Cyrano, as always, has some good thought provoking things to say. I back him up. Sex is a two-way street and we take cues from one another.
Also, is the guy a smoker? That does bad things for the pecker. Drugs--normal drugs like alcohol or prescription meds can do the same.
It's not the woman's job to cure him, but I think it takes the man working with the dr. and keeping his woman in the loop--a team approach.