Hyperthyroidism is the most common endocrine disease of older cats, with untreated cases causing weight loss, cardiac disease, and hypertension - but multiple effective treatments now exist with good welfare outcomes.
Hyperthyroidism causes significant welfare impairment through chronic metabolic stress - affected cats are effectively running a physiological marathon continuously, experiencing elevated heart rate, weight loss despite good appetite, gastrointestinal upset, and anxiety-like behavioral changes. The good news is that effective treatments are available and most cats improve dramatically with intervention. Welfare-centered decision-making considers the cat's ability to tolerate daily oral medication, the owner's capacity for compliance, the risk of concurrent renal disease being unmasked, and the cat's quality of life throughout treatment. Regular post-treatment monitoring ensures that therapeutic goals are met and concurrent conditions are identified.