Hyperthyroidism is the most common hormonal disease in older cats. Early recognition and appropriate treatment significantly improve welfare outcomes for affected animals.
Feline hyperthyroidism affects a substantial proportion of older cats and causes genuine welfare harm through its systemic effects: weight loss, cardiovascular stress, hypertension, and the hyperactivity and restlessness that owners sometimes mistake for increased youthfulness. The welfare-positive response is early detection through routine blood screening and prompt, appropriate treatment. All major treatment modalities are effective; selection depends on owner capacity, cat temperament, and facility availability. Radioactive iodine is particularly welfare-positive as a one-time curative treatment eliminating the need for daily medication that many cats resist. Untreated hyperthyroidism progresses to heart failure and death, making early diagnosis and treatment a fundamental welfare obligation for owners of senior cats.