Hyperthyroidism is the most common endocrine disorder in older cats, causing significant welfare impacts if untreated. Multiple treatment options exist with different welfare implications for long-term management.
Hyperthyroid cat welfare involves both the disease burden of untreated disease and the treatment burden of management. Untreated hyperthyroidism causes progressive deterioration including cardiac hypertrophy, hypertension, retinal detachment, and severe weight loss - significant suffering that compounds over months. Treatment welfare depends on the method chosen: radioactive iodine is curative with minimal ongoing stress, while daily tablet administration creates repeated handling stress across a lifetime. The welfare-positive treatment choice depends on individual factors including cat temperament, owner capacity, and veterinary access. An important welfare consideration is that treating hyperthyroidism may unmask previously hidden kidney disease as blood flow normalizes.