Cat Hyperthyroidism and Welfare | Animal Welfare Hub

Feline hyperthyroidism is the most common endocrine disease in older cats. Recognizing and treating it early protects quality of life and prevents serious secondary complications.

Key Facts

Hyperthyroidism affects approximately 10% of cats over 10 years old, making it highly prevalent.
It is caused by a benign tumor of the thyroid gland that produces excess thyroid hormone.
Signs include weight loss despite increased appetite, hyperactivity, increased thirst, and vomiting.
Untreated hyperthyroidism leads to heart disease, hypertension, kidney problems, and blindness.
Treatment options include daily medication (methimazole), radioactive iodine therapy, surgery, or dietary management.
Radioactive iodine is considered curative and is the gold standard treatment where available.

Welfare Considerations

Hyperthyroid cats often appear superficially healthy — even energetic — while internally experiencing chronic physiological stress and progressive organ damage. Weight loss, anxiety, and gastrointestinal upset cause ongoing discomfort. Heart disease and hypertension secondary to untreated hyperthyroidism can lead to sudden blindness or heart failure. Early diagnosis through routine senior cat screening and prompt treatment dramatically improves welfare and lifespan. Owners of older cats should be alert to subtle changes in appetite, weight, and behavior and seek veterinary assessment promptly.

What You Can Do

Schedule annual or twice-yearly wellness checks for cats over 10 years old, including thyroid screening.
Watch for weight loss despite good appetite, increased thirst, or hyperactivity in senior cats.
If diagnosed, discuss treatment options with your vet including the curative radioactive iodine therapy.
Ensure blood pressure monitoring is part of your hyperthyroid cat's treatment plan.
Support shelter programs that provide senior cat health care to improve outcomes for older rescue cats.