HRT Explained: Benefits, Risks, and Options

Introduction

Hormone replacement therapy (HRT) — also known as menopausal hormone therapy (MHT) — is one of the most effective and most misunderstood treatments in women's health.

In the early 2000s, the Women's Health Initiative (WHI) study caused widespread alarm about HRT's risks, leading millions of women to stop treatment. Since then, 20+ years of follow-up research has substantially revised our understanding — clarifying which risks are real, which were overstated, and who benefits most.

This guide gives you the updated, evidence-based picture: what HRT is, what it does, what the real risks are for different groups of women, and what your options are.

What Is HRT?

HRT replaces the oestrogen (and usually progesterone) that the ovaries stop producing during and after menopause.

Why oestrogen matters:

Oestrogen receptors exist throughout the body — in the brain, bones, blood vessels, heart, vagina, urinary tract, skin, and joints. Oestrogen's withdrawal affects all of these systems, driving the symptoms of menopause. Replacing it addresses symptoms at their hormonal root.

Why progesterone is needed (for most women):

Oestrogen alone can stimulate growth of the uterine lining (endometrium), increasing the risk of endometrial cancer. Women who still have their uterus need progesterone (or a synthetic progestogen) to protect the endometrium.

Women who have had a hysterectomy (uterus removed) can take oestrogen alone.

What Does HRT Treat?

HRT is the most effective treatment for:

Vasomotor Symptoms (Hot Flushes and Night Sweats)

HRT reduces the frequency and severity of hot flushes by approximately 75–90%, making it substantially more effective than any non-hormonal alternative.

Sleep Disruption

By reducing night sweats and directly modulating sleep-regulating pathways, HRT improves sleep quality in the majority of symptomatic women.

Mood and Psychological Symptoms

Anxiety, irritability, and low mood related to the menopause transition typically improve with HRT, particularly in the perimenopause phase. HRT also reduces the risk of menopausal depression.

Genitourinary Syndrome of Menopause (GSM)

Vaginal dryness, discomfort during sex, urinary urgency, and recurrent UTIs are all driven by oestrogen deficiency in local tissues. HRT (particularly local vaginal oestrogen) is highly effective and is the first-line recommended treatment.

Bone Protection

Oestrogen is essential for bone remodelling. HRT prevents the accelerated bone loss of the menopause transition and significantly reduces fracture risk. It is a recognised treatment for osteoporosis prevention.

Cognitive Function

Emerging evidence suggests that oestrogen may help maintain cognitive function and reduce the risk of Alzheimer's disease when started near the time of menopause (the "timing hypothesis" or "critical window"). Studies of women who start HRT more than 10 years after menopause show less clear benefit.

Types of HRT

By Oestrogen Route

Oral HRT (tablets):

• Convenient, widely available, well-studied
• First-pass liver metabolism increases some clotting factors — slightly elevated VTE (blood clot) risk compared to transdermal

Transdermal HRT (patches, gels, sprays):

• Bypasses liver first-pass metabolism
• No increased VTE risk — important for women with higher baseline clotting risk
• Patches changed every 1–3 days; gels applied daily

Vaginal oestrogen (cream, ring, pessary, tablet):

• Local treatment for GSM
• Very low systemic absorption
• Considered safe even for women who cannot use systemic HRT (e.g., some breast cancer survivors — discuss with oncologist)

By Progesterone Type

Micronised progesterone (body-identical, e.g., Utrogestan):

• Most closely resembles natural progesterone
• Oral (also used vaginally)
• Associated with better tolerability and lower breast cancer risk than synthetic progestogens in observational studies

Synthetic progestogens (progestins, e.g., norethisterone, medroxyprogesterone acetate):

• Widely used in combination HRT pills
• The WHI study used medroxyprogesterone acetate, which had less favourable findings than micronised progesterone

Levonorgestrel IUS (hormonal coil, e.g., Mirena):

• Provides endometrial protection locally
• Allows systemic oestrogen (patch or gel) to be combined with local progestogen — minimising systemic progestogen exposure

Combined vs Sequential

Combined (continuous) HRT: Oestrogen and progesterone taken daily. Usually used by women who are at least 12 months past their last period. Aim: no monthly bleed.

Sequential (cyclical) HRT: Oestrogen taken continuously; progesterone added for 12–14 days per month. Causes a monthly withdrawal bleed. Usually used in perimenopause.

The Real Risk Picture: What the Evidence Now Shows

Breast Cancer Risk

This is the most discussed risk — and the one most distorted by initial WHI findings.

Current understanding:

• Oestrogen alone (for women without a uterus): Does NOT appear to increase breast cancer risk, and may even slightly reduce it, based on the WHI oestrogen-alone trial results (PMID: 19996755)
• Combined oestrogen + synthetic progestogen: Associated with a small increased risk of breast cancer, particularly with longer duration of use. The absolute risk increase is approximately 4–8 extra cases per 1,000 women over 5 years — comparable to the risk associated with drinking one glass of wine per day
• Oestrogen + micronised progesterone: Observational data from the ESHRE suggests lower breast cancer risk than synthetic progestogens (e.g., the Fournier et al. studies from the E3N cohort)
• Transdermal route: Appears to have lower breast cancer risk than oral progestins in some observational studies

In context: The absolute risk increase from combined HRT is small, particularly for women who start HRT before age 60 or within 10 years of menopause.

Venous Thromboembolism (Blood Clots)

• Oral HRT is associated with a small increased VTE risk (approximately doubled from a low baseline risk)
• Transdermal HRT does NOT increase VTE risk — this is now well-established across multiple studies (PMID: 15867640)
• Women with personal or family history of VTE should use transdermal oestrogen and discuss options with their doctor

Cardiovascular Disease

This was the other major WHI concern. Updated analysis and subsequent research reveals:

• The timing hypothesis is now well-established: HRT started within 10 years of menopause or before age 60 is associated with reduced cardiovascular disease risk
• HRT started late (over 10 years post-menopause) may increase cardiovascular risk in some groups
• The 2023 international menopause society guidelines confirm a favourable cardiovascular benefit for HRT in younger menopausal women

Endometrial Cancer

Oestrogen alone increases endometrial cancer risk. This is effectively eliminated with adequate progesterone co-administration. This is why progesterone is always prescribed for women with an intact uterus.

Who Should and Shouldn't Use HRT?

HRT is generally appropriate for:

• Symptomatic women under 60 or within 10 years of menopause
• Women with premature ovarian insufficiency (strongly recommended until average age of menopause)
• Women with significant GSM
• Women at risk of or with established osteoporosis (as part of management)

HRT requires careful individual assessment for:

• Personal or strong family history of breast cancer
• History of VTE (transdermal route preferred)
• History of cardiovascular disease (timing and route matter)
• Active liver disease
• Undiagnosed vaginal bleeding (must be investigated first)

HRT is contraindicated for:

• Current, suspected, or recent oestrogen-sensitive cancer (e.g., some breast cancers)
• Active thromboembolism
• Unexplained vaginal bleeding

Starting HRT in Singapore

HRT is available in Singapore by prescription from licensed doctors. Consultation at a women's health clinic — including a full history, symptom assessment, and consideration of individual risk factors — is required before initiating treatment.

Follow-up is typically at 3 months after starting, then annually to review tolerability, effectiveness, and ongoing risk-benefit balance.

The Bottom Line

HRT is the most effective treatment available for menopausal symptoms — and for most healthy women under 60 or within 10 years of menopause, the evidence strongly supports its use when symptoms affect quality of life.

The risks are real but modest, and depend heavily on the type, route, timing, and duration of HRT. The conversation has evolved significantly since the early 2000s.

You deserve an informed discussion — not alarm, not dismissal.

Want to understand if HRT is right for you? Speak with a Zoey doctor for a personalised, evidence-based assessment.