The treatment options for a common malady

Q:  I have an older calico cat and I recently brought her in to my veterinarian for her annual check up.  She had lost 2 lbs from the year before and I didn’t even notice.  My veterinarian did some blood tests and told me that she has .  He said this is very common in older cats and that she needed to start taking pills to control it.  I travel a lot and I’m not sure if I can give her the medication regularly.  Are there any other options?

A:  Your question is a great one.  Hyperthyroidism is one of the most common diseases that we see in older cats.  It is a condition that results from the excessive production of thyroid hormones by the thyroid gland.  Although a malignant growth is possible, more than 95% of cats have a benign growth causing the disease.  Your cat is showing the most common sign seen with hyperthyroidism:  weight loss.  Other clinical signs include an increased appetite, hyperactivity, increased thirst/urination and intermittent vomiting and diarrhea.  Although oral medication (methimazole) is a very common treatment, up to 20% of cats can have side effects and as you mentioned, reliable administration can also be problematic.  Some cats will respond to topical forms of methimazole if oral methimazole is not an option. 

The alternative to oral medication is radioactive iodine which is considered the gold standard of treatment.  Radioactive iodine (I-131) enters the thyroid gland and destroys the abnormally functioning cells, thereby reducing the size of the gland and decreasing its ability to produce thyroid hormones.  This treatment is extremely safe for your cat.  Steps would need to be taken to ensure your cat is a good candidate for the treatment.  There are precautions that need to be taken when handling radioactive medication, therefore, referral to a specialist is often necessary to have the treatment performed.  Although hyperthyroidism can be controlled with medication or cured with radioactive iodine, lack of treatment can be fatal so I wouldn’t wait too long to decide what you want to do with your cat.  Good luck!

Laura Sartor, DVM, DACVIM (Internal Medicine)

Dr. Sartor graduated from the Atlantic Veterinary College in Prince Edward Island. She completed a rotating internship in small animal medicine and surgery at the Western College of Veterinary Medicine in Saskatchewan and a residency in small animal internal medicine at the University of Wisconsin Veterinary Hospital in Madison. Dr. Sartor is board certified by the American College of Veterinary Internal Medicine, and is in charge of Oradell Animal Hospital's Nuclear Medicine Program utilizing radioiodine for the treatment of hyperthyroidism in cats. Her special interests also include liver disease, coagulation disorders and anemias. Dr. Sartor enjoys traveling and shopping.