Hyperthyroidism has become the number one endocrine disease among cats even though it only began in the late 1970s. I'm not a vet, but videos on the channel share what I've learned over the last 10+ years of dealing with our own hyperT cats plus a few thousand in the online groups. The channel includes information about kidney disease, cat food, coping with loss, and more.
I hope it helps, but keep in mind that this isn't formal medical advice, just experience (and conversations with some vets as well). I'm not trying to replace your vet, and neither of us should replace doing your own thinking.
Videos are all free, but your support certainly helps, especially since we currently care for 12 cats, many of whom have health issues. If you'd like to Buy Me a Coffee. https://buymeacoffee.com/ginfor