Recent reports indicate that testosterone therapy increases the expression of fibroblast growth factor 2 (FGF2) and decreases myogenic regulatory factor 4 (MRF4) and myostatin in skeletal muscle from men suffering hypogonadotropic hypogonadism, suggesting that the expression of these proteins contribute to muscle growth after testosterone therapy (65). The gene discussed is FGF2; the disease is hypogonadotropic hypogonadism.