Older cat urinating and defecating in her bed

Question
My cat is 14-15 years old, very active and is being treated for hyperthyroidism.  Recently, she has refused to use her litter box for defecating.  She then stopped using her litter box for urinating.  (There have been no changes to her litter box or litter.  After her behaviors escalated to urination, we tried different litters and different boxes with no luck.)  Instead, she has been using the dogs beds and coverings as her litter box.  We took her to the vet for her quarterly check up and were told that this is more of a behaviorial problem than medical.  The vet advised that we place her in the bathroom with food, H2O, litter box and a bed to retrain her.  We did to discover that she began pooping and peeing in her bed which she then slept in.  A wet, dirty and smelly bed did not seem to phase her at all. This doesn't seem normal.  Do you have any advice for us to try in redirecting her back to her litter box?

Answer
Hi Monica,

First off she is sick. She has hyperthyroidism. Cats go off their cleanliness habits when they are sick. She is stressed from her disease. You may have to do a few things to get her back to using a litter box. First, try a product called Feliway. This mimics a cat's happy pheromones. See if this helps. Next try this litter product. http://www.preciouscat.com/
PetSmart carries it. See if this works. Then I would ask your vet about putting her on Elavil. It is a mild tranquilizer and should calm her down. But I would use that as a last resort. I hope this helped you. Also one thing, keep an eye on her for signs of kidney disease and hypertension. These go hand and hand with the Thyroid disease in cats. Good luck.

Ciao, Karen