Hyperthyroidism is the most common endocrine disease in older cats and has multiple treatment options with different welfare profiles that require careful individualised selection.
Untreated hyperthyroidism causes progressive welfare harm through weight loss despite ravenous appetite, hypertension, cardiac changes, and hyperactivity that distresses some cats. All available treatments significantly improve welfare outcomes compared to no treatment. Treatment selection should be guided by individual cat circumstances - anxiety levels, owner ability to medicate, renal function, and cardiac status all affect which treatment option best serves the individual's welfare.