Feline hyperthyroidism is the most common endocrine disease in senior cats and causes significant welfare compromise if undiagnosed, making routine screening important for cat welfare.
Feline hyperthyroidism causes significant and prolonged welfare compromise in affected cats because the condition develops gradually and owners often interpret weight loss and behavioral changes as normal aging. Affected cats experience the welfare equivalent of a continuously revving engine - elevated heart rate, hypertension, weight loss despite increased appetite, and anxiety from excess thyroid hormone stimulation. The cardiac effects can cause life-threatening hypertrophic cardiomyopathy and secondary hypertensive retinal detachment leading to sudden blindness. Early diagnosis through routine blood screening allows treatment before these sequelae develop, and effective curative treatment with radioactive iodine can restore full health and normal welfare in most cats.