In 2002, the Women's Health Initiative published findings suggesting that combined oestrogen-progestogen HRT increased breast cancer, coronary heart disease, and stroke risk. Prescriptions fell by more than 50 percent in the following two years. Women in severe menopausal distress stopped treatment. In subsequent years, researchers re-analysed the WHI data and found that the original conclusions were substantially distorted by the age profile of participants, the average age was 63, well beyond the window of HRT initiation for menopausal women, and by the use of conjugated equine oestrogen and synthetic progestins that are no longer first-choice treatments. The clinical landscape has changed considerably since.
The Timing Hypothesis
The timing hypothesis, now well supported by multiple re-analyses and subsequent trials, holds that HRT started within 10 years of the menopause, or before age 60, has a substantially different risk-benefit profile from HRT started in older postmenopausal women. In the younger initiation group, the cardiovascular risks observed in the WHI are not seen. In fact, oestrogen-only HRT in women under 60 is associated with reduced all-cause mortality in several analyses. The window of opportunity principle means that the same treatment that is risky in older women is protective or neutral in those initiating it earlier.
Breast Cancer Risk: The Current Picture
The most current data from a large 2019 observational study in the Lancet by Collaborative Group on Hormonal Factors in Breast Cancer confirmed a small but real increased risk of breast cancer with combined HRT. The absolute risk increase is approximately 1 in 50 over five years for combined preparations. Oestrogen-only HRT in women who have had a hysterectomy shows no significant increase, and some data suggest a reduction. Micronised progesterone, which is the progestogen type used in body-identical prescribing and is now available on the NHS, appears to carry a lower breast cancer risk than synthetic progestins such as medroxyprogesterone acetate.
What HRT Demonstrably Prevents
HRT prevents menopausal bone loss and reduces fracture risk significantly. It reduces cardiovascular risk when started early. It substantially reduces vasomotor symptoms, improving sleep, quality of life, and mood. It maintains urogenital tissue health, reducing urinary symptoms and sexual dysfunction. And it reduces the risk of type 2 diabetes and metabolic syndrome in menopausal women. The NICE guideline recommendation is that for most women under 60 initiating HRT within 10 years of the menopause, the benefits substantially outweigh the risks.
- Discuss HRT with an informed GP or menopause specialist, not one using 2002-era risk communication
- Body-identical HRT using transdermal oestrogen and micronised progesterone is the current evidence-based first choice
- If you have a uterus, progestogen must be included to protect the uterine lining
- If you are within 10 years of your menopause, the timing hypothesis substantially changes the risk-benefit calculation
- Review with a healthcare provider every 12 months: the decision to continue should be individually reassessed, not assumed
Sources
- NICE. (2015, updated 2019). Menopause: diagnosis and management. NICE guideline NG23.
- Collaborative Group on Hormonal Factors in Breast Cancer. (2019). Type and timing of menopausal hormone therapy and breast cancer risk. Lancet, 394(10204), 1159-1168.
- Manson, J.E., et al. (2013). Menopausal hormone therapy and health outcomes during the intervention and extended post-stopping phases of the WHI randomized trials. JAMA, 310(13), 1353-1368.