Hyperthyroidism is the most common endocrine disease in older cats, causing significant welfare impacts that are highly treatable with appropriate veterinary intervention.
Hyperthyroidism in cats causes sustained welfare impacts that owners often attribute incorrectly to normal aging: weight loss despite eating well, restless behavior, disrupted sleep patterns, and vomiting. The cat experiencing these symptoms for months or years before diagnosis is suffering from a treatable disease. Once diagnosed and treated, the welfare transformation can be dramatic: cats regain weight, become calmer, and show improved quality of life indicators. The welfare imperative is prompt diagnosis through routine senior wellness testing (blood thyroid levels), followed by evidence-based treatment selection. The methimazole vs. radioactive iodine decision involves practical considerations, but welfare-centered medicine would minimize treatment burden and maximize quality of life — considerations that generally favor curative radioactive iodine where accessible.