Hyperthyroidism is the most common endocrine disease of cats, causing weight loss, hyperactivity, hypertension, and cardiac changes that significantly impair quality of life in affected older cats if untreated.
Feline hyperthyroidism causes a progressive deterioration in quality of life that owners sometimes mistake for normal aging. Affected cats are genuinely uncomfortable: their hearts race, they cannot gain weight despite ravenous hunger, they may vomit regularly, and hypertension can cause sudden blindness from retinal detachment. Early diagnosis and treatment dramatically reverse these signs and restore quality of life. The decision between treatment options involves balancing cure rate, cost, practicality, and the cat's overall health status. Radioactive iodine offers the most complete resolution but requires brief hospitalisation. Oral medication is effective but requires daily administration and regular monitoring. All options are superior to no treatment for a disease that progressively worsens.