Hyperthyroidism is the most common endocrine disorder in older cats. Left untreated, it causes progressive suffering, but several effective treatments exist that restore quality of life when applied promptly.
Hyperthyroidism causes significant suffering through muscle wasting, cardiovascular strain, gastrointestinal disturbance, and hypertensive damage to the eyes, brain, and kidneys. Because weight loss is often gradual, owners may mistake it for normal ageing. Early diagnosis through routine blood screening of senior cats allows intervention before secondary organ damage occurs. Treatment options — daily medication, prescription diet, radioiodine therapy, or surgery — each have welfare implications, and the choice should balance effectiveness, stress of administration, and concurrent conditions. Regular monitoring ensures treatment remains effective as cats age.