Hyperthyroidism affects a significant proportion of senior cats, causing chronic discomfort and organ damage — early detection and treatment dramatically improve welfare outcomes.
Feline hyperthyroidism causes genuine ongoing welfare harm that is often underappreciated because affected cats appear active and hungry — signs that owners often associate with health rather than disease. But the hyperactivity of hyperthyroidism reflects the uncomfortable physiological state of an overactive thyroid, not wellbeing; and the weight loss despite increased appetite reflects the body consuming itself. Untreated cats experience cardiac complications, progressive muscle wasting, and systemic deterioration. The good news is that effective treatments exist and produce excellent welfare outcomes — radioactive iodine provides a cure in most cases with a brief hospitalization period. Early detection through annual thyroid screening for senior cats is the key welfare intervention.