Dr. Kumar’s Take
This review is important because it shows that how testosterone is given makes a difference. Injections consistently increased lean mass and strength, while gels and oral options had more mixed results. That means therapy decisions are not just about convenience, but about effectiveness. For men who need TRT primarily for muscle and strength, injectable routes may deliver the best outcomes.
Key Takeaways
✔ Testosterone injections produced the largest and most reliable increases in muscle mass.
✔ Topical gels and oral therapies showed smaller and less consistent benefits.
✔ Strength gains mirrored mass changes, with injections showing stronger effects.
✔ Route of administration should be tailored to patient goals, tolerance, and safety.
Actionable Tip
If muscle mass and strength are a priority in testosterone therapy, ask your doctor whether injectable testosterone is right for you. Gels and oral routes may be easier to use but may not provide the same level of muscular benefit.
Brief Summary
This systematic review and meta-analysis looked at randomized controlled trials comparing different testosterone administration routes. The authors evaluated lean body mass and muscle strength in men undergoing therapy. Findings revealed that intramuscular injections consistently improved both lean mass and strength, while topical and oral forms were less predictable. These differences highlight the clinical importance of administration route selection.
Study Design
Researchers systematically searched clinical trial databases and included studies that compared different testosterone delivery methods in men with low testosterone. Outcomes measured were changes in lean body mass, fat-free mass, and muscle strength (such as leg press and grip tests). The analysis pooled results across studies to determine the relative effectiveness of injections, gels, and oral formulations.
Results
- Injections showed the greatest increase in lean body mass, averaging several kilograms of gain across trials.
- Strength improvements were strongest with injections, particularly in lower body strength.
- Topical gels had modest effects on lean mass and inconsistent results for strength.
- Oral therapies were the least effective for muscle outcomes.
- Side effects varied by route, with higher hematocrit observed more often in injection groups.
Why Route of Administration Matters for Muscle
The route of testosterone delivery affects blood hormone levels. Injections create higher peaks, which may stimulate muscle protein synthesis more effectively. Gels provide steady but lower levels, while oral testosterone has limited bioavailability. These pharmacological differences explain the variability in muscle response.
Related Studies and Research
Podcast: Testosterone Replacement Therapy Explained – Anchor episode on routes, dosing, and monitoring.
How TRT Builds Muscle and Strength – Meta-analysis showing consistent gains in lean mass.
Subcutaneous vs Intramuscular Testosterone – Patient-preferred alternative with stable levels.
TRT and Sexual Function in Hypogonadism – Clinical data on sexual health and symptom relief.
Frequently Asked Questions
Why do injections work better than gels or oral testosterone?
Injections produce higher peaks in blood testosterone, which may better stimulate muscle protein synthesis. Gels provide steadier but lower levels, while oral testosterone is less efficiently absorbed.
Are injections the only option?
No. Gels and oral forms can be effective for some men, especially if muscle health is not the main concern. They may be more convenient and better tolerated.
Are injections riskier?
Injections may increase hematocrit more than other routes, which requires careful monitoring. The choice should balance goals, risks, and lifestyle.
How quickly do muscles respond?
Most studies reported measurable lean mass gains within 3–6 months. Strength changes can take longer and are most reliable when therapy is combined with resistance training.
Conclusion
Not all testosterone replacement therapies are equal when it comes to muscle. This review confirms that injections are the most effective for increasing lean mass and strength, while gels and oral therapies may provide more modest results. For men prioritizing physical performance and muscle health, the administration route should be a key part of the treatment decision.