Our customer asked:
Do you do anything, please, in non-prescription that might help a cat with an overactive thyroid?
The only non-prescription product which makes any difference is an iodine-restricted diet. There is only one commercially available - Hills y/d cat food. It is marketed under the name of prescription food to signify it is not suitable for all cats, but there are no legal controls on buying it so you can just order it off the website, as long as you are sure your cat is hyperthyroid. It works through the fact that iodine is needed to make thyroid hormone in the body. If the diet only contains a small amount of iodine, then only a smaller, normal amount of thyroid hormone can be made by cats affected with this condition. Their thyroid levels return to normal quite quickly on this food.
There are mixed feelings about how well cats do on this food, mostly because it is not very tasty and they do not eat it well. Certainly some cats do marvellously on it and live healthily for many years with no other treatment. Personally I would certainly recommend you try it. If you do, then you cannot give any other food at all, and just plain water to drink. Ideally talk to your own vet about it.