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Testosterone isn’t just a sex hormone. In men, it plays an important role in many other systems in the body — including the heart. And when testosterone levels are abnormal, the heart can experience issues.

“The strongest evidence is that abnormally low testosterone is not good cardiovascularly,” says Geoff Werstuck, Ph.D., a professor of medicine at McMaster University who specializes in heart health.

In the mid-1980s, scientists measured the testosterone levels of 794 older men, and followed them for the next two decades. The results, published in 2008 in the Journal of Clinical Endocrinology and Metabolism, found that men with the lowest testosterone levels were 38% more likely to die of a cardiovascular event like a stroke or heart attack.

In another analysis, Belgian researchers aggregated results from 19 different studies on testosterone and heart health. They found that men over 70 who had high testosterone were 16% less likely to experience a cardiovascular event than men with low T.

Why do we see this relationship between testosterone and heart health? Scientists aren’t sure. These population studies don’t necessarily show that low testosterone causes cardiovascular problems. It could be that low T is simply a symptom of poor overall health, or, as an article published in the journal Evolution, Medicine, and Public Health theorized, it could caused by another condition that tends to occur alongside heart problems. For example, heart disease is often associated with higher body fat, which in turn can lower testosterone levels.

That said, some studies do suggest a more direct relationship between testosterone and heart problems. Werstuck conducts most of his research in mice, and has found that when mice are castrated, they quickly begin showing signs of atherosclerosis — hardening of the arteries that can contribute to heart problems.

We see similar patterns in men treated with androgen deprivation therapy, a treatment for prostate cancer that forces the body to produce very little testosterone. In a 2001 study comparing 26,570 men undergoing this therapy to 46,626 men with prostate cancer who didn’t receive it, men receiving androgen deprivation therapy were 16% more likely to have coronary heart disease and 11% more likely to have a heart attack.

One hypothesis as to why this relationship exists is that testosterone directly impacts our genetic material in ways that decrease inflammation. Like a key fitting into a keyhole, testosterone binds to androgen receptors, which are located on most cells in the body. That grants testosterone access to DNA within the cell. It locks onto sites on the DNA that are built to interact with the hormone and changes the way the body reads and expresses that genetic code.

Experiments show that when testosterone changes gene expression, it can counter inflammation in the body. Inflammation is a state where the body releases white blood cells and chemicals to fight disease and injury — good in the short term, but harmful to the heart when it becomes a chronic state.

If you’re experiencing symptoms of low T — such as fatigue, erectile dysfunction, low libido, depression, and loss of muscle mass — it might be worth getting your levels checked. From there, have a conversation with your doctor about treatment.

But be aware that it may not protect your heart. Testosterone replacement therapy (TRT), in which synthetic testosterone is administered as an injection or topical ointment, can help raise testosterone levels, but there isn’t good evidence that it reduces the risk of heart problems, Werstuck says. In fact, some studies suggest it might increase this risk. That doesn’t mean you should rule out TRT, but don’t spring for it without a conversation with a medical professional.