Estrogen, Cancer, Heart Disease, Stroke & Blood Clots: What You Actually Need to Know About Menopause Hormone Therapy

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Today, we’re continuing our discussion of the risks and benefits of estrogen. And this week, we’re tackling some of the bigger health concerns: heart disease, stroke, blood clots, and cancer.

There is a lot of information here, so find a comfy chair and a fan (if you’ve got hot flashes, like me), and let’s get started.

Coronary Heart Disease

Heart disease is the number one cause of death in women, both in the United States and worldwide.

Anatomical illustration of the heart highlighting ongoing discussions about cardiac risks related to hormone therapy.

So, does estrogen increase your risk of heart disease?

Multiple studies—including the ELITE study, the Danish Osteoporosis Prevention Study, and a 2015 Cochrane meta-analysis—have provided evidence supporting the idea that the cardiovascular effects of hormone therapy may depend on when it is started.

Women who start hormone therapy within 10 years of menopause and before age 60 appear to have a more favorable cardiovascular risk profile than women who start later.

I’m including the names of these studies because I want to emphasize that we’re not talking about a handful of women. These studies looked at a combined total of more than 70,000 women.

That’s pretty good data.

If that’s the case, then why isn’t everyone clamoring to get on estrogen?

Enter 2002.

The Women's Health Initiative (WHI), which ultimately included more than 160,000 women across its various clinical trials and observational studies, released the initial results of its estrogen-plus-progestin trial in 2002. That trial included more than 16,000 women. The initial results suggested that combination estrogen/progestin therapy increased the risk of heart disease.

SCREEEEEEEEEEECH!

That’s the sound of the medical community hitting the brakes on hormone replacement therapy.

And it changed the course of women’s health for years.

Subsequent analyses helped clarify something important:

Timing matters.

The cardiovascular risks appear to be different depending on when hormone therapy is started. Women who begin hormone therapy more than 10 years after menopause—and particularly those who begin it 20 or more years after menopause—have a less favorable cardiovascular risk-benefit ratio.

So what does this mean?

As with so many things in medicine and love lives:

Timing matters.

Also—and this is important—at this time hormone therapy is not recommended specifically to prevent heart disease. 

Stroke

Stroke follows a similar pattern.

Studies have generally found a lower stroke risk profile in women who start hormone therapy before age 60 or within 10 years of menopause, although individual risk factors still matter.

There was, however, an increased risk among women who initiated hormone therapy after age 60 and/or more than 10 years after menopause.

There is also some observational evidence suggesting that lower-dose estrogen and transdermal estrogen (the patch) may have less effect on stroke risk.

Venous Thromboembolism

Now let’s talk about blood clots.

There is an increased risk of venous thromboembolism (VTE) with oral estrogen, regardless of the age at which it is started.

However, observational studies suggest that transdermal estrogen and lower doses of oral estrogen may have less effect on VTE risk.

This is one reason you'll hear me talk about the estrogen patch—and why I, myself, am on it. Of course, that doesn't mean the patch is right for everyone.

It’s not just a matter of convenience.

How estrogen gets into your body matters.

Breast Cancer

The relationship between hormone therapy and breast cancer is complicated, and the type of hormone therapy matters.

In the Women’s Health Initiative, women who received conjugated estrogen alone had a nonsignificant reduction in breast cancer risk after an average of 7.2 years of treatment.

On the other hand, continuous combined therapy with conjugated equine estrogen (CEE) plus medroxyprogesterone acetate (MPA) was associated with an increased risk of breast cancer.

A woman prepares for a mammogram, highlighting the importance of breast cancer detection.

So, once again, it’s not simply: Estrogen = breast cancer.

The formulation, the combination of hormones, and the duration of treatment all matter.

The attributable risk of breast cancer in women (mean age of 63 years) randomized to CEE plus MPA in the WHI was less than one additional case of breast cancer per 1,000 users annually.

To put that into perspective, this is similar to the risk with obesity, low physical activity, and some medications.

That doesn't mean we should ignore the risk. It means we need to put the risk into perspective and understand that the absolute increase in risk is small.

Duration matters, too.

Some studies have shown an increased risk of breast cancer with longer durations of hormone therapy.

Different hormone therapy regimens can also increase breast density, which can lead to additional imaging and biopsies.

This happened to me.

And let me tell you—being called back for additional breast imaging (and a biopsy) is not exactly my idea of a fun afternoon. (See my previous post: https://www.rx4trauma.com/post/the-squeeze-the-squish-the-press)

Some observational studies, particularly in women with BRCA mutations who undergo risk-reducing removal of their ovaries, have been reassuring regarding short-term hormone therapy use. However, these decisions are individualized and require a discussion of personal and family history.

Systemic hormone therapy is generally not recommended for breast cancer survivors, although, as with almost everything in medicine, individual circumstances require an individualized discussion of risks and benefits.

Endometrial Cancer

If you have a uterus, we also have to talk about the lining of the uterus.

Hormone therapy may be considered in women with symptoms who have had treatment for early-stage, low-risk endometrial cancer.

For women with more advanced or higher-risk endometrial cancer, nonhormonal treatments are generally recommended.

And, of course, this is another reason why the type of hormone therapy matters.

If you have a uterus and are taking systemic estrogen, you generally need protection for the uterine lining with progesterone.

Ovarian Cancer

Available observational data have not consistently demonstrated an increased risk of ovarian cancer with hormone therapy, but the data are limited.

Colorectal Cancer

Observational studies suggest that hormone therapy may actually be associated with a reduced incidence of colorectal cancer, particularly when started earlier in menopause.

Again, this is an observed benefit—not a reason to prescribe hormone therapy specifically for cancer prevention.

Lung Cancer

The relationship between hormone therapy and lung cancer is complicated. Some studies have not found a meaningful effect on lung cancer, while the WHI found an increased risk of death from lung cancer with combined estrogen/progestin therapy.

Either way, if you smoke, quitting smoking is going to have a much bigger impact on your health than whether you're using an estrogen patch or pill.

Please stop smoking.

Seriously.

X-ray images highlighting lung health and reinforcing the critical importance of avoiding smoking to maintain respiratory well-being.

So...Should You Take Estrogen?

After all of that, you may be wondering:

“Okay, so is estrogen good or bad?”

A woman ponders the complex role of estrogen with curiosity and concern, illustrated by question marks surrounding her thoughtful expression.

Since the original Women's Health Initiative results came out in 2002, we've learned a lot more about hormone therapy. In 2026, the FDA even updated the labeling for several hormone therapy products, removing some of the broad cardiovascular disease, breast cancer, and dementia language from the boxed warning.

That doesn't mean hormone therapy is suddenly risk-free. It isn't.

And unfortunately, I don’t have a one-word answer to my question.

That’s because estrogen isn’t simply good or bad.

Your age matters.

Your symptoms matter.

How long it has been since menopause matters.

Your personal medical history matters.

Your family history matters.

The type and dose of estrogen matter.

Whether you have a uterus matters.

And the way you take estrogen matters.

This is why I get frustrated when hormone therapy gets reduced to a headline:

“Estrogen causes cancer.”

Or:

“Estrogen prevents heart disease.”

Neither statement tells the whole story.

We’re talking about a hormone that may increase some risks, decrease others, and have different effects depending on when you start it and what formulation you use.

Welcome to menopause medicine. Nuanced women’s health.

There are no absolutes and while that is frustrating, it may actually be a good thing.

It means we can have a conversation about you rather than trying to apply a one-size-fits-all rule to every woman going through menopause.

And maybe that’s the most important thing I want you to take away from this entire series:

Hormone therapy isn’t a yes-or-no decision.

It’s a risk-versus-benefit decision.

And you deserve enough information to actually participate in that decision.