Between Strength and Strain: The Link Between Testosterone Therapy and Heart Disease

Introduction

Testosterone is a hormone made mainly by the testicles in males. It plays a key role in the development of male physical features such as facial hair, deep voice, and muscle mass. It also helps maintain bone strength, sex drive, mood, and energy levels. As men get older, their testosterone levels naturally drop. In some men, the drop is larger than normal. This condition is called hypogonadism, and it can cause symptoms such as tiredness, low sex drive, weight gain, and even depression.

To treat this, many men are given testosterone therapy (TT). This therapy helps bring testosterone levels back to normal. TT is available in many forms, including injections, skin patches, gels, and small pellets placed under the skin. The goal of TT is to improve quality of life by treating the symptoms caused by low testosterone. Over the past two decades, more men have started using testosterone therapy, especially those over the age of 40. Some of this rise is due to more awareness, advertising, and easier testing.

At the same time, heart disease continues to be the number one cause of death worldwide. Heart disease includes conditions like heart attacks, strokes, high blood pressure, and heart failure. Many of the same men who take testosterone therapy are already at higher risk for heart problems because of age, obesity, diabetes, or high cholesterol. These shared risk factors raise an important question: Could testosterone therapy increase the risk of heart disease?

Some early studies and reports suggested that testosterone therapy might lead to heart attacks, strokes, or other serious problems. This caused health agencies like the U.S. Food and Drug Administration (FDA) to warn the public and doctors to be cautious. Other studies, however, have shown that testosterone therapy might be safe or even helpful for some men, especially those with very low levels. The research is mixed, and doctors and scientists are still trying to understand the full picture.

The concern comes from how testosterone affects the body. It can raise red blood cell counts, which may thicken the blood and increase the risk of clots. It can also affect cholesterol levels, blood pressure, and how blood vessels function. Some of these changes might protect the heart, while others could harm it. That’s why researchers have been studying testosterone therapy closely to learn more about its risks and benefits.

The goal of this article is to explain what is known so far about testosterone therapy and heart disease. It looks at how testosterone works in the body, how it might affect the heart, and what studies have found. It also answers common questions people ask, such as whether testosterone therapy is safe, who should use it, and how to monitor its effects.

Understanding the link between testosterone and heart health is important for patients, families, and healthcare providers. Making the right decision about testosterone therapy involves knowing both the risks and the benefits. Each person’s health is different, and what works for one man may not be safe for another. That’s why experts recommend regular testing and close follow-up when using testosterone therapy, especially in men with other health problems.

As science continues to study testosterone therapy, more clear answers are expected in the coming years. In the meantime, the decision to start therapy should be made carefully and based on good information. A careful look at the latest research, medical advice, and safety guidelines can help make sure that the benefits of testosterone therapy outweigh the risks, especially when it comes to heart health.

What Is Testosterone Therapy and Who Needs It?

Testosterone is a hormone made mainly in the testicles. It plays a key role in male development. It helps with muscle growth, bone strength, body hair, and a deeper voice. It also supports sex drive, sperm production, and red blood cell levels. As men get older, their testosterone levels usually drop. Some men develop very low testosterone levels, a condition called hypogonadism. When this happens, doctors may recommend testosterone therapy.

What Is Testosterone Therapy?

Testosterone therapy (TT) is a medical treatment that adds testosterone to the body. It is used when the body does not make enough of the hormone on its own. This treatment is only given after lab tests confirm low levels of testosterone. Symptoms such as tiredness, low sex drive, and poor concentration may also be present.

TT is not the same as using testosterone without a medical need. Some people take testosterone for muscle gain or sports performance, but this is not safe or legal. True testosterone therapy is given under the care of a doctor.

How Testosterone Is Given

There are several ways to take testosterone. The doctor and patient choose the form based on health, lifestyle, cost, and preference.

1. Gels and Creams
   Testosterone gels are applied to the skin, usually on the shoulders, upper arms, or abdomen. They are used daily and let testosterone enter the blood slowly. One important caution is that the hormone can transfer to others through skin contact, so users must wash their hands and cover the area.

2. Injections
   Testosterone can be injected into the muscles, often in the buttocks or thigh. Injections can be weekly, every two weeks, or longer with special long-acting types. Blood levels may rise and fall between doses, which can cause mood or energy changes in some men.

3. Patches
   Skin patches are worn daily, often on the back, arms, or thighs. They provide steady hormone release. Skin rashes or irritation are common side effects with patches.

4. Pellets
   Small pellets are placed under the skin, often in the hip area. They slowly release testosterone for 3 to 6 months. This method requires a minor procedure but needs fewer follow-ups.

5. Oral and Buccal Forms
   Some forms are taken by mouth or placed in the cheek. These are less common because they may affect the liver or cause uneven hormone levels.

Each method has its own risks, side effects, and benefits. Doctors check blood levels and side effects often, especially in the first year of treatment.

Who Needs Testosterone Therapy?

Testosterone therapy is only for men who have clinically low testosterone and related symptoms. The main cause is hypogonadism, which can be:

• Primary hypogonadism: This happens when the testicles do not make enough testosterone. Causes can include injury, infection, or certain genetic conditions such as Klinefelter syndrome.

• Secondary hypogonadism: This happens when the brain fails to send signals to the testicles to produce testosterone. It can be caused by problems in the pituitary gland or hypothalamus. Tumors, chronic illness, or obesity can also play a role.

The diagnosis is confirmed by measuring testosterone levels in the blood, usually in the morning. The test is repeated to make sure it is accurate. Doctors also check other hormones to understand the cause.

TT is not given just because testosterone levels are a little low. Normal levels vary by age, and some symptoms like tiredness or low mood may have other causes. Treatment is usually only given when both low levels and clear symptoms are present.

Who Should Avoid Testosterone Therapy?

TT is not safe for everyone. Men with certain health problems should not use it. These include:

• Prostate cancer or breast cancer

• High red blood cell count (called polycythemia)

• Untreated sleep apnea

• Severe heart failure

Men trying to have children should also avoid TT. It can lower sperm count and may reduce fertility.

Doctors review each person’s health and risk factors before starting treatment. If approved, the patient will be monitored regularly to make sure the treatment is working and safe.

Testosterone therapy can help the right patients feel better and improve quality of life. However, careful testing and doctor guidance are essential to avoid harm.

How Does Testosterone Affect the Cardiovascular System?

Testosterone is a hormone that plays many important roles in the body. It helps with muscle strength, bone health, energy levels, and sex drive. But it also affects the heart and blood vessels. Understanding how testosterone works in the cardiovascular system helps explain why there is concern about its safety when used as therapy.

Effects on Blood Vessels and Blood Flow

Testosterone can change how blood vessels behave. It helps relax the smooth muscles in blood vessel walls, which can improve blood flow. This process is called vasodilation. Some studies show that testosterone helps widen arteries by increasing nitric oxide, a natural chemical in the body that helps vessels open up. Better blood flow means the heart does not have to work as hard to pump blood to the rest of the body.

However, too much testosterone can have the opposite effect. High levels might cause the walls of blood vessels to become stiff or thick over time. This can lead to higher blood pressure and a higher risk of heart problems, especially in men who already have heart disease.

Impact on Cholesterol and Fat Levels

Cholesterol is a fat-like substance in the blood. There are different types of cholesterol, including HDL (good cholesterol) and LDL (bad cholesterol). Testosterone can change the balance of these levels. In some men, testosterone therapy may lower HDL cholesterol, which is not good for heart health. HDL cholesterol helps remove LDL cholesterol from the bloodstream. If HDL goes down, LDL can build up, leading to blocked arteries.

At the same time, some studies suggest testosterone may lower total cholesterol and triglycerides, which are other types of fats in the blood. These changes can be helpful or harmful depending on a person’s overall health. Researchers are still trying to understand which effects are stronger and how they affect long-term heart risk.

Blood Sugar and Insulin Sensitivity

Testosterone plays a role in how the body uses sugar. Low testosterone is linked with insulin resistance, a condition where the body does not respond well to insulin. This can lead to high blood sugar and, over time, type 2 diabetes. Diabetes is a major risk factor for heart disease.

Testosterone therapy might improve insulin sensitivity in some men, especially those with low testosterone levels. It may help lower blood sugar levels and reduce belly fat, which is linked to heart problems. These changes can be good for the heart. But not all men respond the same way to therapy, and the benefits may not last if the treatment is stopped.

Effects on Inflammation

Inflammation is the body’s response to injury or infection, but long-term inflammation can harm the heart. Low testosterone levels have been linked to higher levels of inflammatory markers in the blood, such as C-reactive protein (CRP) and interleukin-6 (IL-6). High levels of these markers are tied to a greater risk of heart disease.

Testosterone therapy may lower these markers in some men, which could reduce heart disease risk. Still, this effect is not always seen in every study. Inflammation is complex, and many factors affect how the body responds.

Changes in Blood Thickness

One of the most important effects of testosterone on the heart is how it affects blood thickness. Testosterone therapy often increases the number of red blood cells in the body. This is called erythrocytosis. While this might sound like a good thing, it can make the blood thicker. Thick blood flows more slowly and can increase the risk of blood clots, strokes, and heart attacks.

Doctors usually check a man’s hematocrit level (the percentage of red blood cells in the blood) before and during testosterone therapy. If this level goes too high, therapy might need to be stopped or the dose lowered.

Testosterone affects the cardiovascular system in many ways. It can help improve blood flow, reduce blood sugar, and lower inflammation. But it can also lower good cholesterol, thicken the blood, and possibly raise blood pressure. These effects can be helpful or harmful, depending on the person’s health, age, and how testosterone is used. Because of these mixed effects, doctors need to be careful when prescribing testosterone therapy, especially for men with heart problems.

What Does the Evidence Say? An Overview of Major Studies

Over the past two decades, many studies have tried to understand how testosterone therapy (TT) affects heart health. Some studies say TT may raise the risk of heart problems. Others say it may help or have no effect at all. This has led to confusion among patients and doctors. To better understand the risks and benefits, it's helpful to look at the major clinical trials and reviews.

The TOM Trial (Testosterone in Older Men)

One important study was the TOM Trial, done in 2010. It looked at older men, all over age 65, who had low testosterone and physical limitations. These men were given either testosterone gel or a placebo (a fake treatment) for six months. The goal was to see if testosterone would help them build strength and improve walking.

However, the trial was stopped early. This was because more men in the testosterone group had heart problems like chest pain, irregular heartbeats, and even heart attacks. Even though the number of heart problems was small, it was enough to cause concern. Since the men in this study were older and already had health problems, it was unclear if testosterone or their overall poor health caused the issues.

The TTrials

Another important set of studies is called the TTrials (Testosterone Trials), published in 2016 and 2017. These were a group of seven linked studies done in men aged 65 and older with low testosterone. The TTrials looked at many health areas, including sexual function, physical ability, memory, and heart health.

One part of the TTrials focused on the heart. It used a special test called a coronary artery CT scan to check for non-calcified plaque, which can lead to clogged arteries. After one year of testosterone treatment, the men had more plaque buildup in their heart arteries compared to those on placebo. This finding suggested that testosterone might speed up early heart disease, but the study did not show whether this led to more heart attacks or strokes. It also only looked at changes after one year, which may be too short to see long-term effects.

Observational Studies

Other types of studies called observational studies have looked at men taking testosterone in real-world settings. These studies often use health records to compare men on testosterone with those who are not. Some of these studies have shown higher risks of heart attacks and strokes shortly after starting testosterone. One well-known study in 2013 by Vigen et al. found that men with heart disease who took testosterone had more heart problems than those who did not.

But not all observational studies agree. Another study in 2014 by Sharma et al. found the opposite. In this study, men whose testosterone levels returned to normal after treatment had lower risks of heart attacks and death compared to men whose levels stayed low. These mixed results make it hard to draw firm conclusions.

Meta-Analyses and Reviews

Researchers have also done meta-analyses, which combine results from many studies to look for patterns. Some meta-analyses have shown no strong link between testosterone therapy and heart problems. Others have found slight increases in risk, especially in older men or those with pre-existing heart disease.

For example, a 2015 review published in the Mayo Clinic Proceedings looked at more than 100 studies. It found no clear evidence that testosterone increased the risk of major heart events. But another review in PLOS ONE the same year found that TT might increase the risk of heart problems in some men, especially soon after starting treatment.

Limitations and Concerns

All studies have limitations. Some clinical trials are small or do not last long enough to detect heart problems. Others may not include enough older men or those with high heart risk. Observational studies can be biased because men who take testosterone may differ in many ways from those who do not. For example, they may be more health-conscious or have more regular doctor visits. These factors can change the results.

It is also hard to compare different studies because they use different testosterone doses, types (gels, injections, etc.), and patient groups. These differences can affect heart health in different ways.

So far, research on testosterone therapy and heart disease has given mixed results. Some studies raise concerns, especially in older men or those with heart problems. Others show benefits or no major risks. More long-term studies with large groups of men are needed to get clear answers. Until then, doctors must carefully weigh the risks and benefits of testosterone therapy for each patient, especially those with a history of heart disease.

Is Testosterone Therapy Safe for Men With Pre-Existing Heart Disease?

Testosterone therapy (TT) can help men with low testosterone levels feel more energetic, improve muscle mass, and restore sex drive. However, for men who already have heart problems, the safety of testosterone treatment is not always clear. Some doctors worry that using testosterone might increase the risk of heart attacks, strokes, or other cardiovascular issues. Others believe that, if managed carefully, testosterone therapy can still be safe for men with a history of heart disease. Understanding the current medical knowledge is important for making the best treatment choices.

Risks for Men With Heart Conditions

Men with pre-existing heart disease—such as a history of heart attack, heart failure, stroke, or blocked arteries—already have a higher risk of future heart problems. When testosterone therapy is added, it may increase certain risks. One concern is that testosterone can raise the number of red blood cells in the blood. This condition, called polycythemia, makes the blood thicker and harder to pump. Thicker blood increases the chance of forming clots, which can lead to heart attacks or strokes.

Testosterone may also affect blood pressure. Some studies have shown small increases in blood pressure after starting testosterone therapy. High blood pressure adds more stress on the heart and arteries. For men who already have heart problems, even small changes in blood pressure could be dangerous.

In some cases, testosterone therapy may increase fluid retention, especially in men with heart failure. This can worsen swelling in the legs and make it harder for the heart to pump blood properly. Because of this, doctors are especially careful when treating men with severe heart failure.

What the Research Shows

Research on testosterone therapy and heart safety in men with existing cardiovascular disease has shown mixed results. Some studies suggest there is a higher risk of heart attacks in older men or in those with known heart disease, especially in the early months of starting therapy. For example, a well-known study called the TOM Trial (Testosterone in Older Men with Mobility Limitations) was stopped early because men taking testosterone had a higher rate of cardiovascular events, including heart attacks.

On the other hand, other studies have found no increase in risk, and some even suggest that testosterone therapy might lower the chance of heart-related problems. This may be because low testosterone levels themselves are linked to poor heart health. Men with very low testosterone are more likely to have high cholesterol, obesity, type 2 diabetes, and clogged arteries. For these men, raising testosterone levels to a normal range might improve some of these risk factors.

Because the findings are not all the same, most experts agree that more research is needed. Large, high-quality studies are underway to better understand the long-term safety of testosterone therapy, especially in men with heart conditions.

Guidelines and Medical Advice

Most medical organizations advise doctors to be cautious when prescribing testosterone therapy to men with heart disease. For example, the U.S. Food and Drug Administration (FDA) has warned that testosterone products may increase the risk of heart attack and stroke, especially in older men. As a result, doctors are advised to weigh the risks and benefits carefully before starting therapy.

The Endocrine Society recommends that testosterone therapy should not be given to men who have had a recent heart attack or stroke within the past six months. It also advises against using testosterone in men with uncontrolled heart failure. However, if a man has stable heart disease and shows clear symptoms of low testosterone, therapy may be considered, but only under close medical supervision.

Doctors usually perform several tests before starting testosterone therapy. These may include blood tests, an electrocardiogram (EKG), and sometimes imaging studies of the heart. Once therapy begins, patients should be monitored closely. Regular blood tests are needed to check testosterone levels, red blood cell counts, and cholesterol. Blood pressure and heart function should also be watched over time.

Balancing Benefits and Risks

For men with pre-existing heart disease, testosterone therapy is not automatically ruled out. Instead, doctors look at the whole picture. If a man has low testosterone symptoms that affect his quality of life and his heart disease is stable, therapy might be helpful. But the treatment plan must be carefully managed to lower the chances of side effects.

Monitoring is key. If the man’s red blood cell count gets too high or if heart symptoms get worse, doctors may lower the dose or stop the treatment. A team approach—often including a primary care doctor, a cardiologist, and an endocrinologist—can help ensure that therapy is both safe and effective.

Testosterone therapy may offer benefits, but for men with heart disease, it should be used with caution. Medical evaluation, regular follow-up, and shared decision-making are essential parts of managing treatment safely.

Can Testosterone Therapy Cause Heart Attacks or Strokes?

Testosterone therapy has grown more common in recent years, especially among older men and those with symptoms of low testosterone. While many patients report feeling stronger, more energetic, or more focused after starting therapy, some studies suggest that testosterone therapy may raise the risk of serious heart problems such as heart attacks and strokes. Understanding how this might happen is important for anyone thinking about starting treatment.

How Testosterone Might Affect the Heart

Testosterone is a hormone that has effects throughout the body. It can influence blood pressure, red blood cell levels, cholesterol, and inflammation. These are all factors that play a role in heart health. When testosterone levels in the body increase quickly, or when they rise above normal ranges, there can be changes in how the heart and blood vessels work.

One of the main concerns is that testosterone therapy can raise the number of red blood cells in the body. This is called polycythemia. It makes the blood thicker and harder to pump through the heart. Thicker blood increases the risk of blood clots, which can block blood vessels in the heart or brain, leading to a heart attack or stroke. This risk is even greater in men who already have other risk factors like smoking, high blood pressure, or a history of heart problems.

Testosterone can also affect blood pressure. Some studies show that it can cause slight increases in blood pressure, which may not seem like a big problem. But over time, higher blood pressure can strain the heart and arteries. This can increase the chance of a stroke caused by a broken blood vessel or a blocked artery in the brain.

Another possible effect of testosterone therapy is its impact on cholesterol levels. Some older studies suggested that testosterone might help reduce total cholesterol or improve the balance between good (HDL) and bad (LDL) cholesterol. However, more recent findings have shown that these changes are small or inconsistent. In some men, testosterone may even lower HDL, the “good” cholesterol that protects the heart. If HDL goes down while LDL stays the same or increases, this can raise the risk of heart disease.

Inflammation is also an important part of heart health. When blood vessels become inflamed, it can lead to plaque buildup inside the arteries. Some evidence suggests that testosterone therapy may increase markers of inflammation in certain people. This could make plaques more likely to break apart and cause a blockage in a blood vessel—another way that testosterone might contribute to heart attacks or strokes.

What Studies Have Found

Several studies have looked at the link between testosterone therapy and heart problems, but the results have not always been the same. One early study, called the TOM trial, was stopped early because men receiving testosterone had a higher number of heart-related problems. These included chest pain, irregular heartbeat, and even heart attacks. The men in this study were older and had limited mobility, which may have affected the results.

Other studies have shown mixed findings. Some large reviews of multiple studies, called meta-analyses, found a slightly higher risk of heart attacks in men taking testosterone. However, other reviews found no increase in risk—or even a small benefit—in some groups, such as younger men or those with very low testosterone levels before treatment.

A more recent and ongoing trial, called TRAVERSE, is looking at over 5,000 men aged 45 to 80 with low testosterone and existing heart risk factors. This study is designed to give more reliable answers by following men for a longer period. Early reports suggest that the overall risk may depend on age, pre-existing conditions, and how testosterone is used and monitored.

What This Means for Patients

The risk of heart attack or stroke from testosterone therapy is not the same for everyone. Men with a history of heart disease, uncontrolled high blood pressure, or who are at risk for blood clots may face a higher chance of problems. For these men, careful testing and regular check-ups are important before and during therapy. Doctors often check hematocrit levels (a measure of how many red blood cells are in the blood), as well as blood pressure and cholesterol, to help reduce these risks.

In healthy men with low testosterone and no major heart problems, the risks may be lower, especially if therapy is closely monitored. But it is still important to weigh the benefits against the possible risks. Testosterone therapy should not be used without clear medical reasons, and it should always be started under the care of a licensed health provider.

Understanding the possible heart risks can help patients and doctors make better decisions together. More research is still needed to fully understand how testosterone affects the heart over time. Until then, caution and careful medical guidance are the safest path forward.

Does Low Testosterone Alone Increase the Risk of Heart Disease?

Low testosterone, also called hypogonadism, happens when the body does not make enough of the hormone testosterone. This condition is more common in older men, but it can also affect younger men due to certain medical problems, injuries, or lifestyle factors. Research has shown that low testosterone is linked to a higher risk of heart disease, stroke, and even early death. Scientists have found several ways that low testosterone levels may affect the heart and blood vessels.

Link Between Low Testosterone and Atherosclerosis

Atherosclerosis is a condition where plaque builds up inside the arteries. Plaque is made up of fat, cholesterol, and other substances. Over time, it can harden and narrow the arteries, making it harder for blood to flow. This can lead to chest pain, heart attacks, or strokes.

Studies have shown that men with low testosterone levels are more likely to have thickened artery walls and early signs of plaque buildup. Testosterone may help protect the blood vessels by relaxing them and improving blood flow. When testosterone is low, this protection may weaken, leading to damage in the artery walls. This may be one reason why low testosterone is linked to higher rates of heart disease.

Testosterone and Coronary Artery Disease

Coronary artery disease (CAD) is the most common form of heart disease. It happens when the arteries that supply blood to the heart become narrow or blocked. Several studies have found that men with low testosterone are more likely to develop CAD. In fact, in some hospital studies, men with the lowest testosterone levels had more blocked arteries than men with normal levels.

Some researchers believe that testosterone helps keep the heart muscle strong and supports the blood vessels that feed the heart. When testosterone is too low, the heart and arteries may not work as well. This may make it easier for CAD to develop and cause serious problems like heart attacks.

Low Testosterone and Metabolic Risk Factors

Men with low testosterone often have other health problems that raise the risk of heart disease. These include obesity, type 2 diabetes, high blood pressure, and unhealthy cholesterol levels. Together, these problems are called metabolic syndrome. Men with metabolic syndrome have a much higher risk of heart disease and stroke.

Low testosterone may play a role in causing or making metabolic syndrome worse. It can lead to weight gain, especially in the belly area. It may also make it harder for the body to use insulin, the hormone that controls blood sugar. This can lead to insulin resistance, a condition that often comes before type 2 diabetes. All of these changes make heart disease more likely.

At the same time, metabolic syndrome can also lower testosterone levels. Fat tissue, especially belly fat, makes an enzyme that turns testosterone into estrogen. This process can reduce the amount of testosterone in the blood. So, low testosterone and metabolic syndrome can feed into each other, creating a cycle that raises the risk for heart problems.

Impact on Mortality and Cardiovascular Events

Several large studies have followed men over many years to see how testosterone levels affect their health. These studies found that men with lower testosterone levels were more likely to die early, especially from heart disease. Some studies even found a direct link between low testosterone and a higher chance of having a heart attack or stroke.

For example, one study looked at over 800 men for about 20 years. The men with the lowest testosterone levels had a much higher chance of dying from heart-related causes than those with normal levels. These results suggest that low testosterone may be more than just a symptom of poor health—it could also be part of the cause.

Complex Relationship With Heart Health

Even though many studies show a strong link between low testosterone and heart disease, it is not always clear whether low testosterone causes heart disease, or if heart disease lowers testosterone levels. Some experts believe both may be true. Chronic illnesses, such as heart disease, may lower testosterone. At the same time, low testosterone can lead to changes in the body that make heart disease worse.

Doctors continue to study this relationship. While low testosterone is clearly linked with heart problems, more research is needed to understand exactly how and why this happens. This is important because it can help guide future treatments and improve care for men at risk for both low testosterone and heart disease.

How Are Testosterone Levels and Heart Disease Risk Monitored During Therapy?

When someone starts testosterone therapy, careful monitoring is important to keep the body safe and healthy. This is especially true for the heart and blood vessels. Some people may respond well to testosterone, but others may experience changes that increase their risk for heart problems. That’s why doctors follow specific steps to watch hormone levels and check for early warning signs.

Testosterone Testing

The first step in monitoring is checking testosterone levels in the blood. Doctors usually look at two types:

• Total testosterone: This includes all testosterone in the blood, both bound and free.

• Free testosterone: This is the part that is not attached to proteins and is active in the body.

Blood tests are often done early in the morning, when testosterone levels are highest. Levels are checked before starting therapy and then again a few weeks or months after treatment begins. Once levels are stable, tests may be repeated every 6 to 12 months. The goal is to keep testosterone within the normal range—high enough to improve symptoms, but not so high that it causes harm.

Hematocrit and Red Blood Cells

Testosterone can increase the number of red blood cells in the body. This leads to a higher hematocrit, which is the percentage of red blood cells in the blood. If hematocrit gets too high, the blood becomes thicker. Thick blood can lead to clots, strokes, or heart attacks.

Doctors usually test hematocrit levels before starting treatment and then again every 3 to 6 months after therapy begins. If levels go above 54%, the treatment may need to be stopped or the dose reduced. Sometimes, doctors may suggest donating blood to lower hematocrit safely.

Blood Pressure and Heart Function

Testosterone therapy can sometimes raise blood pressure. High blood pressure can damage the heart, kidneys, and blood vessels over time. Doctors will check blood pressure regularly during therapy. If blood pressure becomes too high, the dose of testosterone may be adjusted, or blood pressure medicine may be needed.

Some people on testosterone therapy may also need extra tests to check how well the heart is working. These tests may include:

• Electrocardiogram (EKG): This test checks the heart’s electrical signals and rhythm.

• Echocardiogram: This is an ultrasound of the heart. It shows how well the heart pumps and if there are any signs of strain.

• Stress test: This checks how the heart responds to physical activity and helps detect problems with blood flow.

These heart tests are not needed for everyone but may be recommended for older adults or people who already have heart disease.

Lipid Profile (Cholesterol Levels)

Testosterone can affect cholesterol levels in the blood. Cholesterol includes both “good” (HDL) and “bad” (LDL) types. Some studies show that testosterone may lower HDL cholesterol, which protects the heart. That could increase the risk of heart disease in some people.

A lipid panel is a blood test that checks levels of:

• Total cholesterol

• LDL (low-density lipoprotein)

• HDL (high-density lipoprotein)

• Triglycerides

These levels should be checked before starting therapy and at least once a year after treatment begins. If unhealthy changes are found, doctors may recommend diet changes, more exercise, or cholesterol-lowering medications.

Blood Sugar and Insulin Resistance

Low testosterone is linked to insulin resistance and type 2 diabetes. Some men on testosterone therapy see better blood sugar control. But not everyone responds the same way. That’s why it is important to monitor fasting blood glucose and HbA1c levels, especially in men with diabetes or prediabetes.

Prostate-Specific Antigen (PSA) and Prostate Health

Even though testosterone therapy is not proven to cause prostate cancer, it may speed up the growth of cancer that already exists. That’s why doctors check PSA levels in the blood. PSA is a protein made by the prostate, and high levels can be a sign of prostate problems, including cancer.

PSA tests are done before starting testosterone and again every 6 to 12 months. If PSA levels rise too quickly, further tests like a prostate exam or biopsy may be needed.

Regular monitoring during testosterone therapy helps find problems early and keeps the treatment safe. These tests let doctors adjust therapy if needed and protect heart health over time. By staying within safe limits and catching changes early, the risks linked to testosterone therapy can be reduced.

What Do Professional Guidelines Say About Testosterone Therapy and Heart Health?

Testosterone therapy is used to treat men with low testosterone levels, especially when caused by medical conditions like hypogonadism. Over the past decade, more men have been prescribed testosterone therapy, often for symptoms such as fatigue, low libido, and muscle loss. At the same time, questions have been raised about how this treatment affects the heart. Several professional organizations have released guidelines to help doctors make safe decisions about when and how to use testosterone therapy, especially in men who may have or be at risk for heart disease.

American Urological Association (AUA)

The American Urological Association is one of the main groups that provides guidance for doctors treating men with low testosterone. The AUA recommends testosterone therapy only for men who have symptoms of low testosterone and confirmed low levels on two separate blood tests taken in the morning. They stress that testosterone therapy should not be used without both symptoms and lab evidence of deficiency.

The AUA also gives advice about heart health. The group notes that there is no strong evidence proving that testosterone therapy causes heart attacks or strokes. However, because some studies have shown possible risks, the AUA suggests doctors talk with patients about the benefits and risks of treatment. For men who already have heart disease, doctors should be extra cautious and may need to monitor them more closely. The AUA also supports regular testing during treatment to check testosterone levels, red blood cell counts, and other markers that may affect the heart.

Endocrine Society

The Endocrine Society also provides widely used guidelines. Like the AUA, the Endocrine Society recommends testosterone therapy only for men who have both symptoms of testosterone deficiency and confirmed low blood levels. Their guidelines strongly discourage the use of testosterone therapy for age-related decline in testosterone when there is no clear medical cause.

Regarding heart disease, the Endocrine Society takes a more careful approach. It warns that testosterone therapy may not be safe for men with recent heart attacks, strokes, or serious heart failure. The group suggests that doctors avoid starting therapy in these patients until their heart condition is stable. For men with stable heart disease, treatment may be considered but must be carefully discussed and monitored.

The Endocrine Society also advises regular follow-up, especially in the first year of treatment. Patients should be checked for changes in red blood cell levels, prostate-specific antigen (PSA), and other signs that might suggest a higher risk of complications.

U.S. Food and Drug Administration (FDA)

The FDA is the agency that regulates medicines in the United States. In 2015, the FDA added a warning to all testosterone products. The agency said that testosterone therapy is only approved for men with low testosterone due to medical causes, such as certain genetic conditions or damage to the testicles. The FDA warned that using testosterone therapy for age-related low testosterone has not been proven to be safe or effective.

The FDA also noted that some studies had shown an increased risk of heart problems in men taking testosterone therapy. Because of these concerns, the agency required companies to conduct more research and update product labels. The FDA advises doctors to be cautious and only prescribe testosterone therapy when clearly needed.

European Association of Urology (EAU)

In Europe, the European Association of Urology provides similar guidance. The EAU recommends testosterone therapy only for men with a confirmed diagnosis of testosterone deficiency. Like other groups, they do not support using testosterone therapy in men who are simply getting older but do not have a medical cause for low levels.

The EAU recommends screening men for risk factors such as obesity, high blood pressure, and diabetes before starting therapy. If a man has a history of heart disease, the EAU recommends working closely with a heart specialist. Regular follow-up is also important to reduce the risk of blood clots, prostate issues, and heart problems.

All major professional groups agree that testosterone therapy should only be used in men who truly need it, based on symptoms and blood tests. They also agree that treatment in men with heart disease must be done with care. Most guidelines advise against starting therapy in men with unstable or recent heart problems. Ongoing monitoring is a must, especially in the first 6 to 12 months of treatment.

Doctors are advised to talk with patients about the possible risks and benefits. This helps men make informed decisions based on their health history and personal goals. Guidelines may vary slightly, but the message is the same: testosterone therapy should be used carefully, especially when heart health is a concern.

Special Populations: Age, Obesity, and Comorbidities

Testosterone therapy affects people differently. For some, it may help with low energy, low muscle mass, or reduced sex drive. But in others—especially those with certain health conditions—it can raise the risk of heart problems. Age, obesity, and other illnesses can change how the body responds to testosterone. These special groups need extra attention when starting or continuing testosterone therapy.

Older Adults (Men Over 65 Years Old)

Age plays a big role in how testosterone affects the heart and blood vessels. As men age, natural testosterone levels drop. Some older men have symptoms like tiredness, low libido, and mood changes. These may look like signs of low testosterone, but they can also happen due to aging itself or other health problems.

Research shows that older men are more likely to develop heart disease. They also often take medications for high blood pressure, high cholesterol, or diabetes. These factors make it harder to know if testosterone therapy is helping or causing harm. Some studies found that older men who use testosterone have a higher risk of heart attacks and strokes. One well-known study called the TOM trial had to stop early because older men in the study had more heart-related problems while using testosterone.

Because of this, experts often recommend that testosterone therapy in men over 65 be used carefully. Doctors may suggest it only when blood tests clearly show low testosterone, and when symptoms are serious. Even then, the risks and benefits must be weighed closely. Monitoring should include regular blood work and heart checks to catch any signs of trouble early.

Obese Men

Obesity can lower testosterone levels. Fat cells, especially those around the belly, turn testosterone into estrogen. This leads to even lower testosterone. Obese men may feel tired, lose muscle, or have a reduced sex drive. These are similar to symptoms of low testosterone from other causes.

Some studies suggest that testosterone therapy may help obese men lose fat and gain lean muscle. It might also improve insulin resistance, which is common in people with obesity. However, the results are mixed. Not all obese men respond the same way.

Obesity also increases the risk of heart disease. Extra weight puts pressure on the heart and blood vessels. When testosterone therapy is added, it may raise red blood cell counts (hematocrit), which can thicken the blood and increase the chance of clots. For obese men who already have high blood pressure, cholesterol issues, or a history of heart problems, this can be dangerous.

Doctors treating obese men with testosterone usually recommend close follow-up. Tests should include cholesterol levels, blood pressure checks, blood thickness (hematocrit), and blood sugar levels. Lifestyle changes such as exercise and a healthy diet are important alongside any hormone therapy.

Men With Diabetes, High Blood Pressure, or Other Illnesses

Many men seeking testosterone therapy also have conditions like type 2 diabetes, high blood pressure, or sleep apnea. These conditions already increase the risk of heart disease. Adding testosterone may either help or harm depending on the person.

In some men with type 2 diabetes, testosterone therapy has been shown to improve blood sugar control. It may also help with energy and weight loss. However, other research shows that the benefits may not last long and could come with added heart risk, especially in those who already have blocked arteries or heart failure.

Sleep apnea is another concern. Testosterone therapy can worsen breathing problems during sleep. Untreated sleep apnea can increase the risk of heart attacks and strokes. For men with this condition, doctors often recommend treating the apnea before starting testosterone.

People with a history of blood clots or thick blood also need to be cautious. Testosterone increases red blood cell production. This thickens the blood, making clots more likely. For men with a past clot, the added risk from testosterone could be serious.

Because of all these issues, guidelines often suggest extra care before starting testosterone in men with multiple health problems. A full check-up is usually needed. This includes heart exams, blood tests, and sometimes a sleep study. The goal is to make sure testosterone therapy does more good than harm.

Different Responses in Special Groups

Testosterone therapy does not affect every group the same way. Older men, obese men, and those with chronic conditions may experience stronger side effects or different benefits compared to healthy younger men. Personal medical history, family history of heart disease, and current medications can all change how the body responds.

Doctors often take a case-by-case approach. Treatment should be guided by clear symptoms, lab tests showing low testosterone, and careful monitoring. Shared decision-making between doctor and patient is key. In many cases, lifestyle changes such as weight loss, better sleep, and regular exercise can improve testosterone levels naturally, with fewer risks.

Special populations such as older adults, obese men, and those with health conditions need close care when using testosterone therapy. While some may benefit, the risk of heart problems is higher, and careful screening and follow-up are essential.

Ongoing Research and Future Directions

Research on testosterone therapy and its connection to heart disease is ongoing and constantly growing. While past studies have given mixed results, new research is helping doctors better understand who might benefit from testosterone therapy and who may be at greater risk for heart problems. Scientists are working to answer key questions and improve treatment options for men with low testosterone levels.

Large Clinical Trials Underway

One of the largest and most important studies on testosterone and heart health is the TRAVERSE study (Testosterone Replacement Therapy for Assessment of Long-term Vascular Events and Efficacy Response in Hypogonadal Men). This clinical trial was launched in response to concerns raised by earlier studies showing a possible link between testosterone therapy and heart attacks or strokes.

TRAVERSE includes over 5,000 men aged 45 to 80 who have low testosterone and a high risk of heart disease. Participants are randomly given either testosterone gel or a placebo and are followed for several years. The study tracks major cardiovascular events such as heart attack, stroke, and death from heart problems. It also looks at other areas such as sexual health, bone strength, and mood.

The results of TRAVERSE will help answer important questions, such as whether testosterone therapy increases, decreases, or has no effect on heart disease risk in older men. Early findings from this study are expected to help create clearer treatment guidelines.

Understanding Why Results Vary

Researchers are also studying why testosterone therapy may help some men but harm others. One goal is to understand the role of individual factors, such as age, weight, smoking status, and existing health problems. These factors may influence how the body responds to testosterone and how likely a person is to experience heart-related side effects.

For example, some evidence suggests that men with metabolic syndrome or type 2 diabetes may see improvements in blood sugar control and fat levels with testosterone therapy. This could lower their overall risk of heart disease. On the other hand, men with high red blood cell counts or severe heart failure may be at greater risk for complications such as blood clots or worsening symptoms.

Search for Safer Testosterone Formulations

Another area of research focuses on making testosterone therapy safer. Scientists are working to develop new formulations of testosterone that avoid rapid spikes in hormone levels, which may be linked to heart risks. These newer versions aim to release testosterone slowly and evenly into the bloodstream.

In addition, some researchers are looking into selective androgen receptor modulators (SARMs). These medications are designed to mimic the effects of testosterone in muscles and bones without affecting other organs such as the heart or prostate. Although still in early stages, SARMs could become a safer alternative for men who need hormone support but face high cardiovascular risk.

Personalized Medicine and Risk Prediction

Another important area of research involves personalized medicine, where treatment is matched to a person’s unique risk profile. Scientists are exploring the use of genetic testing, hormone levels, and heart imaging to predict which patients will do well on testosterone therapy and which ones might develop side effects.

For example, a man with certain gene markers, high blood pressure, or early signs of plaque in his arteries might be monitored more closely or advised against therapy. Personalized treatment could help reduce the chance of serious heart problems while still allowing safe use of testosterone in those who truly need it.

Improving Long-Term Monitoring

To improve safety, researchers are also working on better long-term monitoring systems. Many studies now focus on tracking testosterone users for several years to gather more data on delayed side effects. New digital tools, such as wearable devices and online health records, may help detect early warning signs of heart strain in real time.

Doctors may soon be able to use these tools to check blood pressure, oxygen levels, heart rhythm, and other signs of stress from testosterone therapy. Regular lab tests, such as hematocrit and cholesterol, will remain important, but new technology may make it easier to catch problems before they become serious.

Research into testosterone therapy and heart disease is advancing quickly. Large studies like TRAVERSE, along with improved understanding of individual risks, are helping doctors make better decisions. New forms of testosterone, potential future drugs like SARMs, and advanced monitoring tools may all play a role in improving safety and outcomes. As science continues to grow, the hope is that men with low testosterone can be treated more effectively, with fewer risks to their hearts.

Conclusion

Testosterone therapy has become more common in recent years, especially among men with low testosterone levels due to age or medical conditions like hypogonadism. As the number of men using testosterone therapy grows, so do concerns about its safety—particularly its possible link to heart disease. Many studies have tried to answer whether testosterone therapy raises the risk of heart attacks, strokes, and other serious heart problems. The results have not always been clear. Some research shows a possible increase in heart risks, while other studies find no major danger or even suggest some heart health benefits. This has created confusion for patients and doctors.

Testosterone plays a key role in the body. It helps maintain muscle strength, bone density, sex drive, and energy levels. It also has effects on the heart and blood vessels. Normal testosterone levels help the heart work properly by improving blood flow, reducing inflammation, and keeping fat and sugar levels in balance. But giving testosterone as a treatment changes how the body works, especially when it is given in high doses or to people who do not really need it.

Some of the most important studies on testosterone therapy have shown mixed results. For example, one study called the TOM trial had to stop early because of a higher number of heart problems in men taking testosterone. But other studies like the TTrials did not find the same risks. In fact, some reports show that men with low testosterone may have a higher risk of heart disease even without treatment, which raises another question: does the hormone itself protect the heart, or is it the way it is used that causes problems?

Doctors often have to decide whether testosterone therapy is right for someone who already has heart disease or other health problems. This is not always easy. Some people might benefit from treatment, but others may face more harm than good. For example, testosterone therapy can increase red blood cell levels, which may make the blood thicker and raise the risk of clots. These clots can lead to heart attacks or strokes. It may also raise blood pressure or affect cholesterol levels in some people. Because of these risks, doctors need to carefully check a person’s health history before starting therapy and monitor them closely during treatment.

At the same time, men with very low testosterone might also be at risk of heart disease. Studies show that low levels of testosterone are linked to problems like high blood pressure, type 2 diabetes, obesity, and unhealthy cholesterol levels. All of these increase the chance of heart disease. This means that for some people, not treating low testosterone might be just as risky as taking testosterone therapy. The key is to find the right balance based on each person’s health.

To help guide decisions, medical groups have created rules for who should take testosterone and how they should be watched during treatment. These include checking hormone levels, keeping an eye on the heart, and testing blood for changes that might signal risk. Guidelines from the American Urological Association, the Endocrine Society, and others offer advice, but they also admit that more research is needed to fully understand the risks.

Certain groups of people need special care when considering testosterone therapy. Older men, especially those over age 65, may be more likely to have heart problems. Men with obesity or diabetes might already have some damage to their heart and blood vessels. For these people, the risks and benefits of treatment should be weighed carefully. A one-size-fits-all approach does not work.

New studies are underway to better understand how testosterone therapy affects the heart over time. These include large clinical trials with thousands of men. Researchers are also looking for better ways to predict who might face problems during treatment. The future may bring safer forms of testosterone and better tools to decide who should get it.

Testosterone therapy and heart health are closely linked, but not in simple ways. The treatment may help some men feel better and improve their health, but it may harm others if not used properly. The decision to start testosterone therapy should be made with care, using clear guidelines, regular testing, and a full understanding of the risks. There is still much to learn, and ongoing research will continue to shape the way testosterone is used in the years to come.