Hyperthyroidism is the most common endocrine disorder in older cats, causing chronic welfare compromise if undiagnosed and requiring lifelong management once identified.
Feline hyperthyroidism causes progressive welfare decline when unrecognised. The classic presentation - weight loss in an eating, active cat - is easily attributed to normal ageing. Untreated, thyroid hormone excess causes cardiac hypertrophy, hypertension, and eventual heart failure alongside progressive weight loss. Once treated, the welfare outcome is generally excellent - most cats regain weight, become less anxious, and live comfortably for further years. The treatment choice involves welfare trade-offs: daily oral medication is straightforward but compliance-dependent; radioactive iodine offers a one-time cure but requires isolation during treatment. Both achieve good welfare outcomes when managed correctly.