I hope my Dh has much more interesting things to talk about with his colleagues than my periods.
My periods are a lot more interesting than some of the crap my male colleagues talk about! 
The only way I can imagine a conversation going is along the lines of, "Look, can I ask you a really weird question? I'm worried about my wife and I think she needs to see the doctor about her periods, but I have nothing to compare it to, and she says she's too busy, but I wondered whether this is like your wife or not..." Or alternatively, on a night out down the pub (this happens once or twice a year,) a few pints in, I can imagine them having a discussion about whether they'd do it "when she's on the rag." Most of the time, they're talking about motorbikes or formula 1 or cricket, though.