Hyperthyroidism is the most common hormonal disorder in older cats. Effective treatment dramatically improves welfare and quality of life.
A hyperthyroid cat experiences a body running at too high a metabolic rate: ravenous despite eating constantly, losing muscle mass, often anxious and vocal, and developing secondary heart and kidney disease. The welfare transformation that treatment offers is remarkable - within weeks of achieving normal thyroid levels, cats regain weight, calm behavioral presentation, and comfortable daily existence. The choice between daily medication, dietary iodine restriction, or radioactive iodine treatment involves welfare trade-offs that owners should discuss carefully with their vet.