Hyperthyroidism is common in older cats and treatment is usually straightforward.
Hyperthyroidism is the most common endocrine condition in middle-aged to senior cats. It occurs in 10% of the cat population over 10 years of age. Hyperthyroidism is caused by excess production of thyroid hormones by the thyroid gland.
Common signs of hyperthyroidism:
An oversupply of thyroid hormone makes all body systems work harder.
Common causes of hyperthyroidism:
The majority of cases are due to the benign form and respond well to treatment
Diagnosis is based on history, clinical signs and blood tests to determine thyroid hormone levels. The health of other organs like the liver and kidneys is also assessed and treatment tailored to the individual.
Treatment can involve one or more of the following:
Radioactive iodine therapy
Radioactive iodine therapy means that the cat has low-level radioactivity when discharged from the veterinary speciality centre. Therefore, it is important to minimise exposure to the cat's bodily secretions such as saliva, urine for 3-4 weeks after treatment.
Cure rate >95%
Relapse rate 5%
Simple treatment of one injection or an oral capsule
Serious side effects are rare
Minimal risk of hypothyroidism
Requires specialty facility with relevant licenses
Hospitalisation stay can be days to weeks
Owner cannot visit the hospital
Strict home confinement for 2 weeks after discharge
Owner must collect wastes for 2 weeks after discharge
Owner cannot cuddle cat for long intervals for 2 weeks after discharge
Medical management requires life-long treatment. Tablets once or twice a day or a gel applied to the inner ear are available. Occasionall there are side effects such as loss of appetite, vomiting, lethargy, skin rashes and face swelling, but mostly medication is well tolerated.
Response rate >95%
Medication formula comes in tablets, liquids or topical gels
Requires no hospitalisation
No risk of permanent hypothyroidism
Best if kidneys not functioning well
Relapse 100% if medications stop
Requires medications once or twice a day
Frequent blood tests are required to monitor effectiveness and safety
Drugs reactions like facial itching, vomiting, liver failure, and abnormal blood cells may occur
A benign tumour may become malignant
We don't recommend surgery.
A special diet which slows the thyroid down but doesn't cure the condition is available. Malignancy is a risk on the diet. We only recommend it if other options are not affordable.
Only a change in diet is required
Control rate >80%
Safe in cats with kidney disease
Cannot eat any other foods
Strict low-iodine diet
Relapse is 100% when off the diet
Your veterinarian will discuss the various options available with you.
Treatment improves a hyperthyroid cat's quality of life and life expectancy.