What Does Testosterone do: Roles, Effects, and Impact on Health

What do you picture when you hear the word “testosterone”? Stereotypes of overly macho behavior, aggression, impatience, or even violence and road rage might spring to mind. However, the idea that testosterone solely contributes to such behaviors is more myth than reality. Beyond these misconceptions, testosterone plays a myriad of significant roles in both health and disease, offering surprising insights into its importance.

Did you know, for instance, that testosterone is critically involved in prostate cancer? Or is it essential for women’s health as well?

Testosterone is more than just a catalyst for controversial behavior. Dive into the comprehensive guide on this sex hormone to uncover its primary benefits and the extensive impact it has beyond the myths.

What is Testosterone?

Testosterone is classified as a sex hormone, which falls under the broader category of hormones—chemical messengers within the body. These messengers embark on journeys from one organ to another, often via the bloodstream, influencing various bodily functions.

In males, testosterone stands as the primary sex hormone, playing a pivotal role in the development of male physical features and growth patterns.

Testosterone production is a finely tuned process initiated by signals from the brain to the pituitary gland at the brain’s base. The pituitary gland, in turn, communicates with the testes, prompting testosterone production.

This process is governed by a “feedback loop” system, ensuring hormone levels within the blood remain balanced. Should testosterone levels climb too high, the brain intervenes, instructing the pituitary gland to dial back production.

What Does Testosterone do?

Testosterone significantly impacts various bodily functions, including:

  • Developing the penis and testes
  • Deepening the voice during puberty
  • Initiating the growth of facial and pubic hair at puberty and possibly influencing balding later in life
  • Enhancing muscle size and strength
  • Strengthening bones
  • Boosting sex drive (libido)
  • Producing sperm

If adolescent boys have too little testosterone, they might not undergo average masculinization. This deficiency can lead to underdeveloped genitals, sparse facial and body hair, and a voice that doesn’t deepen as expected.

Testosterone also plays a role in maintaining an everyday mood. It may have other vital functions that researchers have yet to uncover.

Can You Have Too Much Testosterone?

Men rarely face the issue of naturally high testosterone levels, which might come as a surprise considering the behaviours often attributed to testosterone excesses, such as road rage, aggressive disputes at children’s sports events, and sexual promiscuity.

This perception partly stems from challenges in defining what constitutes “normal” testosterone levels and behavior. Testosterone levels fluctuate significantly over time and even throughout a single day. Moreover, behaviors that signal testosterone excess might not be linked to this hormone.

Our primary understanding of unusually high testosterone levels in men is through the observation of athletes who abuse anabolic steroids and related hormones to bulk up and enhance performance.

Artificially elevated testosterone levels can lead to several issues, including:

  • Low sperm counts, testicular shrinkage, and impotence, which may seem paradoxical
  • Damage to heart muscle and a higher risk of heart attacks
  • Prostate enlargement, leading to urination difficulties
  • Liver diseases
  • Acne and skin conditions
  • Fluid retention, causing swollen legs and feet
  • Weight gain, possibly tied to increased appetite
  • Elevated blood pressure and cholesterol levels
  • Sleep disorders
  • Headaches
  • Increased muscle mass
  • Higher risk of developing blood clots
  • Growth impairment in adolescents
  • Potentially aggressive behavior, though this is not thoroughly researched or confirmed
  • Mood swings, euphoria, irritability, poor judgment, and delusions

For women, polycystic ovary syndrome (PCOS) is often the culprit behind high testosterone levels, affecting 6% to 10% of premenopausal women. Women with PCOS may have ovaries with multiple cysts and exhibit symptoms like irregular menstrual cycles, decreased fertility, excessive or coarse hair in various body parts, male-pattern baldness, thickened, dark skin, weight gain, and psychological issues. 

Spironolactone, a diuretic inhibiting male hormone effects, is one treatment option for several symptoms.

Women with elevated testosterone, whether due to PCOS or drug use, may also experience reduced breast size and voice deepening, along with many of the issues mentioned for men.

Can You Have Not Enough Testosterone?

Recently, the focus among researchers and pharmaceutical companies has shifted towards the effects of testosterone deficiency, particularly in men. Testosterone levels in men decrease gradually as they age, by about 1% to 2% annually, which is much slower compared to the swift decline in estrogen that leads to menopause. 

This decline is due to the testes producing less testosterone and receiving fewer signals from the pituitary gland to generate the hormone. Additionally, older men’s livers produce more sex hormone-binding globulin (SHBG), which binds to testosterone in the bloodstream, reducing the amount of active (free) testosterone.

Consequently, over a third of men older than 45 may have testosterone levels considered lower than expected. However, defining what “optimal” is can be complex and somewhat contentious.

Symptoms of testosterone deficiency in adult men may include:

  • Diminished body and facial hair
  • Muscle mass loss
  • Decreased libido, impotence, smaller testicles, reduced sperm count, and infertility
  • Increased breast size
  • Hot flashes
  • Irritability, poor concentration, and depression
  • Loss of body hair
  • Weaker bones and a higher risk of fractures

Men with low testosterone who show symptoms or conditions linked to this deficiency may see improvement with testosterone replacement therapy. For instance, testosterone replacement can enhance bone strength and lower fracture risks in men with osteoporosis and low testosterone levels.

Interestingly, women can also suffer from the effects of testosterone deficiency. Issues with the pituitary or adrenal glands may lead to decreased testosterone production in women, who might experience symptoms such as low libido, weaker bones, poor concentration, or depression.

Conditions That Affect Testosterone

Men may see a decline in testosterone levels due to various conditions or diseases that affect:

  • The testes, through direct injury, castration, infection, radiation therapy, chemotherapy, or tumors
  • The pituitary gland or hypothalamus, due to tumors, medications (notably anabolic steroids), certain infections, and autoimmune diseases

Genetic disorders can also impact testosterone levels. For example, Klinefelter syndrome, where a man has an additional X chromosome, and hemochromatosis, where a genetic abnormality causes excessive iron buildup throughout the body, including the pituitary gland, affect testosterone production.

Similarly, women can experience testosterone deficiency due to problems with the pituitary, hypothalamus, or adrenal glands or following the removal of the ovaries. Estrogen therapy, which increases sex hormone-binding globulin (SHBG), decreases the amount of free, active testosterone in the body, mirroring the process observed in aging men.

Did You know?

  • Low testosterone isn’t always detrimental, with prostate cancer being a prime example. Testosterone can fuel the growth of both the prostate gland and prostate cancer. That’s why treatments that reduce testosterone levels, such as leuprolide, are frequently used for men with this diagnosis. Men on testosterone replacement therapy need close monitoring for prostate cancer. While testosterone can accelerate cancer growth, it’s not confirmed that testosterone therapy directly causes cancer.
  • The body synthesizes testosterone from cholesterol, but high cholesterol doesn’t guarantee high testosterone levels. The brain regulates testosterone levels too meticulously for such a direct correlation.

Testosterone Therapy

Testosterone therapy has gained approval for treating delayed puberty in males and abnormally low testosterone production due to testes, pituitary, or hypothalamus malfunction.

Men might qualify for testosterone therapy if they exhibit significantly low levels of active (free) testosterone along with symptoms such as:

  • General weakness
  • Low energy
  • Disabling frailty
  • Depression
  • Sexual dysfunction
  • Cognitive issues

The presence of these symptoms in men with normal testosterone levels complicates the direct linkage between testosterone levels and symptoms, sparking debate over who genuinely benefits from supplemental testosterone.

For women with low testosterone levels and symptoms potentially stemming from this deficiency, testosterone therapy could be a rational choice, albeit the effectiveness and advisability of such treatment remain under scrutiny.

The Risks of Testosterone Therapy?

Some men and women immediately face side effects from testosterone treatment, such as acne, sleep apnea, breast swelling or tenderness, and ankle swelling. Doctors also remain vigilant for elevated red blood cell counts, heightening clotting risks.

While testosterone therapy doesn’t seem to increase the risk of developing prostate cancer, it can accelerate the growth of existing prostate cancer cells. Given prostate cancer’s prevalence, doctors often hesitate to prescribe testosterone to men at an above-average risk for undiagnosed prostate cancer.

For men with low testosterone levels in the blood and symptoms indicative of such a deficiency, the advantages of hormone replacement therapy typically surpass the potential dangers. Yet, for most other men, deciding on testosterone therapy involves a collaborative discussion with their doctor.


Understanding what testosterone does sheds light on its vital role in shaping male physiology and its broader implications for health and well-being. Testosterone’s influence extends from developing male sexual characteristics to its significant effects on bone density, muscle strength, mood, and cognitive functions.

Its significance is equally remarkable in women, influencing libido, bone health, and muscular strength, thereby highlighting the hormone’s pivotal role across all genders.

The balance of testosterone levels is vital. Both deficiencies and excesses can lead to health complications, ranging from cardiovascular risks and bone density issues to impacts on mood and cognitive function. The careful management of testosterone levels can help mitigate these risks, highlighting the need for medical oversight in testosterone therapy, particularly given its complex effects on conditions like prostate cancer and cardiovascular health.

This comprehensive overview of testosterone’s roles and effects underscores the hormone’s significance beyond its stereotypical associations, offering insights into its nuanced impact on health.

It’s clear that testosterone is more than just a driver of male characteristics—it’s a crucial component of the body’s endocrine system, affecting a wide range of bodily functions and contributing to overall health and well-being.