Cat Hyperthyroidism: Treatment Options and Welfare

Hyperthyroidism is the most common endocrine disorder in older cats and is highly treatable, but causes significant suffering when undiagnosed.

Key Facts

Hyperthyroidism results from excess thyroid hormone production, usually due to a benign thyroid tumour
Affected cats show weight loss despite increased appetite, increased thirst, vomiting, and hyperactivity
Diagnosis is confirmed by total T4 measurement — a simple blood test routinely included in senior cat profiles
Treatment options include daily oral medication (methimazole), radioactive iodine (curative), surgical thyroidectomy, and dietary management
Radioactive iodine treatment is considered the gold standard — it is curative, safe, and requires only brief hospitalisation

Welfare Considerations

Hyperthyroid cats experience chronic physical discomfort including muscle wasting, gastrointestinal disturbance, and elevated heart rate. Many affected cats are restless and vocalise excessively, reflecting their physiological distress. The condition is entirely treatable, and cats that receive appropriate treatment typically show rapid and dramatic improvement in wellbeing.

What You Can Do

Include T4 measurement in annual blood panels for all cats over the age of 10
Discuss radioactive iodine treatment with your vet if your cat is otherwise healthy — it offers a permanent cure
Administer medication consistently and schedule regular rechecks to monitor thyroid levels and kidney function
Seek diagnosis promptly if your older cat is losing weight despite good appetite