Hyperthyroidism is the most common hormonal disorder in older cats, causing significant welfare compromise when untreated but offering excellent prognosis with appropriate management.
Feline hyperthyroidism creates a welfare burden that intensifies with disease progression, ultimately affecting cardiac function, blood pressure, and neurological health. Because cats mask illness well, owners often attribute weight loss and hyperactivity to normal aging until disease is advanced. Annual senior blood screening from age 10 is the most impactful intervention, enabling early diagnosis when treatment is most effective and organ damage is minimal. Of available treatments, radioactive iodine offers the best welfare outcome — curative with a single treatment and no ongoing medication stress — though home isolation requirements must be carefully managed. The welfare goal is disease-free old age rather than managed chronic disease wherever possible.