Hormones & Breast Cancer: What’s Fact, What’s Fiction?
If you’ve ever thought about hormone therapy but immediately felt a wave of fear, because you were told it causes cancer, you’re not alone.
One of the most common things I hear from women is, “I was told I can’t do hormones because of breast cancer.”
Or, “My doctor said hormones are dangerous—especially with my family history.”
Let’s take 10 minutes to clear this up. Because what you’ve been told is not the whole story. And in many cases, it’s simply not true.
Where Did the Fear Come From?
It all started in 2002 with a large study called the Women’s Health Initiative (WHI), the biggest trial ever done on postmenopausal women in the U.S. The goal was to look at how hormone therapy affected long-term health outcomes like heart disease, cancer, and bone fractures.
What most people don’t know is that the WHI used only one type of hormone therapy: a single, fixed-dose pill combining synthetic estrogen (Premarin) and synthetic progestin (medroxyprogesterone acetate). These aren’t the same as the bioidentical hormones, estradiol and micronized progesterone, we use today.
The WHI study made headlines when it reported that women taking a combination of estrogen and progestin (not progesterone - more on that later) had an increased risk of breast cancer, strokes, heart disease, and blood clots. The media ran wild. Doctors panicked. And almost overnight, millions of women were taken off their hormones.
The WHI data was overinterpreted, misunderstood, and sensationalized. While the study showed a slight increase in breast cancer incidence in women using estrogen + progestin, the finding was statistically insignificant, and in medicine, we do not base treatment decisions on data that lacks clinical significance. Importantly, the study showed no increase in breast cancer mortality. And women on estrogen alone had a reduced risk of developing and dying from breast cancer, a finding that never made the headlines.
What’s worse? The absolute risk increase was only 0.1%—just one additional case per 1,000 women per year. And yet, an entire generation of women was scared away from hormone therapy. Doctors were never re-trained. The medical curriculum never caught up. And we’re now left with a healthcare system that continues to deprive women of lifesaving therapy based on outdated assumptions, not on current evidence.
Here's What Was Missed (and Never Corrected)
What the media—and most clinicians—didn't share was this:
The increased risk was seen only in the women who were given synthetic progestin, not natural progesterone.
Women who took estrogen alone (without progestin) actually had a lower risk of breast cancer.
Most women in the study were already 10-20 years into menopause, had multiple risk factors like obesity and smoking, and were given oral horse estrogens—not the safer, bioidentical options we use today.
That nuance didn’t make the headlines. Fear did.
The Aftermath? Women Lost Access to Lifesaving Therapy
After the WHI scare:
HRT use dropped by over 70%.
Breast cancer rates did not decline (as you’d expect if HRT was the cause).
In fact, after 2008, when HRT use was at its lowest, breast cancer rates began to rise again.
Fractures, dementia, cardiovascular disease, and even early death started climbing, because women were no longer protected by hormones.
What We Know Now (But Your Doctor May Not)
Since then, multiple follow-up studies, including analyses by the original authors, have shown that the WHI data was:
Overinterpreted
Misreported
And incorrectly applied to younger, healthier women who would benefit most from HRT.
Even the National Cancer Institute and journals like Climacteric, The Journal of the American College of Cardiology, and the Journal of the National Cancer Institute have acknowledged that HRT does not cause breast cancer when used properly.
Starting hormone therapy early, around the time of menopause, reduces risk of:
Heart disease
Osteoporosis and hip fractures
Cognitive decline and dementia
All-cause mortality (your overall risk of dying from any cause)
Let’s Talk About Progestin vs. Progesterone
This part is important. The WHI study used progestin, a synthetic drug designed to act like progesterone. But it doesn't fit into the body’s receptors the same way and has different, sometimes harmful effects.
What most women benefit from today is bioidentical progesterone—the same molecule your body used to make. It’s anti-inflammatory, supports brain health, reduces anxiety, and protects the uterus safely.
What About Women With a History of Breast Cancer?
This is where things get even more misunderstood. There is no blanket ban on HRT for women with a history of breast cancer.
Recent studies, including from respected cancer journals, show that in carefully selected women:
HRT did not increase recurrence rates.
In some cases, HRT was associated with a lower risk of metastasis and lower mortality.
Vaginal estrogen therapy and transdermal estrogen have shown no increased risk of breast cancer recurrence.
In fact, the 2022 Journal of the National Cancer Institute report concluded that there was no increased risk of recurrence or death in postmenopausal breast cancer survivors using HRT or vaginal estrogen.
Why This Still Matters Today
Despite all this newer evidence, many clinicians still quote the WHI as gospel. But the truth is:
Hormone therapy is one of the most powerful tools we have to protect women’s long-term health.
The risks of not using hormones—heart disease, osteoporosis, dementia—are often far greater than the risk of breast cancer.
Using the right type, dose, and delivery of HRT matters. Transdermal estrogen and micronized progesterone are not the same as old-school hormone pills.
You Deserve Better Care
If your doctor tells you “hormones cause cancer,” ask them to show you the data. And if they can't go beyond the WHI headlines, it might be time to find a provider who can. You deserve a full, informed conversation, not fear-based decisions based on outdated studies.
Bottom line? Hormones don’t deserve the bad reputation they’ve been given. And women deserve the truth. Let’s stop letting fear dictate our health decisions and start leaning into what the science really says.
Looking for more resources on this topic?
Check out the following podcasts on this topic.
Podcast episode with Dr. Peter Attia and Dr. Rachel Rubin - Jump ahead to 20:15 for discussion about HRT and the WHI
Podcast episode with Dr. Corinne Menn & Dr. Louise Newson talking about shared decision-making and advocating for HRT in women with breast cancer or with a history of breast cancer.
Podcast episode with Dr. Sarah Glynn and Dr. Louise Newson - Advancing Menopause Care After Breast Cancer**
Exploring experiences of menopausal women after breast cancer, with Dr Sarah Ball and Dr. Louise Newson - Great conversation about post-breast cancer options for menopausal women
The Menopause & Cancer Instagram page and podcast - Excellent resources
Podcast Episode with Dr. Casperson - You Are More Than Just Your Breast Cancer - Hormones and Breast Cancer
Podcast Episode with Dr. Casperson- Sex after cancer
Dear Menopause podcast with Dr. Menn - Breast Cancer and Menopause Management
Podcast episode with Dr. Hirsch - When Menopause Is A Surprise, with Dr. Corinne Menn
Podcast Episode with Dr. Avrum Bluming - Estrogen Matters
References
Bluming, Avrum, and Carol Tavris. Estrogen Matters: Why Taking Hormones in Menopause Can Improve Women’s Well-Being and Lengthen Their Lives—Without Raising the Risk of Breast Cancer. Little, Brown Spark, 2018.
Canonico, Marianne, et al. “Hormone Replacement Therapy and Risk of Venous Thromboembolism in Postmenopausal Women: Systematic Review and Meta-Analysis.” BMJ, vol. 336, no. 7655, 2008, pp. 1227–1231. https://doi.org/10.1136/bmj.39555.441944.BE.
Creasman, William T. “Hormone Replacement Therapy after Cancers.” Current Opinion in Oncology, vol. 17, no. 5, 2005, pp. 493–499. https://doi.org/10.1097/01.cco.0000174034.62032.08.
Endocrine Today. “Early Initiation of Menopausal HT Reduces All-Cause Mortality, CHD Events in Women.” By Michael Monostra, 3 Dec. 2020. https://www.healio.com/news/endocrinology/20201203/early-initiation-of-menopausal-ht-reduces-allcause-mortality-chd-events-in-women.
Hodis, Howard N., and Wendy J. Mack. “Menopausal Hormone Replacement Therapy and Reduction of All-Cause Mortality and Cardiovascular Disease: It Is About Time and Timing.” Cancer Journal (Sudbury, Mass.), vol. 28, no. 3, 2022, pp. 208–223. https://doi.org/10.1097/PPO.0000000000000591.
Hodis, Howard N., et al. “Vascular Effects of Early versus Late Postmenopausal Treatment with Estradiol.” The New England Journal of Medicine, vol. 374, no. 13, 2016, pp. 1221–1231. https://doi.org/10.1056/NEJMoa1505241.
Langer, R. D., et al. “Menopausal Hormone Therapy for Primary Prevention: Why the USPSTF Is Wrong.” Climacteric, vol. 20, no. 5, 2017, pp. 402–413. https://doi.org/10.1080/13697137.2017.1362156.
Paganini-Hill, Annlia, et al. “Increased Longevity in Older Users of Postmenopausal Estrogen Therapy: The Leisure World Cohort Study.” Menopause (New York, N.Y.), vol. 25, no. 11, 2018, pp. 1256–1261. https://doi.org/10.1097/GME.0000000000001227.
Reiss, Uzzi, and Billie Fitzpatrick. The Good News About Estrogen: The Truth Behind a Powerhouse Hormone. Avery, 2020.
Schuetz, Florian, et al. “Reduced Incidence of Distant Metastases and Lower Mortality in 1072 Patients with Breast Cancer with a History of Hormone Replacement Therapy.” American Journal of Obstetrics and Gynecology, vol. 196, no. 4, 2007, pp. 342.e1–9.
Shapiro, Samuel, et al. “Risks and Benefits of Hormone Therapy: Has Medical Dogma Now Been Overturned?” Climacteric, vol. 17, no. 3, 2014, pp. 215–222. https://doi.org/10.3109/13697137.2014.905529.
Sprague, Brian L., Amy Trentham-Dietz, and Kathleen A. Cronin. “A Sustained Decline in Postmenopausal Hormone Use: Results From the National Health and Nutrition Examination Survey, 1999–2010.” Obstetrics & Gynecology, vol. 120, no. 3, 2012, pp. 595–603. https://doi.org/10.1097/AOG.0b013e318265df42.