Estrogen-containing hormone therapy and Alzheimer's disease risk: understanding discrepant inferences from observational and experimental research

Estrogen has the potential to influence brain processes implicated in Alzheimer's disease pathogenesis. With the loss of ovarian estrogen production after menopause, estrogen-containing hormone therapy might be expected to influence the risk of Alzheimer's disease. Observational data link use of hormone therapy to reductions in Alzheimer risk, but experimental evidence from the Women's Health Initiative Memory Study trial demonstrates that oral estrogen, with or without a progestin, increases the incidence of dementia for postmenopausal women age 65 years or older. Mechanisms of harm in this setting are unknown. Bias and unrecognized confounding in observational research are leading candidates for discrepant results between observational studies and the Women's Health Initiative Memory Study trial. Studies are also distinguished by differences in outcome measures, hormone therapy formulations, prevalence of menopausal symptoms among study participants, and participant age. Finally, Women's Health Initiative Memory Study findings may not generalize to estrogen use by relatively young women during the menopausal transition or early postmenopause, a class of women who were ineligible for the Women's Health Initiative Memory Study trial. In observational studies, hormone therapy exposure often included use by younger women for menopausal vasomotor symptoms. Although there is no clinical trial evidence that hormone therapy at any age protects against Alzheimer's disease, it remains to be determined whether the age at which hormone exposure occurs or the timing of hormone therapy initiation in relation to the menopause (the critical window hypothesis) modifies treatment outcomes on dementia risk.     

Depression, estrogen, and the Women's Health Initiative

This clinical observation report compares hormone use and clinical presentation in a series of middle-aged depressed women before and after publication of the Women's Health Initiative. Depressed women over age 40 seen at a general hospital academic women's affective disorders practice 6 months before and after publication of the Women's Health Initiative were compared for medication changes, hormone therapy, lifetime depressive episodes, time since last episode, time to depression recurrence after hormone cessation, symptoms, and treatment response. More women stopped hormone therapy and reported onset of depression within 3 weeks of hormone discontinuation after than before publication of the Women's Health Initiative. Depression in most women responded to reinstitution of estrogen or initiation or increase in antidepressant dose. Discontinuation of hormone therapy appears to be associated with the rapid recurrence of depression in some women with a history of depression. Randomized controlled trials in middle-aged depressed women of estrogen or a selective estrogen receptor modulator as monotherapy or as an augmentation agent are urgently needed.     

Postmenopausal hormone therapy: new questions and the case for new clinical trials

Observational studies suggest that postmenopausal hormone therapy (HT) prevents coronary heart disease, whereas randomized clinical trials have not confirmed a cardioprotective effect. Although observational studies may have overestimated the coronary benefit conferred by postmenopausal hormone use, there are other plausible explanations for the apparent discrepancy between previous results and the less favorable findings from clinical trials such as the large Women's Health Initiative. There is now a critical mass of data to support the hypothesis that age or time since menopause may importantly influence the benefit-risk ratio associated with HT, especially with respect to cardiovascular outcomes, and that the method of administration, dose, and formulation of exogenous hormones may also be relevant. Although the weight of the evidence indicates that older women and those with subclinical or overt coronary heart disease should not take HT, estrogen remains the most effective treatment currently available for vasomotor symptoms, and its effects on the development of coronary disease in newly postmenopausal women remain unclear. Moreover, effects of HT on quality of life and cognitive function in recently postmenopausal women merit further study. These unresolved clinical issues provide the rationale for the design of the Kronos Early Estrogen Prevention Study, a 5-year randomized trial that will evaluate the effectiveness of low-dose oral estrogen and transdermal estradiol in preventing progression of atherosclerosis in recently postmenopausal women.     

Lessons to be learned from animal studies on hormones and the breast

The relation of hormone use by postmenopausal women to breast cancer risk has been controversial and unclear. A recent large randomized trial, the Women's Health Initiative (WHI) and a large observational study (Million Women Study) provided somewhat conflicting answers. The WHI found an increased incidence of breast cancer among women given hormone therapy (conjugated equine estrogen plus medroxyprogesterone acetate) but no increase in those given estrogen only therapy (conjugated equine estrogen alone). Whereas, the Million Women Study found an increased breast cancer risk among the estrogen plus progestin and the estrogen only users. This review brings comparative perspective to the issue of the effects of estrogen plus progestin versus estrogen only effects on breast cancer and is focused particularly on nonhuman primates. Although data from rodents is mixed, studies of monkeys suggest that estrogen only treatment has little or no effect on breast cell proliferation, and by inference, on breast cancer risk. On the other hand, data from both mouse and monkey studies strongly support the conclusion that the co-administration of a progestogen with an estrogen markedly increases breast cell proliferation and the potential for breast cancer promotion.     

New evidence regarding hormone replacement therapies is urgently required transdermal postmenopausal hormone therapy differs from oral hormone therapy in risks and benefits

Controversies about the safety of different postmenopausal hormone therapies (HTs) started 30 years ago and reached a peak in 2003 after the publication of the results from the Women Health Initiative (WHI) trial and the Million Women Study (MWS) [Writing group for the women's health initiative investigations. Risks and benefits of estrogen plus progestin in healthy postmenopausal women. JAMA 2002;288:321-33; Million women study collaborators. Breast cancer and hormone-replacement therapy in the million women study. Lancet 2003;362:419-27]. The single HT formulation used in the WHI trial for non hysterectomized women-an association of oral conjugated equine estrogens (CEE-0.625 mg/day) and a synthetic progestin, medroxyprogesterone acetate (MPA-2.5 mg/day)-increases the risks of venous thromboembolism, cardiovascular disease, stroke and breast cancer. The MWS, an observational study, showed an increased breast cancer risk in users of estrogens combined with either medroxyprogesterone acetate (MPA), norethisterone, or norgestrel. It is unclear and questionable to what extent these results might be extrapolated to other HRT regimens, that differ in their doses, compositions and administration routes, and that were not assessed in the WHI trial and the MWS. Significant results were achieved with the publication of the WHI estrogen-only arm study [Anderson GL, Limacher M, Assaf AR, et al. Effects of conjugated equine estrogen in postmenopausal women with hysterectomy: the Women's Health Initiative randomized controlled trial. JAMA 2004;291:1701-1712] in which hormone therapy was reserved to women who had carried out hysterectomy. What emerged from this study will allow us to have some important argument to develop.     

Potential age-dependent effects of estrogen on neural injury

In 2000, approximately 10 million women were receiving hormone replacement therapy (HRT) for alleviation of menopausal symptoms. A number of prior animal studies suggested that HRT may be neuroprotective and cardioprotective. Then, in 2003, reports from the Women's Health Initiative (WHI) indicated that long-term estrogen/progestin supplementation led to increased incidence of stroke. A second branch of the WHI in women with prior hysterectomy found an even stronger correlation between estrogen supplementation alone and stroke incidence. Follow-up analyses of the data, as well as data from other smaller clinical trials, have also demonstrated increased stroke severity in women receiving HRT or estrogen alone. This review examines the studies indicating that estrogen is neuroprotectant in animal models and explores potential reasons why this may not be true in postmenopausal women. Specifically, age-related differences in estrogen receptors and estrogenic actions in the brain are discussed, with the conclusion that animal models of disease must closely mimic human disease to produce clinically relevant results.     

Results from the Estonian postmenopausal hormone therapy trial [ISRCTN35338757

OBJECTIVES: At present the Women's Health Initiative trial is the only reported randomised controlled trial studying the effects of hormone therapy among healthy postmenopausal women. The Women's Health Initiative reports have been criticized for lacking in generalisability, due to the characteristics of the trial population. We aimed to compare the health effects of oral continuous combined hormone therapy with a placebo and non-treatment among healthy Estonian women. METHODS: Eligible women were randomised into a blind group of hormone therapy versus placebo and into a non-blind group of open label hormone therapy versus non-treatment. One thousand seven hundred and seventy-eight postmenopausal women aged 50-64 at the time of sampling were recruited in 1999-2001 at three clinical centers in Estonia. Participants received conjugated equine oestrogens, 0.625 mg/d, plus medroxyprogesterone acetate, 2.5mg/d, or conjugated equine oestrogens, 0.625 mg/d, plus medroxyprogesterone acetate, 5mg/d, if less than 3 years had passed since menopause at recruitment, or matched placebo or non-treatment. Trial treatment was stopped gradually from 1 January 2004 to 31 May 2004. RESULTS: After a follow-up period from 2.0 to 5.0 years the combined hazard ratio, stratified by blinding and adjusted for age at recruitment and former oral contraceptive use was 1.12 (95% confidence interval [CI]: 0.90-1.40) for coronary heart disease, 1.24 (95% CI: 0.85-1.82) for cerebrovascular disease, 1.36 (95% CI: 0.73-2.52) for total cancer, and 0.61 (95% CI: 0.42 to 0.89) for bone fractures. CONCLUSIONS: The results from the Estonian Postmenopausal Hormone Therapy randomised trial are consistent with the Women's Health Initiative findings.     

Effects of specific post-menopausal hormone therapies on bone mineral density in post-menopausal women: a meta-analysis

BACKGROUND: Long-term post-menopausal hormone therapy (pHT) was often regarded as first-line therapy to prevent fractures in post-menopausal women, a recommendation under scrutiny given the benefit-risk profile of the Women's Health Initiative results of the estrogen-progestin combination. Apart from controlled clinical studies providing data with fractures as an end point, measures of lumbar and hip bone mineral density (BMD) may be used to assess bone-related effects of pHT. The objective of this study was to conduct a systematic review of 2-year trials, published between 1990 and December 2002, and assessing changes in BMD by any estrogen including ethinyl estradiol, any estrogen plus any progestin, or tibolone. METHODS: We searched MEDLINE, EMBASE and systematic reviews. Thirty-nine randomized, prospective, controlled 2-year trials were analysed in pre-specified groups according to the profile of the compounds. RESULTS: Virtually all pHT regimens at least maintain BMD at the lumbar spine and the hip compared with baseline; there is no apparent difference between the various estrogenic compounds. Tibolone, a synthetic progestin, appears to be as effective as any estrogen. Most trials were conducted in early post-menopausal women, fewer in women with hysterectomy and/or bilateral oophorectomy. CONCLUSIONS: The size of impact on BMD does not appear to differ between tibolone and any estrogen compound studied.     

Association of pelvic organ prolapse and fractures in postmenopausal women: analysis of baseline data from the Women's Health Initiative Estrogen Plus Progestin trial

OBJECTIVE: Testing a hypothesis that pelvic organ prolapse (POP) is a focal manifestation of disordered connective tissue, we evaluated whether there is an association between POP and history of fracture. DESIGN: This was a case-control study. Baseline data were from postmenopausal women aged 60 years or older enrolled in the Women's Health Initiative Estrogen Plus Progestin trial. Distinct variants (cystocele, rectocele, and uterovaginal) and severity (mild, moderate, or severe) of POP were recognized. A history of "fracture after age 55" was considered as the event of interest. RESULTS: Moderate to severe POP was identified in 9% of 11,096 participants aged 60 years or older. Women with moderate to severe rectocele were significantly more likely to report fracture (odds ratio: 1.37, 95% CI: 1.06-1.77, P = 0.02) compared with those with absent to mild prolapse. Of the subset of participants who underwent bone mineral density assessment, those with moderate to severe prolapse demonstrated significantly lower whole-body bone mineral density ([beta] = -0.03, SE 0.02); this difference was of borderline significance (P = 0.05) compared with that for participants with absent to mild POP. Multivariate logistic regression analysis confirmed an independent association between moderate to severe rectocele and fracture (odds ratio: 1.45, 95% CI: 1.08-1.95, P = 0.01). CONCLUSIONS: We demonstrate a relationship between moderate to severe POP and low bone mineral density in postmenopausal women enrolled in the Women's Health Initiative Estrogen Plus Progestin trial. Our findings of an association between clinically significant (moderate to severe) POP, specifically rectocele, and a history of fracture suggest that suboptimal collagen status purported to associate with POP may also involve bone collagen and hence translate into skeletal compromise.     

Commentary on the Women's Health Initiative

The Women's Health Initiative (WHI), established by the National Institutes of Health in 1991, is a long-term national health study that focuses on strategies for preventing heart disease, breast and colorectal cancer and osteoporosis in postmenopausal women. These chronic diseases are the major causes of death, disability and frailty in older women of all races and socioeconomic backgrounds. The WHI a 15-year multi-million dollar endeavor, and one of the largest U.S. prevention studies of its kind. The study involves over 161,000 women aged 50-79, and is one of the most definitive, far reaching clinical trials of women's health ever undertaken in the U.S. The WHI Clinical Trial and Observational Study will attempt to address many of the inequities in women's health research and provide practical information to women and their physicians about hormone replacement therapy, dietary patterns and calcium/vitamin D supplements, and their effects on the prevention of heart disease, cancer and osteoporosis. Emerging information from the NIH Women's Health Initiative and other studies of women's health begun in the 1990's should be changing the landscape of options for older women in the years to come.     

The role of testosterone in the management of hypoactive sexual desire disorder in postmenopausal women

At least 16 million women over the age of 50 currently experience low sexual desire, with approximately 4 million women exhibiting hypoactive sexual desire disorder (HSDD). Although early research established that testosterone therapy improves sexual desire in postmenopausal women, safer and more efficacious administration routes were explored. Large randomized, double-blinded placebo-controlled studies demonstrate that transdermal testosterone improves sexual function and activity in postmenopausal women with HSDD. Large multi-center Phase III trials further confirm the positive effects of the testosterone patch in the treatment of HSDD. More recent studies are exploring the utility of testosterone gels. Based upon data from two recent clinical relevance studies, physicians can be reassured that postmenopausal women with HSDD report a meaningful benefit with testosterone therapy, and further, women will only continue therapy if they experience a meaningful benefit. Although most trials combined testosterone with estrogen/progesterone therapy, the recent APHRODITE trial examined testosterone alone, showing increased sexual desire with mild adverse events. Concerns regarding the long-term safety profile of transdermal testosterone must be addressed before the FDA will approve a testosterone product for women. Although some fear an increased risk of breast cancer with exogenous testosterone administration, recent studies support the idea that androgens can play a role in suppressing the proliferative effects of estrogen and progesterone. Long-term safety data is now being collected and analyzed and Phase III trials focusing on long-term risks are underway. In the meantime, transdermal testosterone appears to be a safe and effective therapy for postmenopausal women with HSDD [Swanson S, DeRogatis L, Snabes M, Simes S, Zborowski J. Treatment of HSDD in surgically menopausal women: a newly initiated Phase III, randomized, double-blind, placebo-controlled, multi-center study of the safety and efficacy of LibiGel. Presented at the Annual Meeting of the International Society for the Study of Women's Sexual Health, February 22–25, Orlando, FL; 2007].     

Estrogen receptor alpha and beta polymorphisms: is there an association with bone mineral density, plasma lipids, and response to postmenopausal hormone therapy?

OBJECTIVE AND DESIGN: A cross-sectional segregation analysis of polymorphisms in the estrogen receptor (ER) genes (Pvull and Xbal in ERalpha, and Alul in ERAbeta with bone mineral density in the lumbar spine and forearm and with lipid profile was performed in 1098 postmenopausal women. Additionally, in a subpopulation of 280 women, who completed 1 year of treatment with estrogen plus progestin, the association between genotypes and the response to treatment in both plasma lipids and bone was investigated. In another untreated subpopulation of 443 women, genotype influence on the prevalence of vertebral fractures and on annual rate of bone loss during a mean follow-up period of 11 years was estimated. RESULTS: Baseline plasma lipids, bone mineral density, annual rate of bone loss and prevalence of spinal fractures were not significantly associated with polymorphisms in the ERbeta gene. The ERA polymorphism was significantly associated with bone loss from the distal forearm (P = 0.04) but not with bone loss from the spine. After 1 year of treatment with hormone therapy there was also a significant association between the ERbeta polymorphism and the response in total cholesterol (P = 0.02); while the ERalpha gene polymorphisms did not significantly influence the response to hormone therapy. CONCLUSIONS: In a large white population of postmenopausal women, ERalpha gene polymorphisms were not associated with bone mineral density or lipid profile at baseline or after hormone therapy. Conversely, the ERbeta genotype appeared to segregate with bone loss from the forearm and to modulate the decrease in total cholesterol during hormone therapy.     

Recency and duration of postmenopausal hormone therapy: effects on bone mineral density and fracture risk in the National Osteoporosis Risk Assessment (NORA) study

OBJECTIVES: Results from the Women's Health Initiative showed that postmenopausal hormone replacement therapy (HRT) prevents fractures but has an overall unfavorable risk:benefit ratio, leading to the recommendation that HRT be used only for women with troublesome menopause symptoms, and for as short a time as possible. This recommendation has important implications for the timing and duration of HRT and the prevention of osteoporosis. The large number of women participating in the National Osteoporosis Risk Assessment (NORA) program provided the opportunity to evaluate bone mineral density (BMD) and 1-year fracture risk in analyses stratified by duration and recency of HRT. DESIGN: Participants were 170,852 postmenopausal women aged 50 to 104, without known osteoporosis, who were recruited from primary physicians offices across the US. BMD was measured at one of four peripheral sites, and the 1-year risk of osteoporotic fracture was assessed by questionnaire. RESULTS: At baseline, current HRT users had the highest T-scores at every age. Among current hormone users, women who had used HRT longest had the highest BMD levels. Women who had stopped HRT more than 5 years previously, regardless of duration of use, had T-scores similar to never-users. Current but not past hormone use at baseline was associated with a 25% to 29% lower risk of osteoporotic fracture (P < 0.0001) in 1 year, compared with nonusers. These findings were independent of age, ethnicity, body mass index, lifestyle, years postmenopausal, and site of BMD measurement. CONCLUSIONS: We conclude that postmenopausal BMD and fracture are closely associated with current, but not prior, HRT use. Use of HRT for 5 years or less, as proposed for treatment of symptomatic women during menopause transition, is unlikely to preserve bone or significantly reduce fracture risk in later years.     

Esterified estrogen therapy in postmenopausal women. Relationships of bone marker changes and plasma estradiol to BMD changes: a two-year study

OBJECTIVE: To determine the relationships among bone mineral density changes, bone marker changes, and plasma estrogens in postmenopausal women receiving estrogen replacement therapy. DESIGN: A total of 406 postmenopausal women received 1,000 mg calcium and continuous esterified estrogens (0.3 mg, 0.625 mg, or 1.25 mg) or placebo daily for up to 24 months. Bone mineral density and bone marker measurements were determined at 6-month intervals; plasma estrogens were measured in a subset after 12, 18, and 24 months. RESULTS: Esterified estrogens produced significant increases in bone mineral density (lumbar spine, hip) compared with baseline and placebo at 6, 12, 18, and 24 months. Bone markers decreased from baseline with all esterified estrogen doses relative to placebo. Bone marker changes at 6 months correlated negatively with bone mineral density changes at 24 months (correlation coefficient range = -0.122 to -0.439). The strongest correlation was noted for spine bone mineral density changes and serum osteocalcin. Mean plasma estrogen levels increased with esterified estrogen dose, and bone mineral density changes correlated positively with plasma estrogen levels. Positive bone mineral density changes were noted in treatment groups with plasma estradiol levels at and above 25 pg/mL. CONCLUSIONS: Esterified estrogens, at doses from 0.3 mg to 1.25 mg/day, unopposed by progestin, increase bone mineral density of the spine and hip in postmenopausal women. These bone mineral density changes correlated significantly with bone marker changes at 6 months and with plasma estrogens at 12, 18, or 24 months. Data variability minimizes the predictive value of the bone marker changes in monitoring individual therapy.     

Breast cancer incidence in postmenopausal women using testosterone in addition to usual hormone therapy

OBJECTIVE: There is now convincing evidence that usual hormone therapy for ovarian failure increases the risk for breast cancer. We have previously shown that ovarian androgens normally protect mammary epithelial cells from excessive estrogenic stimulation, and therefore we hypothesized that the addition of testosterone to usual hormone therapy might protect women from breast cancer. DESIGN: This was a retrospective, observational study that followed 508 postmenopausal women receiving testosterone in addition to usual hormone therapy in South Australia. Breast cancer status was ascertained by mammography at the initiation of testosterone treatment and biannually thereafter. The average age at the start of follow-up was 56.4 years, and the mean duration of follow-up was 5.8 years. Breast cancer incidence in this group was compared with that of untreated women and women using usual hormone therapy reported in the medical literature and to age-specific local population rates. RESULTS: There were seven cases of invasive breast cancer in this population of testosterone users, for an incidence of 238 per 100,000 woman-years. The rate for estrogen/progestin and testosterone users was 293 per 100,000 woman-years--substantially less than women receiving estrogen/pro-gestin in the Women's Health Initiative study (380 per 100,000 woman-years) or in the "Million Women" Study (521 per 100,000 woman-years). The breast cancer rate in our testosterone users was closest to that reported for hormone therapy never-users in the latter study (283 per 100,000 woman-years), and their age-standardized rate was the same as for the general population in South Australia. CONCLUSIONS: These observations suggest that the addition of testosterone to conventional hormone therapy for postmenopausal women does not increase and may indeed reduce the hormone therapy-associated breast cancer risk-thereby returning the incidence to the normal rates observed in the general, untreated population.     

Long-term compliance with estrogen replacement therapy in surgical postmenopausal women: benefits to bone and analysis of factors associated with discontinuation

OBJECTIVE: To evaluate prospectively the effects of long-term estrogen replacement therapy (ERT) on bone density in surgical postmenopausal women treated for 5 years with two different modalities and to determine the factors associated with discontinuation of ERT. DESIGN: We included in the present study 165 women (mean age, 46.8 +/- 4.6 years) who had undergone surgical menopause. ERT was prescribed immediately after surgery, and bone mineral density was measured at the lumbar spine before the women entered the study and at 12, 24, 36, 48, and 60 months after being included. Treated patients were assigned at random to one of two groups. The first group received conjugated equine estrogens 0.625 mg/day continuously, and the second group received transdermal 17beta-estradiol 50 mg/day continuously. Treated groups were compared with a nontreated control group. RESULTS: Our data showed that although ERT clearly protected against bone loss in women who had experienced surgical menopause, only one third of the treated patients continued ERT at the end of follow-up. The main reason for discontinuation was fear of cancer (36.1 % of cases). In addition, no differences were observed between oral and transdermal groups of treatment. CONCLUSIONS: Long-term ERT may have a protective effect against bone loss in surgically postmenopausal women; however, two thirds of treated patients discontinued therapy after 5 years and 43% of them presented a negative balance on bone mass in one or more bone density assessments. For this reason, enhancing compliance and monitoring treatment are mandatory.     

Issues to debate on the Women's Health Initiative: failure of estrogen plus progestin therapy for prevention of breast cancer risk

Several studies on hormone replacement therapy (HRT) in the USA have been published. They revealed that the risk of breast cancer is increased with HRT more than with estrogen alone (ERT). A progestin has been given with each dose of ERT, as was the case in the Women's Health Initiative (WHI) study. The results of studies in Europe show similar trends. The increased risk of breast cancer in the WHI study was significantly higher only in women who had used HRT for several years before entering the study. The study was non-blind in 3444 cases, i.e. 40.5% of women in the estrogen plus progestin group and 6.8% in controls. If the women in the HRT group had more mammographic examinations it could change the validity of the results of the study. Estradiol-containing drugs have now been added to the list of carcinogens and the packages of these drugs have warning labels. The results of the WHI study do not support this labelling. The results of the WHI study show that the administration of HRT increases the risks of stroke and pulmonary embolism. It is reasonable to think that in the case of bleeding, at least at weekends in nursing homes (when staff levels may be low) patients were immobilized in their beds. Immobilization among women on HRT could have been more dangerous than the HRT itself. Progestins need to be delivered to the endometrium in a manner that will have the least effect on the breast. Systemic administration can be replaced by releasing progestin locally in the uterine cavity. Endometrial protection with a levonorgestrel-releasing intra-uterine system (IUS) is well tolerated. The high hepatic concentrations of estrogens given orally could be avoided by transdermal administration. New studies should be planned to reflect the situation in clinical practice. The time to start HRT in healthy menopausal women is between the ages of 45 to 55 years.