reassurance that HT utilized in appropriately selected younger postmenopausal women close to the onset of menopause is safe from a cardiovascular perspective, in line with consensus recommendations.

Hormone replacement therapy - where are we now?

Hormone replacement therapy (HRT) was the standard of care for menopause management until 2002, when perceptions changed following release of the initial results from the Women's Health Initiative (WHI) trial. Fears of breast cancer and heart attacks engendered by that report were not supported by the data, especially for recently menopausal women. Clinically, HRT is usually initiated near menopause. The WHI tested something different - the effects of HRT started a decade or more after menopause. As it turned out, age at starting HRT is critical in determining benefit/risk. HRT use plummeted following the WHI in 2002 and has remained low, prompting strong interest in alternative treatments. None provide the range of benefits across multiple organ systems offered by estrogen. Most have concerning adverse effects in their own right. HRT can provide effective relief for a wide range of health conditions, potentially avoiding the need for multiple treatments for separate problems. Unfortunately, among many women and clinicians, the perception of HRT benefit/risk is distorted, and its use avoided, leading to unnecessary distress. Following the WHI, many clinicians have not received adequate training to feel comfortable prescribing HRT. When initiated within 10 years of menopause, HRT reduces all-cause mortality and risks of coronary disease, osteoporosis, and dementias.

Determinants of attained estradiol levels in response to oral estradiol plus progesterone therapy.

OBJECTIVES: Among postmenopausal women taking hormone therapy (HT), the estradiol (E2) dose and E2 levels were differentially associated with change in metabolic measures. We evaluated determinants of attained E2 levels in response to HT. METHODS: Postmenopausal women from the REPLENISH trial tested four formulations of oral combined E2 and progesterone compared with placebo. Mixed-effects linear models assessed characteristics associated with E2 levels among women with ≥80% HT compliance, adjusted for E2 dose and baseline E2 level. RESULTS: Among 1173 postmenopausal women with mean (standard deviation) age 55 (4.3) years and 5.2 (4.8) years since menopause, higher treated E2 levels were significantly related to younger age, more recent menopause, and current alcohol use, while lower E2 levels were related to current smoking. Both age and time since menopause were significantly inversely associated with E2 levels; time since menopause had a stronger association with E2 levels. In the final multivariable model, E2 levels were positively associated with current alcohol use, and inversely associated with time since menopause and current smoking. CONCLUSION: Adjusting for E2 dose and baseline E2 level, on-trial E2 levels were significantly associated with time since menopause, current smoking, and current alcohol use. Practitioners should consider these factors in individual women to achieve a desirable E2 level during HT.

Association of oral estradiol dose/levels with coagulation measures in early/late postmenopausal women.

Objective: This study evaluated associations of estradiol (E2) dose and serum E2 levels with coagulation/anti-coagulation measures in early (<6 years) compared with late (≥10 years) postmenopausal women.Methods: Postmenopausal women from the REPLENISH trial tested four formulations of oral combined E2 and progesterone compared with placebo. Mixed-effects linear models tested the association of E2 dose and serum E2 levels with the prothrombin time (PT), the activated partial thromboplastin time (APTT), antithrombin (ATHRM), fibrinogen (FIBRINO), protein C (PROTC), and protein S (PROTS), assessed five times over 12 months.Results: Among 1215 early and 297 late postmenopausal women, the E2 dose was statistically significantly inversely associated with the APTT in early postmenopause, PROTC in late postmenopause, and with the PT, ATHRM, and PROTS in both groups. Serum E2 levels were statistically significantly inversely associated with the APTT, PROTS, and FIBRINO in early postmenopause, the PT in late postmenopause, and ATHRM and PROTC in both groups. With longer time since menopause, the inverse E2 dose effect and serum E2 effects became stronger.Conclusion: Increasing E2 dose and serum E2 levels were associated with changes in coagulation/anti-coagulation measures. The associations were stronger among women ≥10 years since menopause when initiating E2. The timing of E2 therapy, E2 dose, and serum E2 levels relative to time since menopause may modify the venous thromboembolism risk.

Hierarchical measurement structure in the Women's Health Questionnaire: a confirmatory factor analysis.

Purpose: This study conducted confirmatory factor analysis (CFA) to examine the measurement structure of the Women's Health Questionnaire (WHQ) and how its components were organized. Methods: Participants were 448 postmenopausal women, with a mean age of 63.3 years. CFA was conducted to test how well several proposed measurement models fit the data. Results: The single-factor model performed poorly, indicating the presence of multiple factors. The model with seven correlated factors fit the data well, although the varying degrees of inter-factor correlations suggested grouping of similar factors. The hierarchical measurement structure, with seven first-order factors organized under two second-order factors of physical health and mental health functioning, demonstrated a good fit with the data (χ2(367) = 694.05, p < 0.001; root mean square error of approximation = 0.05; comparative fit index = 0.95) and a meaningful pattern. The Mental Health factor was represented by Depressed Mood, Anxiety/Fear, Memory/Concentration Problems, and Sleep Problems. The Physical Health factor was manifested mainly by Somatic Symptoms, Menstrual Symptoms, and Vasomotor Symptoms, and, to a lesser extent, also by Sleep Problems and Memory/Concentration Problems. Conclusion: Findings suggested that, in addition to a global index and subscale scores, the WHQ may produce summary scores of physical health and mental health functioning in evaluation of well-being among postmenopausal women.

Menopausal hormone therapy and breast cancer: what is the evidence from randomized trials?

The relationship between menopausal hormone therapy (HT) and breast cancer is complex and further complicated by misinformation, perception, and overgeneralization of data. These issues are addressed in this mini-review through the lens of the Women's Health Initiative (WHI) that has colored the view of HT and breast cancer. In the WHI, unopposed conjugated equine estrogen (CEE) reduced breast cancer risk and mortality. In the WHI CEE plus continuously combined medroxyprogesterone acetate (MPA) trial, although the hazard ratio (HR) was elevated it was statistically non-significant for an association between CEE + MPA and breast cancer. In fact, the increased HR was not due to an increased breast cancer incidence rate in women randomized to CEE + MPA therapy but rather due to a decreased and unexpectedly low breast cancer rate in the subgroup of women with prior HT use randomized to placebo. For women who were HT naïve when randomized to the WHI, the breast cancer incidence rate was not affected by CEE + MPA therapy relative to placebo for up to 11 years of follow-up. The current state of science indicates that HT may or may not cause breast cancer but the totality of data neither establish nor refute this possibility. Further, any association that may exist between HT and breast cancer appears to be rare and no greater than other medications commonly used in clinical medicine.

Menopausal hormone therapy for primary prevention: why the USPSTF is wrong.

The US Preventive Services Task Force (USPSTF) Draft Recommendation statement on Menopausal Hormone Therapy: Primary Prevention for Chronic Diseases, released in May 2017, perpetuates a major disconnect between the primary population affected, women within roughly 10 years of menopause, and the data cited. Furthermore, major elements of the evidence relied upon have been misinterpreted or misstated, particularly in regard to coronary heart disease and breast cancer, for which there is no statistically significant evidence of harm. As currently drafted, the recommendations reiterate the USPSTF statements of 2012, 2005 and 2002, and will perpetuate egregious harm to the public health. In an attempt to avoid that outcome and to facilitate a return to rational discourse regarding menopausal hormone therapy, an ad hoc group of experts in menopausal health submitted this comprehensive response to the USPSTF.

Prevention of diseases after menopause.

Women may expect to spend more than a third of their lives after menopause. Beginning in the sixth decade, many chronic diseases will begin to emerge, which will affect both the quality and quantity of a woman's life. Thus, the onset of menopause heralds an opportunity for prevention strategies to improve the quality of life and enhance longevity. Obesity, metabolic syndrome and diabetes, cardiovascular disease, osteoporosis and osteoarthritis, cognitive decline, dementia and depression, and cancer are the major diseases of concern. Prevention strategies at menopause have to begin with screening and careful assessment for risk factors, which should also include molecular and genetic diagnostics, as these become available. Identification of certain risks will then allow directed therapy. Evidence-based prevention for the diseases noted above include lifestyle management, cessation of smoking, curtailing excessive alcohol consumption, a healthy diet and moderate exercise, as well as mentally stimulating activities. Although the most recent publications from the follow-up studies of the Women's Health Initiative do not recommend menopause hormonal therapy as a prevention strategy, these conclusions may not be fully valid for midlife women, on the basis of the existing data. For healthy women aged 50-59 years, estrogen therapy decreases coronary heart disease and all-cause mortality; this interpretation is entirely consistent with results from other randomized, controlled trials and observational studies. Thus. as part of a comprehensive strategy to prevent chronic disease after menopause, menopausal hormone therapy, particularly estrogen therapy may be considered as part of the armamentarium.

Long-term soy isoflavone supplementation and cognition in women: a randomized, controlled trial.

OBJECTIVE: To determine the cognitive effects of long-term dietary soy isoflavones in a daily dose comparable to that of traditional Asian diets. METHODS: In the double-blind Women's Isoflavone Soy Health trial, healthy postmenopausal women were randomly allocated to receive daily 25 g of isoflavone-rich soy protein (91 mg of aglycone weight of isoflavones: 52 mg of genistein, 36 mg of daidzein, and 3 mg glycitein) or milk protein-matched placebo. The primary cognitive endpoint compared between groups at 2.5 years was change from baseline on global cognition, a composite of the weighted sum of 14 neuropsychological test score changes. Secondary outcomes compared changes in cognitive factors and individual tests. RESULTS: A total of 350 healthy postmenopausal women aged 45-92 years enrolled in this trial; 313 women with baseline and endpoint cognitive test data were included in intention-to-treat analyses. Adherence in both groups was nearly 90%. There was no significant between-group difference on change from baseline in global cognition (mean standardized improvement of 0.42 in the isoflavone group and 0.31 in the placebo group; mean standardized difference 0.11, 95% confidence interval [CI] -0.13 to 0.35). Secondary analyses indicated greater improvement on a visual memory factor in the isoflavone group (mean standardized difference 0.33, 95% CI 0.06-0.60) but no significant between-group differences on 3 other cognitive factors or individual test scores, and no significant difference within a subgroup of younger postmenopausal women. CONCLUSION: For healthy postmenopausal women, long-term dietary soy isoflavone supplementation in a dose comparable to that of traditional Asian diets has no effect on global cognition but may improve visual memory. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that long-term dietary supplementation with isoflavone-rich soy protein does not improve global cognition of healthy postmenopausal women.

The timing hypothesis for coronary heart disease prevention with hormone therapy: past, present and future in perspective.

Over the past decade, two informative events in primary prevention of coronary heart disease (CHD) have occurred for women's health. The first concerns hormone replacement therapy (HRT) where data have come full circle from presumed harm to consistency with observational data that HRT initiation in close proximity to menopause significantly reduces CHD and overall mortality. The other concerns sex-specific efficacy of CHD primary prevention therapies where lipid-lowering and aspirin therapy have not been conclusively shown to significantly reduce CHD and, more importantly, where there is lack of evidence that either therapy reduces overall mortality in women. Cumulated data support a 'window-of-opportunity' for maximal reduction of CHD and overall mortality and minimization of risks with HRT initiation before 60 years of age and/or within 10 years of menopause and continued for 6 years or more. There is a substantial increase in quality-adjusted life-years over a 5-30-year period in women who initiate HRT in close proximity to menopause, supporting HRT as a highly cost-effective strategy for improving quality-adjusted life. Although primary prevention therapies and HRT contrast in their efficacy to significantly reduce CHD and especially overall mortality in postmenopausal women, the magnitude and types of risks associated with HRT are similar to those associated with other medications commonly used in women's health. The cumulated data highlight the importance of studying the HRT cardioprotective hypothesis in women representative of those from whom the hypothesis was generated.

HRT and breast cancer risk: a realistic perspective.

A new analysis from the Women's Health Initiative included data on breast cancer incidence over a 11-year period from the randomized trial of conjugated equine estrogens (CEE) plus medroxyprogesterone acetate (MPA) and a subsequent observational follow-up. The conclusions were that CEE/MPA use was associated with an increase in both breast cancer incidence and mortality. We have concerns over the validity of their statistical analyses, as adjustments for baseline characteristics or for multiple comparisons demonstrate no significant differences in incidence between those allocated to CEE/MPA or placebo. We suspect that the apparent increase in mortality is the result of surveillance and detection bias rather than a true cause and effect. Even if such an effect were true, mortality from breast cancer would still be a very rare event. We also question the clinical relevance and applicability of their findings. The data over the 11 years show no increased risk of breast cancer with CEE/MPA in women who had not previously used hormone replacement therapy (HRT), and the vast majority of women on HRT would not be prior users at initiation. It should be remembered that women using CEE alone showed a significant decrease in breast cancer risk in the WHI trial and follow-up. Even if combined estrogen?progestogen HRT did cause an increase in breast cancer risk, and this is not proven, the magnitude of that risk is small, and less than that risk seen with many lifestyle factors. HRT is a benefit, not a risk, for those women requiring it.

Effect of statins on estrogen and androgen levels in postmenopausal women treated with estradiol.

OBJECTIVE: A considerable number of postmenopausal women who receive estrogen therapy are also treated for hypercholesterolemia with cholesterol-lowering statins. Statins and steroid hormones can compete for the same steroid-metabolizing enzymes. We investigated whether long-term administration of statins had an effect on serum estrogen and androgen levels in postmenopausal women receiving and not receiving oral estrogen therapy. METHODS: A subgroup analysis from the Estrogen in the Prevention of Atherosclerosis Trial, a randomized, double-blind, placebo-controlled trial, was performed. A total of 222 women were randomized to receive either placebo or 1 mg of oral micronized 17ß-estradiol daily for 2 years. In both the placebo and treatment groups, participants with low density lipoprotein cholesterol levels >160 mg/dl were treated with statins. Blood samples were obtained at baseline and every 6 months during the trial. Serum levels of dehydroepiandrosterone, androstenedione, testosterone, estrone and 17ß-estradiol were measured by radioimmunoassay. RESULTS: Among 86 placebo- and 90 estradiol-treated subjects with baseline and on-trial hormone measurements, no significant differences were observed between the statin-free and statin-treated groups in mean changes from baseline to on-trial levels in any of the androgens or estrogens, whether or not the postmenopausal women were treated with estrogen. CONCLUSION: The results suggest that estrogen therapy and statins can be used simultaneously with no deleterious effects on circulating hormone levels.

Coronary heart disease and hormone replacement therapy after the menopause.

The discordance in coronary heart disease (CHD) outcome between randomized, controlled trials and observational studies of hormone replacement therapy (HRT) is likely the result of the dissimilar cohorts studied. This observation led to the formation of the timing hypothesis that benefits and risks of HRT depend upon age of HRT initiation and/or time of HRT initiation in relation to menopause. This hypothesis has been supported with data from large, randomized, controlled trials that have studied HRT and selective estrogen receptor modulators (SERMs) in the prevention of CHD. Initiation of HRT in women <60 years of age and/or within 10 years of menopause reduces both CHD and total mortality; SERMs have been shown to reduce CHD in women <60 years. What has become clear from the cumulated literature is that in young postmenopausal women who initiate HRT in close proximity to menopause, the adverse effects of HRT are rare and no greater than those of other commonly used pharmacological agents and that the primary prevention benefits for CHD are at least equivalent to those of other commonly used therapies. Additionally, the literature indicates that the duration of HRT confers greater CHD benefit especially in women <60 years who initiate therapy. The cumulated literature dispels misperceptions concerning HRT and CHD.

Using basic science to design a clinical trial: baseline characteristics of women enrolled in the Kronos Early Estrogen Prevention Study (KEEPS).

Observational and epidemiological studies suggest that menopausal hormone therapy (MHT) reduces cardiovascular disease (CVD) risk. However, results from prospective trials showed neutral or adverse effects most likely due to differences in participant demographics, such as age, timing of initiation of treatment, and preexisting cardiovascular disease, which reflected in part the lack of basic science information on mechanisms of action of hormones on the vasculature at the time clinical trials were designed. The Kronos Early Estrogen Replacement Study (KEEPS) is a prospective, randomized, controlled trial designed, using findings from basic science studies, to test the hypothesis that MHT when initiated early in menopause reduces progression of atherosclerosis. KEEPS participants are younger, healthier, and within 3 years of menopause thus matching more closely demographics of women in prior observational and epidemiological studies than women in the Women's Health Initiative hormone trials. KEEPS will provide information relevant to the critical timing hypothesis for MHT use in reducing risk for CVD.

Postmenopausal oral estrogen therapy affects hemostatic factors, but does not account for reduction in the progression of subclinical atherosclerosis.

BACKGROUND: Hemostatic factors influenced by postmenopausal hormone therapy may contribute to atherosclerosis. The Estrogen in the Prevention of Atherosclerosis Trial (EPAT), a 2-year, randomized, double-blind, placebo-controlled trial, demonstrated reduced subclinical atherosclerosis progression measured by change in common carotid artery intima-media thickness (CIMT) with unopposed oral 17beta-estradiol. OBJECTIVES: To assess the effect of postmenopausal hormone therapy on the levels of several hemostatic factors, and the relationship between these factors and the progression of subclinical atherosclerosis. PATIENTS AND METHODS: We measured tissue plasminogen activator (t-PA) antigen, factor (F) VII, D-dimer and albumin longitudinally, and plasminogen activator inhibitor type 1 (PAI-1) and fibrinogen at trial-end, in 186 postmenopausal women. RESULTS: Estradiol vs. placebo was associated with greater FVII and lower t-PA, albumin, PAI-1 and fibrinogen (all P < or = 0.001), with no estradiol effect on D-dimer (P = 0.42). Only mean on-trial t-PA was positively associated with the absolute level of CIMT on-trial (r = 0.29, P < 0.0001), but this was attenuated with age and body mass index adjustment. No longitudinally measured hemostatic factor was associated with CIMT progression. However, higher CIMT during the trial was significantly related to increases in t-PA. CONCLUSIONS: These results confirm previous findings regarding estrogen's effect on hemostatic factors and show that albumin is negatively associated with estrogen therapy. These hemostatic factors did not account for the reduction of CIMT progression with 17beta-estradiol seen in EPAT. Atherosclerosis itself may affect levels of hemostatic factors (reverse causality), with subsequent involvement in atherosclerosis-associated thrombosis.

Validation of thoracic quantitative computed tomography as a method to measure bone mineral density.

The purpose of this study was to measure precision of thoracic quantitative computed tomography (QCT) bone mineral density (BMD) and correlation to lumbar spine QCT bone density. We measured the reproducibility of thoracic QCT; two consecutive thoracic QCT scans of the T9, T10, and T11 vertebrae were performed on 95 subjects (49 females, 46 males; mean age, 62.5 years) undergoing coronary scanning. In order to correlate the thoracic to standard lumbar measurement, the subjects also underwent a lumbar QCT scan of the L1, L2, and L3 vertebrae as part of an abdominal aortic scanning study. The variation of thoracic BMD was assessed in different ethnic subgroups. Consecutive thoracic QCT measurements showed good agreement (r=0.98; RMS CV=5.78%). Thoracic bone density was significantly higher than lumbar bone density results (paired t-test, P=0.003), but the two methods correlated well (r=0.86). The regression equation for the relationship between lumbar (X) and thoracic (Y) QCT was Y=0.87X + 22.97. The standard error of estimate was 19.0 mg/cm3. Thoracic QCT from coronary calcium thoracic scans is able to measure BMD with rescan precision and regression errors that are small compared to the biologic variability in the population. Given the relatively small precision error and the reasonable correlation to lumbar BMD, an ancillary assessment of thoracic BMD in a cardiac scan is likely to be a useful assessment of bone mineral status in the general population.

The association of smoking and subclinical atherosclerosis in Type 2 diabetes: modification by duration of diabetes.

BACKGROUND: Diabetes is a relatively common disease in the United States, and cardiovascular disease is the major cause of morbidity and mortality among persons with diabetes. While smoking is one of the most well-established risk factors for heart disease and atherosclerosis, the effect of smoking on atherosclerosis among diabetic patients has not been thoroughly investigated. The primary objective of this paper was to evaluate the impact of smoking on atherosclerosis among Type 2 diabetic patients and to evaluate whether smoking associations with atherosclerosis are modified by diabetes-related variables. METHODS: We used cross-sectional baseline data from a randomized controlled trial to evaluate the associations between smoking and common carotid artery intima-media thickness (IMT) in 299 subjects with Type 2 diabetes. There were 34 (11%) current cigarette smokers, 73 (24%) former cigarette smokers, and 192 (64%) subjects who had never smoked regularly. RESULTS: There was an increasing trend in mean carotid IMT with both longer duration and increased frequency of smoking (adjusted P for trend 0.04 and 0.02, respectively). The mean +/- SE carotid IMT was non-significantly thicker (0.872 +/- 0.01 mm) in diabetic patients who had ever smoked than never smokers (0.842 +/- 0.01 mm) after controlling for age, gender and other potential confounders (P = 0.08). The negative effects of ever smoking (P = 0.01 for interaction), number of cigarettes smoked daily (P = 0.003 for interaction) and duration of smoking (P = 0.03 for interaction) on carotid IMT were accentuated with longer duration of diabetes. CONCLUSION: Smoking is associated with subclinical atherosclerosis in diabetic persons and interacts with duration of diabetes to accentuate atherosclerosis. The association between carotid IMT and duration of diabetes increases with both the frequency and duration of smoking.

Estrogen in the prevention of atherosclerosis. A randomized, double-blind, placebo-controlled trial.

BACKGROUND: Although observational studies suggest that estrogen replacement therapy (ERT) reduces cardiovascular morbidity and mortality in postmenopausal women, use of unopposed ERT for prevention of coronary heart disease in healthy postmenopausal women remains untested. OBJECTIVE: To determine the effects of unopposed ERT on the progression of subclinical atherosclerosis in healthy postmenopausal women without preexisting cardiovascular disease. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: University-based clinic. PATIENTS: 222 postmenopausal women 45 years of age or older without preexisting cardiovascular disease and with low-density lipoprotein cholesterol levels of 3.37 mmol/L or greater (>/=130 mg/dL). INTERVENTION: Unopposed micronized 17beta-estradiol (1 mg/d) or placebo. All women received dietary counseling. Women received lipid-lowering medication if their low-density lipoprotein cholesterol level exceeded 4.15 mmol/L (160 mg/dL). MEASUREMENTS: The rate of change in intima-media thickness of the right distal common carotid artery far wall in computer image processed B-mode ultrasonograms obtained at baseline and every 6 months during the 2-year trial. RESULTS: In a multivariable mixed-effects model, among women who had at least one follow-up measurement of carotid intima-media thickness (n = 199), the average rate of progression of subclinical atherosclerosis was lower in those taking unopposed estradiol than in those taking placebo (-0.0017 mm/y vs. 0.0036 mm/y); the placebo-estradiol difference between average progression rates was 0.0053 mm/y (95% CI, 0.0001 to 0.0105 mm/y) (P = 0.046). Among women who did not receive lipid-lowering medication (n = 77), the placebo-estradiol difference between average rates of progression was 0.0147 mm/y (CI, 0.0055 to 0.0240) (P = 0.002). Average rates of progression did not differ between estradiol and placebo recipients who took lipid-lowering medication (n = 122) (P > 0.2). CONCLUSIONS: Overall, the average rate of progression of subclinical atherosclerosis was slower in healthy postmenopausal women taking unopposed ERT with 17beta-estradiol than in women taking placebo. Reduction in the progression of subclinical atherosclerosis was seen in women who did not take lipid-lowering medication but not in those who took these medications.

Markedly elevated levels of estrone sulfate after long-term oral, but not transdermal, administration of estradiol in postmenopausal women.

OBJECTIVE: To compare serum estrone sulfate (E1S) levels in postmenopausal women during long-term treatment with commonly prescribed doses of oral and transdermal estradiol (E2). DESIGN: A retrospective study performed in a University setting in the United States involving 33 healthy postmenopausal women. Two groups of postmenopausal women were studied: group 1 (n = 10) received 1 mg oral micronized E2 daily for 16 months; blood was drawn at 0, 7, and 15 months. Group 2 (n = 23) was randomized into three subgroups. Two of the subgroups (n = 8; n = 7) received E2 delivered at a rate of 0.05 mg/day and 0.1 mg/day, respectively, by transdermal patch, changed twice weekly; the third subgroup received a placebo (without E2) patch for 9 continuous months. Blood samples were drawn at 0, 6, and 9 months. Serum E1S and E2 were quantified by specific radioimmunoassays. Statistical analysis was performed by analysis of variance. RESULTS: After oral E2 treatment, E1S levels increased significantly (p < 0.01) from baseline, reaching an average level of 38.8 ng/mL at 15 months. After transdermal E2 treatment, E1S levels increased significantly, yet to a much lesser extent, reaching levels of 1.8 ng/mL and 3.2 ng/mL after 9 months of treatment with the 0.05 mg/day and 0.1 mg/day patches, respectively. CONCLUSIONS: Markedly elevated levels of E1S were found after long-term oral estrogen treatment. In comparison to the increase in E1S levels after long-term oral estrogen treatment, there was only a small increase in E1S levels after transdermal E2 therapy. This difference may be attributed to the higher dosage of oral E2 that is required because of the low bioavailability compared with the transdermal dosages.