2665 5 Mile Rd. NE Grand Rapids, MI 49525

Phone : (616) 364-1211

Fax : (616) 364-9571


Doctor's Referral Letter

Dear Colleague:

Thank you for your radioactive iodine referrals. We appreciate them! In general, we treat four to ten I-131 patients per month at our Kentwood Cat Clinic. We have even treated several cats from northern Michigan and from northern Indiana.

We have had a few questions regarding what needs to be done for I-131 treatment. Prior to your client’s visit here, we need a history and physical findings, full CBC, serum chemistry with screening T4 level, thoracic radiographs (2 views) and a urinalysis. These should be performed no greater than 30 days before treatment. Please fax lab results to us one to two weeks prior to the appointment to enable us to order the appropriate dose of I-131. The dose is dependent on the T4 level present. We use a typical screening T4 level to calculate the dose, not a T4 by dialysis. Your patient must be off Tapazole for a minimum of two weeks before I-131 therapy, and the T4 level needs to be a non-Tapazole treated T4. For example, if your patient is currently on Tapazole, please discontinue the Tapazole for at least two weeks and then take a T4. The CBC and chemistry samples can be taken while they are still on Tapazole if needed. Cats with renal disease may or may not be able to be treated depending on the severity of their disease. If chest x-rays appear normal to you, the client may bring them to the I-131 appointment. Please mail them (or email at appt@catclinics.com) to us earlier if abnormalities are present, especially if chest masses or pleural effusion are noted. Abnormalities should be reported to us as soon as possible prior to the client’s visit to ensure that treatment will be possible and prevent the inconvenience and cost of the canceled I-131 treatment to your client. The client will be charged $250.00 for the I-131 if the treatment is canceled less than three days before the scheduled treatment due to the nuclear pharmacy advance order requirements.

Radioactive iodine provides a simple, effective, and safe treatment for cats with hyperthyroidism. The basic principle behind treatment of hyperthyroidism with radioiodine is that thyroid cells do not differentiate between stable and radioactive iodine; therefore, radioiodine, like stable iodine, is concentrated by the thyroid gland after administration, In cats with hyperthyroidism, radioiodine is concentrated primarily in the hyperplastic or neoplastic thyroid cells where it irradiates and destroys the hyperfunctioning tissue. Normal thyroid tissue, however, tends to be protected from the effects of radioiodine, since the uninvolved thyroid tissue is suppressed and atrophied and receives only a small dose of radiation (unless very large doses are administered). The radioisotope used to treat hyperthyroidism is I-131. Iodine-131 has a half-life of eight days and emits both beta-particles and gamma-radiation. The beta-particles, which cause 80 percent of the tissue damage, travel a maximum of 2-5 mm in tissue. Therefore, beta-particles are locally destructive but spare adjacent hypoplastic thyroid tissue, parathyroid glands, and other cervical structures.

We utilize a single dose method of between 4.0 – 8.0 mCi of I-131 orally. The cat will be hospitalized for four days. The cat will need to be isolated at home in a separate room for one week if no children are involved and two weeks if children are present in the home.

Two weeks post discharge we request you perform a full CBC, serum chemistry with T4 level and forward the results to us along with the physical findings.

Current cost of I-131 treatment for all Cats Radioiodine treatment affiliates is $1200 for routine referrals. In general, we will be scheduling these treatments on Mondays and Tuesdays.

We now have a photo book explaining the I-131 treatment to clients. Please let us know if you have not received a copy.

Please feel free to contact us with any questions you may have. We look forward to helping you provide your patients with the best possible treatment for hyperthyroidism.


Tammy P. Sadek, DVM & Dr. Alyson Coppens
Cat Clinic North & Kentwood Cat Clinic | ABVP Feline Practice

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