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General Endocrinology

SAT-839 - Impact of the Timing of Hormone Therapy Initiation on Cardiovascular Outcomes in Postmenopausal Women: A Systematic Review and Meta-Analysis

Saturday, June 13, 2026
9:30 AM - 4:30 PM CT


Introduction: Hormone therapy (HT) is the most effective treatment for menopausal vasomotor symptoms. The “timing hypothesis” suggests that initiation timing modifies cardiovascular effects. In November 2025, the FDA updated HT safety recommendations, reflecting improved understanding of risks when appropriately used.

Objective: To evaluate the impact of HT initiation timing on cardiovascular outcomes, comparing early versus late initiation, considering route of administration and progestogen type.

Methods: Systematic review following PRISMA guidelines. PubMed and Cochrane Library (January 2006–March 2026) identified 46 studies; 14 were included after independent, blinded dual screening (Rayyan). Early ( < 10 years since menopause or < 60 years) versus late (≥10 years or ≥60 years) initiation was compared, with stratification by time since menopause, route, and formulation. Methodological quality was assessed using Cochrane RoB 2.0. Results were synthesized descriptively due to high heterogeneity.

Results: HT effects varied by timing, formulation, and route. Early initiation was associated with reduced coronary artery disease risk (RR 0.52; 95%CI 0.29–0.96) and all-cause mortality (RR 0.70; 95%CI 0.52–0.95). Finnish registry data (n=498,105) confirmed lower CAD mortality when initiated before age 60. WHI analyses showed no difference between early and late initiation, based on post hoc data. A 2025 WHI analysis found no increased atherosclerotic cardiovascular risk in women aged 50–59 (estrogen: HR 0.85; estrogen+progestogen: HR 0.84). Stroke risk was similar to placebo with estrogen alone but higher with combined therapy. Transdermal estrogen ( < 50 μg/day) showed a safer stroke profile than oral. Venous thromboembolism (VTE) risk was increased with oral HT regardless of timing (RR 1.74–1.96), while transdermal estrogen showed no increased risk (OR 0.93). Micronized progesterone did not increase VTE (RR 0.93), unlike medroxyprogesterone acetate (RR 2.77). A real-world study (n=36,061) showed lower VTE incidence with estradiol, micronized progesterone vs conjugated equine estrogen, medroxyprogesterone (IRR 0.70). Women ≥70 years had increased cardiovascular risk (HR up to 3.22).

Conclusion: These findings support the timing hypothesis with important nuances. Early initiation ( < 60 years or < 10 years since menopause) provides a more favorable cardiovascular profile, especially with transdermal estrogen and micronized progesterone. HT relieves vasomotor symptoms without increasing cardiovascular risk in women aged 50–59 but should be avoided at older ages. VTE risk is lower with transdermal versus oral HT. Evidence is largely based on post hoc analyses, lacking prospective trials specifically designed to test the timing hypothesis.

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