The study found men using methadone, which is used for opioid addiction treatment, have significantly suppressed testosterone levels of about a quarter of the testosterone of men not using opioids.  Low testosterone in men has been associated with poor quality of life as well as erectile dysfunction, fatigue, and mood disturbances. – See more at: http://dailynews.mcmaster.ca/article/methadone-treatment-suppresses-testosterone-in-opioid-addicts/