Understanding the Link Between Testosterone Levels and Kidney Function

Introduction

Testosterone is a hormone that plays a key role in many processes in the human body. It is often known as the male sex hormone, but both men and women produce it. In men, testosterone helps control muscle growth, bone density, red blood cell production, and sexual function. In women, it supports similar functions but in smaller amounts. Testosterone levels naturally change with age. As people grow older, the body makes less testosterone, which can lead to a condition called low testosterone or hypogonadism.

At the same time, the kidneys are vital organs that perform many important jobs. They filter waste and extra fluid from the blood, help control blood pressure, balance minerals like sodium and potassium, and help make red blood cells. Healthy kidneys are needed for the body to work properly. When the kidneys do not function well, waste builds up, and this can affect almost every part of the body.

Over the past few years, doctors and researchers have started to look more closely at how testosterone levels may be connected to kidney health. Some studies have found that people with low testosterone levels are more likely to have problems with their kidneys. Others have looked at how testosterone therapy—where a person is given extra testosterone through injections, patches, or gels—might help or harm the kidneys. There is also growing interest in how kidney disease may itself lead to lower testosterone levels. This makes the relationship between testosterone and kidney function complex and worth exploring.

More men are now being tested for low testosterone, especially as they get older or experience symptoms like tiredness, low sex drive, or muscle weakness. At the same time, chronic kidney disease (CKD) is becoming more common due to factors like high blood pressure, diabetes, and obesity. Because both low testosterone and CKD are more common in older adults, the overlap between the two is also growing. That has led to many questions about how one may affect the other, and what role, if any, testosterone therapy should play in people with kidney problems.

Some people wonder if low testosterone causes kidney damage. Others ask if taking testosterone could help improve kidney function. There are also concerns about whether testosterone therapy could make kidney function worse, especially in people who already have some level of kidney disease. Since the kidneys help control blood pressure and hormone levels, changes in testosterone could have both direct and indirect effects on the kidneys.

Doctors are still learning about the full effects of testosterone therapy on kidney health. Research is ongoing, and not all studies have come to the same conclusions. Some show potential benefits, while others suggest there could be risks. What is clear is that both testosterone levels and kidney function affect each other in many ways, and both are important to monitor in patients who are aging or who have health conditions like diabetes, obesity, or high blood pressure.

Understanding how testosterone and kidney function are connected can help improve patient care. It may guide doctors in deciding whether to start testosterone therapy, how to monitor it safely, and when to avoid it. It can also help people understand the signs and symptoms of both low testosterone and kidney problems. This knowledge may lead to earlier testing, better treatment, and improved health outcomes.

Learning more about the link between testosterone and the kidneys is important not just for people already receiving hormone therapy but also for those at risk of kidney disease. As research continues to grow, medical guidelines may change to reflect new findings. But for now, clear information can help patients and healthcare providers make informed choices based on the current evidence.

What Is Testosterone and How Does It Affect the Body?

Testosterone is a hormone that plays a very important role in the human body. It is known as the primary male sex hormone, but both men and women produce it. In men, testosterone is mostly made in the testicles. In women, smaller amounts are made in the ovaries and adrenal glands.

Testosterone belongs to a group of hormones called androgens. These are also known as "male hormones" because they help with male development. Testosterone is the most active androgen in the body. It starts working before birth and continues to be important throughout life.

Functions of Testosterone

Testosterone controls many important functions in the body. Some of these are related to physical growth and development, while others affect mood and metabolism.

1. Sexual Development and Function
   Testosterone is key for developing male sexual organs before birth. During puberty, it causes changes such as deepening of the voice, growth of facial and body hair, and the development of the penis and testicles. It also helps with sperm production and supports a healthy sex drive (libido) in adults.

2. Muscle and Bone Health
   Testosterone helps the body build muscle mass and strength. It also helps keep bones strong by supporting bone growth and bone density. Low levels of testosterone can lead to weaker bones and a higher risk of fractures.

3. Red Blood Cell Production
   The hormone helps the body make red blood cells in the bone marrow. These cells carry oxygen throughout the body. Low testosterone can sometimes cause anemia, which is when the body doesn’t have enough healthy red blood cells.

4. Mood and Mental Health
   Testosterone can affect mood, focus, and energy levels. Low testosterone levels have been linked to depression, tiredness, and irritability. However, these symptoms can also be caused by other health problems, so it is important to look at the full picture.

5. Fat Distribution and Metabolism
   This hormone also plays a role in how the body stores fat. It can affect where fat is stored and how the body uses energy. When testosterone is low, it may be harder to lose weight or keep a healthy body fat percentage.

Types of Testosterone: Natural and Therapy

Testosterone in the body can be either endogenous or exogenous.

• Endogenous testosterone is the testosterone the body makes naturally.

• Exogenous testosterone comes from outside the body and is usually given as a treatment, known as testosterone therapy.

Testosterone therapy is often used to treat a condition called hypogonadism, which means the body doesn’t make enough testosterone. Therapy may come in several forms, including injections, gels, patches, or pellets placed under the skin.

This treatment can help improve symptoms caused by low testosterone, such as low energy, loss of muscle, reduced sex drive, and mood changes. However, it must be prescribed and carefully managed by a doctor because of possible risks and side effects.

Normal Testosterone Levels

Testosterone levels are usually measured with a blood test. Levels can change based on age, health, and even the time of day. Testosterone levels are typically higher in the morning and lower in the evening.

In adult men, normal total testosterone levels usually fall between 300 and 1,000 nanograms per deciliter (ng/dL). In adult women, levels are much lower, usually between 15 and 70 ng/dL.

As people age, testosterone levels naturally decrease. This slow drop usually starts around age 30 and continues through life. Not everyone experiences symptoms from lower levels, but some may notice changes in energy, strength, or sexual function.

Testosterone is a powerful hormone that affects many systems in the body. It supports physical growth, muscle strength, bone density, blood cell production, and mental well-being. It also plays a key role in sexual health and reproduction. Whether made naturally by the body or given as therapy, the effects of testosterone are wide-reaching. Understanding how it works helps provide a better view of how it might also affect other organs—like the kidneys—which will be explored in later sections.

How Do the Kidneys Function and What Do They Do?

The kidneys are two small, bean-shaped organs located near the middle of the back, just below the ribcage. Each kidney is about the size of a fist. Despite their small size, the kidneys do a lot of important work for the body every day. Without healthy kidneys, the body would not be able to maintain balance or remove waste properly.

Filtering Waste From the Blood

One of the main jobs of the kidneys is to filter the blood. The body produces waste all the time. This waste comes from digesting food, breaking down old cells, and using muscles. The kidneys remove this waste from the blood and send it out of the body through urine.

Inside each kidney are about one million tiny filters called nephrons. Each nephron has two main parts: the glomerulus and the tubule. The glomerulus is a tiny group of blood vessels that act like a sieve. It lets small particles, like water and waste, pass through but keeps larger things, like blood cells and proteins, inside the bloodstream. The filtered fluid then goes into the tubule, where the body decides what to keep and what to send out as urine.

Balancing Water and Electrolytes

The kidneys also help control how much water and salt the body keeps. This balance is important for blood pressure, nerve function, and muscle activity. The kidneys respond to signals from the brain and hormones to decide how much water to keep and how much to release in the urine.

Besides salt and water, the kidneys also regulate electrolytes like potassium, calcium, magnesium, and phosphorus. These minerals help the heart, muscles, and nerves work properly. When kidneys are not working well, these levels can become too high or too low, leading to health problems.

Controlling Blood Pressure

The kidneys help control blood pressure in a few ways. First, by adjusting the amount of fluid in the body. More fluid means more pressure in the blood vessels. Second, the kidneys release a hormone called renin. Renin starts a chain reaction that helps narrow blood vessels and raise blood pressure when it is too low. This system is called the renin-angiotensin-aldosterone system (RAAS).

When kidney function is damaged, this system may not work properly. This can lead to high blood pressure (hypertension), which then causes more harm to the kidneys. Over time, this cycle can make kidney disease worse.

Helping Make Red Blood Cells

The kidneys make a hormone called erythropoietin (EPO). This hormone tells the bone marrow to make red blood cells. Red blood cells carry oxygen to all the cells in the body. When kidneys are not healthy, they may not make enough EPO. This can lead to anemia, a condition where the body does not have enough red blood cells. Anemia causes tiredness, weakness, and shortness of breath.

In people with chronic kidney disease (CKD), anemia is a common problem. Doctors often need to treat it with medications or injections that replace EPO.

Supporting Healthy Bones

The kidneys also help control bone health. They do this by balancing calcium and phosphorus levels and by activating vitamin D. The form of vitamin D made in the skin or taken in through food is inactive. The kidneys change it into an active form that helps the body absorb calcium from food.

When kidney function drops, the body may not get enough active vitamin D. This can lead to weak bones, a condition called renal osteodystrophy. This problem can cause bone pain and increase the risk of fractures.

Removing Drugs and Toxins

Besides waste from the body’s own cells, the kidneys also help remove drugs and other chemicals. Many medicines are filtered through the kidneys. If the kidneys are not working well, these substances can build up in the body and cause harm. This is why doctors often check kidney function before prescribing certain medications.

How Kidney Function Is Measured

Doctors use several tests to check how well the kidneys are working. The main one is called the glomerular filtration rate (GFR). This test estimates how much blood the kidneys filter each minute. A normal GFR is about 90 to 120 milliliters per minute. A lower number can be a sign of kidney disease.

Other common tests include:

• Serum creatinine: Measures the level of a waste product called creatinine in the blood.

• Blood urea nitrogen (BUN): Measures the amount of nitrogen in the blood that comes from waste called urea.

• Urine albumin: Checks for protein in the urine, which can be an early sign of kidney damage.

These tests help doctors decide how healthy the kidneys are and whether treatment is needed.

Understanding how the kidneys work makes it easier to see why keeping them healthy is so important. The kidneys do much more than just make urine — they help manage blood pressure, support healthy blood and bones, and remove waste and toxins from the body. When kidney function is affected, many other systems in the body are also impacted.

Is There a Link Between Low Testosterone and Chronic Kidney Disease (CKD)?

Low testosterone is common in people with chronic kidney disease (CKD). Several studies show that men with CKD often have lower levels of testosterone compared to healthy men. The reason for this connection is not completely understood, but doctors and researchers believe there are several causes and effects working together.

Testosterone Levels in CKD Patients

Many men with CKD have lower-than-normal levels of testosterone. This is especially true as kidney disease becomes more serious. In fact, research shows that up to 50% of men with stage 3 to 5 CKD may have low testosterone levels, also known as hypogonadism. Low testosterone is even more common in patients on dialysis.

There are different reasons for this. One reason is that healthy kidneys help balance hormones in the body. When kidneys don’t work properly, hormone levels can change. The kidneys also help control levels of a hormone called luteinizing hormone (LH), which tells the body to produce testosterone. When the kidneys are damaged, LH may not work well, and the body may make less testosterone.

How Kidney Disease Can Lower Testosterone

Kidney disease can lead to inflammation throughout the body. Inflammation can lower testosterone by interfering with how hormones are made and controlled. People with CKD also often have higher levels of substances called uremic toxins in their blood. These toxins build up because the kidneys can’t filter them out properly. Some of these toxins can directly harm the glands that make testosterone.

Another problem in CKD is that the body often becomes resistant to signals from the brain that tell it to make hormones. In men, the brain releases signals that go to the testicles to tell them to produce testosterone. In CKD, this signaling pathway can become blocked or weakened. As a result, testosterone levels drop.

Other problems linked to CKD may also affect testosterone. These include anemia (low red blood cell count), poor nutrition, low physical activity, and other health conditions like diabetes and high blood pressure. All of these can reduce testosterone levels as well.

How Low Testosterone May Affect Kidney Function

Just as CKD can lead to lower testosterone, low testosterone might also make kidney problems worse. Testosterone helps protect muscle mass, supports red blood cell production, and may improve how well blood vessels work. Without enough testosterone, people may become weaker, have less energy, and develop more body fat. These changes can raise the risk of other health problems that affect the kidneys, such as high blood pressure, insulin resistance, and heart disease.

Low testosterone is also linked to higher levels of inflammation and oxidative stress. Oxidative stress happens when harmful molecules called free radicals build up in the body. This can damage cells, including those in the kidneys. Inflammation and oxidative stress are already common in CKD, and low testosterone may make them worse.

A Two-Way Relationship

The link between low testosterone and kidney disease is likely a two-way street. Kidney disease may lower testosterone levels, and low testosterone may make kidney disease worse. This makes the relationship complex. It also means that treating one problem may help the other. For example, improving testosterone levels in men with CKD may lead to better energy, muscle strength, and blood sugar control—all of which are good for kidney health.

However, researchers are still studying how strong this relationship is and whether treating low testosterone in people with CKD leads to better kidney outcomes. Some studies suggest possible benefits, but more large, long-term studies are needed to fully understand the risks and rewards.

Low testosterone is common in men with chronic kidney disease. This may be caused by hormone changes, inflammation, toxin buildup, and other health problems linked to CKD. At the same time, low testosterone may also affect kidney health in negative ways, by increasing inflammation and lowering physical strength. The connection between the two is complex and may go both ways. Understanding this link is important for improving health in people living with kidney disease.

Can Testosterone Therapy Improve Kidney Function?

Testosterone therapy is often used to treat men with low testosterone levels. Some research shows that it may also help certain parts of the body work better, including the kidneys. However, the link between testosterone therapy and kidney function is complex. Some studies show benefits, while others raise concerns. It is important to look at what scientists have found so far.

How Testosterone Affects the Body and the Kidneys

Testosterone is a hormone made mostly in the testicles. It helps control things like muscle strength, bone growth, red blood cell production, and sex drive. When levels of testosterone fall too low, a man may feel tired, weak, or have trouble building muscle. Some men may also develop anemia or problems with blood pressure and sugar levels.

The kidneys are key organs that filter waste from the blood, control fluid levels, and help balance blood pressure. Healthy kidneys also help make a hormone called erythropoietin, which tells the body to make red blood cells. When testosterone levels are too low, some of these systems may stop working properly, which could lead to problems over time.

Because testosterone plays a role in many body systems, doctors and researchers have wondered whether replacing low testosterone could help improve kidney function, especially in people with chronic kidney disease (CKD).

Studies That Show Possible Benefits

Several studies have looked at men with low testosterone and CKD to see what happens when they receive testosterone therapy. Some of these studies suggest that testosterone therapy may have small but helpful effects on kidney health.

One area of interest is how testosterone may improve renal blood flow. In some animal studies, testosterone helped relax blood vessels, which improved blood flow to the kidneys. Better blood flow may help the kidneys filter blood more effectively.

Other studies suggest that testosterone therapy may reduce protein in the urine, also known as proteinuria. Proteinuria is a sign that the kidneys are damaged. One small study found that men with low testosterone and mild CKD had less protein in their urine after receiving testosterone treatment. However, these findings are early, and larger studies are needed to confirm them.

Testosterone therapy may also help with muscle strength and metabolism, which can help reduce the workload on the kidneys. For example, better muscle mass and insulin sensitivity can lower the risk of diabetes, a major cause of kidney damage.

Some research shows that testosterone can improve anemia, especially in men with kidney disease. This is because testosterone helps the body make more red blood cells. Low red blood cell levels are common in CKD, and improving them can make patients feel better and may help protect the heart and kidneys.

Benefits in Older Men or Those With CKD

In older men or those with early-stage kidney disease, testosterone therapy may have additional benefits. These men often have low testosterone and are more likely to develop muscle loss, weakness, and other problems. Improving testosterone levels in these patients could support overall health and slow down some of the effects of kidney disease.

However, testosterone therapy is not a cure for CKD, and it should not be seen as a way to reverse kidney damage. It may only help support better outcomes in some areas when used carefully and under medical supervision.

Limitations and What Is Still Unknown

While some early studies show promising results, many questions remain. Most studies so far have been small and short-term. Researchers still do not know how testosterone therapy affects the kidneys over many years. Some of the benefits seen in early studies may not last over time.

There is also a lack of information on how testosterone therapy affects people with advanced kidney disease or those on dialysis. These patients are often excluded from clinical trials. That makes it hard to know if testosterone is safe or helpful for them.

In addition, testosterone therapy may affect different people in different ways. For example, men with other health problems—like heart disease, high blood pressure, or diabetes—may respond differently to treatment. This makes it even more important to look at the whole health picture before starting therapy.

Because the kidneys play such an important role in hormone balance, there is concern that changing hormone levels with testosterone therapy could have both helpful and harmful effects, depending on the person’s overall health.

Some research shows that testosterone therapy may help improve certain signs of kidney function, such as better blood flow, reduced protein in urine, or higher red blood cell counts. These effects could support better health, especially in men with low testosterone and early-stage CKD. However, the evidence is still limited. Long-term safety and full benefits are not yet clear. More large studies are needed to understand how testosterone therapy truly affects kidney health over time.

Careful medical supervision is needed to decide whether testosterone therapy is a good choice for men with kidney concerns. Each case is different, and the risks and benefits must be considered based on the patient’s overall health.

Does Testosterone Therapy Pose Any Risks to the Kidneys?

Testosterone therapy is commonly used to treat men with low testosterone levels. While it can help improve muscle strength, energy levels, and mood, it may also cause side effects. One important area of concern is how testosterone therapy may affect the kidneys. The kidneys are sensitive to changes in blood pressure, fluid balance, and blood thickness. Testosterone can influence all of these factors. For people with healthy kidneys, the effects might be small. But for those with kidney disease or at risk of kidney problems, testosterone therapy may have bigger effects.

Fluid Retention and Kidney Strain

Testosterone therapy can cause the body to hold on to more water and salt. This is called fluid retention. When the body keeps more fluid, blood volume increases. This can make the heart and kidneys work harder. For healthy people, the kidneys can usually manage this extra fluid. But for someone with chronic kidney disease (CKD) or poor kidney function, fluid buildup can be dangerous.

Extra fluid in the body can lead to swelling, especially in the legs and feet. It can also raise blood pressure, which increases the risk of further kidney damage. The kidneys are responsible for controlling the body’s fluid balance, and too much fluid can overwhelm them. In people already at risk for heart failure, fluid retention caused by testosterone may worsen both heart and kidney function.

High Blood Pressure (Hypertension)

Testosterone can affect the way the body handles sodium and water, which are closely linked to blood pressure. Higher testosterone levels may lead to increased sodium reabsorption in the kidneys. This means the body keeps more sodium, which pulls in more water and raises blood pressure.

Long-term high blood pressure is a leading cause of kidney disease. It can damage the tiny blood vessels inside the kidneys that filter waste. Even small increases in blood pressure over time can lead to kidney damage, especially in those already at risk. Some studies have found that men on testosterone therapy may see a rise in their blood pressure, especially if they are older or have other health conditions like diabetes or obesity.

Because high blood pressure often has no symptoms, people may not know it's happening. Regular blood pressure checks are important during testosterone therapy, especially for those with any history of kidney problems.

Polycythemia and Kidney Risk

Another known side effect of testosterone therapy is polycythemia, which means the body makes too many red blood cells. Testosterone increases the production of a hormone called erythropoietin, which signals the bone marrow to make red blood cells. While this can be helpful in people with anemia, too many red blood cells can thicken the blood.

Thicker blood can slow circulation and make it harder for the heart to pump. This can raise the risk of blood clots, stroke, and heart attack. For the kidneys, thick blood can reduce blood flow through the delicate filtering units, leading to reduced kidney function. Over time, this strain may cause long-term damage.

People on testosterone therapy should have their hematocrit levels (a measure of red blood cell concentration) checked regularly. If levels get too high, doctors may lower the testosterone dose or stop the therapy.

Risk in People With Pre-Existing Kidney Disease

People who already have kidney disease may be more sensitive to the effects of testosterone therapy. Their kidneys are less able to handle fluid overload, changes in blood pressure, and thickened blood. For these individuals, even mild side effects can lead to serious health problems.

Also, some people with kidney disease take medications like diuretics or blood pressure pills, which can interact with testosterone therapy. These drug interactions can worsen side effects or make them harder to control.

In advanced kidney disease or people on dialysis, testosterone therapy is sometimes used to help with symptoms like low energy or muscle wasting. But in these cases, treatment must be closely watched by a healthcare provider. Frequent blood tests and check-ups are needed to reduce the risk of harm.

Importance of Monitoring

Because testosterone can affect the kidneys in several ways, regular monitoring is essential. Doctors may check:

• Kidney function tests like creatinine and eGFR

• Blood pressure readings

• Hematocrit and hemoglobin levels to watch for polycythemia

• Signs of fluid retention, such as swelling or weight gain

Testosterone therapy can help many people with low hormone levels, but it also carries risks, especially for the kidneys. Fluid retention, high blood pressure, and thickened blood are the main concerns. These effects may be mild in healthy people but can be dangerous in those with kidney disease. Careful monitoring and regular check-ups help reduce these risks and keep treatment safe.

How Do Testosterone Levels Affect Blood Pressure and Kidney Health?

Testosterone is a hormone made mainly in the testicles in males and in smaller amounts by the ovaries in females. It plays an important role in many body systems, including the muscles, bones, and heart. Testosterone can also affect how the body controls blood pressure. Since blood pressure and kidney function are closely linked, changes in testosterone levels can have an impact on kidney health as well.

Testosterone and Blood Pressure Control

Blood pressure is the force of blood pushing against the walls of the arteries. When this pressure is too high over time, it is called hypertension. High blood pressure makes the heart work harder and can cause damage to the blood vessels, including those in the kidneys. Over time, this can lead to chronic kidney disease (CKD) or worsen existing kidney problems.

Testosterone can affect blood pressure in several ways. One way is by influencing how the blood vessels expand or tighten. Healthy blood vessels can relax and widen when needed, which helps control blood pressure. Testosterone may help blood vessels relax by affecting how the inner lining of blood vessels, called the endothelium, works. This lining plays a role in the release of nitric oxide, a chemical that helps widen blood vessels. Some studies suggest that normal levels of testosterone may help keep this system working well. But very high or very low testosterone levels may cause problems.

Testosterone can also affect blood pressure by changing how the kidneys handle salt and water. When the body keeps too much salt, it holds onto water, which raises blood volume and increases blood pressure. Some research shows that testosterone may make the body keep more salt, especially when used in high doses or as a medication. This effect may be stronger in people who already have high blood pressure or kidney issues.

Low Testosterone and Blood Pressure

Low testosterone, also called hypogonadism, can lead to other health problems that raise blood pressure over time. People with low testosterone are more likely to gain weight, especially around the stomach. They may also develop insulin resistance, which can lead to type 2 diabetes. Both obesity and diabetes are major risk factors for high blood pressure.

Low testosterone levels may also cause a drop in muscle mass and energy, making it harder to stay active. Less physical activity can lead to weight gain and worsening blood pressure control. Some men with low testosterone have higher levels of inflammation in their bodies. Inflammation can damage blood vessels and make them stiff, which also raises blood pressure.

High Testosterone Levels and Kidney Strain

While low testosterone may lead to health issues over time, high levels—especially from testosterone replacement therapy (TRT)—can also cause concerns. One of the side effects of TRT is fluid retention. This means the body may hold on to more water and salt, which increases blood pressure. High blood pressure puts extra stress on the kidneys, making it harder for them to filter waste from the blood.

Another risk of high testosterone levels is the thickening of the blood. Testosterone therapy can raise red blood cell count, a condition known as polycythemia. Thicker blood makes it harder for the heart to pump and increases the risk of blood clots. These clots can reduce blood flow to the kidneys, which may harm kidney function.

Because of these effects, people using testosterone therapy should have their blood pressure and kidney function checked regularly. Doctors often monitor creatinine levels, estimated glomerular filtration rate (eGFR), and blood pressure readings to catch problems early.

The Link Between Blood Pressure and Kidney Health

The kidneys and the circulatory system are closely connected. The kidneys help control blood pressure by adjusting the amount of salt and water in the body and by making hormones that affect blood vessels. When blood pressure is too high for too long, it damages the tiny blood vessels in the kidneys. This damage reduces kidney function and can eventually lead to kidney failure.

When testosterone affects blood pressure, either by raising or lowering it, it indirectly affects the kidneys as well. Maintaining balanced hormone levels helps support both healthy blood pressure and kidney function.

Testosterone has several effects on blood pressure and, through this, on kidney health. Normal levels may support blood vessel function and blood pressure control. Low levels are linked to weight gain, diabetes, and inflammation—all of which raise blood pressure. High levels, especially from testosterone therapy, may lead to fluid retention and blood thickening, which also raise blood pressure and can harm the kidneys. Regular monitoring of blood pressure and kidney markers is important for anyone undergoing testosterone therapy or experiencing hormone imbalances.

Are Men With CKD More Likely to Have Hormonal Imbalances?

Men with chronic kidney disease (CKD) often have lower levels of important hormones, including testosterone. This condition is called hypogonadism, which means the body is not making enough testosterone. Research has shown that hypogonadism is more common in men with CKD than in the general population. Several reasons explain why this happens, and these reasons are linked to how CKD affects the body’s hormone system.

How CKD Causes Hormonal Changes

As kidney function gets worse, waste products begin to build up in the blood. These wastes include urea and toxins that healthy kidneys would normally remove. When these substances build up, they can interfere with how the pituitary gland and testicles work together to control hormone production.

The pituitary gland, located in the brain, sends signals to the testicles to make testosterone. It does this by releasing hormones called LH (luteinizing hormone) and FSH (follicle-stimulating hormone). In CKD, this system does not work properly. The pituitary gland may not release enough LH and FSH, or the testicles may not respond to them. This leads to low testosterone levels in the blood.

Inflammation is also a problem in CKD. When the kidneys are not working well, the body often has chronic inflammation. Inflammatory substances called cytokines can block testosterone production and disturb the body’s hormone balance.

Testosterone and Dialysis

Many men with late-stage kidney disease require dialysis, a treatment that removes waste from the blood when the kidneys can no longer do so. Studies have found that men on dialysis often have even lower testosterone levels than those with early-stage CKD.

Dialysis can worsen hormone problems for several reasons. First, the stress of being on dialysis may affect the body's hormone system. Second, some vitamins and minerals are lost during dialysis, which may reduce hormone production. Third, men on dialysis often suffer from other health problems like anemia, low appetite, and muscle wasting, which are also linked to low testosterone.

Also, many men on dialysis experience low libido (sex drive), fatigue, depression, and reduced bone density, which are signs of low testosterone. These symptoms can make it harder for doctors to tell whether the problem is from CKD or hormone imbalance, since both conditions cause similar problems.

Effects of Low Testosterone in CKD Patients

Low testosterone in men with CKD can lead to many health problems. Some of the main effects include:

• Loss of muscle mass and strength: Testosterone helps build and maintain muscles. Low levels can lead to muscle weakness, which is already a common issue in CKD.

• Low bone density and higher risk of fractures: Testosterone helps keep bones strong. Men with CKD are already at risk for weak bones due to poor calcium and vitamin D balance. Low testosterone increases this risk.

• Decreased red blood cell production (anemia): Testosterone helps the body make red blood cells. CKD also causes anemia, so low testosterone can make this problem worse.

• Sexual problems: Many men with CKD and low testosterone experience erectile dysfunction and loss of sexual desire.

• Mood changes and fatigue: Low testosterone can cause depression, lack of motivation, and tiredness. These symptoms are also common in CKD, which may worsen the person’s quality of life.

Clinical Importance

Because of these effects, it is important for doctors to check testosterone levels in men with moderate to severe CKD, especially if they show signs of hormonal imbalance. Measuring total and free testosterone, along with LH and FSH levels, can help figure out if the problem is in the testicles or the brain’s signaling system.

Treating low testosterone in men with CKD may help improve muscle strength, energy, mood, and quality of life. However, testosterone therapy must be used carefully in this group, since CKD patients often have other health problems like heart disease and high blood pressure.

Low testosterone is common in men with CKD due to hormonal disruptions, chronic inflammation, and the effects of dialysis. These hormone changes can affect muscle, bone, mood, and sexual health. Recognizing and managing this imbalance is important for the overall health and well-being of men with kidney disease.

Should Kidney Function Be Monitored During Testosterone Therapy?

Monitoring kidney function is an important part of safely using testosterone therapy. This is especially true for people who already have kidney problems or risk factors for kidney disease. Even for those with healthy kidneys, testosterone can affect the body in ways that may place extra stress on the kidneys over time. Regular checkups and lab tests help doctors find problems early and adjust treatment if needed.

Why Monitoring Is Important

Testosterone therapy can change how the body works in several ways that may affect the kidneys. For example, testosterone can cause the body to hold onto more fluid and salt. This can raise blood pressure and put more strain on the kidneys. In some cases, testosterone therapy may also increase the number of red blood cells in the blood. When blood becomes thicker, it can make it harder for the kidneys to filter waste.

People with chronic conditions like high blood pressure, diabetes, or heart disease already have higher chances of kidney damage. Testosterone therapy may make these problems worse if not closely watched. For this reason, doctors usually recommend regular tests to keep track of kidney health during treatment.

Tests That Should Be Done

Several blood and urine tests can show how well the kidneys are working. These tests help doctors look for early signs of kidney stress or damage:

• Serum Creatinine: Creatinine is a waste product made by muscles. Healthy kidneys remove creatinine from the blood. If the level of creatinine in the blood is high, it may mean the kidneys are not working well.

• Estimated Glomerular Filtration Rate (eGFR): This number is calculated using creatinine levels, age, sex, and sometimes race. It tells how well the kidneys are filtering blood. A lower eGFR means reduced kidney function.

• Blood Urea Nitrogen (BUN): Urea nitrogen is another waste product. High levels in the blood can be a sign that the kidneys are having trouble.

• Urine Albumin or Protein: Healthy kidneys do not leak protein into the urine. If protein shows up, it could mean the kidneys are damaged or under stress.

Doctors may also check electrolyte levels, such as sodium and potassium, to see if the kidneys are keeping the right balance of minerals in the blood.

How Often to Check Kidney Function

How often kidney function should be checked depends on the person’s health, age, and risk factors. In most cases, doctors recommend checking kidney function before starting testosterone therapy. This gives a clear picture of how well the kidneys are working at the beginning.

Once treatment starts, testing may be done every 3 to 6 months during the first year. After that, testing may happen once or twice a year if there are no problems. If the person has diabetes, high blood pressure, or kidney disease, testing may be needed more often.

If any tests show signs of kidney problems, doctors may stop or adjust testosterone therapy. They may also send the patient to a kidney specialist, called a nephrologist.

What to Watch For During Treatment

Even between doctor visits, certain signs and symptoms may point to kidney trouble. These include:

• Swelling in the legs, feet, or hands

• Sudden weight gain from holding too much fluid

• Shortness of breath

• Feeling tired all the time

• High blood pressure that is hard to control

These symptoms should be reported to a healthcare provider right away. They may mean the kidneys are not working as well as they should.

Tailoring Therapy for People With Kidney Concerns

For people with existing kidney problems, doctors may be more careful about using testosterone therapy. The dose might be lower, and the form of testosterone (such as gel, injection, or patch) might be chosen based on the person’s overall health. Some forms of testosterone may raise red blood cell levels more than others, so doctors take this into account.

It is also important to manage other health issues at the same time. Keeping blood sugar, cholesterol, and blood pressure under control can help protect the kidneys. A team-based approach, involving primary care doctors, hormone specialists, and kidney doctors, often leads to the best results.

Monitoring kidney health during testosterone therapy helps reduce risks and allows for early action if problems develop. With the right testing schedule and medical care, many people can use testosterone safely while protecting their kidney function.

How Does Testosterone Influence Other Factors That Affect Kidney Health (e.g., Metabolic Syndrome, Diabetes, Obesity)?

Testosterone plays an important role in many systems in the body, including those related to metabolism, body fat, and blood sugar control. These areas are closely linked to kidney health. When testosterone levels are not in the normal range—either too low or too high—it can lead to or worsen problems that increase the risk of kidney damage. Some of the most important factors influenced by testosterone include metabolic syndrome, type 2 diabetes, and obesity. Each of these conditions has been linked to a higher chance of developing chronic kidney disease (CKD).

Metabolic Syndrome and Testosterone

Metabolic syndrome is a group of health problems that happen together. It includes high blood pressure, high blood sugar, unhealthy cholesterol levels, and extra fat around the belly. These problems increase the risk of heart disease, stroke, and kidney disease. Research shows that men with low testosterone levels are more likely to have metabolic syndrome.

Low testosterone can lead to an increase in fat mass, especially around the abdomen. This type of fat, called visceral fat, surrounds internal organs and is more harmful than fat just under the skin. Visceral fat can cause the body to become inflamed and resistant to insulin. This state is bad for the kidneys because it increases the strain on small blood vessels, including those in the kidneys.

When testosterone levels are normal or increased through therapy, it may help reduce belly fat, improve cholesterol, and lower blood sugar levels. These changes can reduce the pressure placed on the kidneys over time. However, this effect is not guaranteed in all patients and depends on many factors like age, activity level, and other medical problems.

Diabetes and Blood Sugar Control

Diabetes is one of the top causes of kidney disease worldwide. It happens when blood sugar levels stay high for a long time. High blood sugar can damage the blood vessels in the kidneys, making it harder for them to filter waste. This condition is called diabetic nephropathy.

Low testosterone has been linked with insulin resistance. Insulin is the hormone that helps the body use sugar properly. When the body becomes resistant to insulin, blood sugar levels rise. Over time, this leads to type 2 diabetes.

Studies suggest that men with low testosterone are more likely to develop type 2 diabetes. When testosterone is replaced in men who need it, insulin sensitivity can improve. This means their bodies can use insulin better, which helps lower blood sugar. Better blood sugar control is key to slowing the damage to the kidneys. Testosterone therapy may help reduce the risk of diabetic kidney damage in some cases, but more long-term studies are needed.

It is also important to note that not all patients respond to testosterone therapy the same way. Some may have other health conditions that affect how their body reacts. That is why doctors usually check blood sugar levels and kidney function during therapy.

Obesity and Fat Distribution

Obesity puts extra strain on nearly every organ in the body, including the kidneys. People who are overweight or obese are more likely to have high blood pressure, high cholesterol, and diabetes—all of which are major risk factors for kidney disease. Fat tissue also produces hormones and inflammatory substances that can make kidney function worse over time.

Low testosterone levels often go hand in hand with obesity. Men with obesity often have lower levels of testosterone, and this can make weight gain worse. It becomes a cycle: low testosterone leads to more fat gain, which then lowers testosterone even more.

Testosterone affects the way the body stores and uses fat. Normal levels of testosterone help increase lean muscle mass and reduce fat, especially belly fat. Muscle burns more calories than fat, even at rest. When muscle mass increases and body fat decreases, the risk of developing health problems like diabetes and kidney disease also drops.

Testosterone therapy may help some men with low levels reduce body fat and improve their metabolism. In turn, this can lower the risk of kidney damage caused by obesity-related conditions. However, testosterone should only be used under the care of a doctor, especially for people with existing kidney problems or other chronic diseases.

Testosterone plays a key role in controlling body fat, blood sugar, and metabolism. These areas have a big impact on kidney health. When testosterone levels are low, it can lead to problems like metabolic syndrome, type 2 diabetes, and obesity. These problems increase the chances of kidney disease. Improving testosterone levels through healthy lifestyle changes or therapy may help lower these risks for some people.

However, testosterone therapy is not a cure-all. It must be used carefully and only when there is a clear medical need. Regular check-ups, blood tests, and monitoring of kidney function are important when using testosterone treatment. Maintaining a healthy weight, staying active, and managing blood sugar and blood pressure are also key to protecting the kidneys—whether testosterone therapy is used or not.

What Do Current Clinical Guidelines Say About Testosterone Therapy in Patients With Kidney Disease?

Testosterone therapy is often considered for men with low testosterone levels, especially when symptoms such as fatigue, low sex drive, or muscle loss are present. For men with kidney disease, however, using testosterone requires extra care. Clinical guidelines from various medical organizations provide recommendations to help doctors make safe decisions. These guidelines are based on research, expert opinions, and clinical experiences.

Guidelines for Patients With Mild Kidney Disease

For men with early-stage kidney disease, testosterone therapy may still be used, but only after a careful health review. The Endocrine Society, a leading medical organization in hormone health, recommends that testosterone therapy should only be started if a man has both low blood levels of testosterone and symptoms linked to low testosterone, like reduced muscle mass or low libido.

Doctors are advised to check kidney function before starting treatment. This includes blood tests such as serum creatinine and estimated glomerular filtration rate (eGFR). These tests help show how well the kidneys are working. Men with mild kidney disease can often continue with testosterone therapy, but they must have regular checkups. The goal is to make sure the treatment does not cause further kidney damage or lead to other health problems like high blood pressure or fluid retention.

Guidelines for Advanced Kidney Disease

Men with advanced kidney disease, especially those in stages 4 or 5, need more detailed care. The National Kidney Foundation advises caution when using testosterone therapy in these patients. People with severe kidney damage may already have low testosterone levels due to poor kidney function. In such cases, low testosterone is linked to anemia, bone weakness, and muscle wasting.

Some doctors may still consider testosterone therapy in these cases, especially if the man is experiencing serious symptoms. However, the therapy should only be started after checking that the benefits are greater than the risks. Doctors must also watch for side effects, such as worsening blood pressure or fluid buildup, which are more common in patients with poor kidney function.

Use of Testosterone in Dialysis Patients

Men on dialysis often have very low testosterone levels. This is due to many factors, such as uremia (a buildup of waste products in the blood), inflammation, and reduced hormone production. Research shows that these men may benefit from testosterone therapy. Some studies suggest that it may improve mood, energy levels, and bone strength.

Still, most guidelines say that testosterone therapy in dialysis patients should be used carefully. Before treatment begins, it is important to measure hormone levels more than once. The patient’s symptoms must clearly match what would be expected from low testosterone. If therapy is started, the dose should be low at first and adjusted slowly. Regular lab tests must be done to monitor hormone levels, red blood cell counts, and kidney-related values like blood urea nitrogen (BUN) and creatinine.

Special Considerations for Kidney Transplant Patients

Men who receive a kidney transplant sometimes continue to have low testosterone levels even after transplant. This may happen due to long-term use of certain drugs that affect hormone production, such as corticosteroids or calcineurin inhibitors. Low testosterone in transplant patients can increase the risk of weak bones, reduced muscle mass, and low energy.

However, testosterone therapy is not always recommended right away for transplant patients. Most guidelines suggest waiting at least 6 to 12 months after the transplant before thinking about hormone treatment. This waiting period allows the body to stabilize and gives doctors time to understand how the new kidney is working.

If testosterone is used, transplant patients should be watched very closely. There may be a risk of increasing hematocrit levels (which can thicken the blood), worsening blood pressure, or causing unwanted interactions with transplant medications. Hormone levels, kidney function, and overall health must all be monitored throughout therapy.

Overall Recommendation from Guidelines

Across all types of kidney disease, medical groups stress that testosterone therapy should only be used when clearly needed. It should never be given just to increase hormone levels without symptoms. The therapy must be personalized based on a man’s stage of kidney disease, other health conditions, and risk factors.

Doctors are advised to re-check testosterone levels in the morning, on two different days, before starting treatment. If therapy begins, the patient should be seen regularly to track hormone levels, kidney function, red blood cell counts, and side effects.

Testosterone therapy may help some men with kidney disease, but it must be used with caution. Guidelines from trusted health groups provide a clear message: safety, monitoring, and good clinical judgment are essential when considering this therapy in men with any level of kidney impairment.

Conclusion

Testosterone and kidney function are two important parts of overall health, and research shows they are closely connected. Testosterone is a hormone that helps control many body functions like muscle strength, red blood cell production, and metabolism. The kidneys are vital organs that filter waste from the blood, balance fluids and electrolytes, and help manage blood pressure. When either testosterone levels or kidney function is out of balance, the effects can impact the rest of the body.

Many studies have found that low testosterone levels are common in people with chronic kidney disease (CKD). Men with CKD often have hormonal imbalances, especially lower levels of testosterone. This drop in testosterone may be due to several factors, such as chronic inflammation, buildup of waste in the blood (uremia), and changes in how the brain signals hormone production. These hormone problems can lead to fatigue, weak muscles, bone loss, and reduced quality of life.

On the other hand, low testosterone itself may also affect how well the kidneys work. Research suggests that low testosterone levels may increase the risk of problems such as high blood pressure, obesity, insulin resistance, and inflammation. All of these can damage the kidneys over time. Because of this two-way relationship, doctors and researchers are studying how treating low testosterone might help protect kidney function.

Testosterone therapy is used to raise low hormone levels in men who are diagnosed with hypogonadism, a condition where the body does not make enough testosterone. Some clinical trials have looked at how testosterone therapy affects kidney function. In certain studies, patients receiving testosterone showed better blood flow to the kidneys, lower levels of protein in the urine, and improved blood sugar control. These improvements may reduce some of the risks that lead to kidney damage.

However, testosterone therapy is not without risks. It can cause side effects such as water retention, increased red blood cell count, and higher blood pressure. These problems may place extra stress on the kidneys, especially in people who already have reduced kidney function. Some patients may also develop or worsen swelling in the legs, a sign that the kidneys or heart may be under pressure. For these reasons, testosterone therapy should be used carefully, especially in men who have chronic kidney disease or other health conditions.

Doctors often recommend checking kidney function before and during testosterone treatment. Simple blood and urine tests can measure important kidney markers like serum creatinine, estimated glomerular filtration rate (eGFR), and albumin levels in the urine. Keeping track of these values helps make sure that therapy is safe and not causing harm to the kidneys. If problems are found, the treatment plan can be adjusted or stopped.

In some cases, testosterone therapy may not directly affect the kidneys, but it can improve other conditions that impact kidney health. For example, higher testosterone levels have been linked to better control of blood sugar and lower body fat in some men. These changes reduce the risk of diabetes and obesity, both of which are leading causes of kidney disease. By improving overall health, testosterone therapy might support kidney health in an indirect way.

Experts from organizations like the Endocrine Society and nephrology groups have released clinical guidelines to help doctors decide when and how to use testosterone therapy in men with kidney problems. These guidelines stress the importance of testing, monitoring, and using caution in men with moderate to severe kidney disease. Patients who are on dialysis or have had a kidney transplant need special attention, as their bodies may respond differently to hormone therapy.

The link between testosterone and kidney function is complex, and more research is still needed. Long-term studies are important to better understand how testosterone therapy affects the kidneys over time. More data will help doctors create safer and more effective treatment plans for men with low testosterone and kidney problems.

Testosterone therapy may be helpful for some men, but it is not right for everyone. The risks and benefits must be carefully weighed for each person. Proper screening, regular checkups, and close communication with healthcare providers are key to using hormone therapy safely. As science learns more, better treatments may be developed to support both hormone health and kidney function.