Cat Hyperthyroidism: Diagnosis and Treatment Options

Hyperthyroidism is the most common endocrine disorder of older cats. Early diagnosis and appropriate treatment significantly improve quality of life and life expectancy.

Key Facts

Hyperthyroidism affects around 10% of cats over 10 years old
Clinical signs include weight loss, increased appetite, vomiting, and hyperactivity
Total T4 blood test is the primary diagnostic tool
Four treatment options: medication (methimazole), surgery, radioiodine, or dietary iodine restriction
Radioiodine is the gold standard treatment with high cure rates and minimal side effects
Concurrent CKD complicates treatment because treating hyperthyroidism can worsen kidney function

Welfare Considerations

Untreated hyperthyroidism causes progressive deterioration including cardiac hypertrophy, hypertension, and eventual heart failure. Cats experience the distress of unintentional weight loss despite voracious appetite, and the discomfort of hypertension. Treatment dramatically improves quality of life - appetite normalises, weight stabilises, and cardiovascular strain is relieved. The challenge of concurrent CKD requires careful staged treatment and specialist veterinary guidance.

What You Can Do

Seek veterinary assessment if your older cat is losing weight despite good appetite
Agree a treatment plan based on your cat's overall health, your circumstances, and vet guidance
Ask about radioiodine treatment at specialist centres for a potential cure
Monitor blood pressure and kidney function during treatment
Continue twice-yearly monitoring even after successful treatment to detect recurrence