I'm having a similar issue with my cat. I've discussed her here before, this is my mom's cat, who is 19, and pretty much a scroungy mess. She's still affectionate and loves to eat, but she pisses all over the house. Has gone from peeing on the floor of the bathroom to the dining room and now that we've put hardwood in the dining room that's not fun anymore, so she is peeing in my son's room and now goes all the way down to the lower-level to pee there, too. And if we leave anything on the floor, like a towel or sweater, she will pee on it.
Vet says we can pay a few hundred bucks and treat whatever thyroid problem vet suspects, but who knows if that will stop her behavior? OTOH, I feel an obligation to this cat because she's my mom's, and we inherited all kinds of good stuff from mom when she died, seems cold to not take the bad with the good.
On the 3rd hand (ha) that was 2 years ago and I think by living in a house that smells like cat piss for two years we have fulfilled our obligation.
Kitty is quarantined in the bathroom now and may be paying a very special visit to the vet in the next couple days.
