HRT Explained: Menopause Hormone Therapy and the 2025 Paradigm Shift
WELLNESS Guide

HRT Explained: Menopause Hormone Therapy and the 2025 Paradigm Shift

By Polly · · HRT (Hormone Replacement Therapy)

HRT (Hormone Replacement Therapy)

HRT (Hormone Replacement Therapy), increasingly referred to as MHT (Menopausal Hormone Therapy), replaces estrogen and progesterone that decline around menopause. The 2002 WHI study triggered two decades of caution, but the FDA’s November 2025 removal of the black-box warning signals a pivotal shift in how the evidence is now understood.

  • Classification: hormone
  • Related: estrogen, progesterone, menopause, hot flash, osteoporosis, FSH, MHT

What HRT Is

HRT delivers estrogen, progesterone, or both through prescription formulations to compensate for the hormonal decline that occurs at menopause. The name MHT (Menopausal Hormone Therapy) has become more common in clinical literature as a more precise term.

The formulation depends on whether the uterus is present. Women who still have a uterus require a progestogen (progesterone or a synthetic progestin) alongside estrogen, because unopposed estrogen stimulates endometrial growth. Women who have undergone hysterectomy can use estrogen alone.

The two main estrogen types in use are:

Bioidentical estradiol (E2): structurally identical to the body’s own estrogen. Most transdermal formulations use this form.

Conjugated equine estrogen (CEE): a mixture derived from horse urine, used in the original WHI trial and still available in oral form.

Progestogens also fall into two categories with meaningfully different safety profiles: bioidentical progesterone and synthetic progestins (medroxyprogesterone acetate, norethindrone, drospirenone). The distinction between these two categories has become increasingly relevant in risk discussions.

How Delivery Routes Differ

Oral tablets

The most familiar route. Convenient, but oral estrogen undergoes first-pass metabolism in the liver, which increases production of clotting proteins and raises the risk of venous thromboembolism compared to transdermal delivery.

Transdermal patch

Estradiol absorbed directly through the skin into the bloodstream, bypassing the liver. The thrombotic risk with transdermal estradiol is comparable to placebo in most data. Patches are applied to the abdomen, thigh, or buttock and changed every 3 to 7 days depending on the product.

Gel

Estradiol gel rubbed onto the skin shares the same absorption pathway as patches. Useful when skin adhesive irritation from patches is a problem.

Vaginal preparations

Vaginal creams, tablets, suppositories, and rings deliver estrogen locally to the vaginal mucosa with minimal systemic absorption. Used primarily for genitourinary syndrome of menopause (vaginal dryness, dyspareunia, recurrent urinary tract infections). Appropriate when systemic symptoms are not the primary concern.

Subcutaneous pellets

Crystalline hormone pellets implanted under the skin that release slowly over 3 to 6 months. No FDA-approved pellet product exists. Offered at compounding pharmacies and specialty menopause clinics. Limitations include difficulty adjusting dosing and inability to remove once placed.

Why the First 10 Years After Menopause Matter

The timing of when HRT begins substantially affects outcomes. This is called the “window of opportunity” hypothesis, or the timing hypothesis.

In the years immediately after menopause, vascular endothelial cells and cardiac tissue still have abundant estrogen receptors. When estrogen is replenished in this window, it can preserve arterial elasticity, suppress atherosclerosis, and improve lipid profiles. These cardiovascular protective effects are consistently seen when HRT is started before significant atherosclerotic disease has developed.

After more than 10 years without estrogen, existing arterial plaques may become destabilized by sudden reintroduction of estrogen, increasing the risk of cardiovascular events rather than reducing them.

The same window applies to bone density. The fastest period of bone loss occurs in the first 1 to 2 years after menopause. Starting HRT early can blunt this loss; starting after substantial bone mineral density decline cannot fully reverse what has already been lost.

A 2022 cohort analysis published in Menopause found that women who began HRT before age 60 or within 10 years of menopause had measurable reductions in cardiovascular risk, while those who started outside this window did not.

The Long Shadow of the 2002 WHI Trial

The Women’s Health Initiative trial, funded by the National Heart, Lung, and Blood Institute, enrolled 16,608 postmenopausal women in a randomized comparison of oral conjugated equine estrogen combined with medroxyprogesterone acetate versus placebo. The trial was stopped early at 5.2 years.

The HRT group showed elevated risks for breast cancer (26%), heart attack (29%), stroke (41%), and pulmonary embolism (113%). The results led to widespread prescription declines worldwide and prompted the FDA to add a black-box warning to all estrogen products.

Subsequent re-analysis revealed significant limitations.

The average age of participants was 63. Most were more than 10 years past menopause, placing them outside the timing window where cardiovascular benefit is expected. Applying findings from this cohort to women in early menopause overstated the risk for the most likely HRT candidates.

The progestogen used (MPA, medroxyprogesterone acetate) is a synthetic progestin. Later data, notably the French E3N cohort of 83,000 women, found no increase in breast cancer risk with the combination of transdermal estradiol and bioidentical progesterone, the formulation most used in contemporary practice.

By 2017, the North American Menopause Society (NAMS) had formally stated that for women under 60 or within 10 years of menopause, the benefits of HRT outweigh the risks.

What the 2025 FDA Black-Box Removal Means

In November 2025, the FDA removed the black-box warning from transdermal estrogen products. This was the first structural revision to estrogen labeling since 2003.

The decision drew on more than two decades of post-WHI research. Transdermal estradiol showed no statistically significant increase in thrombotic risk compared to placebo. Cardiovascular harm was not demonstrated in women under 60 or within 10 years of menopause onset. The cumulative data supported distinguishing transdermal estradiol from the oral CEE formulation used in the WHI trial.

The Korean Society of Menopause updated its clinical guidance in the same period, formalizing a preference for transdermal over oral estrogen and affirming that the timing hypothesis, previously a matter of debate, is now the clinical standard.

Two practical shifts follow from this. Prescribers face less labeling-driven hesitation when offering HRT to appropriate candidates. And patients who had internalized a years-long message that HRT was inherently high-risk now have a more accurate basis for their decision.

The change applies specifically to transdermal estrogen. Oral estrogen retains warnings related to thrombotic risk.

Who Benefits and Who Should Not Use HRT

Most appropriate candidates

  • Under 60 years of age, or within 10 years of menopause
  • Moderate to severe vasomotor symptoms (hot flashes, night sweats, sleep disruption)
  • Early or surgical menopause (premature ovarian insufficiency, bilateral oophorectomy)
  • High risk for osteoporosis (low T-score, prior fragility fracture)
  • Genitourinary syndrome of menopause (vaginal dryness, dyspareunia, recurrent UTIs)

Absolute contraindications

  • Active breast cancer or history of estrogen receptor-positive breast cancer
  • Unexplained uterine bleeding
  • Active venous thromboembolism (DVT, pulmonary embolism)
  • Active arterial thromboembolic disease (recent heart attack or stroke)
  • Uncontrolled liver disease

Situations requiring careful individual assessment

  • Family history of breast cancer (evaluate individual risk profile: BRCA status, breast density, obesity, alcohol use)
  • Personal history of venous thromboembolism (transdermal route preferred; oral route avoided)
  • Hypertriglyceridemia (oral estrogen increases triglycerides; transdermal does not)
  • History of endometriosis or endometrial hyperplasia

Non-Hormonal Alternatives

For those who cannot or choose not to use HRT.

Fezolinetant (Veozah)

FDA approved in 2023. A neurokinin B receptor antagonist that acts on KNDy neurons in the hypothalamus to suppress vasomotor symptoms without estrogen. Clinical trials showed roughly 55 to 65 percent reduction in hot flash frequency versus placebo. Available for women with breast cancer history.

SSRIs and SNRIs

Paroxetine mesylate (Brisdelle, 7.5 mg) is the only FDA-approved non-hormonal option specifically for hot flashes. Venlafaxine and desvenlafaxine are used off-label. Particularly useful when mood disturbance or anxiety accompanies vasomotor symptoms.

Gabapentin

Reduces night sweats and sleep disruption. Sedation is the main dose-limiting side effect.

Phytoestrogens

Soy isoflavones, S-equol, and red clover extracts bind estrogen receptors weakly. Effect sizes are smaller than HRT and individual response varies widely. Caution is warranted in those with estrogen receptor-positive breast cancer history.

Clinical Practice in South Korea

HRT prescribing rates in South Korea remain lower than in Europe and North America. Data from the Health Insurance Review and Assessment Service estimate that roughly 3 to 5 percent of menopausal women are currently using HRT.

The Korean Society of Menopause formally endorsed the position that HRT benefits outweigh risks in healthy women under 60 or within 10 years of menopause, consistent with international societies. Following the 2025 FDA revision, transdermal estradiol is now specifically recommended as the preferred route in updated Korean clinical guidance.

The most commonly prescribed regimen in Korea remains oral combined preparations (estradiol with drospirenone or norgestrel). Transdermal patches and gels are growing in use as their thrombotic safety advantage gains recognition.

Initial evaluation before prescribing typically includes FSH and estradiol levels, endometrial thickness by ultrasound, mammography, blood pressure, and a lipid panel.

Starting, Stopping, and Monitoring

When to consider starting

Vasomotor symptoms (hot flashes, night sweats, sleep disruption) or genitourinary symptoms that affect daily function are the primary indicators. FSH above 40 mIU/mL and estradiol below 20 pg/mL support a diagnosis of menopause.

Monitoring schedule

  • 3-month follow-up: symptom response, side effects (breast tenderness, headache, spotting, fluid retention)
  • Every 6 to 12 months: mammography, endometrial ultrasound if on cyclic progestogen, blood pressure, lipid panel

How to stop

Abrupt discontinuation can cause rebound vasomotor symptoms. Gradual dose reduction over 3 to 6 months is standard.

Duration of use

The “5-year limit” that dominated clinical practice after 2002 is no longer the default position in major guidelines. NICE, NAMS, and the Korean Society of Menopause all now support ongoing use in appropriate candidates, with annual risk-benefit review replacing arbitrary time cutoffs.

  • Estrogen — the central component of HRT. Estradiol (E2) most closely matches the body’s natural form.
  • Hot Flash — the symptom most responsive to HRT. Up to 80 to 90 percent of users see improvement.
  • Osteoporosis — estrogen loss accelerates bone resorption; HRT initiated early can preserve bone density.
  • FSH — a key diagnostic marker for menopause. FSH above 40 mIU/mL is a standard reference threshold.
  • Menopause — the transition that defines the primary indication for HRT.