If you want to gain a good picture of a man’s overall health, measure his testosterone levels. Testosterone isn’t just important for libido, strength, and energy — it also plays a role in bone health, cardiovascular health, and the immune system. And increasingly, research suggests the hormone is a reliable indicator for disease and longevity.
Researchers have found that men with low testosterone are more likely to suffer from a number of ailments, from heart attacks to diabetes — and they may not live as long.
“There’s a clear association between testosterone and mortality,” says Hugh Jones, an endocrinologist for the Barnsley Hospital NHS Foundation Trust and a professor at the University of Sheffield in England.
So what does this mean for the roughly quarter of men over 40 who have low testosterone? And is it possible to ward off some of the negative health effects associated with low T?
The Link Between Low T And Mortality
In 2022, scientists at Baylor University and the University of Texas at San Antonio took a deep dive into the relationship between testosterone and early death. Pulling up records for 10,225 patients who had participated in the National Health and Nutrition Examination survey between 1999 and 2004, the researchers found that the lower a man’s testosterone levels, the more likely he was to die of disease before 2019. That likelihood was especially high for heart disease, but lower testosterone was also associated with a higher chance of dying from respiratory disease and Alzheimer’s.
Previous research supports these findings. A 2021 study published in the journal European Urology Open Science found that among 1,792 men who filled out a national survey between 1999 and 2014, those with low testosterone were more than twice as likely to be dead by 2015 compared to men with higher testosterone levels. They were also more likely to have BMIs in the obese category, diabetes, high blood pressure, and risk factors for heart disease.
Digging Deeper Into The Connection
So do these studies mean that low testosterone causes disease and early death?
“Yes and no,” Jones says. In his own research, he’s found that low testosterone does seem to worsen men’s health. In one study, Jones and his colleagues looked at almost 1,000 men with coronary artery disease, in which arteries that supply blood to the heart become dangerously narrow. They compared this population to men who did not have heart disease and found that the men with coronary artery disease had lower overall testosterone.
Additionally, low testosterone was one of the most reliable predictors of death in both groups, surpassed only by weakening of the heart muscle tissue. Men with low T were more than twice as likely to die due to a cardiovascular problem compared to men with normal testosterone levels.
These same scientists then followed 500 patients with diabetes over a period of six years. They found that by the end of the study, 17.2% of patients with low testosterone levels had died, compared to 9% of patients with testosterone in the normal range.
In a different study, Hugh and his colleagues were able to partially reverse the relationship between low T and higher mortality risk from diabetes in a subset of men who received testosterone replacement therapy. In that population, 8.6% of patients died by the end of the study compared to 19.2% who did not receive treatment.
The Role Of Disease
“It may be that low testosterone does put you in a position where you have health consequences,” Jones says. However, the relationship is likely more complicated than that, he adds. In many cases, disease can actually be what causes low T, which could drive the link between low T and death in many cases.
Disease likely lowers testosterone as the body diverts resources away from the reproductive system towards keeping the body healthy. In addition, major causes of death, such as heart disease and diabetes, are often associated with higher body weight, which may exert its own dampening effect on testosterone — because fat cells convert testosterone into estrogen. That can create a negative feedback loop, Jones says: “If you have a disease, it may lower your testosterone, which may make that disease worse.”
So why does low testosterone worsen disease? The answer to this question is murky, but scientists have a few ideas.
One of them has to do with inflammation, the body’s response to acute illness or injury, in which the immune system releases chemicals and blood cells to fight foreign invaders and heal itself. In the short term, inflammation is a good thing, but chronic inflammation puts stress on the body, making it more susceptible to conditions like heart disease and diabetes.
Testosterone is what scientists call an immune modulator, Jones says — after inflammation is no longer needed, it reduces the number of inflammatory proteins called cytokines in the body. So low T could mean the body is worse at tamping down inflammation.
Another possible explanation: In animal studies, testosterone seems to impact the way the body stores fat, Jones says. Rodents with normal testosterone tend to store fat under the skin, whereas those with lower testosterone tend to store more fat around their organs and within the walls of their arteries. In humans, fat stored in these areas is a major predictor of deadly conditions like heart disease.
If You Have Low T, Should You Be Worried?
If you do have low testosterone or suspect that to be the case, you don’t need to panic, says Michael Muehlenbein, Ph.D., a biological anthropologist studying evolutionary endocrinology at Baylor University.
“Low testosterone may be a predictor of mortality in some cases,” he says, but the relationship is “not necessarily causal.”
Besides, what constitutes low testosterone is a controversial question, and many men who have testosterone levels below the normal range remain healthy.
Still, it’s a good idea to get your levels checked out if you’re experiencing symptoms such as erectile dysfunction, reduced libido, or fatigue. And if you do have low low testosterone, it may be worth talking to your doctors if it could be the result of another condition. That may then inform whether you should start testosterone replacement therapy.
“The trick will be determining if low T is a cause of a disease — which would then potentially warrant hormone adjustment — or is a consequence of having the disease,” Muehlenbein says.