Is hormone therapy safe?

For most healthy women under 60, or within 10 years of menopause, the benefits of hormone therapy typically outweigh the risks. Modern evidence — which revised the early over-interpretation of the Women's Health Initiative trial — supports HRT as safe and effective for this group. Risks depend on the formulation, route, dose, duration, and individual health history. Transdermal oestrogen carries lower clot risk than oral preparations. Decisions should be made individually with your doctor.

Does HRT cause breast cancer?

The picture is more nuanced than early headlines suggested. Combined oestrogen-progestogen therapy (EPT) is associated with a small increase in breast cancer risk with longer-term use — approximately equivalent to drinking one or two alcoholic drinks per day. Oestrogen-only therapy (for women after hysterectomy) is associated with neutral or even slightly reduced risk in some analyses. The absolute risk increase is small for most women in the first 5–7 years, and benefits often outweigh this risk for women with moderate-to-severe symptoms.

Does HRT cause blood clots?

Oral oestrogen is associated with a small increase in venous thromboembolism (VTE) risk. Transdermal oestrogen (patches, gels, sprays) does not appear to carry this risk at standard doses and is preferred for women with VTE risk factors. If you have a personal or family history of DVT or pulmonary embolism, transdermal delivery is the preferred route.

Can HRT protect my heart?

The relationship between HRT and cardiovascular disease is strongly influenced by timing. Starting HRT within 10 years of menopause or before age 60 — the 'timing hypothesis' or 'window of opportunity' — is associated with cardiovascular benefit or neutrality in most analyses. Starting HRT more than 10 years after menopause in older women is associated with possible harm. HRT is not prescribed for primary cardiovascular prevention, but it does not worsen cardiovascular outcomes when started appropriately.

How long can I take HRT?

There is no fixed maximum duration. Most guidelines recommend annual review of symptoms, risks, and the decision to continue. Many women use HRT for 3–7 years for symptom management, while women with early menopause or premature ovarian insufficiency may use it until the natural age of menopause (51–52 years). Duration should be individualised based on symptoms, risks, and personal priorities.

Hormone Therapy for Menopause: Benefits, Risks, and Who It Suits

What Is Hormone Therapy?

Hormone therapy — referred to as HRT (hormone replacement therapy) or MHT (menopausal hormone therapy) — involves replacing the oestrogen (and usually progestogen) that the ovaries stop producing at menopause. It is the most effective treatment for menopausal symptoms and has additional benefits for bone health and, when started early, possibly cardiovascular health.

For most healthy women under 60 or within 10 years of their final period, benefits typically outweigh risks. The evidence base for this has strengthened considerably since the early 2000s, when an over-interpretation of the Women’s Health Initiative (WHI) trial led to widespread fear and underprescription that persisted for two decades.

Key Points

HRT is the most effective treatment for vasomotor symptoms (hot flushes, night sweats) — reducing frequency by 70–90%.
Benefits also include improved sleep, mood, genitourinary health, and bone protection.
Risks depend on the formulation (oestrogen-only vs combined), route (oral vs transdermal), dose, duration, and individual health history.
Transdermal oestrogen carries lower VTE (clot) risk than oral preparations.
The “timing hypothesis” — starting HRT early in the transition — is important for cardiovascular outcomes.
Breast cancer risk with combined HRT is small and context-dependent; oestrogen-only therapy shows neutral or lower risk.
HRT is not a single drug — there are multiple formulations, routes, and regimens, each with a different risk-benefit profile.

Types of Hormone Therapy

Oestrogen-Only Therapy (ET)

For women who have had a hysterectomy. Oestrogen alone without progestogen. This formulation has the most favourable risk profile.

Combined Oestrogen-Progestogen Therapy (EPT)

For women with a uterus intact. Progestogen is essential to protect the endometrium from oestrogen-driven overgrowth (endometrial hyperplasia and cancer). Available as:

Sequential (cyclical) — progestogen taken for 10–14 days per month; produces a monthly withdrawal bleed; used for perimenopausal women
Continuous combined — both hormones taken daily; no scheduled bleed; used for postmenopausal women (at least 1 year after final period)

Local Vaginal Oestrogen

Low-dose oestrogen applied directly to the vagina (cream, pessary, tablet, or ring). Primarily absorbed locally with minimal systemic effect. Used for genitourinary syndrome of menopause (GSM): vaginal dryness, discomfort, painful intercourse, and recurrent UTIs. Generally safe even for women who cannot use systemic HRT — including most women with a history of breast cancer (discuss with your oncologist). Does not require progestogen.

Routes of Administration

Route	Forms	Key Consideration
Transdermal	Patches, gels, sprays	Preferred for women with VTE risk; no hepatic first-pass effect; steady hormone levels
Oral	Tablets	Convenient; hepatic first-pass increases clotting factors slightly — raises VTE risk
Vaginal	Creams, pessaries, rings	Local effect for GSM; minimal systemic absorption

For most women — and particularly for women with VTE risk factors, migraines, or liver or gallbladder conditions — transdermal oestrogen is preferred.

Benefits

Vasomotor Symptom Control

HRT reduces hot flush frequency and severity by approximately 70–90%. Night sweats diminish substantially. For women with moderate-to-severe vasomotor symptoms, this effect is life-changing. No other treatment comes close in effectiveness.

Sleep

Sleep improvements are primarily indirect — through reduction of night sweats — but oestrogen also has direct effects on sleep architecture. Progesterone (particularly micronised progesterone) has mild sedative properties that may further support sleep quality. Most women report meaningful sleep improvement within weeks of starting HRT.

Mood and Cognitive Symptoms

For women whose mood symptoms are driven by hormonal fluctuation (rather than primary depression), HRT often improves mood, irritability, and the “brain fog” characteristic of the perimenopausal transition. This effect is most pronounced when initiated during perimenopause, while hormones are still actively fluctuating.

Genitourinary Syndrome of Menopause (GSM)

Oestrogen-deficient thinning of vaginal and urethral tissue causes dryness, irritation, painful intercourse, and recurrent UTIs — symptoms that worsen over time if untreated. Local vaginal oestrogen is highly effective and safe for long-term use.

Bone Health

Oestrogen inhibits bone resorption (breakdown) by osteoclasts. Women on HRT have significantly lower rates of osteoporotic fractures while on therapy. HRT is one of the most effective interventions for preventing the accelerated bone loss of the menopausal transition, which can amount to 10–20% of bone mineral density in the decade around menopause.

This bone-protective effect wanes after HRT is stopped, but the benefit during use is well established. For women with premature ovarian insufficiency or early menopause, HRT is particularly important for long-term bone protection.

Cardiovascular Considerations and the Timing Hypothesis

The relationship between HRT and cardiovascular outcomes is strongly time-dependent — a concept known as the “window of opportunity”:

Starting HRT within 10 years of menopause or before age 60 is associated with neutral or beneficial cardiovascular outcomes in most analyses
Starting HRT more than 10 years after menopause or at an older age is associated with possible cardiovascular risk, likely because established atherosclerosis responds differently to oestrogen

HRT is not prescribed for primary cardiovascular prevention. But when started appropriately — early in the menopausal transition in a healthy woman — it does not worsen, and may modestly protect, cardiovascular health.

Risks

Venous Thromboembolism (VTE) — Blood Clots

Oral oestrogen is associated with a small increase in VTE risk (deep vein thrombosis, pulmonary embolism)
Transdermal oestrogen at standard doses does not appear to carry this risk and is the preferred route for women with any VTE risk factors
Risk is modified by: personal or family history of VTE, obesity, immobility, thrombophilia (e.g. Factor V Leiden)

If you have a history of DVT or pulmonary embolism, use transdermal oestrogen and discuss the decision carefully with your doctor.

Breast Cancer

This is the risk that most concerns women, but the picture is more nuanced than early headlines suggested:

Combined oestrogen-progestogen therapy (EPT) is associated with a small increase in breast cancer risk with longer use, particularly beyond 5–7 years
The absolute increase in risk is modest for most women — broadly comparable in magnitude to the risk from regular alcohol consumption or obesity
Oestrogen-only therapy (ET) in women who have had a hysterectomy is associated with neutral or even slightly reduced breast cancer risk in some analyses
The type of progestogen matters: micronised progesterone appears to carry a lower breast cancer risk than synthetic progestogens in observational data
Risk is modified by age, BMI, prior breast biopsies, and family history

For many women with moderate-to-severe menopausal symptoms, the quality-of-life benefit and other health gains outweigh the small increase in breast cancer risk, particularly in the first 5–7 years of use.

Stroke

Oral oestrogen is associated with a small increase in ischaemic stroke risk, largely attenuated with transdermal preparations. Risk is primarily relevant at older ages and in women with pre-existing cardiovascular risk factors.

Other Considerations

Condition	What to Know
Migraine with aura	Use transdermal oestrogen; avoid oral; discuss with GP
Liver or gallbladder disease	Use transdermal oestrogen (avoids hepatic first-pass)
Hypertension	Transdermal oestrogen preferred; monitor blood pressure
Obesity	Higher baseline VTE risk — use transdermal oestrogen
Prior VTE	Use transdermal oestrogen; may still be appropriate with haematology input

Who May Benefit

HRT is most appropriate for:

Women with moderate-to-severe vasomotor symptoms affecting quality of life
Women experiencing sleep disruption driven by night sweats
Women with genitourinary symptoms (vaginal dryness, painful intercourse, recurrent UTIs)
Women with premature ovarian insufficiency (POI) or early menopause — HRT is particularly recommended until the natural age of menopause to protect bone, heart, and brain health
Women concerned about bone loss during the transition

The benefits are greatest when initiated within 10 years of menopause or before age 60.

Who Should Approach With Caution

Discuss carefully with your doctor before starting:

Personal history of hormone-receptor-positive breast cancer (coordinate with oncologist; local vaginal oestrogen may still be appropriate)
Active or recent VTE (DVT or pulmonary embolism)
Active or recent arterial cardiovascular disease (heart attack, stroke)
Active liver disease
Unexplained vaginal bleeding (investigate cause before starting HRT)
Untreated high blood pressure (treat first, then HRT is usually appropriate)

There are no absolute contraindications to local vaginal oestrogen in most conditions — its use should be discussed individually even in women with breast cancer history.

Common Misconceptions

“HRT is only for short-term use.” There is no fixed maximum duration. Duration should be reviewed annually and based on the individual woman’s symptoms, risks, and priorities. Some women use HRT for many years; this is appropriate with proper monitoring.

“You should wait until menopause to start HRT.” HRT can be started during perimenopause when symptoms are significantly impacting quality of life. It does not need to wait until 12 months after the last period.

“HRT prevents dementia.” The evidence for cognitive protection is insufficient to recommend HRT for dementia prevention. There may be a modest window-of-opportunity effect, but this is not an established indication.

“Natural or bioidentical hormones are safer.” Compounded “bioidentical” hormones are not regulated to the same standard as pharmaceutical preparations and do not have proven safety or efficacy data. Regulated bioidentical options — such as micronised progesterone (Prometrium) and transdermal oestradiol — are the better-evidenced choice.

“If you feel well, you don’t need HRT.” Not all menopausal harm is symptomatic. Bone loss proceeds silently. Women with premature ovarian insufficiency should use HRT regardless of symptom burden.

Starting and Reviewing HRT

Initiating

A typical shared decision-making process includes:

Assess symptoms and their impact on daily life
Screen for contraindications and risk factors (cardiovascular, VTE, breast cancer history)
Choose route (prefer transdermal), type (ET vs EPT), and formulation
Review progestogen choice (micronised progesterone preferred by many guidelines for its more favourable tolerability and possibly lower breast cancer signal)
Start at the lowest effective dose and adjust after 3 months

Ongoing Review

Annual review of symptoms, risks, and the decision to continue
Blood pressure monitoring
Mammography as per national screening schedule
Discuss duration based on evolving evidence and personal circumstances

Stopping

Most women taper HRT rather than stopping abruptly, to reduce the risk of acute symptom recurrence. This can be achieved by reducing dose over 3–6 months.