Found this post by Dr. Mehmet Oz, at
www.sharecare.com/question/can-enlarged-prostate-erectile-dysfunction:
Begin quote
Having an enlarged prostate may be annoying, but it does not cause erectile dysfunction. However, certain treatments for enlarged prostate can raise the risk for problems getting and sustaining an erection.
An enlarged prostate, also called benign prostatic hyperplasia (BPH), may not cause any symptoms. Yet many men with BPH develop maddening problems such as a frequent and urgent need to urinate. Others can only manage a dribble when they attempt to pee. Many find themselves climbing out of bed several times a night to use the bathroom.
Most men with BPH manage the condition by making lifestyle changes or taking oral medications. Unfortunately, some common drugs prescribed to treat BPH can cause erectile dysfunction, though the problem goes away if you stop taking the medicine. Furthermore, serious cases of BPH may require surgery to remove excess prostate tissue that's causing all the problems. A small number of men may develop erectile dysfunction following these surgical procedures, though most appear to regain sexual function again over time. End quote