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 .
Testosterone administration to older men improves muscle function: molecular and physiological mechanisms.
We investigated the effects of 6 mo of near-physiological testosterone administration  to older men on skeletal muscle function and muscle protein metabolism .  Twelve older men ( > or = 60 yr ) with serum total testosterone concentrations < 17 nmol/l ( 480 ng/dl ) were r and omly assigned in double-blind manner to receive either placebo ( n = 5 ) or testosterone enanthate ( TE ; n = 7 ) injections . Weekly intramuscular injections were given for the 1st mo to establish increased blood testosterone concentrations at 1 mo and then changed to biweekly injections until the 6-mo time point . TE doses were adjusted to maintain nadir serum testosterone concentrations between 17 and 28 nmol/l . Lean body mass ( LBM ) , muscle volume , prostate size , and urinary flow were measured at baseline and at 6 mo . Protein expression of and rogen receptor ( AR ) and insulin-like growth factor I , along with muscle strength and muscle protein metabolism , were measured at baseline and at 1 and 6 mo of treatment . Hematological parameters were followed monthly throughout the study . Older men receiving  testosterone increased total and leg LBM , muscle volume , and leg and arm muscle strength after 6 mo . LBM accretion result ed from an increase in muscle protein net balance , due to a decrease in muscle protein breakdown . TE treatment increased expression of AR protein at 1 mo , but expression returned to pre-TE treatment levels by 6 mo . IGF-I protein expression increased at 1 mo and remained increased throughout TE administration . We conclude that physiological and near-physiological increases of testosterone in older men will increase muscle protein anabolism and muscle 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 .