Companion Cat Hyperthyroidism Management and Welfare

Hyperthyroidism is one of the most common conditions in older cats. Without treatment it causes progressive welfare deterioration, but management options are excellent with early intervention.

Key Facts

Feline hyperthyroidism affects approximately 10% of cats over 10 years old
Caused by a benign adenoma of the thyroid gland causing excess thyroid hormone production
Clinical signs include weight loss despite good appetite, vomiting, hyperactivity and diarrhoea
Secondary hypertension and cardiac disease complicate untreated cases significantly
Treatment options include medication (methimazole/carbimazole), radioactive iodine, surgery and dietary management
Radioactive iodine is curative in 95%+ of cases with a single treatment
Dietary management using iodine-restricted food (Hill's y/d) is effective but requires strict compliance

Welfare Considerations

Untreated hyperthyroidism causes a state of chronic physiological overdrive - the equivalent of living with a constantly racing heart rate and elevated metabolism. Affected cats lose body condition despite ravenous appetite, experience intermittent vomiting and diarrhoea, and may become hypertensive enough to suffer retinal detachment and sudden blindness. The welfare impact accumulates over months or years before the condition is recognised. Early diagnosis and treatment dramatically improves quality of life - radioactive iodine treated cats return to normal thyroid function within weeks and often regain lost body condition and vitality.

What You Can Do

Include thyroid testing in your cat's annual blood panel from age 8 onwards
Seek veterinary advice promptly if your older cat loses weight despite a good appetite
Discuss all treatment options with your vet - radioactive iodine is highly effective if available
Ensure blood pressure monitoring is included in hyperthyroidism management
If using dietary management, ensure strict compliance - even small amounts of iodine-containing food reduce effectiveness