If you need a more accessible version of this website, click this button on the right. Switch to Accessible Site


You are using an outdated browser. Please upgrade your browser to improve your experience.

Close [x]


Learn about the signs, symptoms, and treatment of hyperthyroidism in cats.


The thyroid gland is responsible for regulating basal metabolic rates. Hyperthyroidism in cats is most often due the development of a benign tumor on the thyroid gland that secretes excessive amounts of active thyroid hormones resulting in a quickening of the metabolic rate.

Clinic Signs:

Thyroid disease tends to affect middle-aged to older cats. The most striking sign is weight loss in the face of a strong appetite. Cats may also exhibit vomiting, restlessness or lethargy. One of the important sequelae to untreated hyperthyroidism is thickening of the heart muscle and hypertension. These cats may have heart murmurs or arrhythmias and if left untreated may develop heart failure or thrombembolii (blood clots) that may be fatal.


The diagnosis of hyperthyroidism is relatively straightforward. Physical examination will often reveal an enlarged thyroid gland on the underside of the neck near the trachea. Blood tests are necessary to confirm and quantify the disease. Other diseases such as diabetes and chronic renal failure may mimic the disease and can occur concomitantly with hyperthyroidism.

Once thyroid disease has been confirmed, your cat should also be screened for hypertension and heart disease.


The treatment of choice for hyperthyroidism is radioactive iodine therapy. This is a very effective, one-time treatment that has a cure rate of over 90%. While the initial expense is significant, in the long run it is far less expensive than the other treatment options that require long-term administration of anti-thyroid drugs and regular monitoring of thyroid levels by the veterinarian. For more information on radioactive iodine therapy, visit www.radiocat.com.

In addition to medical treatment, surgical removal of the thyroid gland has been advocated in the treatment of hyperthyroidism. In light of the greater safety and higher efficacy of radioactive iodine therapy, there is no good reason to opt for surgical treatment rather than medical.

Exclusive Offer

New client exams are only $30!

Office Hours

Monday Tuesday Wednesday Thursday Friday Saturday Sunday
8:00am 8:00am 8:00am 8:00am 8:00am 9:00am Closed
6:00pm 6:00pm 6:00pm 6:00pm 6:00pm 4:00pm Closed