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Why Understanding Your Estrogens Matters for Hormone-Positive Breast Cancer


In the world of women’s health, especially for those concerned with hormone-positive breast cancer, estrogen is not just one hormone, but a family of related compounds. The most commonly discussed are Estradiol (E2), Estrone (E1), and Estriol (E3). Understanding how they differ and why measuring estrone in addition to estradiol can be crucial, gives deeper insight into estrogen metabolism, risk, and strategies for long-term breast health.


The Three Main Estrogens — What They Are & When They Dominate


Estradiol (E2)

Estradiol is the primary estrogen during the reproductive years for pre-menopausal women. It’s mainly produced by the ovaries and drives regular menstrual cycles, supports bone health, and influences brain and metabolic function.


Estrone (E1)

Estrone becomes more predominant after menopause, or when ovarian production of estradiol declines. It is largely synthesized outside the ovaries, particularly in fat tissue, adrenal glands, and via peripheral conversion of adrenal precursors (e.g., DHEA) in non-ovarian tissues. Because estrone persists after menopause, it plays a critical role in maintaining estrogenic activity (for bone, cardiovascular health, etc.) in post-menopausal women.

Estriol (E3)

Estriol is the weakest of the three, and becomes relevant primarily during pregnancy, produced in large amounts by the placenta. In non-pregnant women, estriol levels are typically low.


Why Many People Overlook Estrone — And Why That’s a Problem in Hormone-Positive Breast Cancer


In the conventional breast cancer setting, the primary clinical focus is blocking estradiol (E2). Treatments like aromatase inhibitors (Letrozole, Anastrozole, Exemestane), ovarian suppression (Zoladex), or SERMs (Tamoxifen) are designed to lower or block estradiol because E2 is the most potent estrogen and the dominant hormone during reproductive years.

But here’s the missing piece: estradiol isn’t the only estrogen that matters and after ovarian suppression or menopause, estrone (E1) becomes the dominant estrogen in the body.

Emerging research shows that estrone (E1) may have stronger pro-cancer effects than estradiol in certain contexts. Estrone is more pro-inflammatory, increasing cytokine activity and inflammatory signaling, promotes epithelial-to-mesenchymal transition (EMT) — the process by which cancer cells become more mobile, invasive, and resistant to treatment; and enriches cancer stem cell–like features, which are associated with recurrence, metastasis, and therapy resistance.


Mad yet? Even though estradiol levels drop, estrone often doesn't. And in some women, estrone may even remain high or become higher due to:

  • High body fat, because estrone is produced in fat tissue

  • High adrenal conversion of DHEA, because estrone is produced by the adrenals

  • Impaired estrogen detoxifincation

  • High reabsorption of estrogen in the gut

  • Genetic variations in estrogen metabolism


This means that even when estradiol is effectively suppressed, estrone can continue to stimulate pro-cancer pathways if it is not measured and managed.


What You Can Do: How to Measure Estrone and Reduce Its Harmful Effects


1. Ask for Estrone Testing — Not Just Estradiol

Most standard oncology blood panels do not include estrone unless specifically ordered. Women, especially those in medically induced menopause, can request:

2. Support Healthy Estrone Metabolism

Because estrone itself is not the only issue — how your body processes estrone matters too.

Women can focus on:

  • Nutrition that supports estrogen detoxification: cruciferous vegetables (broccoli, cabbage, cauliflower, kale), high-fiber plant foods, green tea, flaxseed, dark leafy greens, foods rich in antioxidants (berries, turmeric, mushrooms). These support Phase I and Phase II liver detoxification and help shift estrogen metabolism toward safer 2-OH pathways.

  • Supplements shown to support estrogen clearance: like DIM (Diindolylmethane), Calcium-D-Glucarate, Sulforaphane, Green tea extract (EGCG), Omega-3s and probiotics. Always reviewed with your oncology and integrative team before startting any new supplements.

  • Address body composition: since estrone is produced in fat tissue, reducing visceral fat through nutrition, gentle detoxification, and strength training can lower estrone production.

  • Improve gut health: the gut determines how much estrogen is reabsorbed vs excreted. Balancing the estrobolome is essential for women on endocrine therapy.

  • Reduce inflammation: estrone’s pro-inflammatory nature means lowering inflammation is especially protective.


The Bottom Line


Blocking estradiol is only part of the story. Estrone doesn’t disappear during treatment and may play an even bigger role in driving inflammation, EMT, and cancer-stem behavior.


By monitoring estrone, supporting safe estrogen metabolism, and creating a holistic lifestyle strategy, women — especially those in medically induced menopause — can take an active, empowered role in improving hormone-related outcomes alongside their oncology treatment.


If you’d like one-on-one support, you can book a consultation with me and we’ll create a personalized, evidence-based plan tailored to your unique needs. You can also s for holistic breast cancer support, recipes, and hormone-health insights. And if you enjoy daily tips, education, and behind-the-scenes support, come connect with me on Instagram @Nutriditions.


This information is for educational purposes only and is not intended to diagnose, treat, or replace medical advice. Hormone-positive breast cancer is a complex medical condition, and any nutrition, lifestyle, or supplement changes should be discussed with your oncology team and healthcare providers. Always consult your oncologist before adding new supplements or making changes to your treatment plan.


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