ELI5 How does too much adrenaline affect a man’s erection?

I want to date a guy; we’ve talked about a lot, including sex. Says he needs to use a cock ring in order to maintain an erection, or ejaculate. Because, he has “too much adrenaline“, that his penis can’t hold the blood flow (I’m paraphrasing but this is the gist). Tried to Google this, and got back a whole lot of stuff about ED that I found it a bit overwhelming to wade through.

i’m just wondering what the biology is behind all this, I don’t want to ask him too many questions, so as not to embarrass him. I like this guy and want to give him every benefit of the doubt. Too, he’s seen a specialist and had tx.