Before I answer your question I need to say a few things...First, let me congratulate you for being concerned for your partner's well being, and, trying to become more informed for his sake and/or yours. Second, understand that the harmful effects of steroids are often overblown and exaggerated by the media. Yes, steroids can be quite harmful, but alot of it also depends on which steroids are used, how often, and in what amounts. In addition, one's genetic predisposition to side effects will also play a big role. Some people can take large amounts of anabolics with little to no ill effects, while others will have problems with the smallest of dosages. That being said, you should also know that as a natural bodybuilder myself, I do not use or condone the use of steroids by anyone. However, I also believe in the right to do what you wish with your own body...as long as you do not harm anyone else in the process. Also, as a contest prep coach to bodybuilders and fitness athletes, I work with competitors that choose to use steroids and other drugs. I do not turn them away. In these situations I do everything I can to help them, while keeping them as safe as possible. The only times that I will openly and fervently show my disgust for someone using steroids are: A) when they are used in preperation for a NATURAL contest, B) when they are used by someone that has not trained for at least 3 solid years, and C) when they are used by someone that has not fully educated himself on the subject first. The obvious should also be pointed out that steroids are illegal to use and even possess!
Now to the list of POSSIBLE side effects...
-gynecomastia aka "bitch tits"
-stunted growth...in teens
-immune system changes
-blood clotting changes
-birth defects...for children of pregnant women