Do you know what to do in case your cat developes hyperthyroidism?

If you ever have an elderly cat and she starts losing weight, get her to the vet for an exam. She could have hyperthyroidism which will make them lose weight, and could die. There is a treatment of 3 month's of radiation called radio-iodine that is costly but worth it if it's caught soon enough to save their life. To make this a question so it doesn't get deleted....Would you spend the $800-900 for the treatment?