Menopause Hormone Therapy: Benefits and Risks

Menopause hormone therapy (HRT) relieves hot flashes effectively, protects bone, and in women under 60 who start it close to menopause, does not increase cardiovascular risk — and may reduce it. The risks are real but depend heavily on age, timing, the type of hormones used, and personal medical history. For most healthy women in their 50s with moderate to severe menopausal symptoms, the benefits outweigh the risks. For women who are older, have a history of blood clots, or are many years past menopause, the calculus shifts.

This explainer draws on peer-reviewed research from four endocrinologists and internists listed in the Convene directory: Emily Szmuilowicz, M.D., at Northwestern Medicine, who published on cardiovascular risk in women with vasomotor symptoms and co-authored a 2025 paper in JAMA Internal Medicine on HRT and cardiovascular disease; Eliot Brinton, MD, at Intermountain Medical Center, who co-authored the landmark KEEPS cognitive and affective trial; Sundeep Khosla, M.D., at Mayo Clinic, whose foundational research established estrogen deficiency as the driver of bone loss in postmenopausal women; and Ellen Seely, MD, at Brigham and Women's Hospital and Harvard Medical School, who studied how estradiol combined with progesterone affects the blood vessels of postmenopausal women.

What hormone therapy actually does

Menopause happens when the ovaries stop producing estrogen (and, to a lesser degree, progesterone). That estrogen drop drives most of the symptoms women associate with menopause: hot flashes, night sweats, vaginal dryness, sleep disruption, and mood changes. It also accelerates bone loss and affects how blood vessels function.

Hormone therapy replaces some of that lost estrogen. Women who still have a uterus also take progesterone (or a synthetic version called progestin) to protect the uterine lining — estrogen alone raises the risk of uterine cancer if the uterus is present. Women who have had a hysterectomy can take estrogen alone.

The formulations matter. Estradiol is the main estrogen in most HRT. Progesterone can be given as micronized progesterone (closer to the body's own hormone) or as synthetic progestin. Route matters too: transdermal estrogen (patch or gel) delivers the hormone directly into the bloodstream through the skin and avoids the liver-first pass that oral estrogen undergoes, which has implications for clotting risk.

Hot flashes and sleep

The most immediate reason women seek HRT is symptom relief, and here the evidence is consistent. Hot flashes — technically called vasomotor symptoms — occur when estrogen withdrawal disrupts the body's temperature regulation. Research from Emily Szmuilowicz and colleagues has tracked the relationship between vasomotor symptoms and cardiovascular disease in postmenopausal women [2]. That work established that severe hot flashes are not just discomfort; they signal underlying vascular changes.

Hormone therapy is the most effective treatment for hot flashes. Clinical trials consistently show a 75 to 80 percent reduction in frequency compared to placebo. Low-dose oral contraceptives, antidepressants like venlafaxine, and the non-hormonal medication fezolinetant are alternatives for women who cannot or choose not to use HRT, but none match HRT's effect size.

Night sweats and sleep disruption usually improve along with hot flash control. That matters beyond comfort: fragmented sleep is associated with depression, metabolic changes, and cognitive decline.

Bone loss and fracture risk

This is one of HRT's clearest benefits. Estrogen maintains bone density by slowing the breakdown of existing bone. When estrogen drops at menopause, bone resorption outpaces formation, and bone density falls.

Research by Sundeep Khosla at Mayo Clinic provided the mechanistic foundation for this understanding. His work showed that estrogen deficiency is the primary driver of both early postmenopausal bone loss (type I osteoporosis) and the slower bone loss that continues into later life (type II osteoporosis) [4]. His subsequent work on sex steroids and skeletal biology confirmed that estrogen plays a larger role in maintaining adult bone than testosterone — in both women and men [6]. Taken together, this body of work explains why HRT is so effective at preserving bone: it restores the signal the skeleton needs to stay in balance.

HRT reduces the risk of hip fracture, vertebral fracture, and wrist fracture. For women at elevated fracture risk who are also dealing with menopausal symptoms, HRT can address both problems at once. For women whose only concern is bone health and who have no menopausal symptoms, other options (bisphosphonates, denosumab) exist and are often preferred. The landmark Lancet review on osteoporosis treatment summarizes the evidence hierarchy across drug classes [5].

Cardiovascular effects: the timing hypothesis

No aspect of HRT has generated more confusion than its cardiovascular effects. The short version: timing matters enormously.

In 2002, the Women's Health Initiative (WHI) reported that HRT increased heart disease risk, which led millions of women to stop treatment. Later analysis found that the WHI population was older (average age 63, well past menopause) and that many women already had subclinical cardiovascular disease before starting treatment. The "timing hypothesis" emerged from that reanalysis: HRT started close to menopause (within 10 years, or before age 60) appears to be cardioprotective; HRT started much later, when atherosclerosis is already established, may accelerate existing disease rather than prevent it.

Ellen Seely and colleagues contributed an important piece of this puzzle. A 1998 randomized crossover trial published in Circulation tested whether adding micronized progesterone to estradiol therapy would blunt estradiol's favorable effect on blood vessel function in postmenopausal women [7]. It did not. Micronized progesterone left estradiol's vasodilatory effect intact. That finding mattered because an earlier concern had been that the progesterone component of combined HRT was responsible for cardiovascular harm — and Seely's work helped clarify that formulation choices (specifically, using micronized progesterone rather than synthetic progestin) could preserve vascular benefit.

A 2025 analysis published in JAMA Internal Medicine, with Emily Szmuilowicz among the investigators, extended this evidence into the current era [1]. It specifically examined HRT and cardiovascular outcomes in women who had vasomotor symptoms — a group who may experience the most cardiovascular benefit from treatment, because their hot flashes reflect underlying vascular instability that estrogen directly addresses.

At a glance

Cognition and mood

The KEEPS trial (Kronos Early Estrogen Prevention Study) tested two forms of HRT versus placebo in recently postmenopausal women, with a cognitive and affective substudy. The KEEPS-Cognitive and Affective Study, published in PLoS Medicine, found that hormone therapy — whether oral or transdermal — did not improve or worsen cognitive function or mood compared to placebo in this recently postmenopausal group [3]. Eliot Brinton was among the co-investigators. This was a carefully designed trial in a population with less than three years since menopause, and its reassuring result contrasts with older data suggesting potential cognitive harm from HRT started much later in life.

The key takeaway from the KEEPS findings: starting HRT soon after menopause does not appear to harm memory or mood, and does not appear to help them either. The cognitive harms associated with HRT in some older studies likely reflect the same timing problem as the cardiovascular data — HRT started years after menopause, in older women.

Breast cancer risk

This is where the evidence is most nuanced and most personal. Combined estrogen-plus-progestin therapy is associated with a small increase in breast cancer risk. The absolute numbers matter: in the WHI, combined HRT added roughly 8 additional breast cancer cases per 10,000 women per year compared to placebo. Estrogen-only therapy (for women without a uterus) does not increase breast cancer risk and may reduce it slightly.

Duration of use matters too. Longer use carries more risk. Women with a personal history of breast cancer are generally advised against HRT. Women with a family history need individualized assessment. The type of progestogen used also appears to matter: some data suggest micronized progesterone carries less breast cancer risk than synthetic progestins, though this is not definitively established from randomized trials.

Blood clot risk

Oral estrogen increases the risk of venous thromboembolism (VTE) — blood clots in the leg or lung. Transdermal estrogen, absorbed through the skin rather than the gut, appears to avoid this effect. The current leading explanation is that oral estrogen is processed by the liver, where it triggers clotting-factor changes that transdermal estrogen does not. For women with a personal or family history of blood clots, transdermal delivery is generally preferred when HRT is being considered.

Who benefits most from HRT

The clearest candidate is a woman under 60, within 10 years of menopause, with moderate to severe hot flashes, no personal history of breast cancer or blood clots, and no major cardiovascular disease already established. In that group, HRT reliably reduces symptoms, protects bone, and likely carries favorable or neutral cardiovascular effects.

Women with premature menopause (before age 40) or early menopause (before 45) are a special case. For them, HRT is not just symptom management — it is replacing hormones the body should naturally have had for another decade or more, and most guidelines recommend HRT until the typical age of menopause unless there is a specific contraindication.

Women who are significantly older, have established cardiovascular disease, or are many years past menopause without having used HRT before may face a less favorable balance of benefits and risks. The same is true for women with prior blood clots, active liver disease, or estrogen-sensitive cancers.

Questions to ask your doctor

• How severe are my symptoms, and how much are they affecting my sleep, mood, and quality of life?
• What is my personal risk for breast cancer, cardiovascular disease, and blood clots?
• How long ago did I go through menopause, and does that affect whether HRT is appropriate for me?
• Should I consider transdermal estrogen rather than oral, given my clot risk?
• What type of progesterone would you recommend, and why?
• If I decide to try HRT, how long should I plan to use it, and how will we reassess?
• If HRT is not right for me, what non-hormonal options would you consider for my specific symptoms?

The bottom line

Menopause hormone therapy is not a one-size-fits-all decision. For women in their 50s with significant symptoms who start treatment close to menopause, HRT is highly effective for hot flashes, clearly beneficial for bone, and probably favorable — or at least neutral — for cardiovascular health. The breast cancer risk from combined HRT is real but small, and formulation choices (micronized progesterone, transdermal estrogen) can reduce several of the risks most often cited against it. The women for whom HRT is most clearly not appropriate are those significantly past menopause, with established cardiovascular disease, prior blood clots, or estrogen-sensitive cancer history. For everyone else, the conversation with an endocrinologist or internist who knows your personal history is the right starting point.