Testosterone is one of the most talked about and least understood hormones in men’s health.
Many men associate it exclusively with sex drive or muscle building, but that fails to account for much of what testosterone does. Testosterone influences nearly every system of the male body, from bones to muscles to mood to metabolism. (1)
For men, understanding what testosterone actually does is not just about optimizing performance or vitality. It is about recognizing how hormonal health affects energy, focus, emotional health, and overall quality of life. When testosterone levels fall outside a healthy range, the effects can be subtle at first, but they may compound over time.
In this guide, we’ll break down what testosterone does for men, how it works in the body, and why it matters at every stage of adulthood. We’ll also explain how professional evaluations of your T levels from a trusted clinician can help men make informed decisions about their health.
What Is Testosterone?
Testosterone is a hormone classified as an androgen. Androgens are responsible for the development and maintenance of male characteristics, but testosterone’s influence goes far beyond physical traits.
In men, testosterone is primarily produced in the testicles. A smaller amount is produced by the adrenal glands, which sit on top of the kidneys. Production is regulated by a communication loop between the brain and the testes known as the hypothalamic-pituitary-gonadal-axis. This system ensures that testosterone levels stay within a range that supports normal bodily functions. (2)
Once produced, testosterone circulates through the bloodstream in a few different forms. Some testosterone is bound tightly to proteins like sex hormone binding globulin, making it unavailable for use by tissues. Some is loosely bound to albumin, and some circulates as free testosterone. Free and loosely bound testosterone are considered biologically active and are responsible for most of the hormone’s effects. (3)
Testosterone also converts into other important hormones in certain tissues. For example, it can convert into dihydrotestosterone, which plays a role in prostate health and hair follicles, or into estradiol, a form of estrogen that is essential for bone density and cardiovascular health in men. (4)
Testosterone’s Role in Physical Health
For men, testosterone plays a significant role in physical structure and strength levels throughout their life. Muscle development is one of the most well-known roles testosterone plays in the body. It stimulates protein synthesis, which helps build and maintain muscle mass. Men with healthy testosterone levels generally find it easier to gain muscle and maintain strength, even as they age. Low testosterone levels are generally considered those under 300 ng/dL, although this threshold can vary slightly with age and other factors. (5)
Bone health is another critical area influenced by testosterone. Testosterone helps maintain bone mineral density by supporting the activity of bone forming cells. When testosterone levels decline, bones can become less dense and more prone to fractures over time.
Testosterone also affects how the body stores and distributes fat. Healthy T levels tend to support lean body mass and limit excess fat accumulation, particularly in the abdominal area. When levels are low, men may notice increased body fat even if their diet and activity levels have not changed. (6)
Another important function of testosterone is its role in red blood cell production. Testosterone stimulates the bone marrow to produce red blood cells, which are essential for carrying oxygen throughout the body. This is one reason men with low testosterone may experience fatigue or reduced exercise tolerance. (7)
Testosterone and Sexual Health
When it comes to sexual health, testosterone can play a significant role, although its effects are frequently misunderstood. Healthy testosterone levels support healthy libido. When T levels are low, men may experience a lack of sexual desire that persists over time.
The relationship between testosterone and erectile function is more complex. Testosterone does not directly cause erections, but adequate testosterone levels do help maintain nitric oxide signaling, blood flow, and the health of penile tissue, all of which are needed to avoid erectile dysfunction. (8) Low testosterone can make erections less reliable or reduce responsiveness to stimulation, especially when combined with other factors like cardiovascular disease or stress.
Fertility is another area where testosterone plays a key role. Testosterone is necessary for sperm production within the testes. However, this process requires a careful balance. Extremely high or externally supplemented testosterone can actually suppress natural sperm production in some cases. (9) This is why professional oversight is essential for men who are concerned about both hormone levels and fertility.
Testosterone’s Impact on Mental and Emotional Health
Testosterone influences the brain as much as it does the body. One of its key roles is in mood regulation. Men with balanced testosterone levels are less likely to experience emotional instability, irritability, or anxiety. (10)
Motivation and confidence are also closely linked to testosterone. The hormone interacts with neurotransmitters in the brain that influence drive, assertiveness, and goal oriented behavior. Men with declining testosterone may notice that daily tasks suddenly require extra effort or that their confidence level has gone down.
Testosterone also supports aspects of memory, focus, and mental clarity. While it is not the sole factor in cognitive health, low levels have been associated with difficulty concentrating and mental fog in some men. (11) Maintaining healthy testosterone levels can support sharper thinking and sustained attention, especially during demanding work or daily responsibilities.
Testosterone and Metabolic Health
Metabolism refers to how the body converts food into energy and manages blood sugar, fat storage, and overall energy balance. Testosterone plays a meaningful role in this process.
Men with healthy testosterone levels often report more consistent energy throughout the day. Testosterone supports mitochondrial function, which helps cells produce energy efficiently. Low levels can contribute to persistent fatigue, even when sleep and nutrition appear adequate.
Insulin sensitivity is another key factor when it comes to testosterone. Testosterone helps the body respond effectively to insulin, the hormone that regulates blood sugar. Lower testosterone levels have been linked to increased insulin resistance, which can raise the risk of type 2 diabetes over time. (12)
Body composition is also closely tied to metabolic health. Testosterone supports a higher ratio of muscle to fat, which in turn helps maintain a healthy metabolism. As muscle mass declines and fat mass increases, metabolic efficiency often decreases, creating a cycle that can be difficult to reverse without addressing underlying hormonal factors.
How Testosterone Levels Change With Age
Testosterone levels naturally change throughout a man’s life. During puberty and early adulthood, levels rise rapidly, supporting growth, muscle development, and sexual maturation. Peak levels are typically reached in late adolescence or early adulthood.
Beginning in the thirties, testosterone levels gradually decline. This decline is often described as about 1% per year, though the rate varies widely between individuals. (13) Genetics, lifestyle, stress, sleep quality, and overall health are just some of the factors that influence how quickly levels change.
Symptoms related to declining testosterone vary because men respond differently to hormonal shifts. Some men may notice changes early, while others may maintain normal function for months or years despite having lower levels.
Signs Testosterone Levels May Be Low
Low testosterone does not look the same in every man, but there are common symptoms that often appear together. These include:
- Fatigue that does not improve with rest
- Reduced libido or interest in sex
- Loss of muscle mass or strength
- Increased body fat, especially around the midsection
- Mood changes such as irritability or low motivation
- Difficulty concentrating or mental fog
Experiencing just one or even two of these symptoms at once does not automatically mean you have low testosterone. However, a consistent pattern of these symptoms can warrant further evaluation from a trusted professional.
How Testosterone Levels Are Evaluated
Testosterone levels are typically evaluated through blood testing. A simple blood draw can measure total testosterone, and in some cases free testosterone, to provide insight into how much hormone is available to the body.
Testing is typically done when testosterone levels are highest, which is usually in the morning. However, it’s important to remember that numbers alone don't tell the entire story. Your clinician can help you interpret your testosterone levels alongside your symptoms, medical history, and overall health profile.
Professional evaluation ensures that testing is accurate and meaningful. Hormone levels can fluctuate due to illness, stress, sleep deprivation, or medications. A qualified clinician can determine whether results reflect a true imbalance or are only temporary changes that should revert back to normal in time.
Why Balanced Testosterone Matters
Testosterone levels that are too low can negatively affect physical health, mental wellbeing, and metabolic function. Over time, this imbalance may increase the risk of conditions like osteoporosis, cardiovascular issues, and metabolic disease.
Levels that are too high also carry risks. Excess testosterone can contribute to cardiovascular strain, changes in cholesterol levels, and suppression of the body’s natural hormone production. Self-treatment or unregulated supplementation of testosterone increases these risks significantly. (14)
Balanced testosterone is about supporting the body, not overriding it. Medically supervised care focuses on restoring and maintaining levels within a healthy range while monitoring for safety and effectiveness. This approach prioritizes long term health over short term gains.
How Gameday Men’s Health Supports Testosterone Health
At Gameday Men’s Health, we take a comprehensive approach to testosterone health. Treatment begins with thorough hormone testing so our physicians can understand each individual’s baseline levels.
From there, treatment options are tailored to each individual’s specific needs, taking into account their unique symptoms, lab results, and overall health goals. At Gameday, we know that there’s no one-size-fits-all option when it comes to testosterone levels, and eligibility for treatment therapies like testosterone replacement are determined on a case-by-case basis.
Ongoing monitoring is a critical part of the process. Regular follow up testing and check ins allow clinicians to adjust care as needed and ensure that hormone levels remain balanced over time.
Understanding what testosterone does for men is the first step toward taking control of hormonal health. If you’re curious to learn more about how testosterone affects the body, or if you’re ready to get your levels checked, contact your local Gameday Men’s Health location to schedule a consultation.
