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 .
A population-level decline in serum testosterone levels in American men.
CONTEXT Age-specific estimates of mean testosterone ( T ) concentrations appear to vary by year of observation and by birth cohort , and estimates of longitudinal declines in T typically outstrip cross-sectional decreases . These observations motivate a hypothesis of a population -level decrease in T over calendar time , independent of chronological aging . OBJECTIVE The goal of this study was to establish the magnitude of population -level changes in serum T concentrations and the degree to which they are explained by secular changes in relative weight and other factors . DESIGN We describe a prospect i ve cohort study of health and endocrine functioning in r and omly selected men of age 45 - 79 yr . We provide three data collection waves : baseline ( T1 : 1987 - 1999 ) and two follow-ups ( T2 : 1995 - 1997 , T3 : 2002 - 2004 ) . SETTING This was an observational study of r and omly selected men residing in greater Boston , Massachusetts . PARTICIPANTS Data obtained from 1374 , 906 , and 489 men at T1 , T2 , and T3 , respectively , totaling 2769 observations taken on 1532 men . MAIN OUTCOME MEASURES The main outcome measures were serum total T and calculated bioavailable T. RESULTS We observe a substantial age-independent decline in T that does not appear to be attributable to observed changes in explanatory factors , including health and lifestyle characteristics such as smoking and obesity . The estimated population -level declines are greater in magnitude than the cross-sectional declines in T typically associated with age . CONCLUSIONS These results indicate that recent years have seen a substantial , and as yet unrecognized , age-independent population -level decrease in T in American men , potentially attributable to birth cohort differences or to health or environmental effects not captured in observed data
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 .