If cats get thyroid problems it seems to HYPERthyroidism rather than hypo. There are specialized vets who can give ATD’s of RAI. They also have a special waste facility for taking the used cat litter after your cat has RAI. That info plus $1.00 will get you a cup of coffee….BTW, I have 10 cats, 4 rabbits, 1 horse and 1 DH.