Does Estrogen Cause Breast Cancer? Part II

by Magnolia on October 19, 2015

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Today’s post is a continuation of  Dr. Joseph Mazzei’s post on the relationship between estrogen therapy and breast cancer. 

The views expressed in this post are not necessarily the views held by The Perimenopause Blog and are for informational purposes only.

Please see your physician or healthcare provider for personal medical evaluations. 

Let us continue our conversation from my last post by considering estrogen metabolism.  Estrogen, whether you take it as a supplement or your body makes it, will be metabolized as your body tries eliminate it.

Estrogen gets broken down into other substances, known as estrogen metabolites.  These metabolites are active and perform functions of their own.  Some of these metabolites are beneficial and protect against breast cancer and uterine cancer.  Other metabolites are harmful and are known to cause cancer and promote abnormal breast tissue growth.

Enzymes regulate the chemical reactions that metabolize estrogen.  Unfortunately, some people have certain enzymes that do not work very well or their genes have not been activated to produce enzymes needed for healthy estrogen metabolism.  These people end up with high levels of harmful estrogen metabolites and not enough protective metabolites.  Subsequently, they are at higher risk to develop cancer.

This probably explains why some studies show an increased incidence of breast cancer in groups of women who have been exposed to high levels of estrogen for longer periods of time such as an early age of first period, the late onset of menopause or they have never been pregnant.

If you consider two groups of women, statistically, there is most likely an equal proportion of women in each group with poor estrogen metabolism.  If one of the groups is exposed to high levels of estrogen for longer periods of time, their poor metabolizers will have a longer exposure to harmful estrogen metabolites. This will increase their chance of developing breast cancer when compared to the other group. The problem in this case, is not with estrogen, but rather with estrogen metabolism.

Our DNA (genes) is responsible for producing the enzymes that regulate estrogen metabolism.  Activation of those genes and enzyme function is influenced by one’s internal environment.  I measure estrogen metabolites in my patients to determine which enzymes are working and which metabolites are being produced.

If a patient more readily metabolizes estrogen into harmful metabolites, I will use nutrition, supplements, and other therapies to push their metabolism in a more favorable direction.  Then estrogen can be administered more safely.  Estrogen metabolism is good to check whether you are on estrogen therapy or not, especially if you have a family history of breast cancer.  You may uncover a genetic predisposition for poor estrogen metabolism and be able to improve it, lowering your risk for breast cancer. risk.

The Important Relationship Between Progesterone and Estrogen

One should also consider the hormone environment in which estrogen operates.  Estrogen acts in concert with other hormones, influencing a lot of activity, but not always good activity.

Progesterone acts as a mitigating influence on estrogen. It tempers and guides estrogen’s activity, helping to maintain a healthy balance. There are studies which show bio-identical, progesterone is protective against breast cancer.  When I prescribe estrogen, I use bio-identical estrogen, and balance it with enough progesterone.  I also monitor levels of both hormones to make sure each remains within normal limits.

Estrogen’s Role in Breast Cancer

To understand estrogen’s role in breast cancer, it is important to look beyond hormones.  Cancer cells form in our body when their DNA is damaged. DNA controls what a cell does, and when it is damaged, it loses control and no longer cooperates with other cells.

These rogue, dysfunctional cells begin to work against other cells, reproducing abnormal cells.  The abnormal cells begin to multiply, form tumors and start to spread.  Sometimes, cancer cells respond to estrogen, and estrogen will make them grow and spread faster. However, this does not mean estrogen caused the cancer in the first place.  Again, we must consider our internal environment.

We are exposed to a variety of toxins in our homes, work place, and recreational venues.  We eat, drink, and breathe toxins every day which pollute our internal environment, and interfere with our health in many ways.  One of these ways is by damaging DNA and producing cancer cells.

This is the environment in which estrogen works.  If toxins are not addressed, then the safety of estrogen therapy (and health in general) is greatly diminished.

Dr. Joseph Mazzei is a Chicago based doctor for BodyLogicMD and specializes in bioidentical hormone therapy. He graduated from the Chicago College of Osteopathic Medicine at Midwestern University and is Board Certified by the American Osteopathic Board of Emergency Medicine (AOBEM). 

He is an Advanced Fellow in the American Board of Anti-Aging and Regenerative Medicine Fellowship, and a member of the American Academy of Anti-Aging Medicine (A4M) and the American Osteopathic Association. (AOA). His Chicago office is located at 65 E. Wacker Place, Suite 600 Chicago, IL 60601 (312) 546-6490  and his Northbrook office is located at 5 Revere Drive, Suite 238 Northbrook, IL 60062 (312) 546-6490

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{ 6 comments… read them below or add one }

Jennifer July 18, 2012 at 4:29 pm

Can you speak to the effectiveness of the supplement DIM in regards to estrogen.


Magnolia July 18, 2012 at 4:35 pm

Hello Jennifer,

I can certainly pass your question on to Dr. Mazzei and let him speak to it. I do not know what DIM is.

Edit…….I just checked to see what DIM is, and learned quickly that it is a phytoestrogen that is often a by-product of certain foods during digestion… that correct?

If I am correct, then I would say that you need to be very careful and mindful of additional estrogen and estrogen behaving compounds in your body if you use estrogen therapy.

Dr. Mazzei addresses that in one of the posts……actually, I think it will be post III that will be up on Friday.

Does that help?



Daniel Soule July 18, 2012 at 4:38 pm

Please remember the role of testosterone for its protective benefits as well as use in the treatment of breast cancer survivors. The use of Testosterone-Anastrozole implants for breast cancer survivors in treating symptoms associated with menopause also seems to be showing promise. Continuous testosterone therapy, delivered by subcutaneous (SC) implant, effectively treats hormone/androgen deficiency symptoms as measured by the HRQOL, Menopause Rating Scale (MRS) in both pre and post menopausal patients. Two recent studies show that women on HRT who get testosterone implants show no increased risk for breast cancer. All good news for women struggling with the symptoms of menopause and suffering rapid aging through age related decline of hormones.


Magnolia July 18, 2012 at 4:40 pm

Thank you, Daniel

I have used testosterone pellets in the past. I know a little bit about their benefit in being a substrate for estrogen development in our body.

But, I do not know much more than that.



Daniel Soule July 18, 2012 at 4:48 pm

Dr. Rebecca Glaser is doing some great work in this area. It’s also great to know that NAMS actually updated their position on BHRT for women.

Thanks for your input and postings.


Magnolia July 18, 2012 at 4:50 pm

Yes, I know Dr. Glaser. She was the physician who implanted my pellets.



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