Testosterone therapy can lead to several physical and physiological changes. Individuals receiving this treatment may notice improvements in energy levels, mood, sexual function, muscle mass, and bone density. However, the degree and timeline of these changes can vary from person to person.
Content
What is Testosterone Therapy: How It Works & What To Know
Reviewed by: Dr Thomas Macsay
Key takeaways
- Beyond sexual function, testosterone is crucial for male reproductive tissues, muscle and bone mass, red blood cell production, fat distribution, and energy levels.
- Testosterone levels are tightly regulated by the brain and naturally decline with age, but are also impacted by sleep, diet, exercise, stress, obesity, and certain medical conditions.
- Testosterone Replacement Therapy (TRT) is a medical treatment for clinically low testosterone (hypogonadism), not for normal age-related decline without symptoms.
- TRT is available through injections, topical gels/patches, and implants, offering various administration methods to suit individual needs and preferences.
- Consulting with a healthcare provider is essential to determine if therapy is appropriate based on individual health conditions and testosterone levels.
As men age, they often face declining energy levels, reduced muscle mass, and a decrease in sex drive. These changes are frequently a result of naturally falling testosterone levels, which decline by about 0.4% to 2% each year after the age of 30. This decrease in testosterone can have a significant impact on overall health and quality of life.
Understanding testosterone and its role in the body
Testosterone is a hormone that the testicles produce starting in puberty. You probably know it as a sex hormone; however, testosterone has more purposes than just improving sex drive and producing sperm.
“Testosterone does more than contribute to sexual function. It helps your body in. many other ways, such as improving your overall health”
Functions of testosterone
In males, testosterone is crucial for the development of male reproductive tissues, including the testes and prostate. It also promotes secondary sexual characteristics, such as increased muscle and bone mass and body hair growth. Beyond these primary functions, testosterone plays a role in red blood cell production, fat distribution, and overall energy levels.
How testosterone levels are regulated
Testosterone levels are regulated through a complex system involving the hypothalamus, which releases gonadotropin-releasing hormone (GnRH). This hormone prompts the pituitary gland to produce luteinizing hormone (LH), which then stimulates testosterone production in the testicles.
The body uses feedback loops to maintain a balance of testosterone. When levels are too high, the brain decreases LH production, and when levels are too low, it increases LH to boost testosterone. This process continuously regulates testosterone levels, which naturally peak in the morning and decline by evening.
Factors influencing testosterone production
Age is a significant factor in testosterone levels, as they naturally decline in men as they get older. Another factor that influences testosterone production may include:
Definition of testosterone therapy
Testosterone therapy, also known as testosterone replacement therapy (TRT) or androgen replacement therapy, is a medical treatment designed to restore testosterone levels to a normal range in individuals diagnosed with clinically low testosterone (hypogonadism). It is not a treatment for normal age-related decline in testosterone unless accompanied by symptoms and a confirmed deficiency.
How does testosterone therapy work
Testosterone therapy works by supplementing the body’s natural testosterone production with synthetic testosterone. This exogenous testosterone binds to androgen receptors throughout the body, mimicking the effects of naturally produced testosterone. As a result, it helps alleviate the symptoms associated with testosterone deficiency.
Eligibility and contraindications
Not everyone with low testosterone is a candidate for TRT. Contraindications include prostate cancer, breast cancer, severe, untreated sleep apnea, uncontrolled heart failure, and polycythemia. A comprehensive medical history and physical examination are crucial to determine eligibility.
Types and methods of testosterone therapy
Testosterone therapy is available in various forms, each with its advantages and considerations. The choice of method often depends on patient preference, lifestyle, and clinical factors.
Testosterone injections
Testosterone injections are one of the most common forms of TRT. They involve injecting testosterone directly into a muscle (intramuscularly) or subcutaneously. Injections are typically administered every 1 to 4 weeks, depending on the specific ester of testosterone used.
Types of injectable testosterone:
Topical and transdermal applications
Topical testosterone, available as gels, creams, or patches, is applied daily to the skin. These methods allow for a more consistent absorption of testosterone into the bloodstream, mimicking the body’s natural circadian rhythm of testosterone production. However, there is a risk of transfer to others through skin contact.
Implants and oral forms
Testosterone pellets are small implants placed under the skin during a minor surgical procedure. These pellets release testosterone slowly over 3 to 6 months. This method provides consistent hormone levels without daily medication or frequent injections. However, it does require a medical procedure for placement and removal.
There are oral testosterone options that exist, but are less commonly prescribed. Some oral forms can affect liver function and require regular monitoring. The FDA has approved specific oral testosterone formulations for treating hypogonadism in men. These medications offer convenience but may have different effectiveness compared to other methods.
Health benefits supported by Science
Scientific research has investigated the potential benefits of testosterone therapy in individuals with diagnosed hypogonadism.
Improved sexual function and libido
Low testosterone directly affects sexual health and performance. Men with testosterone deficiency often experience reduced libido and erectile dysfunction. A study published in the Journal of Clinical Endocrinology & Metabolism concluded that testosterone therapy effectively improves erectile function and sexual desire in hypogonadal men.
Increased energy and mood
Research suggests that TRT can improve energy levels, mood, and overall sense of well-being. A study conducted by the National Institutes of Health found that TRT improved mood and reduced depressive symptoms in men with low testosterone and depression.
Effects on bone and muscle health
Testosterone is essential for maintaining bone density and muscle mass. In men with hypogonadism, testosterone replacement therapy (TRT) has been shown to increase bone mineral density and enhance muscle strength and body composition.
Risks and side effects of testosterone replacement therapy (TRT)
Testosterone therapy offers many potential benefits and is typically safe for most men. However, like any medication, testosterone replacement therapy carries several risks that men should understand before starting treatment. These may include:
- Stimulate the growth of prostate cancer and breast cancer
- Worsening symptoms of benign prostatic hypertrophy
- Liver toxicity and liver tumors
- Enlarged breasts (Gynecomastia)
- Erythrocytosis
- Testicular atrophy and infertility
- Skin diseases
- Exacerbate sleep apnea
Addressing misconceptions and myths
Many false beliefs surround testosterone therapy. These myths can stop people from getting helpful treatment.
Common myths include:
- Only older men need testosterone therapy
- Treatment causes dangerous side effects
- Therapy leads to aggressive behavior
- Women should never use testosterone
The truth about age and treatment
Testosterone therapy helps men of all ages who have low levels. Young men can also have low testosterone due to medical conditions or injury.
“Age alone does not determine who needs treatment. Blood tests and symptoms guide the decision.“
Safety concerns
When doctors monitor treatment properly, testosterone therapy is safe for most people. The key is working with trained medical professionals.
“Regular check-ups help catch any issues early. Most side effects are mild and manageable.“
Testosterone in women
Women naturally produce testosterone, too. It is actually the most abundant active hormone in the female body. For women, testosterone helps with:
- Energy levels
- Mood stability
- Bone health
- Sexual function
Behavioral changes
Testosterone therapy does not make people violent or overly aggressive. This is one of the biggest myths. Research shows testosterone can actually help stabilize mood. Many patients report feeling calmer and more balanced.
Frequently asked questions
Bottom line
Testosterone Replacement Therapy (TRT) offers a medical solution for men with clinically low testosterone (hypogonadism) to address symptoms like low energy and reduced muscle mass. While it provides science-backed benefits, it also carries potential risks and side effects.
Therefore, TRT is a significant medical decision. It’s crucial to consult thoroughly with a healthcare professional to assess your individual needs, understand all benefits and risks, and ensure proper monitoring for your health and safety.
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- National Institutes of Health. 2021. Low-fat diets and testosterone in men.
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- National Institutes of Health. 2018. The Effect of Psychological Stress on Salivary Testosterone in Puberty Children.
- National Institutes of Health. 2014. Lowered testosterone in male obesity.
- National Institutes of Health. 2020. Association between T2DM and the lowering of testosterone levels among Kashmiri males.
- National Institutes of Health. 2010. Male hypogonadism: Symptoms and treatment.
- Mayo Clinic. 2025. Testosterone cypionate (intramuscular route).
- ScienceDirect. 2020. Testosterone Enantate.
- ScienceDirect. 2018. Testosterone Propionate.
- National Institutes of Health. 2023. Safety Aspects and Rational Use of Testosterone Undecanoate in the Treatment of Testosterone Deficiency.
- National Institutes of Health. 2004. Osteopenia and Male Hypogonadism.
- U.S Food & Drug Administration. 2025. FDA issues class-wide labeling changes for testosterone products.
- The Journal of Clinical Endocrinology & Metabolism. 2018. The Efficacy and Adverse Events of Testosterone Replacement Therapy in Hypogonadal Men.
- National Institutes of Health. 2009. The benefits and risks of testosterone replacement therapy.
- National Institutes of Health. 2022. Testosterone Replacement Therapy in the Treatment of Depression.
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