Cat Hyperthyroidism Dietary Management

Feline hyperthyroidism is the most common hormonal disorder in older cats. Dietary iodine restriction offers a non-invasive management option alongside medical treatment.

Key Facts

Hyperthyroidism affects an estimated 10% of cats over 10 years old
The thyroid gland produces excess thyroxine due to benign adenomatous hyperplasia in most cases
Symptoms include weight loss, increased appetite, hyperactivity, and vomiting
Treatments include daily medication with methimazole, radioiodine treatment, surgery, and dietary management
A prescription iodine-restricted diet controls thyroid hormone production by limiting substrate availability

Welfare Considerations

Untreated hyperthyroidism causes progressive weight loss despite good appetite, hypertension, heart disease, and eventually organ failure. Affected cats feel hyperactive and uncomfortable. Treatment restores normal metabolism and dramatically improves quality of life. Methimazole medication can cause side effects in some cats; radioiodine treatment is curative but requires hospitalisation. The prescription iodine-restricted diet provides an alternative for cats where medication causes problems if fed exclusively and strictly.

What You Can Do

Have senior cats checked for hyperthyroidism at annual health checks from age 10
Begin treatment promptly if hyperthyroidism is diagnosed to prevent cardiac and renal complications
Discuss the pros and cons of different treatment options with your veterinarian
If using a dietary iodine-restriction approach, ensure the cat eats only that diet with no other food sources
Monitor blood pressure and kidney function alongside thyroid levels during treatment