Tell him that messing up with testosterone fucks brain a bit. At the beginning he will get more aggressive, perma boner with a will to fuck everything that does not run up the trees. 
Also his balls will get really small coz organism is stopping to produce testosterone. On the other hand it starts to produce estrogen like crazy. After some time he will end up with ridiculous levels of estrogen with organism blocked testosterone production. He will start to feel like shit and may fall into depression. Tell him to google 'gynecomastia'. 
To unfuck this topic he will need to do unblock cycle with other hormones. 
Overall: tell your friend that messing with hormones is usually not worth it. 
Make him go to the gym and lift weights. It will naturally boost testosterone production. 
If he is still willing to go that route tell him to also go to the gym and talk with the big guys there where to get Testo injections.