What is hormone therapy (HRT)?

Summary

Hormone therapy (HRT; increasingly called "menopausal hormone therapy", MHT, in the guidelines) means supplying from outside the estrogen your body no longer makes, together with a progestogen in women who still have a womb. It is the most effective treatment known for hot flashes and night sweats; it prevents bone loss and relieves vaginal dryness. It carries risks, but those risks vary considerably with the type of treatment, the route, the duration and — above all — when it is started. In 2002 the first results of a large trial all but wiped HRT out; the data of the following twenty years corrected the picture substantially. Today's consensus: in a suitable candidate under 60, or within the first 10 years after the final period, started for symptoms, the benefits of HRT generally outweigh the risks. Whether to start is a personal decision, and it is made only with your doctor.

What is happening?

HRT is not one medicine but a family of them. It has two main components:

• Estrogen: The active ingredient that actually relieves symptoms. It can be taken as a tablet, through the skin (gel, spray, patch), or vaginally only. The route changes the risk profile (see the separate article on HRT types and forms).

• Progestogen: If estrogen is given on its own to a woman who still has her womb, the lining of the womb thickens and the risk of womb cancer rises. A progestogen prevents this. It is usually not needed in women whose womb has been removed. A progestogen can be taken "every day" or "on certain days of the month"; the second arrangement produces a regular withdrawal bleed.

The aim of treatment is not to raise hormones to "youthful levels" but to find the lowest effective level that controls symptoms. Dose, form and duration are decided for the individual, and only your doctor makes that decision.

What do we know?

• Benefits: HRT is the most effective treatment for hot flashes and night sweats, reducing symptoms substantially. It preserves bone density and lowers fracture risk. It relieves vaginal dryness and the painful sex that goes with it. Positive effects on sleep and mood in perimenopause have also been shown; it is not, however, a first-line treatment for depression ^{1 2}.

• Timing is decisive: Re-analysis of the WHI trial by age showed that risk varies with the age at which treatment starts. In women starting between 50 and 59, or within the first 10 years after menopause, no increase in cardiovascular or overall mortality risk was seen; over 18 years of follow-up, total mortality among HRT users did not differ from non-users ³. This is called the "timing hypothesis", and it is the foundation of today's guidelines ^{1 10}.

• Breast cancer, the most asked-about risk: When estrogen and a progestogen are used together, risk rises by a small amount after roughly 3 to 5 years; in WHI that increase amounted to fewer than 1 extra case per 1,000 women per year. In women whose womb had been removed, estrogen alone did not show this increase; over long follow-up, both the incidence of breast cancer and death from it were lower ⁴. A large meta-analysis reported some increase with all systemic types other than vaginal estrogen, and showed that the risk rises with duration of use ⁵. For comparison, the risk is of a similar size to the increase that comes with obesity, or with two alcoholic drinks a day ².

• Clots (venous thromboembolism): Estrogen taken by mouth increases the risk of clots. Estrogen applied through the skin has not shown that increase in large observational data ⁶. NICE therefore recommends the transdermal route for women at higher risk of clots ².

• Stroke: There is a small increase with oral estrogen. Under 60 the absolute risk is low. No increase has been shown with low-dose transdermal use ¹.

• Regulators have updated the picture too: In November 2025 the US FDA began the process of removing the "boxed warnings" about cardiovascular disease, breast cancer and dementia from systemic and vaginal estrogen menopause products; the womb-cancer warning was kept on estrogen-only systemic products. The reasoning is the benefit–risk balance seen when treatment is started under 60 or within the first 10 years after menopause ⁹.

• HRT is not given to prevent chronic disease: Starting it in a woman without symptoms in order to "protect the heart" or "slow aging" is not recommended; the evidence does not support it ⁷. In women at high fracture risk who are under 60 or within the first 10 years after menopause, however, HRT is one of the options a doctor may consider for bone protection even without symptoms (see the separate article on bone health).

• Early menopause and POI are a different matter: In women with ovarian insufficiency under 40, or menopause under 45, HRT is recommended at least until the average age of menopause, whether or not there are symptoms; here the aim is to replace a missing hormone, and the benefit–risk balance is entirely different ^{8 2}.

• There is no arbitrary upper limit on duration: The "five years maximum" rule has been removed from the guidelines. The decision is renewed each year, weighing symptoms, age and health together ¹.

What does this give you?

• HRT may or may not be an option for you: Before starting, your doctor looks at your age, how long it has been since menopause, your breast and clot history, your blood pressure and liver, and whether there has been any unexplained bleeding. Active breast cancer, a past clot or stroke, and unexplained vaginal bleeding generally rule HRT out or call for special assessment.

• Don't hear the word "risky" on its own: Risk is shaped by the answers to which hormone, which route, at what age. The profile of a healthy 52-year-old using estrogen through the skin is not the same as that of a 68-year-old starting tablets for the first time.

• What to expect: Improvement in hot flashes usually begins within weeks. Breast tenderness, bloating or irregular spotting can occur in the first months; these are often temporary, but they should be reported to your doctor.

• Follow-up is part of the treatment: Guidelines recommend a review about 3 months after starting and annually thereafter. The symptom and regimen records you keep in Lumia are the most concrete input to those conversations; Lumia only records what you enter, and never recommends a dose.

Sources

1. The Menopause Society. The 2022 Hormone Therapy Position Statement. Menopause. 2022;29(7):767-794.
2. NICE. Menopause: identification and management (NG23). 2015; updated November 2024.
3. Manson JE, et al. Menopausal hormone therapy and long-term all-cause and cause-specific mortality. JAMA. 2017;318(10):927-938.
4. Chlebowski RT, et al. Association of menopausal hormone therapy with breast cancer incidence and mortality. JAMA. 2020;324(4):369-380.
5. Collaborative Group on Hormonal Factors in Breast Cancer. Type and timing of menopausal hormone therapy and breast cancer risk. Lancet. 2019;394(10204):1159-1168.
6. Vinogradova Y, et al. Use of hormone replacement therapy and risk of venous thromboembolism. BMJ. 2019;364:k4810.
7. US Preventive Services Task Force. Hormone therapy for the primary prevention of chronic conditions. JAMA. 2022;328(17):1740-1746.
8. ESHRE/ASRM/CREWHIRL/IMS Guideline Group on POI. Evidence-based guideline: premature ovarian insufficiency. Climacteric. 2024;27(6):510-520.
9. Makary MA, et al. Updated labeling for menopausal hormone therapy. JAMA. 2025; doi:10.1001/jama.2025.22259. FDA press release, 10 November 2025.
10. Panay N, et al. International Menopause Society (IMS) recommendations and key messages on women's midlife health and menopause. Climacteric. 2025;28(6):634-656.

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