Figure 4. Testosterone Dose Response Relationship in Young and Older Men. In this study, healthy, young men (18-34 years of age) and healthy older men (60-75 years of age) were treated with a long acting GnRH agonist plus graded doses of testosterone enanthate for 20 weeks. Shown are mean (±SEM) changes from baseline in fat free mass (upper left), skeletal muscle mass (upper right), fat mass (lower left), and leg press strength (lower right) in young (black bars) and older (lightly shaded bars) men. Adapted with permission from Bhasin et al. J Clin Endocrinol Metab. 2005 Feb;90(2):678-88.