Hyperthyroidism is the most common endocrine disorder in older cats, and early diagnosis combined with appropriate treatment greatly improves welfare.
Hyperthyroid cats experience chronic physiological stress — elevated heart rate, muscle wasting, and gastrointestinal upset — that owners often mistake for normal ageing. Prompt diagnosis after routine annual blood screening allows treatment before secondary organ damage occurs. Welfare during management depends on treatment choice: methimazole requires daily pilling which some cats find highly stressful, while I-131 involves a brief isolation period but delivers long-term relief. Shared decision-making between vets and owners that considers individual cat temperament and owner capacity leads to the best welfare outcomes.