Help needed for my older cat

We aren't cat people, but we took a rescue in 17 years ago. Jamie has been a healthy, well-behaved cat for most of her life. She has a thyroid problem that has been controlled by meds. In the past year or so, Jamie has decided not to use her litter box. She began peeing on our area rugs, so we picked them up. Then she began pooping just outside her litter box. With three dogs who think kitty poop is a delicacy, it has been a race to see who can get to the poop first, unfortunately, the dogs with their superior sense of smell tend to win. The past few months, Jamie has started peeing on the dog beds. We picked up all but those in the bathrooms where the dogs stay when we aren't home. We try to keep the doors to those bathrooms closed, the minute we don't, I end up washing the dog beds. Today, my son woke up and his bed was soaked in cat pee.

We empty the litter box at least once a day, Jamie had a complete physical recently and it healthy other than her thyroid condition and a possible heart murmur. I am at my wits end. Any help is appreciated.

Inappropriate and excessive urination can be a sign of diabetes. A physical may not have checked her sugar level.

I used a liquid low dose of Prozac to cure him (sounds odd-but it really does work. Tapazol causes psychological disturbances). His last year was a happy one.

you mention Tapazole causing mental disturbances -- pretty sure it has the same effect on human hypers too (I have hypothyroidism myself). I would much rather be hypo than hyper! I think with cats its easier to treat a hypo than hyper as well.

Yeah, I agree with the diabetes angle, sounds like a metabolic problem, excessive urination usually due to too high sugar level.