Hyperthyroidism is the most common hormonal disorder in older cats and, while treatable, requires long-term management to prevent suffering from cardiac and metabolic complications.
Hyperthyroid cats suffer a range of welfare-relevant symptoms before diagnosis — chronic hunger despite eating well, progressive muscle wasting, cardiovascular stress, and often anxiety or agitation. Because the condition develops gradually, owners may attribute changes to normal ageing rather than a treatable disease. Routine screening of senior cats for thyroid disease is a significant welfare intervention. Once diagnosed, the treatment decision involves weighing the convenience and cost of daily medication against the curative but more expensive radioactive iodine option. Welfare is well served by any of the available treatments when properly managed, but monitoring is essential because hyperthyroidism can mask concurrent kidney disease that becomes apparent once thyroid function is normalised.