Authored by Gennev Chief Medical Officer, ob/gyn Dr. Rebecca Dunsmoor-Su.

"There's been yet another round of lay-press headlines about how estrogen plus progesterone hormone replacement may increase the breast cancer risk," says OB/GYN Dr. Rebecca Dunsmoor-Su. 

Headlines don't tell the full story, and Dr. Dunsmoor-Su, who is an epidemiologist as well as an OB/GYN, helps us separate fact from fiction in this podcast.

If you're dealing with menopause symptoms and are worried about taking HRT to manage them, you'll want to give this a listen.



Hi, this is Dr Rebecca Dunsmore-Su, the Chief Medical Officer here at Gennev. I wanted to put together a podcast today about hormone replacement therapy [HRT] and breast cancer. 

I'm addressing this again because there's been yet another round of lay-press headlines about how estrogen plus progesterone hormone replacement may increase the breast cancer risk. And that's because of some data presented at a breast conference recently. 

It's important to note that this data is not new data. It is the same data from the Women's Health Initiative that we've been talking about for many, many years. And the data from that study has been analyzed multiple times by multiple other investigators, and they all note that the data does not really show an increase of breast cancer in this population. 

When you actually parse the data out and look at the women who started estrogen and progesterone and have had never seen hormone before and therefore likely younger and more close to the time of transition of menopause, there is no difference in breast cancer rate between them and people given a sugar pill in the same group.

Importantly, the only group in which they found a difference between them and the sugar pill is in women who had taken hormones before and stopped. 

Two big issues with that: One, that's not how we use hormones, and two, the group given a sugar pill in that subgroup actually had a much lower than average rate of breast cancer. So in comparing those two groups, you're actually comparing to the wrong comparative group. 

If you look at that group of women given estrogen plus progesterone, they really actually don't have a higher rate of breast cancer than any other E plus P group that we're not calling significant. 

That's a lot of statistics talk for saying if you work with your data enough, you can make something look like it causes harm. But really when you look at how we use hormones, estrogen plus progesterone really does not increase the risk of breast cancer.

But again, some studies say it does. Some studies say it doesn't. Some big studies say it does. Some big studies say it doesn't. And why are we seeing this back and forth? Why don't we know the answer by now? 

I think there are two real reasons why that's true. The first reason is, in anything that may have a very small or no impact, if you do studies you're going to see studies give you false data on both sides of that true estimate. It's why we do large studies. It's a statistical anomaly and so what we're getting is all of these studies on either side sort of telling us, well maybe the reality is somewhere in the middle or somewhere around zero.

The second reason is probably genetic. Not all women are the same and we know from some studies that there are gene products that probably make it an increased risk to take hormones and with breast cancer and we know from other studies that there are women for whom taking hormones can be protective against breast cancer.

The problem is we just don't know all of the genes that can impact this yet and so you're going to see different responses from different women to hormone replacement therapy. The one thing I do know is that no matter which side of that genetic line you fall on, the actual overall impact of hormones on breast cancer is probably exceedingly low. 

So what, you may ask, does that mean for you? Well, here's how I approach hormone replacement therapy. I approach it by saying, well, what is it good for, and what could the risks be, and how do I balance those for my particular patient? 

Benefits of hormone replacement therapy

So first of all, what is hormone replacement therapy good for? 

Number one, it's good for symptoms. If you are suffering significantly from hot flashes or night sweats or vaginal dryness or any of those symptoms, hormone replacement therapy is actually very a effective medication for that, and only you know how big the impact of those symptoms are on your life and how much you would value taking a medication that can make them go away.

The second thing we know it’s very good for is your bones. It's one of the best medicines for preserving bone strength. We don't typically use it just for that, but we certainly as providers understand that it does one of the best jobs with the least risk for protecting bones. 

The third thing I'll talk about with people is cardiovascular protection from hormone replacement therapy. The answer to that is very complicated and again, women are genetically very different. So there's no one answer for each woman. But we do know that women who have estrogen have a different lipid profile and a different cardiac risk in terms of heart attack than women who are menopausal. 

And so there is probably some protective effect from that perspective. But depending on how you use the hormone, it can also be dangerous because if a woman has already developed atherosclerotic plaques in her arteries, adding estrogen back can cause blood clots to form on top of those and could probably increase her heart attack or stroke risk.

So when you're talking to a doctor about hormone replacement therapy and cardiac risk, you need to be having a very complex discussion about whether it might be beneficial or harmful for you. 

The next thing that we sometimes use hormones for is mood, and in some women it really can be quite beneficial in balancing mood, especially in the perimenopausal time. However, we don't have great evidence that it helps all women. And again, this is likely because women respond differently both to hormone and have different reasons for having mood symptoms. 

And the last things women often ask me about are more what we typically think of as superficial things like their skin, their hair, their nails, and their weight gain. Hormones can be somewhat beneficial for those things, but I certainly don't start women on it just for that because really its impact is quite low in those things and there are other things that are safer that we can use for that.

Risks of hormone replacement therapy

So if those are the things hormone replacement therapy can be good for, what are the risks? In my mind, the biggest risk is actually for blood clotting

So we know that estrogen increases the risk of forming a blood clot in the body. We know that women who are pregnant have a higher risk of that. We know that women before menopause have a higher risk of that. It is a known risk of estrogen. It is not a huge risk. 

The baseline risk of forming a blood clot if you don't have a predisposition is quite low and the increase is relatively small from adding estrogen. But we do talk about it because it can be an important risk, especially in people who might be at higher risk of stroke. So it's important to think about that risk and whether it applies to you.

The second thing we talk about when I counsel patients is breast cancer, and I tell my patients honestly I don't think that estrogen really, on the whole, increases your risk of breast cancer. I think there are certain people for whom that might be true and there are certain people for whom it's protective. But on the whole, for most women, it's probably not a big risk. 

The important thing to keep in mind also is one of the things they show in the Women's Health Initiative that we don't talk about a whole lot and in some of these other large studies is that when women do get breast cancer on hormone replacement therapy, it's often a lower grade or earlier-stage cancer and easier to cure. 

The last thing I always talk to my patients about is that one in eight women will get breast cancer in their lifetime. That's your baseline risk, so it can be really hard to tell if something is actually increasing that risk when the risk is so common. And while breast cancer is very scary to us as women, we think a lot about it, in reality, it kills very few of us, and those of us who are at highest risk of dying from breast cancer and breast cancer complications or those of us getting it at earlier ages, and there's a lot of genetic interplay with that. 

The sort of breast cancer that we see as women age that contributes to the large portion of this one-in-eight risk is generally caught fairly early stage — if you're getting adequate screening — and is curable. 

Many, many, many more women will die of cardiovascular disease and many, many more women will die of hip-fracture related complications. So we need to be thinking and talking much more about cardiovascular disease and bone health in women in menopause.

Taking HRT safely

So I just gave you my counseling session that I give to women in my office for hormone replacement, and many of them after that counseling session say, well, what would you do? Or what should I do? 

And I tell my patients that if you're going to use hormone replacement therapy, which I often recommend, you need to be using it safely, and the most important thing you can do is know what you are taking. 

I see many women in my office who have been told by other providers that they can be given a special, compounded, just-for-them hormone replacement, that will be better than anything made by an evil pharmaceutical company. 

This is not true. 

First myth: there is no “natural” hormone replacement. Estradiol and progesterone are synthetically made. If you get it compounded, it's still synthetically made in the same pharmaceutical company that made the pills that I would prescribe you or the patches that I would prescribe you.

Second, no one can match it to the hormones that you had before menopause because those hormones are gone. We can't predict what those were. So anyone who's saying they're making a blend especially for you really isn't. They're just making a blend that they've been taught to make. 

And the third big thing that I tell people is when you are getting things mixed into creams or rubbing them on your skin, you do not know what dose you are taking. While they try to do their best to get it evenly mixed throughout that compounded cream or lotion or base, it is not evenly mixed and we know it's not. And when the Lin tests have been done on these products, the variation in the amount of hormone actually in any given dose is quite wide. If you're going to take something that might have a risk, you need to be taking something where you know what dose you're getting.

And so I tell my patients, I only use the pharmaceutically generated and regulated products such as estradiol pills, estradiol patches, and progesterone pills and things like that. And that's just for safety's sake. If there might be a risk associated with this thing, I at least want to know what I'm giving you. 

The second thing you can do is get your breast screening, get your mammograms, get your breast exams at the doctor. People don't enjoy getting mammograms. Trust me, I don't enjoy getting them either, but they are our best method of screening for early-stage cancer, and if we catch breast cancer early, it can be cured. 

The third thing you can do is when these articles come out in the lay press, read them with a critical eye. Many headlines are generated to scare so that you'll read the article. So just be aware there may be no new data behind this. They may just be rehashing the same data that we've heard over and over again, trying to get a new article out of it. 

The fourth thing I tell people is, help us to understand better how genetics play into breast cancer risk and hormone. Go to an organization like, and there'll be a link on our website for this. That is a nonprofit organization that's doing genetic research on how different gene factors play into the breast cancer risk in women. And it'd be great to sign up for one of their studies if you qualify. 

And finally, when you're thinking about using hormone replacement, find someone with genuine credentials, find a physician who has some training in menopause and really understands the issues behind this and doesn't automatically do the same thing for every woman. 

This should always be a discussion between you and your doctor and they should have a good understanding of the risks and benefits of hormones and be able to explain that to you and make a tailored decision for you. 

Thank you so much for listening. I know this is a constant question and issue for us here at Gennev. And our goal, as always, is to give you the best, medically valid and evidence-based information we can find.


Join the conversation that continues on about HRT, breast cancer, all things midlife and menopause, and more in our Community forums. You are always invited.



Shannon Perry

December 18, 2019
Director of Programming & Media

Medically Reviewed By

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