That is very interesting about your cat, had read it about dogs.
Our dog is dog agressive and has gotten better, he can go now to the dog park. I slowed down the Iodine to a few times a week. He is still pretty good but started barking at dogs more, now we are back daily and we will see if this helps.
My experience with thyroid in pets is (also from research)that a lot of them have thyroid problems and not every vet tests for it, I had to especially ask for it.