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Radioiodine Therapy for Hyperthyroidism in Pets
Pets that have been diagnosed with hyperthyroidism can be treated with radioactive iodine, which has a high success rate at selectively destroying the overactive parts of the thyroid gland. This treatment is performed more often in cats, although dogs are occasionally diagnosed and treated by this same method, often referred to as Iodine-131 or I-131 therapy or treatment.

​How is Hyperthyroidism Diagnosed?

The diagnosis of hyperthyroidism requires careful consultation with your veterinarian, who also should check your pet for other medical problems such as heart or kidney disease. Your veterinarian will order a blood test to check thyroid hormone levels and to detect over activity in the thyroid gland.  Referring Veterinarian or Client medical consultations and referrals are handled by the CSU Veterinary Teaching Hospital's Internal Medicine Service.  Members of our Nuclear Medicine staff are also available to answer questions about the I-131 treatment and care of your pet during their hospitalization in our Nuclear Medicine ward.

Please contact the Small Animal Internal Medicine Service if you have any questions: or leave a message at (970) 297-4279.

Is the Treatment Right for My Pet?

The treatment of hyperthyroidism has many factors and there are medical considerations that may be unique to your pet.  At CSU, we only accept I-131 patients that have consulted with and been referred for treatment by the Internal Medicine Service.

What is the Schedule for the Treatment?

Prior to I-131 treatment, the Internal Medicine specialist may recommend additional diagnostic tests and diet or medication changes that are specific for your pet. 

Typically, your hyperthyroid pet will be evaluated and admitted on a Monday and a nuclear medicine thyroid scan will be performed later that day to assess for involvement of one or both thyroid lobes, nature of the thyroid changes, presence of ectopic thyroid tissue, and the rare possibility of thyroid carcinoma. On Tuesday morning, the radioiodine treatment will be given.  Your pet will stay hospitalized until the end of the week. Although the majority of treated animals can go home Friday afternoon, occasionally a pet will have to remain in the hospital through the weekend so that the levels of radiation in their body has decreased sufficiently for release. While your pet is undergoing therapy, it will stay in a special radiotherapy hospital ward and be cared for by our staff.

There are additional considerations for dogs. The length of hospitalization for dogs having this treatment is longer than for cats, and depends upon a number of factors.  I-131 or alternative treatments for your dog will be discussed with you in greater detail by your CSU veterinarians.

Please contact the Small Animal Internal Medicine Service at​ or leave a message at (970) 297-4279. We are happy to answer questions and assist you.

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Contact Us:
Colorado State University
Veterinary Teaching Hospital
300 West Drake Road
Fort Collins, Colorado, 80523

​(970) 297-1293

(970) 297-1205