Feline hyperthyroidism is one of the most common endocrine diseases in older cats, causing chronic suffering if untreated but responding well to several management options.
Hyperthyroidism causes significant and progressive suffering in affected cats. Elevated thyroid hormone drives a hypermetabolic state that causes muscle wasting despite ravenous appetite, cardiac hypertrophy that impairs heart function, hypertension causing retinal damage and neurological signs, and gastrointestinal upset. Cats in the late stages of untreated hyperthyroidism are visibly uncomfortable and debilitated. The good news is that excellent treatments exist. Daily methimazole is effective but requires lifelong administration. Radioactive iodine is a single curative treatment available at specialist centers. Early diagnosis and treatment are essential to prevent the chronic welfare harm of prolonged untreated disease.