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 .
Changes in muscle mass, muscle strength, and power but not physical function are related to testosterone dose in healthy older men.
OBJECTIVES To examine the effect of grade d doses of testosterone on physical function and muscle performance in healthy , older men . DESIGN R and omized , double-blind , placebo-controlled clinical trial . SETTING General clinical research center . PARTICIPANTS Community-dwelling healthy men aged 60 to 75 ( N=44 ) . INTERVENTION Monthly treatment with a gonadotropin-releasing hormone agonist plus 25 , 50 , 125 , or 300 mg/wk of intramuscular injections of testosterone enanthate for 20 weeks . MEASUREMENTS Skeletal muscle mass ( SMM ) was estimated using dual-energy X-ray absorptiometry . Leg press strength was measured by one repetition maximum , leg power by Nottingham Leg Rig , and muscle fatigability by repetitions to failure in the leg press exercise .  Stair climbing , 6-meter and 400-meter walking speed , and a timed-up- and -go ( TUG ) test were used to assess physical function . RESULTS Significant testosterone dose- and concentration-dependent increases were observed in SMM ( P<.001 ) and maximal strength ( P=.001 ) but not muscle fatigability . Leg power also increased dose-dependently ( P=.048 ) . In contrast , changes in self-selected normal and fast walking speed over 6 or 400 meters , stair climbing power , and time for the TUG were not significantly related to testosterone dose , testosterone concentrations , or changes in muscle strength or power , or SMM . CONCLUSION Testosterone administration was associated with dose-dependent increases in SMM , leg strength , and power but did not improve muscle fatigability or physical function . The observation that physical function scores did not improve linearly with strength suggests that these high-functioning older men were already in the asymptotic region of the curve describing the relationship between physical function and strength
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 .