Intramuscular TRT is more effective than transdermal formulations at increasing LBM and improving muscle strength  in middle-aged and older men , particularly in the lower extremities
BACKGROUND Inconsistent fat-free mass ( FFM ) and muscle strength responses have been reported in r and omized clinical trials ( RCTs ) administering  testosterone replacement therapy ( TRT ) to middle-aged and older men .
Our objective was to conduct a meta- analysis to determine whether TRT improves FFM and muscle strength in middle-aged and older men and whether the muscular responses vary by TRT administration route .
Effect of testosterone supplementation with and without a dual 5α-reductase inhibitor on fat-free mass in men with suppressed testosterone production: a randomized controlled trial.
CONTEXT Steroid 5α-reductase inhibitors are used to treat benign prostatic hyperplasia and and rogenic alopecia , but the role of 5α-dihydrotestosterone ( DHT ) in mediating testosterone 's effects on muscle , sexual function , erythropoiesis , and other and rogen-dependent processes remains poorly understood . OBJECTIVE To determine whether testosterone 's effects on muscle mass , strength , sexual function , hematocrit level , prostate volume , sebum production , and lipid levels are attenuated when its conversion to DHT is blocked by dutasteride ( an inhibitor of 5α-reductase type 1 and 2 ) . DESIGN , SETTING , AND PATIENTS The 5α-Reductase Trial was a r and omized controlled trial of healthy men aged 18 to 50 years comparing placebo plus testosterone enthanate with dutasteride plus testosterone enanthate from May 2005 through June 2010 . INTERVENTIONS Eight treatment groups received 50 , 125 , 300 , or 600 mg/wk of testosterone enanthate for 20 weeks plus placebo ( 4 groups ) or 2.5 mg/d of dutasteride ( 4 groups ) . MAIN OUTCOME MEASURES The primary outcome was change in fat-free mass ; secondary outcomes : changes in fat mass , muscle strength , sexual function , prostate volume , sebum production , and hematocrit and lipid levels . RESULTS A total of 139 men were r and omized ; 102 completed the 20-week intervention . Men assigned to dutasteride were similar at baseline to those assigned to placebo . The mean fat-free mass gained by the dutasteride groups was 0.6 kg ( 95 % CI , -0.1 to 1.2 kg ) when receiving 50 mg/wk of testosterone enanthate , 2.6 kg ( 95 % CI , 0.9 to 4.3 kg ) for 125 mg/wk , 5.8 kg ( 95 % CI , 4.8 to 6.9 kg ) for 300 mg/wk , and 7.1 kg ( 95 % CI , 6.0 to 8.2 kg ) for 600 mg/wk . The mean fat-free mass gained by the placebo groups was 0.8 kg ( 95 % CI , -0.1 to 1.7 kg ) when receiving 50 mg/wk of testosterone enanthate , 3.5 kg ( 95 % CI , 2.1 to 4.8 kg ) for 125 mg/wk , 5.7 kg ( 95 % CI , 4.8 to 6.5 kg ) for 300 mg/wk , and 8.1 kg ( 95 % CI , 6.7 to 9.5 kg ) for 600 mg/wk . The dose-adjusted differences between the dutasteride and placebo groups for fat-free mass were not significant ( P = .18 ) . Changes in fat mass , muscle strength , sexual function , prostate volume , sebum production , and hematocrit and lipid levels did not differ between groups . CONCLUSION Changes in fat-free mass in response to grade d testosterone doses did not differ in men in whom DHT was suppressed by dutasteride from those treated with placebo , indicating that conversion of testosterone to DHT is not essential for mediating its anabolic effects on muscle . TRIAL REGISTRATION clinical trials.gov Identifier : NCT00493987
Intramuscular TRT is more effective than transdermal formulations at increasing LBM and improving muscle strength  in middle-aged and older men , particularly in the lower extremities
BACKGROUND Inconsistent fat-free mass ( FFM ) and muscle strength responses have been reported in r and omized clinical trials ( RCTs ) administering  testosterone replacement therapy ( TRT ) to middle-aged and older men .
Our objective was to conduct a meta- analysis to determine whether TRT improves FFM and muscle strength in middle-aged and older men and whether the muscular responses vary by TRT administration route .