Plasma concentrations of (A) IGF-1 and (B) myostatin in men with HH after testosterone (n = 12) or placebo (n = 10) treatment for 23 wk. (C) Basal mRNA expression of myostatin in skeletal muscle of eugonadal men and men with HH and change in expression following testosterone treatment for 23 wk in hypogonadal men. *P < 0.05 as compared with 0 wk; ^#P < 0.05 as compared with placebo.