Hyperthyroidism is the most common endocrine disorder in cats over ten years old. Multiple treatment options are available, and choosing among them requires balancing welfare, practicality, and the cat's individual circumstances.
Feline hyperthyroidism welfare involves both the disease burden and the treatment burden. Untreated cats suffer from chronic weight loss, gastrointestinal upset, cardiovascular strain, and the anxiety associated with elevated thyroid hormone. Treatment significantly improves welfare, but the choice of method matters for individual cats. Daily oral methimazole is affordable but requires consistent pilling, which many cats strongly resist — causing repeated stress. Radioactive iodine is curative and stress-free after a brief hospitalisation period. Dietary iodine restriction is non-invasive but requires strict compliance and may not be palatable. A critical welfare consideration is the unmasking of latent CKD after treatment — normalising thyroid function reveals pre-existing kidney disease that was being masked. Staged treatment with methimazole before committing to permanent options allows CKD assessment. Quality of life assessment should guide all treatment decisions.