help

My 17 yr old long hair has overactive thyroid. He eats special food to help him with his symptoms. He's been on the science diet food for almost one year, it has been a miracle in a bag. He won't take regular medicine for his illness, stubborn old man. But in the last few weeks his fur is starting to matte up, i see he still grooms himself. I have been clipping his fur off. I really don't want to take him into the vet for this just yet, he hates the ride in it causes him more stress than needed. But I don't know why this is happening, he's eating and drinking normal. Suggestions on the fur issue, or should I just take him in to the vet. Could the food have stopped working?????? Thank you in advance for your help

When my old guy started to mat, it was because he was getting arthritis and it was hard for him to reach back to all the spots to get them, so he just gradually started to mat.

I understand with that thyroid food, you can't give them anything else, so you may not even be able to treat him for arthritis, right?  But you can at least call you Vet and ask about it, if you suspect he might be getting a little creaky in his joints.  OR, if you suspect the food isn't working anymore, then you definitely should him his blood tested again, because if it isn't working, then you need to go to plan b for some form of medication.

Thank you, it could very well be arthritis.