Does Estrogen Cause Cancer?

Does Estrogen Cause Cancer? This is the million dollar question for a woman, once she’s been through cancer treatment, had a hysterectomy, or entering her menopausal years. 

To begin to answer this question there are three important facts to keep in mind.

1. The majority of breast cancers occur in women over 50, when circulating estrogen is at its lowest during a woman’s lifespan. Menopausal women are no longer producing the loads of estradiol from their ovaries that they were in their fertile years. Let that sink in for a minute. Breast cancer mostly occurs when there is very little estrogen around. 

2. ALL cancers are caused by inflammation which is actually the driver of ALL disease.

3. Cancer is a mis-folding or mis-replication of our DNA which is the blueprint of our cells. This mis-folding is caused by inflammation, lifestyle, our environment and a possible genetic predisposition. But please keep in mind that what we eat and our lifestyle turn on and off our genes.

We probably need to talk about the variety of ways that inflammation is ignited in our bodies. It’s actually quite a long list. And we’re often exposed to these on a daily basis, which makes it important to know, so we can make changes where possible.

(Note: I’ll be making reference to 3 different types of estrogen in this post. If you missed my previous post on types of estrogens or would like to brush up on the importance differences click here)

Inflammation can develop because:

  1. You don’t have the right balance of hormones. Or your estrogen metabolism pathway favors a more inflammatory route, producing a more inflammatory type of estrogen called estrone. Or you’re no longer making estradiol from your ovaries which is actually anti-inflammatory and our fatty tissues start making more estrone which is very inflammatory.    
  2. Being menopausal is inflammatory all by itself.
  3. You don’t have the right nutrients to help your liver do its job or to keep your digestive system humming along so they can both effectively excrete the toxins and estrogens that we no longer need.
  4. You’re leaving out major foods that contain the micronutrients that help to scavenge free radicals (which damage DNA). These micronutrients are mainly found in our fruits and veggies.  
  5. You’ve experienced or experiencing Chronic Stress/Trauma (this is way bigger than most people realize). 
  6. You’re sleep deprived and/or are a night shift worker 
  7. Your body has been exposed to many endocrine disruptors or other harmful chemicals and perhaps your body’s innate ability to wrap up and dump out these chemicals is not as robust as someone else’s. And that can happen genetically and/or again by not getting the necessary nutrients and through too much exposure.
  8. You have inflammation from an underlying chronic infection. 
  9. You have high xenoestrogen exposure from our environment: plastics, pesticides, glyphosate, additives to food and personal items.
  10. You have more than 1-2 alcoholic drinks per night 
  11. You have Diabetes/> than 20 lbs overweight
  12. You have a Sedentary lifestyle 
  13. You have excess visceral fat and or a high fat to lean body mass ratio (aka under muscled)

These last four items, I took straight from the NAMS (North American Menopause Society) 2022 Statement on HRT.[1] These last items along with smoking are the biggest drivers of inflammation and cancers. So again, most women do not get breast cancer when there’s a lot of estrogen in her body. It’s when she loses her hormones that she’s susceptible. And that’s because both estradiol and progesterone are anti-inflammatory. 

Estradiol controls the immune system by keeping it from going into a proinflammatory state.

And remember, inflammation underlies the development of all cancers. If we have a lot of inflammation, our body tends to lay down more visceral fat. That’s the fat that nestles in between our organs and can contribute to that pesky belly fat too. This extra fat makes more of an aromatase enzyme that converts fats into estrogen, but not the kind of estrogen we want. It’s the pro-inflammatory kind, called estrone. 

A quick hormone/breast lesson. 
Surprisingly, the breast has its own capability of making estrogen.[3] No ovaries needed! It produces the more inflammatory and proliferative type of estrogen called estrone, which stimulates the receptor sites which can be problematic when it comes to breast cancer [5].

Since this type of estrogen is more proliferative, it can grow breast cancer, when you have estrogen receptor positive breast cancer. It is made in the breast itself from fat cells with the help of an aromatase enzyme.

Many women who have had hormone positive breast cancer have taken an aromatase inhibitor to block the production of this type of estrogen which is the dominant form circulating in a woman’s body, once in menopause. So Let’s Put This Together! 

What’s the chain of events to breast cancer? First there may be high exposure to xenoestrogens and/or a woman’s ability to metabolize estrogens down a favorable pathway is compromised.[2] Or perhaps there is excess inflammation coming from somewhere. And remember, once you hit menopause, there’s little to no estradiol and progesterone circulating to calm that inflammation, unless a woman is on HRT. This inflammation then causes DNA damage=growth of cancerous cells that begin to replicate. Those cancerous cells cause even more inflammation, all on their own, in the breast tissue surrounding the cancer, including the fatty tissue which is where that aromatase enzyme is made.

Getting a little bit technical here, but I think it’s important. Estrone acts on the alpha receptors. Estradiol (the hormone that is most commonly used in HRT) is both alpha and beta (but mainly beta). Estriol, the weakest form of estrogen, works on the beta receptors-calms. Breast cancer has alpha receptors and responds most to the estrone.

The cause of breast cancer has nothing to do with HRT or using  bio-identical estradiol/estriol and bio-identical progesterone. In fact, there have been meta-analysis studies and again in the NAMS 2022 Statement that indicate the use of Estradiol actually reduces the recurrence of breast cancer by 20-30% and reduces the risk of death from cancer and ALL cause mortality. [1,4,6]

These studies show that estrogen-only HRT reduces the recurrence of breast cancer and bioidentical estrogen and progesterone combined, contrary to the initial report from the Woman’s Health Initiative (WHI) study, also may reduce breast cancer. AND none of the studies show that bioidentical HRT causes more deaths [1,5].

As Dr. Felice Gersh (OBGYN) says, ‘don’t be afraid of our life sustaining hormones but DO be afraid of the chemicals that surround us, including pharmaceuticals’. And do be wise to what we put into our mouths and take a hard look at our lifestyle.

So how could HRT possibly reduce breast cancer? I’ve already mentioned some of the wonderful things that estradiol does in previous posts but let’s review.

Estradiol reduces inflammation. It helps to turn on tumor suppressor genes [5]. Genes that down regulate the ability to create cancer cells. It also promotes a process that takes old cells and gets rid of them which helps new cells stay healthy. Much like trimming dead branches from a tree or removing dead leaves from a plant.

So again, the vast majority of women who develop breast cancer are postmenopausal-women, who don’t have much estrogen.

Now, is it wise to give a woman HRT while she has active cancer? Probably not. All estrogens are somewhat proliferative which means they make things grow, even estriol if in high enough amounts. But this does not mean that exploring the use of HRT to make a woman’s quality of life better after cancer treatment, should not be out of the question, especially vaginal estrogen.

Some may think that I believe HRT is the end-all be-all. I don’t, but I would like Cancer Thrivers and all menopausal women to understand the playing field and know their options so they can advocate for themselves, whatever that might look like for them.

There are many women (young and old), who after their cancer treatments, have a very compromised quality of life because they have no hormones on board. These are the women who have vaginal atrophy, ongoing UTI’s, horrible sleep, debilitating brain fog or depression, signs of dementia, weight gain, osteoporosis, and heart disease (which is the #1 killer of postmenopausal women-NOT cancer). 

Not every woman experiences the above, but I see plenty who do.

Most of my menopausal women who have not had cancer, have never been offered hormone therapy, let alone those women who have had cancer. Why???

Many doctors and women are still misinformed and are afraid of HRT. And I understand! Even AI says that HRT can increase the risk of cancer. If AI has not been able to navigate all of the mixed messaging out there, how is the average woman supposed to figure it out?!?

As always, I like to stress that NO ONE SIZE fits all. And NO ONE has the right to dictate what we can and cannot do for ourselves, even our doctors. But the only way, at least in my mind, to become our own best advocate is to learn. Knowledge is power-truly!

I encourage every woman to educate herself as much as possible and work with her doctor to determine what is the best for her.

Part of my job is to help you become informed, to be a better advocate for yourselves.

I’d like to leave you with these resources so you can further explore on your own and I hope you will. 

From my heart,
Cindy D

Please remember that anything you find written here is for informational purposes only. Nothing here is to replace the care or recommendations of your health care provider.

YouTube: Dr. Felice Gersh, Dr. Louise Newson, Kirsty Lang (Cancer  Thriver and journalist)                       Pulling the Curtain Back On Hormone Replacement Therapy

Book by an Oncologist, Dr. Avrum Bluming: Estrogen Matters 

Website, instagram account of Dr. Corinne Menn who’s an OBGYN and two time breast cancer survivor.

Podcast: Dani Binnington-Breast Cancer survivor. She does a phenomenal job of getting quality doctors and others on her show, addressing the challenges of breast cancer survivors-not just hormones.


    1. The 2022 hormone therapy position statement of The North American Menopause Society.

    1.  Estradiol therapy and breast cancer risk in perimenopausal and             postmenopausal women: a systematic review and meta-analysis  

    1. Unequal risks for breast cancer associated with different hormone replacement therapies: results from the E3N cohort study  

    1. Cancer Breast Adipose Tissue Estrogen Metabolism in Postmenopausal Women With or Without Breast 

    1. Type of estrogen and 17β-HSD enzyme levels in cancer patients and controls. Therapeutic utility of natural estrogen receptor beta agonists on ovarian cancer:Estradiol (E2) as compared to Estrone (E1) has antiproliferative properties in ovarian cancers. Reducing tumor size and inducing apoptosis of tumor cells.

    1. Use of menopausal hormone therapy beyond age 65 years and its effects on women’s health  outcomes by types, routes, and doses 2024

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