The evidence base for HRT: what can we believe?

Area of Science:

• Reproductive Endocrinology
• Clinical Pharmacology
• Women's Health

Background:

• Prevailing view before Women's Health Initiative (WHI) was HRT was low-risk with benefits for menopausal symptoms and chronic disease prevention.
• WHI aimed to test HRT efficacy in women starting therapy well past menopause, not just near menopause.
• Initial WHI report (2002) on CEE+MPA dramatically shifted views on HRT risks and benefits, leading to decreased use.

Purpose of the Study:

• To re-evaluate the benefits and risks of hormone replacement therapy (HRT) in postmenopausal women.
• To understand how age and time since menopause onset influence HRT's effects.
• To clarify appropriate HRT indications and patient selection criteria.

Main Methods:

• Analysis of Women's Health Initiative (WHI) trial data, including continuous conjugated equine estrogens (CEE) and medroxyprogesterone acetate (MPA).
• Comparison of HRT effects based on age at initiation and time since menopause.
• Review of subsequent research and clinical practice shifts following WHI findings.

Main Results:

• The WHI trial of CEE alone suggested potential coronary heart disease prevention in women <60 and reduced breast cancer risk.
• HRT effects vary significantly by age, time since menopause, and specific hormone regimen.
• Subsequent research identified subgroups of women who benefit from HRT, particularly when initiated near menopause.

Conclusions:

• HRT's impact is nuanced, depending critically on initiation timing relative to menopause.
• For women initiating HRT within 10 years of menopause, benefits include symptom relief and long-term protection (bone, cardiovascular).
• Current clinical decisions about HRT often rely on outdated or misapplied information, necessitating updated guidance.