The impotence caused by the ABUSE of the steroid molecule, nandrolone decanoate,commonly known by it's brand name, Deca-Durabolin, including testicular atrophy. Meaning, you can't get it up. Leading to users stacking (combining) it with testosterone based steroids such as proprionate or enthanate to fix this side effect.
Girl: What's wrong sweet heart?
Guy: I got Decca Dick
Girl: damn it! i told you to use proprionate!