Hyperthyroidism is the most common endocrine disorder in older cats. Effective treatment options including radioactive iodine, medication, and diet can restore normal thyroid function and significantly improve welfare.
Hyperthyroid cats live in a state of physiological overdrive: their accelerated metabolism causes weight loss despite ravenous appetite, a pounding heart, elevated blood pressure, and chronic anxiety. Owners often interpret the increased appetite and energy as positive signs, missing the welfare impact of the underlying disease for months. Once treated, the transformation is striking — cats regain weight, their coats improve, and their behavior normalizes. Because untreated hyperthyroidism causes heart disease and hypertension that become irreversible, early diagnosis and treatment has compounding welfare benefits.