How different estrogens affect heart disease risk

Heart disease is a big concern for many people, especially as we get older. One of the main problems is atherosclerosis, which is when fatty buildups, called plaques, clog up our blood vessels. For women, the risk of atherosclerosis goes up after menopause, partly because their bodies make less estrogen. Doctors often prescribe hormone replacement therapy (HRT) to help with menopause symptoms, but there has been a lot of debate about whether HRT helps or hurts the heart.

A recent study published in Scientific Reports sheds some new light on this question by comparing how two different types of estrogen used in HRT affect atherosclerosis in mice (see the original research). The two types they studied were 17β-estradiol (E2), which is the main natural estrogen in humans, and equilin (Eq), which is found in a common HRT called conjugated equine estrogens (CEE) made from horse urine.

Why do doctors use hormone replacement therapy?

HRT is usually given to help women manage symptoms after menopause like hot flashes, mood swings, and to lower the risk of bone loss. For years, doctors also hoped it would protect the heart, since estrogen seems to help keep blood vessels healthy. However, big studies like the Women's Health Initiative (WHI) found that HRT did not lower heart attack risk, and in some cases might even increase it. This led to confusion about whether HRT is safe for the heart or not.

Different kinds of estrogen in therapy

Not all estrogens are the same. Natural estradiol is what our bodies make, while CEE contains a mix of estrogens from horses, including equilin. Scientists wondered if these differences could explain the confusing results from past studies. Some research even suggested that equilin might not protect blood vessels as well, or could even make things worse by increasing inflammation.

The mouse study: What did researchers find?

In the new study, scientists used a special type of mouse that easily develops atherosclerosis, especially when they eat a high-fat diet and no longer have their ovaries—similar to what happens in menopause. The mice were split into groups and given either estradiol, equilin, or a placebo for several weeks. Then, the researchers checked how much plaque built up in the mice's blood vessels.

Both estradiol and equilin helped reduce the formation of atherosclerotic plaques compared to placebo. But estradiol was much better at stopping these buildups, especially over a longer time. In the main blood vessels leading from the heart (the aortic arch and brachiocephalic artery), estradiol had a much stronger protective effect than equilin. This suggests that not all estrogens used in HRT work the same way when it comes to protecting the heart.

Interestingly, neither estrogen type changed the mice's cholesterol or fat levels in the blood. This means their protective effects likely came from how they affected the blood vessels themselves, not from lowering cholesterol. Scientists think this could be because estradiol helps reduce inflammation and keeps the lining of blood vessels healthy. For a deeper dive into how estrogen fights inflammation in blood vessels, you might enjoy this SlothMD article about estrogen and vessel protection.

Why does this matter for people?

While these results are promising, it is important to remember that the study was in mice, not humans. Mouse models help us understand how things might work in people, but our bodies are more complicated. For example, the type and timing of HRT, the age it starts, and each woman's unique health history can all make a difference. Some large human studies even found that starting HRT soon after menopause might be safer for the heart than starting it later.

Also, the study focused on two estrogens, but HRT can include other hormones and different ways of taking them, like pills or skin patches. These details can also change how safe or helpful HRT is for heart health.

What it means for patients

If you or someone you know is considering HRT, this research suggests that using therapies based on natural estradiol might be better for heart health than those containing equilin. However, decisions about HRT should always be made with your doctor, considering your personal risk factors and preferences. More human studies are needed to fully understand the best and safest ways to use HRT.

For those interested in how other factors, like sleep and inflammation, can affect blood pressure and heart health—as well as how health AI tools like SlothMD can help you keep track—check out this SlothMD summary about sleep, inflammation, and blood pressure risk.

Science is always learning more, and research like this helps doctors give better advice. Using health AI platforms such as SlothMD can also help you stay updated with the latest trustworthy information on these complex topics.