Estrogen-only menopause therapy linked to slightly higher autoimmune risk than combo therapy

Hormone therapy formulation may matter for autoimmune risk

A retrospective cohort study of over 54,000 menopausal women found that estrogen-only hormone therapy was associated with a modestly higher risk of developing autoimmune diseases compared to combined estrogen-plus-progestogen therapy. Presented at the 2026 Annual Meeting of The Menopause Society, the study analyzed data from the TriNetX U.S. Collaborative Network and excluded women with pre-existing autoimmune conditions.

Researchers noted that the association wasn't uniform across diseases, suggesting the hormone-autoimmunity relationship may be disease-specific. Experts caution that while the findings are intriguing, the observational design limits causal conclusions — and progestogen should not be added solely to reduce autoimmune risk.

By the Numbers:

• Composite autoimmune disease incidence: 4.9% (estrogen-only) vs. 4.5% (estrogen + progestogen) (HR = 1.08)
• Systemic lupus erythematosus risk: 0.3% vs. 0.2% (HR = 1.33)
• Multiple sclerosis risk: 0.2% vs. 0.1% (HR = 1.69)
• Rheumatoid arthritis risk: 0.8% vs. 0.7% (HR = 1.15)

Why it matters: Autoimmune diseases disproportionately affect women, and menopause marks a period of major hormonal shifts. These findings encourage clinicians to include hormone therapy formulation in patient histories and prompt further research into how estrogen and progestogens interact with immune pathways — potentially paving the way for more individualized treatment.