Does TRT Help Build Muscle? What the Trials Show About Strength, Lean Mass and Lifting

Does TRT help build muscle? Yes. Meta-analyses of randomized trials show testosterone replacement adds lean mass and strength in middle-aged and older men, with injections producing a 5.7% gain in fat-free mass versus 1.7% for gels. In a 10-week trial of a high 600 mg weekly dose in young men, lifting roughly doubled the strength gain; at replacement doses in older men, the added benefit was smaller.

Does TRT help build muscle? Yes. Testosterone replacement therapy reliably increases lean mass and muscle strength in randomized trials, and the gains are larger when men also lift weights. A 2018 meta-analysis by Skinner and colleagues found that intramuscular testosterone raised fat-free mass by 5.7% and strength by 10-13% in middle-aged and older men, while gels produced much smaller changes.

The useful question is how much muscle TRT builds, for whom, and under what conditions. This guide walks through the landmark 1996 New England Journal of Medicine trial, the three-year TEAAM trial in older men, the NIH-funded Testosterone Trials, two meta-analyses and the smaller evidence base for enclomiphene and clomiphene. Every figure below comes from the published trial abstracts.

TRT does help build muscle in men with low or low-normal testosterone, though the effect in replacement doses is modest rather than dramatic. Skinner and colleagues pooled 31 double-blind randomized trials that measured fat-free mass and 17 that measured strength, all comparing testosterone with placebo in middle-aged and older men. Across all delivery routes, testosterone increased fat-free mass, total body strength, upper body strength and lower body strength.

A second meta-analysis by Parahiba and colleagues in Experimental Gerontology (2020) looked only at men aged 40 and older across 11 studies. Testosterone added 2.54 kg of lean body mass on average, improved handgrip strength by 1.58 kgf, and increased leg press strength by 91.23 N and leg extension strength by 144.10 N. The same analysis found no effect on the Physical Performance Test, a measure of everyday tasks, in the two studies that used it.

The TEAAM trial by Storer and colleagues (Journal of Clinical Endocrinology and Metabolism, 2017) shows what long-term replacement looks like. Men aged 60 or older with total testosterone of 100 to 400 ng/dL, or free testosterone under 50 pg/mL, used 7.5 g of 1% testosterone gel or placebo daily for 3 years. Lean mass rose more on testosterone, chest press strength improved by 16.3 N and chest press power by 22.5 W over placebo, and loaded stair-climbing power improved by 22.4 W. The authors described the gains as modest but significant.

The type of TRT matters a great deal for muscle. In the Skinner meta-analysis, intramuscular testosterone produced effects 3-5 times greater than transdermal gels and patches for every outcome measured. Injections raised fat-free mass by 5.7% and strength by 10-13%, while transdermal products raised fat-free mass by only 1.7% and strength by 2-5%.

The leg results stood out most. Transdermal testosterone produced no change in lower-extremity strength compared with placebo in the Skinner analysis, while intramuscular testosterone improved it substantially. The authors concluded that injections are more effective than transdermal formulations for building lean mass and strength in middle-aged and older men, particularly in the legs. Our guide to TRT delivery methods compares injections, gels and pellets on other outcomes too.

Lifting weights on testosterone builds more muscle and strength than either testosterone or training alone, at least at high doses. The clearest evidence is the 1996 trial by Bhasin and colleagues in the New England Journal of Medicine. Researchers randomly assigned 43 normal men to placebo or 600 mg of testosterone enanthate weekly for 10 weeks, with or without supervised weight training three times a week.

In the Bhasin trial, men who took testosterone without training still gained strength: bench press rose by 9 kg versus -1 kg on placebo, and squat capacity rose by 16 kg versus 3 kg. Men who combined testosterone with lifting did best of all, gaining 6.1 kg of fat-free mass, 22 kg on the bench press and 38 kg on the squat. Neither mood nor behavior changed in any group.

The 600 mg weekly dose in the Bhasin trial is several times what a TRT prescription delivers, so these results show what testosterone can do at supraphysiologic levels, not what a man on replacement should expect. The study enrolled healthy young men with normal testosterone, not men with low levels. It answers whether testosterone builds muscle at all, which it clearly does, rather than how much a typical TRT patient will gain.

At replacement doses in older men, the picture is less tidy. Hildreth and colleagues (Journal of Clinical Endocrinology and Metabolism, 2013) randomized 167 healthy men with an average age of 66 and total testosterone of 200-350 ng/dL to testosterone gel or placebo, with or without progressive resistance training, for 12 months. Among men who trained, testosterone added fat-free mass but did not improve strength or function beyond what training alone produced. Among men who did not train, testosterone improved fat-free mass and upper body strength.

TRT makes older men somewhat stronger on lab tests, but the effect on everyday physical function is small. The Testosterone Trials, reported by Snyder and colleagues in the New England Journal of Medicine in 2016, gave 790 men aged 65 or older with testosterone below 275 ng/dL either testosterone gel or placebo for 1 year. Testosterone raised levels to the mid-normal range for men aged 19 to 40.

In the Testosterone Trials, the share of men who improved their 6-minute walk by at least 50 m did not differ significantly in the dedicated Physical Function Trial. Across all participants, 20.5% of men on testosterone reached that threshold versus 12.6% on placebo. A secondary analysis by Bhasin and colleagues in Lancet Diabetes and Endocrinology (2018) found that testosterone did not reduce falls, though men on testosterone were more likely to report that their walking had improved.

Free testosterone tracks with muscle and mobility gains in the trial data, but no trial has tested free testosterone as a separate lever from total testosterone. In the Testosterone Trials secondary analysis, improvements in 6-minute walk distance were significantly associated with changes in total testosterone, free testosterone, dihydrotestosterone and hemoglobin. Several of these markers rose together, so the analysis cannot show which one drove the gains.

The TEAAM trial treated free testosterone as a valid entry criterion, enrolling men with free testosterone below 50 pg/mL even if total testosterone looked acceptable. A separate JAMA trial by Bhasin and colleagues (2012) found that blocking the conversion of testosterone to dihydrotestosterone with dutasteride did not reduce fat-free mass gains across doses of 50 to 600 mg weekly, so DHT itself is not essential for muscle growth. Our explainer on free vs bioavailable testosterone covers how these values are measured.

Whether enclomiphene helps build muscle has not been tested in published trials. The phase III studies reported by Kim and colleagues in BJU International (2016) enrolled overweight men aged 18-60 with total testosterone at or below 300 ng/dL and compared enclomiphene with 1.62% testosterone gel for 16 weeks. The outcomes were testosterone, LH, FSH and sperm counts. The abstract reports no lean mass, muscle or strength data.

The closest evidence comes from clomiphene citrate, a related drug. In a randomized, double-blind trial by Soares and colleagues (International Journal of Obesity, 2018), 78 men with obesity-associated low testosterone and an average age of 36.5 took 50 mg of clomiphene or placebo for 12 weeks. The clomiphene group showed improvements in lean mass, fat-free mass and muscle mass on bioelectric impedance, a less precise method than DEXA, and also saw lower HDL cholesterol. That result is suggestive for the drug class but is not evidence that enclomiphene builds muscle. Our enclomiphene guide explains how it differs from TRT.

Eating protein above the recommended amount did not boost muscle gains from testosterone in a controlled feeding trial. Bhasin and colleagues (JAMA Internal Medicine, 2018) gave 92 functionally limited men aged 65 or older either 0.8 or 1.3 g/kg/d of protein, with weekly 100 mg testosterone enanthate injections or placebo, for 6 months. Extra protein did not increase lean mass or augment the anabolic response to testosterone, though it did lower fat mass.

That trial studied older men who were not lifting weights and whose usual diets already met the recommended intake, so it does not settle protein needs for men who train hard. Our guide to protein intake for men over 40 covers the training-specific research.

This article is for educational purposes only and is not medical advice. It does not diagnose, treat, cure or prevent any disease. Testosterone therapy is a prescription treatment with real risks, so speak with a licensed physician before starting, stopping or changing any hormone therapy.

• Bhasin S et al. The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men. New England Journal of Medicine, 1996. https://doi.org/10.1056/NEJM199607043350101
• Storer TW et al. Effects of Testosterone Supplementation for 3 Years on Muscle Performance and Physical Function in Older Men. Journal of Clinical Endocrinology and Metabolism, 2017. https://doi.org/10.1210/jc.2016-2771
• Snyder PJ et al. Effects of Testosterone Treatment in Older Men. New England Journal of Medicine, 2016. https://doi.org/10.1056/NEJMoa1506119
• Skinner JW et al. Muscular responses to testosterone replacement vary by administration route: a systematic review and meta-analysis. Journal of Cachexia, Sarcopenia and Muscle, 2018. https://doi.org/10.1002/jcsm.12291
• Parahiba SM et al. Effect of testosterone supplementation on sarcopenic components in middle-aged and elderly men: A systematic review and meta-analysis. Experimental Gerontology, 2020. https://doi.org/10.1016/j.exger.2020.111106
• Hildreth KL et al. Effects of testosterone and progressive resistance exercise in healthy, highly functioning older men with low-normal testosterone levels. Journal of Clinical Endocrinology and Metabolism, 2013. https://doi.org/10.1210/jc.2012-3695
• Bhasin S et al. Effect of testosterone replacement on measures of mobility in older men with mobility limitation and low testosterone concentrations: secondary analyses of the Testosterone Trials. Lancet Diabetes & Endocrinology, 2018. https://doi.org/10.1016/S2213-8587(18)30171-2
• Bhasin S et al. Effect of testosterone supplementation with and without a dual 5α-reductase inhibitor on fat-free mass in men with suppressed testosterone production. JAMA, 2012. https://doi.org/10.1001/jama.2012.227
• Bhasin S et al. Effect of Protein Intake on Lean Body Mass in Functionally Limited Older Men: A Randomized Clinical Trial. JAMA Internal Medicine, 2018. https://doi.org/10.1001/jamainternmed.2018.0008
• Soares AH et al. Effects of clomiphene citrate on male obesity-associated hypogonadism: a randomized, double-blind, placebo-controlled study. International Journal of Obesity, 2018. https://doi.org/10.1038/s41366-018-0105-2
• Kim ED et al. Oral enclomiphene citrate raises testosterone and preserves sperm counts in obese hypogonadal men, unlike topical testosterone. BJU International, 2016. https://doi.org/10.1111/bju.13337

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