In short
Overview
The risks of hormone therapy are usually quoted as percentages, which makes them sound larger than they are. Here they are as numbers of women, which is how they should be read.
Direct Answer
For 1000 women aged 50 to 59 treated for five years with combined oestrogen and progestogen, against 1000 untreated:
- 3 extra breast cancers, 2.5 extra heart events, 2.5 extra strokes, 3 extra pulmonary emboli
- 1.5 fewer hip fractures and 5 fewer deaths from any cause
For women who have had a hysterectomy and take oestrogen alone, the picture is more favourable: 5.5 fewer heart events, 2.5 fewer breast cancers, 5.5 fewer deaths.
Who This Applies To
- Women with a history of breast cancer, coronary heart disease, stroke, a previous clot, active liver disease or unexplained vaginal bleeding. Hormone therapy is not used
- Women at high cardiovascular risk, above 10 per cent over 10 years, or at moderate to high breast cancer risk. Non hormonal treatment is suggested instead
- Women starting well after 60, where the risk profile differs
Option Comparison / Decision Criteria
The benefits, plainly
Standard doses clear hot flushes completely in about 80 per cent of women and reduce them in the rest. Across 24 trials in 3329 women, oestrogen cut flushes by about 75 per cent against placebo.
It also improves sleep where flushes are the cause, improves mood during the perimenopausal transition though not after menopause, protects bone, and treats vaginal dryness and painful sex.
The risks, and how to lower them
| Clot and stroke | Lower with a patch or gel than with tablets. Transdermal showed no excess clot risk even in women with a clotting mutation or a high BMI |
| Breast cancer | Micronised progesterone is preferred over the older synthetic medroxyprogesterone, which was linked to excess breast cancer and heart risk in the WHI |
| Womb lining | Prevented entirely by adequate progestogen. Hyperplasia can develop after as little as six months of unopposed oestrogen |
| Overall dose | Lower doses mean less bleeding, less breast tenderness, less effect on clotting markers and possibly lower stroke and clot risk |
What hormone therapy is not for
It is no longer recommended for preventing heart disease, osteoporosis, cognitive decline or dementia. It is used for symptoms, and the bone benefit comes along with that.
Why an In-Person Physician Review Matters
Why risk is calculated before, not after Cardiovascular and breast cancer risk are worked out before starting, because they decide both the route and sometimes whether hormones are appropriate at all.
Moderate cardiovascular risk, 5 to 10 per cent over 10 years: transdermal rather than oral oestrogen, and micronised progesterone rather than a synthetic progestin High cardiovascular risk above 10 per cent, or breast cancer risk of 1.67 per cent or more over five years: non hormonal therapy is suggested The breast cancer risk tool is not accurate for women with several affected first degree relatives, and that limitation is stated rather than glossed over. Why oral tablets are avoided for some women Oral oestrogen should be avoided in women with high triglycerides, active gallbladder disease, migraine, or a known lower risk clotting tendency such as heterozygous factor V Leiden. What is monitored Bleeding pattern. Persisting beyond six months on a continuous regimen needs an endometrial biopsy Mammograms and breast examination, recommended even for short term use. Stopping treatment for one or two months before a mammogram does not reduce recall rates Dose, route and duration, reviewed yearly
Frequently Asked Questions
Combined therapy is associated with about 3 extra breast cancers per 1000 women over five years starting between 50 and 59. Oestrogen alone after hysterectomy was associated with 2.5 fewer. Both figures sit alongside 5 to 5.5 fewer deaths from any cause.
For clot and stroke risk, yes. Transdermal oestradiol avoids the liver first pass and showed no excess clot risk even in women with a clotting mutation or a high BMI. It is the default choice for most women.
No. Both the Menopause Society and ACOG say the decision should be individualised rather than made on age. Over 40 per cent of women aged 60 to 65 still have flushes that disrupt sleep and quality of life.
Tapering is the usual advice. Abrupt stopping clearly brings symptoms back in the short term, though a randomised trial found no difference between the two approaches by 9 to 12 months.
Evidence
Where this information comes from
Every figure on this page is taken from the sources below. All of them are free to read, so you can check them yourself.
This page is general medical information and does not replace a personal consultation. Trial results are averages across large groups, not a prediction for any one person.