Radioactive Iodine Therapy
What is Iodine-131 Therapy and Why is it Useful?
Hyperthyroidism is a very common disease that affects older cats causing a variety of symptoms including hyperactivity, weight loss, excessive appetite, hypertension, and heart disease. It is caused by a tumor of the thyroid glands causing the release of excessive amounts of thyroid hormone. Therapy has included medication that blocks the manufacture of thyroid hormone, surgical excision of the thyroid, and radioactive iodine therapy.
Iodine-131 is a radioactive isotope which is very effective in treating hyperthyroidism in cats non-surgically. A single injection of I-131 will eliminate the disease by destroying the tumor in the thyroid gland. When the I-131 isotope is injected into the patient, the iodine is selectively taken up by the thyroid gland. The radiation given off by the isotope locally irradiates the tumor and destroys it. Other organs in the body are minimally affected and the patient does not have to endure the stress and pain of surgery. I-131 is considered the gold standard for therapy of hyperthyroidism in cats.
Would I-131 Therapy Be Right for My Cat?
Radioactive iodine (I-131) is a safe, and viable treatment option for cats diagnosed with hyperthyroidism; however, our goal is to ensure that your cat has the best chance for successful, long-term treatment. Some cats have underlying concurrent conditions that may not be suitable for I-131 therapy. Cats that may not be ideal candidates for I-131 therapy may include:
Early-stage hyperthyroidism (high-normal total T4 levels)
Cats with aggressive forms of thyroid tumors
Cats with underlying medical conditions than can increase their risk associated with I-131 therapy or post-treatment care and monitoring
Preparing for I-131 Treatment
This process can appear different between medical facilities. At IndyVet, we provide consultation and treatment days on Mondays and Tuesdays depending on the scheduling week. Prior to consultation, baseline blood work, chest x-rays, and blood pressure are required to evaluate your cat's systemic health. These diagnostic tests may be provided either by IndyVet on the day of I-131 consultation or by your referring veterinarian within 1-month prior to I-131 consultation. All diagnostic results collected by referring veterinarians should be submitted to IndyVet so that it can be reviewed at the time of I-131 consultation.
Methimazole therapy is required to be stopped at least 1-month prior to I-131 consultation.
On the day of I-131 consultation, a comprehensive physical exam is performed. We may recommend additional diagnostics for your cat on a case-by-case basis at the time of I-131 consultation. If your cat fully qualifies for therapy, they are treated on the day of consultation and are maintained in a specially designed radiation containment housing ward in our hospital. Each cat's radiation levels are monitored closely until they can be safely released to your care. This is usually in the afternoon or evening of the third day following treatment.
What Do I Need To Know?
Although cats are discharged within the safety guidelines developed by the Nuclear Regulatory Commission for radiation exposure, owners are instructed on the safe handling of the cat’s litter and waste during the following two weeks to minimize any possible radiation exposure to the pet owner.
A recheck appointment is recommended 2 weeks after treatment. Then evaluation of kidney, liver and thyroid values is recommended 4 weeks after treatment. The recheck appointments may be scheduled at the office of the referring veterinarian, or at IndyVet.
We have treated nearly 600 cats over the past eight years and remain pleased to offer this state of the art treatment for feline hyperthyroidism. Please contact us with any questions you may have about this treatment at (317) 782-4484.