Testosterone replacement therapy (TRT) is a medical treatment prescribed for men diagnosed with hypogonadism, a condition characterized by low testosterone levels combined with specific symptoms like low libido, fatigue, and reduced muscle mass [1.3.1, 1.4.2]. While many men report improvements in energy, mood, and sexual function, it's essential to weigh these benefits against the potential risks [1.2.5]. Testosterone injections are a common delivery method, but they come with a unique set of potential complications and side effects that require careful consideration and monitoring by a healthcare professional [1.2.1].
Common and Physical Side Effects
Some of the most frequently reported downsides of testosterone shots involve physical changes and reactions.
- Skin Reactions: Testosterone can stimulate the skin's sebaceous glands, leading to oily skin and acne [1.2.2]. In most cases, this is mild, but severe cystic acne can occur, sometimes requiring the cessation of therapy [1.2.1].
- Fluid Retention: Mild fluid retention, which can cause swelling in the ankles, is a possible side effect [1.2.2]. In patients with a history of heart, kidney, or liver disease, this fluid retention (edema) can be more serious [1.2.3].
- Injection Site Reactions: The injections themselves can cause pain, redness, or hardness at the injection site [1.4.3]. A rare complication is a pulmonary oil microembolism (POME), which happens if the oil-based solution is accidentally injected into the vascular system, leading to coughing, chest pain, and breathing difficulties [1.2.1, 1.2.4].
- Hair Loss: For men genetically predisposed to male pattern baldness, TRT can accelerate hair loss [1.2.1].
Cardiovascular and Circulatory Risks
One of the most debated areas of TRT is its impact on cardiovascular health. The FDA has required labeling to warn of a possible increased risk of heart attack and stroke, though research findings are mixed [1.3.4, 1.3.5].
Polycythemia (Increased Red Blood Cell Count)
Testosterone stimulates the bone marrow to produce more red blood cells [1.4.1]. This condition, known as erythrocytosis or polycythemia, thickens the blood [1.2.2]. While mild increases can improve oxygen-carrying capacity, severe erythrocytosis increases blood viscosity, raising the risk of blood clots, heart attack, and stroke [1.2.1]. This risk may be higher with injections compared to other TRT forms [1.2.1]. Regular blood monitoring is required, and management may involve dose reduction or blood donation (phlebotomy) [1.2.1, 1.4.2].
Other Cardiovascular Concerns
- Blood Clots: Some studies show an increased risk of venous thromboembolism (blood clots in veins) even with a normal red blood cell count [1.2.1].
- Cholesterol Levels: TRT can cause changes in cholesterol levels, though the effects can vary among individuals. It's important to monitor lipid profiles to ensure overall cardiovascular risk is not increased [1.2.1, 1.2.3].
- Blood Pressure: While not common, a small number of men may experience a significant increase in blood pressure after starting TRT [1.2.1]. The FDA has added a warning about this risk to product labeling [1.10.1].
Hormonal and Reproductive Consequences
Introducing external testosterone signals the body to reduce its own natural production. This has several significant consequences:
- Infertility and Testicular Atrophy: Exogenous testosterone suppresses the hypothalamic-pituitary-gonadal axis, leading to a decrease in sperm production and testicular shrinkage (atrophy) [1.2.2, 1.3.2, 1.4.1]. This can result in infertility, making TRT unsuitable for men planning to have children [1.3.5].
- Gynecomastia: The body can convert some testosterone into estrogen. Elevated estrogen levels can lead to the development of breast tissue, a condition known as gynecomastia, as well as breast tenderness [1.2.1, 1.3.2]. This is more likely to occur with testosterone injections [1.2.1].
Prostate Health
Testosterone's effect on the prostate gland has long been a subject of concern. While modern research has provided clarity, vigilance is still necessary.
- Benign Prostatic Hyperplasia (BPH): Testosterone can stimulate the prostate gland, potentially worsening lower urinary tract symptoms associated with an enlarged prostate, such as frequent or difficult urination [1.2.2, 1.4.1].
- Prostate Cancer: A major concern has been whether TRT increases the risk of developing prostate cancer. However, recent large-scale studies, like the TRAVERSE trial, have not found a significant link between TRT and an increased risk of prostate cancer in men who have been carefully screened [1.8.1, 1.8.2]. It is crucial to note that testosterone can stimulate the growth of existing prostate cancer. Therefore, TRT is contraindicated in men with known or suspected prostate cancer [1.3.2, 1.4.2]. Regular monitoring of prostate-specific antigen (PSA) levels is a standard part of TRT management [1.2.2].
Emotional and Psychological Effects
While many men on TRT report improved mood and well-being, adverse psychological effects can occur, particularly if hormone levels are not properly managed [1.6.5].
- Mood Swings: Fluctuations in hormone levels, especially common with the peak-and-trough cycle of injections, can lead to mood swings, irritability, and anxiety [1.2.1, 1.6.5].
- Aggression: The concept of "roid rage" is mostly associated with supraphysiologic doses of anabolic steroids abused for performance enhancement, not medically supervised TRT which aims for normal physiologic levels [1.6.2, 1.6.4]. However, some men may report heightened irritability [1.6.5].
- Sleep Apnea: TRT can cause or worsen sleep apnea, a serious condition where breathing repeatedly stops and starts during sleep [1.3.2, 1.4.1].
Comparison of TRT Administration Methods
| Method | Pros | Cons | Key Side Effects |
|---|---|---|---|
| Injections | Low cost, infrequent dosing (every 1-4 weeks) [1.2.4, 1.3.1]. | Fluctuating hormone levels ("peak and trough"), injection site pain, risk of POME, potentially higher risk of polycythemia and gynecomastia [1.2.1, 1.3.1]. | Mood swings, erythrocytosis, injection site reactions [1.2.1, 1.3.1]. |
| Gels/Creams | Provides stable daily hormone levels [1.11.3]. | Risk of transferring medication to others through skin contact, potential for skin irritation [1.3.1, 1.11.3]. | Skin irritation, risk of secondary exposure to partners/children [1.3.1]. |
| Patches | Convenient daily application, steady hormone dose [1.11.3]. | Can cause significant skin redness and rashes, may not adhere well with sweat [1.3.1, 1.11.3]. | High rate of skin irritation [1.3.1]. |
| Pellets | Long-lasting (implanted every 3-6 months), consistent hormone release [1.3.1]. | Requires a minor surgical procedure for insertion/removal, risk of infection or pellet extrusion [1.3.1]. | Site infection/bleeding (rare), dose may decrease over time [1.3.1]. |
| Oral Capsules (Newer) | Patient preference for a pill, bypasses the liver unlike older oral forms [1.11.1]. | Newer, may be more expensive, requires multiple daily doses for some formulations. | Potential for changes in blood pressure [1.4.3]. |
Conclusion
While testosterone shots can be highly effective for treating diagnosed hypogonadism, they are not without significant downsides. The potential for cardiovascular events, hormonal suppression leading to infertility, prostate stimulation, and psychological effects necessitates a thorough evaluation and an ongoing partnership with a healthcare provider. Anyone considering this therapy must be carefully screened for contraindications, such as prostate cancer or severe heart failure, and must commit to regular monitoring of blood levels and potential side effects to ensure the treatment remains both safe and effective [1.2.1, 1.3.5].
For more information from an authoritative source, consider visiting the Mayo Clinic's page on Testosterone Therapy: https://www.mayoclinic.org/healthy-lifestyle/sexual-health/in-depth/testosterone-therapy/art-20045728
