Its called testosterone replacement therapy (TRT) or Testosterone Replacement Therapy. His body essentially no longer produces "sufficient" quantities of endogenous testosterone on its own, so he must inject exogenous sources.
Get with the program buddy....you still have a LOT to read. Please don't jump to conclusions or act like you know everything now. You were asking me a lot of questions in PM that you could have answered by reading these forums. Clearly you still have a lot of reading to do.