When You Start Estrogen Matters — and Why Vitamin D and Timing Matter for Women’s Health
Understanding Timing, Hormones, and Healthspan
Emerging data continue to reshape how we think about hormone therapy for women. One of the most significant findings this year comes from the 2025 Menopause Society Annual Meeting, where researchers presented results showing that when estrogen therapy begins may profoundly influence long-term outcomes in breast and cardiovascular health¹.
The study, titled “When Women Initiate Estrogen Therapy Matters,” analyzed more than 120 million electronic health records to explore how timing affects disease risk.
Women who began estrogen therapy during perimenopause—and continued for at least 10 years prior to menopause—experienced markedly lower risks of breast cancer, heart attack, and stroke compared with those who started after menopause or never used estrogen.
Women who initiated therapy after menopause still saw some benefits (lower odds of breast cancer and heart attack) but showed a 4.9% higher stroke likelihood than women who had never taken estrogen.
These findings add to the growing body of evidence supporting the “timing hypothesis”—that earlier, physiologic use of estrogen in women’s midlife may be protective rather than harmful.
🔗 Read the full Menopause Society summary
Vitamin D’s Role in Hormone Health
Vitamin D, often known for its role in bone metabolism, also influences hormonal balance, muscle strength, and immune regulation.
Low vitamin D levels are linked with higher rates of metabolic syndrome, insulin resistance, and osteoporosis, conditions that can compound during and after menopause².
Studies suggest that maintaining serum 25(OH)D levels between 40–60 ng/mL may optimize bone and muscle function, while deficiency can blunt the effectiveness of both estrogen and testosterone therapies³.
Women considering hormone therapy should discuss vitamin D status with their clinician, as ensuring sufficiency may enhance therapeutic benefit and overall healthspan.
Regulatory Context: FDA Review and Expert Recommendations (2025)
In July 2025, the U.S. Food and Drug Administration (FDA) convened an expert panel on menopause and hormone replacement therapy to evaluate whether the long-standing boxed (“black box”) warning on estrogen products still reflects the science.
Panelists—including Barbara Levy, MD, Heather Hirsch, MD, and JoAnn Manson, MD—presented data showing that low-dose vaginal estrogen therapies do not carry the same systemic risks as oral estrogen and should not share the same warning label⁴ ⁵.
Several medical societies, including the North American Menopause Society (NAMS), have called for removal or revision of the warning to reflect modern evidence.
While the FDA has not yet issued final labeling changes, this marks a major step toward updating regulations to match the data.
At the same session, experts emphasized the need for a female-specific testosterone product.
There is currently no FDA-approved testosterone therapy for women, despite substantial evidence that low-dose, physiologic testosterone can safely improve hypoactive sexual desire disorder (HSDD) when prescribed under medical supervision⁶ ⁷.
Leading organizations—including The International Society for the Study of Women’s Sexual Health (ISSWSH)—support off-label use when monitored by qualified clinicians.
A detailed Thrive Journal report on the FDA panel and its implications for women’s health regulation will be published soon.
🔗 FDA Expert Panel Summary — The Menopause Society
Evidence and Clinical Context
Recent re-analyses of large-scale hormone therapy studies — including follow-up data from the Women’s Health Initiative (WHI) and subsequent cohort studies — have helped clarify the nuanced risks and benefits of menopausal hormone therapy when individualized by timing, formulation, and dose.
For healthy women under 60 or within 10 years of menopause, the benefit–risk profile is favorable, particularly for vasomotor symptoms, bone density preservation, and metabolic stability⁸ ⁹.
The North American Menopause Society (NAMS) and Endocrine Society emphasize that absolute risks for breast cancer, cardiovascular events, and stroke are rare when hormone therapy is started early and at the lowest effective dose.
The type of estrogen (oral vs. transdermal) and the progestogen formulation both influence safety outcomes.
Rather than viewing the WHI as negative, today’s experts interpret it as a call for precision and personalization in care — recognizing that timing, formulation, and route of hormone therapy profoundly shape outcomes.
What to Discuss With Your Clinician
- Timing: Are you perimenopausal or postmenopausal? The optimal approach may differ.
- Formulation & route: Transdermal, oral, or local (vaginal) therapies have different effects.
- Vitamin D status: Maintaining sufficient levels may complement hormone therapy benefits.
- Personalized plan: Review your family history, cardiovascular risk, and lifestyle factors to tailor care.
The Thrive Takeaway
Hormone therapy isn’t one-size-fits-all — and neither is longevity.
The newest data reinforce that timing, context, and personalization matter.
Thrive for Longevity’s mission is to help women interpret the data, not prescribe the therapy.
Every woman’s biology and journey are unique — and understanding the evolving science empowers each of us to ask better questions and make better decisions.
References
- The Menopause Society. When Women Initiate Estrogen Therapy Matters. Press release; October 14, 2025. menopause.org
- Holick MF. Vitamin D Deficiency. N Engl J Med. 2007;357:266–281.
- Sassi F, Tamone C, D’Amelio P. Vitamin D: Nutrient, Hormone, and Immunomodulator. Nutrients. 2018;10(11):1656.
- RAPS. Panel Urges FDA to Remove Boxed Warning on Women’s Hormone Therapy. July 2025. raps.org
- Medscape. FDA Panel Urges Review of Boxed Warning on Menopause Therapy. October 2025. medscape.com
- Davis SR, Baber R, Panay N, et al. Global Consensus Position Statement on the Use of Testosterone Therapy for Women. J Clin Endocrinol Metab. 2019;104(10):4660–4666. academic.oup.com
- Parish SJ, Simon JA, Davis SR, et al. ISSWSH Clinical Practice Guideline for Systemic Testosterone for HSDD in Women. J Sex Med. 2021;18(5):849–867. jsm.jsexmed.org
- Manson JE, Chlebowski RT, Stefanick ML, et al. Menopausal Hormone Therapy and Health Outcomes During the Intervention and Extended Poststopping Phases of the WHI Randomized Trials. JAMA. 2013;310(13):1353–1368. jamanetwork.com
- Stuenkel CA, Davis SR, Gompel A, et al. Treatment of Symptoms of the Menopause: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2015;100(11):3975–4011. academic.oup.com
Thrive for Longevity Disclaimer
Thrive for Longevity shares evidence-based insights for educational purposes only.
We do not provide medical advice or treatment recommendations.
Every woman’s biology and health journey are unique — please discuss these findings with a trusted, qualified healthcare provider before making any decisions about hormone or vitamin D therapy.
