Hyperthyroidism is the most common endocrine disorder in older cats. Understanding the condition, its welfare impact, and treatment options enables owners and veterinarians to provide effective long-term care.
Feline hyperthyroidism causes significant welfare compromise through the chronic effects of excess thyroid hormone on virtually every organ system. Affected cats lose body condition despite increased food intake, experience muscle weakness, and develop secondary cardiac and hypertensive disease that causes additional suffering. Treatment dramatically improves quality of life in most cases. Daily medication is effective and widely accessible but requires twice-daily dosing for the cat's remaining life. Radioactive iodine is curative and eliminates the need for ongoing medication, but access varies by location and requires temporary separation from the owner during the treatment period. Early diagnosis through routine blood testing in cats over 10 years enables treatment before secondary organ damage develops.