It still may not be too late to see a holistic vet. Go ahead and find one in your area. They may change her diet. What does she eat? If her diet is fish based, some people think that might hurt the thyroid in a cat. A veterinarian might want to put her on a raw food diet. That can be expensive if you buy it from a company, but I’ve heard that if you make it yourself, it is actually cheaper than buying commercial pet food. So you might be able to easily do this. Also, there are natural herbs for this like bugleweed. I don’t really know what a holistic veterinarian would do about this, but you need to ask one. If nothing else, Dr. Jones veterinary secrets on YouTube. He has an e-book that might tell you what to do.
JanaS, I am praying for your cat
JanaS, I am praying for you