Testosterone Replacement Therapy Clinic is one of the most important male hormones, however, as men age, the level of testosterone decreases. Approximately 2-4% of men over the age of 40 are estimated to have low testosterone levels. Low testosterone in men including symptoms such as reduced sexual interest and fatigue can be treated using testosterone replacement therapy (TRT). The TRT is an initiative aimed at restoring normal levels of testosterone to alleviate the symptoms of fatigue, reduced libido, muscle wastage and mood swings that are associated with lower levels of testosterone in males.