A new meta-analysis looks at the studies on fat free mass and strength gains from TRT and finds a difference in results depending on how it is administered. Intramuscular injection was 3-5 times more effective than transdermal application in increasing fat free mass (FFM) and strength.
The full text of the article can be read online.
When administration routes were collectively assessed, TRT was associated with increases in FFM, total body strength, lower-extremity strength, and upper-extremity strength. When administration routes were evaluated separately, the magnitudes were larger and the per cent changes were 3–5 times greater for intramuscular TRT than for transdermal formulations vs. respective placebos, for all outcomes evaluated. Specifically, intramuscular TRT was associated with a 5.7% increase in FFM and 10–13% increases in total body strength, lower-extremity strength, and upper-extremity strength. In comparison, transdermal TRT was associated with only a 1.7% increase in FFM, and only 2–5% increases in total body and upper-extremity strength. Interestingly, transdermal TRT produced no change in lower-extremity strength vs. placebo. Subanalyses of RCTs limiting enrolment to men ≥60 years of age produced similar results.
The full text of the article can be read online.