Feb 24, 2026Testosterone Decline in Men: Natural Trajectory, Functional Impact, and Evidence-Based SupportTestosterone declines approximately 1-2% per year from age 30. The clinical significance of this decline depends on absolute levels and symptoms, not chronological age alone. Testosterone replacement therapy has RCT evidence for improving muscle mass, bone density, and sexual function in men with confirmed hypogonadism. Lifestyle factors significantly modify the trajectory.