The spotlight has again been turned towards the topic of HRT and heart disease, with a recently published review by Taylor et al of the controversies regarding hormone replacement therapy (HRT) for primary prevention of cardiovascular in postmenopausal women. The topic around whether or not HRT reduces or increases the risk of heart disease has been debated for many years.

Almost 40 years ago, observational studies showed that women who took HRT had a lower risk of heart disease than those that did not, leading to many women choosing, and being advised, to take HRT for this benefit.

Confusion and alarm followed when randomised controlled trials in the 1990s showed that the use of HRT may cause harm with increased risk of heart disease. This has led to varying views and recommendations over the years.

More recent studies, and reanalysis of age groups or time since menopause in the previous studies, have highlighted the “timing hypothesis”, whereby HRT started in the early years of the menopause, does provide cardiovascular benefit with reduced risk of cardiovascular disease. The timing hypothesis explains the difference from the early observational studies and the randomised trials in the 1990s because the randomised trials included many women who were several years postmenopausal before starting HRT, whereas the observational studies included women who were in the early menopausal years, choosing to take HRT for symptom control.

The scientific explanation focuses around the known beneficial effects of estrogen on blood vessel function and plaque formation. However, favourable effects are less likely to be achievable if blood vessels have become unhealthy with increasing years from the menopause.

More research is still needed to examine the effects at different menopausal stages of different types and routes of estrogen, the earlier studies mostly involving use of oral HRT, with increased use of transdermal HRT in recent years.

However, while the main indication for HRT will continue to be for control of menopausal symptoms, the message of HRT also providing benefit for reduced risk of cardiovascular disease when started early in the menopausal years, now seems to be loud and clear.

Reference. Taylor JE, Baig MS, Helmy T, Gersh F. Controversies Regarding Post-Menopausal Hormone Replacement Therapy for Primary Cardiovascular Disease Prevention in Women. Cardiol Rev. 2020 Nov 6. doi: 10.1097/CRD.0000000000000353. Epub ahead of print. PMID: 33165087.

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