Hormone Therapy: What the Cardiovascular Evidence Shows

Hormone Therapy: What the Cardiovascular Evidence Shows

Medical Disclaimer: This content is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Information is based on current medical literature and clinical guidelines but may not apply to your specific situation. Individual responses vary based on personal medical history and concurrent conditions. Always consult qualified healthcare providers for medical decisions. Never delay seeking medical care based on content you’ve read. If experiencing a medical emergency, seek immediate medical attention.

These articles provide education to enhance your healthcare partnership. All treatment decisions should involve your healthcare team. Use this knowledge to have informed discussions, not replace medical care.

In Brief

The public conversation about hormone therapy has been distorted for two decades. The 2002 publication of the Women’s Health Initiative caused a generational overcorrection. Hormone therapy prescriptions in the United States fell 32 percent within nine months. (3) Women with disrupting menopausal symptoms went untreated. Women who would have been reasonable candidates for hormone therapy were told it caused heart disease — a conclusion that did not survive a careful reading of the trial.

Two decades of additional research have produced a more textured picture. When a woman starts hormone therapy relative to menopause matters substantially. For a healthy woman within ten years of menopause and without contraindications, hormone therapy is a reasonable treatment for menopausal symptoms or fracture risk; cardiovascular risks in this window are small and the heart-related fear of the post-2002 era was disproportionate. For a woman more than ten years past menopause or starting after age 60, absolute risks rise and the calculation is different. Hormone therapy is not heart disease prevention. (7) This article walks through what the WHI actually showed, the timing hypothesis, the 2017 18-year follow-up, the ELITE trial, contemporary guidance — and a specific warning about compounded “bioidentical” preparations.

How We Got Here

In the 1980s and 1990s, observational studies — most prominently the Nurses’ Health Study — consistently showed that women currently using postmenopausal hormone therapy had substantially lower rates of heart attacks and other cardiovascular events than non-users. The biological reasons were plausible: estrogen improves cholesterol, helps the inner lining of blood vessels function, and modulates how blood vessels relax. By the late 1990s, hormone therapy was widely prescribed for heart disease protection as well as symptom relief. Major guidelines reflected that consensus.

The Women’s Health Initiative was designed to test the cardiovascular hypothesis with the rigor of a randomized trial. The combined estrogen-plus-progestin trial enrolled 16,608 postmenopausal women aged 50 to 79 at 40 US clinical centers between 1993 and 1998, randomly assigning them to oral conjugated equine estrogen 0.625 mg daily plus medroxyprogesterone acetate 2.5 mg daily, or placebo. (1) After a mean of 5.2 years against a planned 8.5, the trial’s Data and Safety Monitoring Board halted the trial because the overall risks exceeded the benefits.

WHI Estrogen-Plus-Progestin Trial — key cardiovascular findings (Rossouw 2002 JAMA; Manson 2003 NEJM; n = 16,608; mean age 63 at enrollment; mean follow-up 5.2 years):

The breast cancer 95% CI is the nominal value; after adjustment for multiple comparisons, the adjusted CI was wider and the breast cancer finding did not reach formal statistical significance in the original 2002 report. Subsequent WHI publications confirmed the breast cancer signal in the combined arm.

The clinical and public response was immediate and disproportionate. Hormone therapy prescriptions in the United States dropped 32 percent within nine months of the WHI publication. (3) The headline — “WHI shows hormone therapy causes heart disease” — entered the public conversation and stayed there for years. Women with severe hot flashes, night sweats, and the urinary and vaginal changes of menopause went without treatment. Clinicians who had been prescribing hormone therapy stopped, or shifted to compounded preparations marketed as safer, or told patients there was simply no good answer. The cost of that overcorrection — measured in untreated menopausal symptoms over two decades — was real, even though it never made the headlines.

The simple negative interpretation of the WHI did not survive a careful reading of the trial. Two features of the WHI design mattered. The average WHI participant was 63 years old at enrollment, with many women more than a decade past menopause — older than the typical woman starting hormone therapy for symptom relief, both then and now. And when the WHI investigators stratified the results by age and years since menopause in a 2007 follow-up analysis, the cardiovascular risk pattern was not uniform across the trial population. Women who started hormone therapy closer to menopause had a different risk-benefit pattern than women who started years later. (4)

This led to what researchers call the timing hypothesis — the idea that hormone therapy affects the heart differently depending on whether arteries are still relatively healthy (early after menopause) or already have established plaque disease (years later). When estrogen reaches healthy artery walls, it may help maintain them. When estrogen reaches already-diseased artery walls, it may trigger inflammation or destabilize existing plaques.

Testing the Timing Hypothesis

The ELITE trial — published in 2016 — was the first randomized controlled trial specifically designed to test the timing hypothesis. (5)

ELITE enrolled 643 healthy postmenopausal women who did not have cardiovascular disease or diabetes. Participants were divided into two strata: those within six years of menopause (n=271; on average 3.5 years past menopause) and those ten or more years past menopause (n=372; on average 14.3 years past menopause). Within each stratum, women were randomly assigned to oral 17β-estradiol 1 mg daily (combined with vaginal micronized progesterone for ten days each month in women with a uterus) or matching placebo. The primary outcome was the rate of carotid intima-media thickness progression — an early-disease marker measured by ultrasound every six months over a median follow-up of about five years.

The findings differed sharply between strata. Among women within six years of menopause, mean CIMT increased by 0.0078 mm per year on placebo versus 0.0044 mm per year on estradiol (P=0.008) — estradiol significantly slowed the rate of plaque buildup. Among women ten or more years past menopause, the rates were similar between groups (0.0100 mm per year on estradiol vs 0.0088 mm per year on placebo, P=0.29). The interaction between strata was statistically significant (P=0.007), providing the first direct randomized confirmation of the timing hypothesis. (5)

Two caveats are essential. ELITE measured a surrogate marker — early artery wall thickness — that predicts future cardiovascular events but is not itself a heart attack or stroke. The trial was not large enough or long enough to count actual events, and CT measures of coronary artery calcium did not differ significantly between groups in either stratum. Whether the favorable CIMT finding in the early-menopause stratum translates into fewer actual heart attacks and strokes has not been formally tested in a randomized trial of the necessary size and duration. And even the “early” group in ELITE began hormone therapy at a median of 3.5 years after menopause — closer to menopause than the WHI participants, but not immediately after.

The Kronos Early Estrogen Prevention Study (KEEPS), published in 2014, addressed a related question. (9) KEEPS enrolled 727 healthy women within three years of their final menstrual period (mean age 52) and randomly assigned them to oral conjugated equine estrogen, transdermal estradiol (both with cyclic micronized progesterone), or placebo for four years. Neither hormone therapy regimen significantly changed the rate of carotid wall plaque buildup compared with placebo. (9) KEEPS showed that hormone therapy started very soon after menopause did not make underlying artery disease worse — a “no harm” finding that contrasts with the increased heart disease risk WHI found in its older women. KEEPS did not show artery disease getting better. Together with ELITE, the two trials suggest that for women starting hormone therapy within roughly six years of menopause, the cardiovascular trajectory is at minimum not worsened and may, by the artery wall thickness measure, be modestly improved.

The Long-Term WHI Follow-Up

The 2017 long-term follow-up of the WHI provided the most authoritative randomized evidence on cumulative outcomes. (6) Manson and colleagues analyzed death rates and causes of death across both WHI hormone therapy trials — the estrogen-plus-progestin trial and a separate estrogen-alone trial in 10,739 women who had undergone hysterectomy and used conjugated equine estrogen without a progestin — over a full 18 years of follow-up, covering both the active-treatment period and the years afterward.

Across the pooled 27,347 women, all-cause mortality did not differ between hormone therapy and placebo (27.1% vs 27.6%; HR 0.99, 95% CI 0.94–1.03). Cardiovascular mortality and total cancer mortality also did not differ. (6)

A pattern consistent with the timing hypothesis emerged when women were separated by age at trial start. During the active intervention phase of the trial, women aged 50 to 59 at randomization had significantly lower all-cause mortality on hormone therapy than placebo (HR 0.69, 95% CI 0.51–0.94), while women aged 70 to 79 did not show this benefit. The ratio of hazard ratios comparing the youngest to the oldest age group was 0.61 (95% CI 0.43–0.87) during intervention — formally significant for age-related differences.

Over the full 18-year cumulative follow-up, however, the age-based pattern attenuated. The ratio of hazard ratios comparing 50 to 59 with 70 to 79 was 0.87 (95% CI 0.76–1.00), with the confidence interval touching 1.00. (6) The accompanying JAMA editorial described the long-term mortality signal in younger women as “suggestive but not definitive.”

The honest characterization: the WHI 18-year data and the ELITE trial both point in the same direction for women starting hormone therapy near menopause, but the cumulative evidence is not strong enough to support a cardioprotective claim. It is strong enough to substantially defuse the post-2002 fear that hormone therapy in this group causes heart disease.

Contemporary Guidance

The 2022 Menopause Society position statement (published under the prior name North American Menopause Society) is the most current and most thoroughly referenced US synthesis on hormone therapy. (7) It frames the cardiovascular conversation around three groups.

For women younger than 60 or within 10 years of menopause who are otherwise healthy, the benefits of hormone therapy generally outweigh the risks for treating bothersome hot flashes and night sweats, for the urinary and vaginal changes of menopause, and for prevention of bone loss in women at high fracture risk. In this group the heart-related risks are generally low, although hormone therapy is still not recommended specifically to prevent heart disease. (7)

For women starting hormone therapy more than 10 years after menopause or after age 60, the risk-benefit balance is less favorable. Absolute risks of coronary heart disease, stroke, and venous thromboembolism are higher, and there is no offsetting cardiovascular benefit. Individualized decisions, closer attention to cardiovascular and cancer risks. (7)

For women with primary ovarian insufficiency, premature menopause, or early menopause, a separate framework applies. The cardiovascular implications of years of premature estrogen deficiency (Article 5 of this series) justify a different approach. Hormone therapy can be considered until at least the average age of natural menopause unless contraindicated, specifically to offset the heart and bone consequences of prolonged early estrogen loss. (7,8)

Primary ovarian insufficiency / premature menopause is a separate framework — hormone therapy is recommended until at least the mean age of natural menopause unless contraindicated. In no group is hormone therapy recommended for primary cardiovascular prevention (2022 Menopause Society; 2022 USPSTF; 2019 ACC/AHA Primary Prevention Guideline).

Delivery route matters, particularly within the favorable window. Transdermal estradiol — patches, gels, sprays — carries lower blood clot risk than oral estradiol and may carry lower stroke risk. (7) For women who are appropriate candidates for hormone therapy but who have a higher background risk of blood clots, transdermal formulations are generally preferred.

The 2022 USPSTF recommendation adds the most authoritative US guidance specifically about using hormone therapy to prevent disease: with moderate certainty, neither combined estrogen-plus-progestin nor estrogen alone has a net benefit for preventing chronic conditions in postmenopausal persons. (10) This recommendation addresses prevention. It does not apply to using hormone therapy for menopausal symptoms, which is FDA-approved.

Compounded Bioidentical Hormones: A Specific Warning

One topic deserves direct treatment because the marketing has outpaced the evidence and women have been harmed by the asymmetry. Compounded bioidentical hormone preparations — products made by compounding pharmacies, often marketed as “natural,” “personalized,” or “safer” alternatives to conventional hormone therapy — are not what their marketing claims.

The compounded preparations are not subject to the same FDA oversight as approved hormone therapy products. They have not been studied in adequately powered cardiovascular outcome trials. Manufacturing consistency varies between compounding pharmacies. The salivary hormone testing often used to “personalize” the dose does not reliably reflect tissue exposure. The marketing implies a safety profile that the evidence does not support.

The 2022 Menopause Society position statement specifically recommends against routine use of compounded bioidentical hormone preparations. (7) FDA-approved hormone therapy products that are themselves bioidentical do exist — estradiol patches, estradiol gels, estradiol vaginal rings, oral micronized progesterone — and these are the appropriate choice when an estradiol or micronized progesterone formulation is clinically preferred. The compounded pharmacy versions are not safer than the FDA-approved versions, are not better-studied (they are worse-studied), and the “natural” framing exploits the post-WHI fear that conventional hormone therapy is dangerous. The fear, as discussed above, was always disproportionate for the women who would benefit. The compounded pharmacy industry has profited from that fear.

If hormone therapy is appropriate, an FDA-approved preparation is the right starting point. There is no current clinical reason to prefer a compounded bioidentical preparation over an FDA-approved bioidentical preparation, and several reasons not to.

What the Evidence Does Not Support

Several claims about hormone therapy and cardiovascular disease that remain in circulation are not supported by contemporary evidence.

Hormone therapy is not a cardiovascular prevention strategy. The 2019 ACC/AHA Primary Prevention Guideline, the 2022 USPSTF recommendation, and the 2022 Menopause Society position statement all agree. (7,10,11) Hormone therapy used for an approved indication may have a low cardiovascular risk profile when started near menopause, but it is not a substitute for the standard heart disease prevention measures — managing cholesterol, blood pressure, blood sugar, weight, physical activity, diet, and tobacco — that have far stronger evidence behind them for reducing heart attacks and strokes.

The timing hypothesis is not a green light for hormone therapy in any woman near menopause. The research applies to women who do not already have established cardiovascular disease. In women with established coronary disease, heart failure, prior stroke, or recent blood clots, hormone therapy carries excess risk regardless of timing.

The cardiovascular profile of newer hormone therapy formulations has not been fully tested. Most of the randomized evidence, including the WHI, used conjugated equine estrogen with or without medroxyprogesterone acetate. Contemporary prescribing increasingly uses estradiol (instead of conjugated equine estrogens), micronized progesterone (instead of synthetic progestins), and transdermal delivery (instead of oral). These newer formulations probably have different cardiovascular profiles, but head-to-head randomized comparisons against the older formulations for actual cardiovascular events are limited. The contemporary literature is, to a substantial degree, extrapolating from older data to newer products.

What Your Visit Should Cover

If you are considering, taking, or revisiting hormone therapy, the cardiovascular elements of the conversation are specific.

Your timing relative to menopause. The cardiovascular risk-benefit calculation is meaningfully different depending on whether hormone therapy is being started within 10 years of menopause and before age 60, or more than 10 years after menopause and after age 60. The conversation should always reference your age at initiation and the time since your final menstrual period.

Your cardiovascular history. Personal or family history of blood clots, prior heart attack or stroke, current or recent venous thromboembolism, uncontrolled hypertension, active hormone-sensitive cancer — each changes the risk calculation. Adverse pregnancy outcomes (Article 3 of this series) and premature or surgical menopause (Article 5) also belong in the conversation.

The indication. Hormone therapy is approved for hot flashes and night sweats, the urinary and vaginal changes of menopause, and prevention of bone loss in women at fracture risk. It is not recommended for cardiovascular prevention. If a clinician suggests hormone therapy primarily to prevent heart disease, major society guidance does not support that.

The formulation and route. Transdermal estradiol carries lower blood clot risk than oral estradiol. Micronized progesterone may have a more favorable cardiovascular and breast profile than synthetic progestins. The default choice today is often different from the conjugated equine estrogen plus medroxyprogesterone acetate used in the WHI. FDA-approved preparations are the right starting point; compounded bioidentical preparations are not.

A reassessment plan. Hormone therapy is not a single decision. Symptoms evolve, the cardiovascular risk profile changes with age, and the indication for continuing should be revisited periodically — typically at least annually, with closer attention as age approaches 60 and 65.

The Bottom Line

For a healthy woman under 60 or within 10 years of menopause, with bothersome menopausal symptoms or high fracture risk and no contraindications, hormone therapy is a reasonable treatment for those indications. The cardiovascular risk is small in this window. The cardiovascular benefit, if any, is suggestive but not strong enough to call hormone therapy cardioprotective. The fear of hormone therapy that dominated the post-2002 era was disproportionate for this group, and the women who went untreated for menopausal symptoms during those two decades paid a real cost — measured in disrupted sleep, disrupted work, disrupted relationships, and disrupted lives — for a misreading of the data that the field has now substantially corrected.

That correction does not make hormone therapy safe for everyone in the favorable window. Small but real increases in blood clot risk remain, particularly with oral preparations. Combined estrogen-plus-progestin therapy is associated with a small increased risk of breast cancer with longer duration of use. The right framing is “reasonable treatment for an approved indication when contraindications are absent and the individualized risk assessment supports it” — not “safe by default.”

For a woman starting hormone therapy more than 10 years after menopause or after age 60, the picture is different. Absolute risks of coronary heart disease, stroke, and blood clots are higher. There is no offsetting cardiovascular benefit. Hormone therapy is not categorically forbidden, but the decision requires individualized care and closer attention to risk.

For a woman with primary ovarian insufficiency, premature menopause, or early menopause, hormone therapy until at least the average age of natural menopause is generally recommended to offset the cardiovascular and bone consequences of prolonged early estrogen deficiency, unless there is a specific contraindication.

For every group, the consensus is consistent: hormone therapy is treatment for menopausal symptoms or bone protection. It is not a heart disease prevention strategy. The conventional cardiovascular prevention measures — blood pressure, cholesterol, glucose, weight, physical activity, diet, smoking — are what reduces heart attacks and strokes. Hormone therapy started in the favorable window does not undermine those measures; it does not replace them either.

And one more thing: if a clinician or marketer suggests that a compounded “bioidentical” preparation is safer or more natural than FDA-approved hormone therapy, the major society guidance disagrees. An FDA-approved bioidentical preparation — estradiol patch, gel, ring, or oral micronized progesterone — provides the same active hormone with manufacturing oversight and clinical study behind it. The compounded versions do not.

The right hormone therapy decision for any individual woman depends on her age, her time since menopause, her cardiovascular and breast cancer risk profile, her symptom burden, and her own preferences. The conversation should be specific. The reassurance should be specific. The framework above is what allows both.

Next: Article 7 covers ischemia with no obstructive coronary artery disease (INOCA) — the syndrome of cardiac chest pain in women whose coronary angiography shows no significant obstruction, why it has been under-recognized, and what the contemporary diagnostic and treatment evidence supports.

Key Terms

Bioidentical hormones: A term referring to hormone preparations chemically identical to those produced endogenously. FDA-approved bioidentical preparations exist (estradiol patches and gels, oral micronized progesterone capsules) and are appropriate when an estradiol or micronized progesterone formulation is preferred. Compounded bioidentical preparations from compounding pharmacies are a separate category, not subject to the same regulatory oversight, and not supported by major society guidance.

Combined hormone therapy: Hormone therapy that includes both estrogen and a progestin (or progesterone), used in women with an intact uterus to prevent endometrial hyperplasia.

Conjugated equine estrogens (CEE): A formulation of estrogens derived from pregnant mare urine. The estrogen formulation used in both Women’s Health Initiative hormone therapy trials.

Data and Safety Monitoring Board (DSMB): An independent committee charged with monitoring an ongoing clinical trial for participant safety, including the authority to halt the trial if accumulating evidence indicates that the risk-benefit balance has shifted unfavorably.

Early versus Late Intervention Trial with Estradiol (ELITE): A 2016 randomized controlled trial of 643 healthy postmenopausal women that tested the timing hypothesis by stratifying participants by time since menopause and randomizing within each stratum to oral 17β-estradiol or placebo. Demonstrated differential effects on subclinical atherosclerosis progression by timing of initiation.

Estrogen therapy (ET): Hormone therapy with estrogen alone, used in women who have had a hysterectomy.

Genitourinary syndrome of menopause (GSM): Vaginal dryness, urinary symptoms, and related changes attributable to estrogen deficiency in postmenopausal women. An FDA-approved indication for both systemic and local vaginal hormone therapy.

Hazard ratio (HR): A measure used to compare the rate of an event between two groups. An HR of 1.0 means equal rates; above 1.0 means higher rates in the treatment group; below 1.0 means lower rates. A 95% confidence interval that crosses 1.0 indicates the difference is not statistically significant.

Kronos Early Estrogen Prevention Study (KEEPS): A randomized controlled trial of 727 healthy postmenopausal women within three years of menopause that compared oral conjugated equine estrogen, transdermal estradiol, and placebo over four years. Found no significant effect on carotid intima-media thickness progression in either hormone therapy arm.

Medroxyprogesterone acetate (MPA): A synthetic progestin used in the combined estrogen-plus-progestin arm of the Women’s Health Initiative.

Micronized progesterone: Bioidentical progesterone formulated for oral absorption. May have a more favorable cardiovascular and breast profile than synthetic progestins, though the data are stronger for surrogate markers than for clinical events.

Menopause Society (formerly North American Menopause Society, NAMS): The leading professional society in North America focused on menopause. Its 2022 hormone therapy position statement (published under the NAMS name; the society has since rebranded to The Menopause Society) is the most current major society synthesis on hormone therapy in the United States.

Timing hypothesis: The hypothesis that the cardiovascular effects of menopausal hormone therapy depend on the timing of initiation relative to menopause, with more favorable effects when initiated near menopause and less favorable effects when initiated more than ten years after menopause.

Vasomotor symptoms (VMS): Hot flashes and night sweats. The most common reason women initiate menopausal hormone therapy and the primary FDA-approved systemic indication.

Women’s Health Initiative (WHI): A series of large randomized trials and observational studies of postmenopausal women’s health, including randomized trials of estrogen plus progestin (n=16,608) and estrogen alone (n=10,739) for primary prevention. The 2002 publication of the initial WHI hormone therapy findings fundamentally changed clinical practice.

References

1. Rossouw JE, Anderson GL, Prentice RL, et al; Writing Group for the Women’s Health Initiative Investigators. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women’s Health Initiative randomized controlled trial. JAMA. 2002;288(3):321–333.
2. Manson JE, Hsia J, Johnson KC, et al; Women’s Health Initiative Investigators. Estrogen plus progestin and the risk of coronary heart disease. N Engl J Med. 2003;349(6):523–534.
3. Majumdar SR, Almasi EA, Stafford RS. Promotion and prescribing of hormone therapy after report of harm by the Women’s Health Initiative. JAMA. 2004;292(16):1983–1988.
4. Rossouw JE, Prentice RL, Manson JE, et al. Postmenopausal hormone therapy and risk of cardiovascular disease by age and years since menopause. JAMA. 2007;297(13):1465–1477.
5. Hodis HN, Mack WJ, Henderson VW, et al. Vascular effects of early versus late postmenopausal treatment with estradiol. N Engl J Med. 2016;374(13):1221–1231.
6. Manson JE, Aragaki AK, Rossouw JE, et al; WHI Investigators. Menopausal hormone therapy and long-term all-cause and cause-specific mortality: the Women’s Health Initiative randomized trials. JAMA. 2017;318(10):927–938.
7. The 2022 Hormone Therapy Position Statement of The North American Menopause Society Advisory Panel. The 2022 hormone therapy position statement of The North American Menopause Society. Menopause.2022;29(7):767–794.
8. American College of Obstetricians and Gynecologists Committee on Gynecologic Practice. Committee Opinion No. 698: Hormone Therapy in Primary Ovarian Insufficiency. Obstet Gynecol. 2017;129(5):e134–e141.
9. Harman SM, Black DM, Naftolin F, et al. Arterial imaging outcomes and cardiovascular risk factors in recently menopausal women: a randomized trial. Ann Intern Med. 2014;161(4):249–260.
10. US Preventive Services Task Force. Hormone therapy for the primary prevention of chronic conditions in postmenopausal persons: US Preventive Services Task Force recommendation statement. JAMA.2022;328(17):1740–1746.
11. Arnett DK, Blumenthal RS, Albert MA, et al. 2019 ACC/AHA guideline on the primary prevention of cardiovascular disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. J Am Coll Cardiol. 2019;74(10):e177–e232.