Feline hyperthyroidism is the most common endocrine disease in older cats, causing significant welfare compromise if untreated but responding well to multiple effective treatments.
Feline hyperthyroidism welfare harm is progressive: early stages cause weight loss and restlessness that owners may mistake for normal ageing; later stages cause cardiac enlargement, hypertension, and systemic effects that significantly impair quality of life. The condition is highly treatable — daily medication, surgery, or radioactive iodine all provide effective control — making undiagnosed or untreated hyperthyroidism a preventable welfare failure. Regular geriatric blood testing from age 10 enables early detection and treatment.