Testosterone replacement therapy (TRT)

TRT restores testosterone in men with documented hypogonadism (low serum testosterone plus symptoms), via gels, injections, or pellets. Benefits include improved libido, mood, lean mass, and bone density. Risks include erythrocytosis, fertility suppression, and possible cardiovascular effects; the recent TRAVERSE trial suggested cardiovascular non-inferiority but not benefit. TRT is not validated as a longevity therapy in eugonadal men and remains controversial outside clinical hypogonadism.