Hyperthyroidism is the most common endocrine disorder in older cats. Multiple effective treatment options exist, and understanding their welfare implications helps owners and veterinarians make the best choices for individual cats.
Untreated hyperthyroid cats experience chronic cardiovascular strain from persistently elevated heart rate and blood pressure, leading to hypertensive retinopathy, cardiac hypertrophy, and renal complications. Despite often appearing energetic and eating well, affected cats suffer from anxiety, gastrointestinal disturbance, and progressive organ damage. Treatment dramatically improves wellbeing — most cats become calmer, gain weight, and show improved coat condition. The choice between radioactive iodine, medication, or diet should be guided by individual patient factors and owner capacity for home medication.