Does Estrogen Cause Breast Cancer?


An article appeared last week in the prestigious British medical journal The Lancet, presenting worldwide epidemiological evidence regarding the type and timing of menopausal hormone therapy and risk of developing breast cancer.

It is one of the most comprehensive articles on the subject.  It is not based on an actual research study, but instead is an assessment of the world’s literature on the subject to date.

They concluded that:

  • Menopausal hormone use of all types is consistent with an increased risk of breast cancer.
  • They found that daily estrogen and progesterone posed the greatest risk, and that less frequent progesterone or intermittent progesterone use was less of a risk.  
  • Hormone usage caused more frequent estrogen positive receptor tumors than negative if used between 5 and 14 years. 
  • There was no difference in risk for women starting hormones at age 40 to 59. 
  • There was an increased risk for women starting hormones after age 60.
  • There was little to no risk for hormone users for less than one year.  
  • There was excess risk for women who were obese or had an elevated BMI.  
  • The risk persisted for up to ten years after discontinuing hormone use.

The increased risk was 1 in 50 users of combined daily estrogen and progesterone, and 1 in 70 women using intermittent progesterone.  Apparently, it made no difference what type of progesterone was used. For women who had hysterectomies, the increased breast cancer risk of using estrogen only with no progesterone was 1 in 200.

They reported little variation in risk between equine estrogen and estradiol, as well as oral versus transdermal administration.  

They did note little risk exists for topical vaginal estrogen use, for no known reason.

It is interesting to note that the breast cancer rate of receptor positive cancers increased in women of higher BMI even if they never used hormones, and actually didn’t increase for them if they did, (because their risk was already elevated) as compared to an increase rate in lean women. 


Trying to understand this data is not easy.

 Breaking it down, the average risk of developing breast cancer in non-hormone users is 6.3 per 100 women in the 20-year range between age 50 and 69.

With fifteen years of combined estrogen and progesterone hormone use, this risk goes up 2 women per hundred to 8.3 per 100.  For those using intermittent progesterone (i.e. half of the month) it is 7.7 per hundred (an increase of approximately one person per 100). For those women using estrogen only (with hysterectomies) it is 6.8 per hundred (virtually no difference)

This is fascinating and useful information as we are continuously working to make hormone replacement as safe an s possible.


I think it is important not to ignore this data. There are a number of issues that were not addressed.  There was no mention of the use of testosterone replacement in women. Testosterone has been reported to lower the risk of breast cancer in general.

There was no attention directed at dosing, monitoring or blood testing of hormone levels. All estrogen derivatives were lumped together. There were no specific numbers of incidence associated with each specific modality of estrogen formula.

In addition, there was no mention of methods that might be used to help reduce the risk of developing breast cancer in general. 

I recommend testosterone supplementation for all women on menopausal hormone replacement.

I also recommend 6.25 mg of Iodine per day, which has been shown to help reduce the amount of “harmful estrogen metabolites” as well as 200 mg of DIM

AND, be sure to avoid ascorbic acid.  Most vitamins contain ascorbic acid confusing it with real Vitamin C.  IT IS NOT VITAMIN C. And, it is harmful. The only way to get real Vitamin C is from fruits and vegetables.  Don’t take ascorbic acid. Don’t take it in I V drips. It is a scam. It is not Vitamin C and can poison your metabolism.

I think it is also important to remember that EVERYTHING in medicine is based upon the premise of “Risk vs. Benefit”. 

And there are multiple benefits of hormone replacement for women in menopause such as less osteoporosis, heart disease, and of course Quality of Life.

The conclusion of the study was what has been espoused about hormone replacement for many years:   Use hormones for the shortest duration possible and to use the lowest doses needed.


I think this report leaves almost as many unanswered questions as it attempts to answer. What are the specific risks of each form of hormone replacement?  Are there variations from different delivery systems? Is it possible to impact the risk with some risk reduction techniques? How frequently were the patients having breast imaging? And what type of imaging?  Are there differences for different socio-economic classes? Etc. 

Also, they found that vaginal estrogen did not increase the risk, neither did estrogen alone without progesterone in women with hysterectomies.

I hear this question about when someone should stop taking hormones almost every day. I have many hormone patients who I have been working with for 10 – 15 years.  Some of these women are over 70. At that age actually, they have already beaten the odds.

But, I tell everyone that the choice to discontinue hormone use is a very personal decision.  I have patients who feel great with the tiniest dose of estrogen, and other women who practically need to take a bath in it to feel good.  Everyone is different and has different needs and risk. Some women go off hormones and still feel great, and others practically can’t leave the house.

The general recommendation is to use the smallest amount of hormone necessary for the shortest amount of time. 


There are many risk factors associated with developing cancer of many types, not just breast cancer.

I believe it is important to maximize one’s health at every stage of their life. This translates into leading a healthy lifestyle.  Try to get enough sleep and rest, minimize stress, decrease alcohol consumption, exercise vigorously, regularly and daily to maintain an ideal body weight and BMI, eat a healthy diet which means avoid sugar, processed carbs, starch, grains, baked goods and all dairy.

Healthy supplements should include 6.25 mg of Iodine daily, 200 mg DIM, 5000 IU Vitamin D3 with K2.


I also believe we need to support our immune systems to help fight cancer. I have been self-injecting with 200 mg of Glutathione subcutaneously every day. Glutathione is one of the most potent antioxidants in our body, and it readily gets depleted which can dramatically adversely affect our immune system.


Be a health advocate, not a victim!


Female hormones can be associated with a small increased risk of developing breast cancer (approximately one person per hundred).

In addition, there appears to be no increased risk if progesterone is not used.  So it seems from this data that progesterone may be the culprit and not estrogen. But it is not advised to take “unopposed estrogen” as the uterus will be overly stimulated and produce a thickened lining that could degenerate into uterine cancer.

This does create a dilemma to female hormone users.

So, we do need to cycle in some progesterone every month for women with an intact uterus.

It is possible to avoid progesterone use entirely in women who have had a hysterectomy.

It behooves us to take every precaution we know of to make post menopausal hormone replacement as safe as possible

  • Do a yearly ultrasound exam of the uterus to monitor the thickness of the lining.
  • Yearly breast imaging
  • Iodine 6.25 mg per day
  • DIM 200 mg per day
  • Vitamin D3 with K2 5000 IU per day
  • Testosterone supplementation
  • Maintain optimal BMI
  • Daily exercise

Remember, everything in medicine is RISK vs BENEFIT!

Its different for everyone, and it has to work for you.

I wish I could say that menopausal hormone replacement is completely safe.  But unfortunately, the literature says otherwise. That does not mean one should stop it completely, as there are significant benefits of taking menopausal hormones. 

 In conclusion, this information is extremely helpful to improve menopausal hormone therapy.  And I believe if we approach the condition of menopause as intelligently as possible and work to maintain optimal health as we age, we can have a significant impact on mitigating the risk and maximizing our health as we age.


Is Bioidentical Hormone Therapy right for you?  Call 310-393-2333 or book online for a consultation with Dr. Liebowitz.

Print Friendly, PDF & Email