Menopause, Perimenopause, and Hormone Therapy (MHT): Why Understanding Changed After WHI 2002

Menopausal hormone therapy was once seen as risky for breast cancer and heart disease, and women and doctors worldwide stopped using it in large numbers after 2002. Today’s understanding is very different. What changed along the way?

First, the terms. Perimenopause is the phase before periods end, when hormones start to fluctuate and symptoms begin. Menopause is the point at which periods have been absent for 12 months. MHT (menopausal hormone therapy) means giving hormones back to relieve symptoms. This article explains how the interpretation of a large trial changed, and who today is or is not a good fit for hormone therapy.

Perimenopause is when hormones begin to fluctuate and symptoms start · Menopause is the point with no periods for 12 months · MHT is hormone replacement to relieve menopausal symptoms

A Three-Line Summary

1. Menopause can begin as early as the late 40s, the transition lasts about 3 to 4 years on average, the average age at menopause is around 52, and the main symptoms are hot flashes (about 80 percent), poor sleep, mood changes, and vaginal symptoms.
2. The 2002 WHI trial made people fear MHT, but the reinterpretation under the timing hypothesis finds that starting before age 60 or within 10 years of menopause usually means benefits outweigh risks.
3. The increased breast cancer risk from estrogen plus progestin is a small absolute number, while estrogen alone in women who have had a hysterectomy is associated with a lower risk in the 20-year follow-up.

Part 1: What Menopause Is and How Symptoms Arrive

Perimenopause can start 8 to 10 years before periods truly end, usually in the late 40s, lasting about 3 to 4 years on average, and as long as 10 years in some women. Menopause is counted once periods have been absent for 12 months, at an average age of around 52.

Symptoms fall into groups.

Symptom group	Detail
Hot flashes and night sweats	About 80 percent, each lasting 1 to 5 minutes, peaking in the 2 years after menopause
Poor sleep	Linked to hot flashes and fluctuating hormones
Mood	Irritability, anxiety, depression
Brain fog	Worse short-term memory and word-finding, usually temporary and self-improving
Genitourinary symptoms (GSM)	About 50 percent of postmenopausal women; vaginal dryness, burning, frequent urination, easy infections

One point to state clearly so no one panics: menopausal brain fog is mostly temporary and improves, and it is not a sign of dementia.

Part 2: The WHI 2002 Story That Reversed Understanding

What 2002 Said

The Women’s Health Initiative was a large randomized trial. Its estrogen-plus-progestin arm (CEE plus MPA) enrolled 16,608 postmenopausal women aged 50 to 79 and was stopped early at about 5.2 years because of increased risks of breast cancer, coronary heart disease, stroke, and venous thromboembolism. The news at the time emphasized the increased relative risk, and MHT use dropped worldwide.

Why the Interpretation Changed

The trial population did not match real-world MHT users. The average age of WHI participants was around 63, and many were more than 10 years past menopause, whereas people who use MHT in practice typically start in their early 50s, close to menopause.

The timing hypothesis proposes that when hormones are started relative to menopause determines whether the result is benefit or risk. The Cochrane review found that in women who started hormones within 10 years of menopause, coronary heart disease risk fell by about 48 percent (RR 0.52) and all-cause mortality by about 30 percent (RR 0.70).

These figures come with an important caveat: the good results appear only in the early-start group. Hormone therapy across everyone does not protect the heart, and even within that same early-start group there was still an increased risk of venous thromboembolism (VTE RR about 1.74).

⚠️ caveat: the timing hypothesis gained direct randomized evidence from the ELITE trial, which found that estradiol slowed thickening of the arterial wall only in the early-start group (less than 6 years after menopause) and had no effect in the late-start group. Work on dementia prevention remains neutral, neither helping nor harming.

Breast Cancer: Separating Incidence From Mortality

The 20-year WHI follow-up separates the two regimens clearly. The estrogen-alone arm (in women who had a hysterectomy) is associated with lower breast cancer incidence (incidence HR 0.78, about 22 percent lower) and lower breast cancer mortality (mortality HR 0.60, about 40 percent lower), which reverses the original fear. The estrogen-plus-progestin regimen is associated with higher incidence (incidence HR 1.28, about 28 percent higher).

Absolute Versus Relative

The increased breast cancer risk from estrogen plus progestin works out to an absolute figure of about 8 cases per 10,000 women per year. The relative risk that sounds frightening comes from a low baseline. Reporting relative risk without the absolute figure was one root cause of the 2002 panic, and it remains a lesson in risk communication.

⚠️ caveat: a large observational study (Collaborative Group, Lancet 2019) gives an absolute frame that is easy to teach. Starting at age 50 and using it for 5 years adds about 1 extra breast cancer per 50 users for daily estrogen plus progestin, versus about 1 per 200 for estrogen alone. But this study found estrogen alone at RR 1.33, which conflicts with the WHI finding of reduced risk. That difference has no answer yet, and it should not be presented as if all studies agree.

Part 3: Today’s Consensus and the Non-Hormonal Options

Who Fits MHT

The NAMS 2022 and IMS 2024 guidance agree that MHT offers benefits over risks in healthy women under 60, or within 10 years of menopause, who have bothersome symptoms. The NAMS 2022 statement is endorsed by more than 20 international organizations.

Points to know before deciding:

• Women who still have a uterus must add a progestin to lower the risk of endometrial cancer, while women who have had a hysterectomy can use estrogen alone.
• Transdermal estrogen carries a lower clot risk than oral. Pooled studies find oral at RR about 1.6 to 2.4, while transdermal is about 1.0, or no increase.
• MHT reduces osteoporotic fractures, lowering hip and spine fractures by about 34 percent, but the effect lasts only while the drug is taken, and fades once it is stopped.

Non-Hormonal Options

For those who cannot or do not want to use hormones, there are evidence-backed options.

Option	Evidence
Paroxetine 7.5mg (Brisdelle)	An FDA-approved SSRI for hot flashes, with a modest effect of about 1 to 2 fewer per day over placebo
Venlafaxine (SNRI)	The MsFLASH trial found it reduced hot flashes by about 48 percent from baseline, or about 20 percent over placebo
Fezolinetant (Veozah)	An NK3 antagonist, not a hormone, FDA-approved in May 2023, with an FDA boxed warning for serious liver injury added in December 2024
Elinzanetant (Lynkuet)	A newer dual NK1 plus NK3 drug, FDA-approved in October 2025
CBT (cognitive behavioral therapy)	Reduces distress from hot flashes but not their frequency (the MENOS1 and MENOS2 trials)

These options help with hot flashes but do not directly address vaginal symptoms or bone. For vaginal symptoms specifically, low-dose vaginal estrogen as cream, tablet, or ring works well and is absorbed into the body very little, and generally needs no added progestin.

Points to Watch: Trend Products With Weak Evidence

Compounded bioidentical hormones lack quality evidence Custom-compounded hormones marketed as natural and safer were found by the NASEM 2020 report to have no quality trials behind them and to fall outside FDA regulation, so their potency and purity are uncertain. They must be separated from FDA-approved bioidenticals such as estradiol and micronized progesterone, which have been studied.

Testosterone in women is proven only for sexual desire Testosterone genuinely helps sexual desire in women with HSDD, but there is no good evidence that it helps hot flashes, mood, memory, or general health, so it is not a general menopause drug as wellness trends claim.

Menopause supplements such as black cohosh, red clover, and soy The evidence is inconsistent and the effect small. ACOG and NAMS do not recommend them as primary treatment, and black cohosh has some case reports of liver safety concerns. Saliva hormone testing to balance hormones is recommended by no medical society.

What We Still Do Not Know

• MHT and long-term dementia prevention, where evidence is still mixed and there is no indication for using it to prevent dementia directly.
• The long-term effects of fezolinetant on the liver and elsewhere still need follow-up.
• The optimal regimen, dose, and type of progestin for breast cancer risk are still an area where data is accumulating.
• Data specifically in Asian and Thai populations is still thinner than Western data.

A Small Step You Can Take

If you are entering menopause and symptoms disrupt your life, talking with a gynecologist or specialist gives a better picture than deciding alone, because MHT is an individual decision that depends on age, time since menopause, health history, and each person’s risk. There is no single formula that fits everyone, and both starting and stopping hormones should be done under a doctor’s guidance. This is a decision made with understanding, not fear.