Steroids used for muscle building are called anabolic steroids.These affect protein synthesis and facillitate maximum utilization of calories from diet to help build muscle mass.They have androgenic effect by hormone testosterone.These have ripple effects that is in later days these men can have baldness, small testicles and develop male boobs , lack of sex drive.They also have cardiovascular issues, can damage liver and is not prescribed.Synthetic testosterone is given only for low testosterone cases.