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Radioactive Iodine Therapy for Hyperthyroidism in Cats

Eighteen Months After Diagnosis - Time for Radioactive Iodine Therapy


veterinarian examining cat

Dr. Melinda palpates Bubba's Kidneys

Franny Syufy
June 3, 2004

It has been almost 18 months since Bubba was first diagnosed with hyperthyroidism, and during that time he has been treated with Tapazole (methimazole), 5 mg once a day. He has also been under close veterinary supervision, and despite repeated short periods of appetite loss, coupled with vomiting, he has remained stable, with excellent kidney, liver, and T4 values.

Recently, however, the vomiting has increased, despite regular pilling with Reglan, and he has suffered noticeable weight loss. During an exam and consultation with Dr. Odom, his current veterinarian, I was reminded of a few things, and also learned something new:

  1. Tapazole may cause certain side effects, including vomiting, anorexia, fever, anemia, and lethargy. (Bubba has recently had all those symptoms except fever and anemia.)
  2. After a period of one year to 18 months, the thyroid gland may become refractory (unresponsive) to methimazole, and hyperthyroid symptoms may slowly gain hold again.
  3. I had also learned in a previous visit that the way hyperthyroidism "masks" kidney problems is that it stimulates the flow of blood through the kidneys, causing them to pump urine out of the system (sort of "kidney overdrive," if you will).

This put us between the proverbial "rock and a hard place," because at (almost) 17, Bubba is at the age when CRF (chronic renal failure) often appears. If the Tapazole treatment was no longer doing its job, Bubba was in the position of either having untreated hyperthyroidism, or he could be cured of that disease with radioactive iodine therapy, and face the potential of CRF. Dr. Odom was able to give me perspective when he told me an old veterinary maxim of treat what is treatable. Hyperthyroidism can not only be treated, it can be cured, with radioactive iodine therapy (the cure rate is approximately 95% after one treatment.) Although CRF is incurable, with careful management of diet and fluids, a reasonably good quality of life may be maintained for months, if not years.

With those considerations in mind, the appointment was made for the radioactive iodine (¹³¹I) therapy at a clinic about 80 miles distant. Dr. Odom arranged for the appointment and faxed all of Bubba's medical records to the clinic.

Bubba's Big Adventure

Thursday, June 3, 2004, we made the trip to Sacramento, to the Nuclear Medicine for Pets clinic, owned and operated by Melinda K. Van Vechten, D.V.M., D.A.C.V.I.M. (Diplomate American College of Veterinary Internal Medicine.) Dr. Van Vechten is a specialist in veterinary oncology and internal medicine.

Bubba was a real trooper in the car. He settled down in his carrier in the back seat and immediately went to sleep, and didn't awaken again until we arrived at the clinic. Inside, Carol Slattery, Dr. Van Vechten's able technician and assistant, gave us a short financial agreement to fill out, then we were taken to the examination room, where the vet gave Bubba a thorough examination. "Dr. Melinda" (as I'm inclined to want to call her), weighed Bubba (he had gained 1/2 pound in a week), palpated his thyroid, kidneys, and other organs, and listened to his heart, then asked a number of questions as she reviewed his records. Apparently satisfied with all she had learned, Dr. Melinda proclaimed Bubba a good candidate for the ¹³¹I therapy.

We said our "goodbyes" to Bubba, told him we love him, promised that we would see him very soon; and he was then taken to a "holding room" at the rear of the facility, where another cat (a lovely tortie) and a doggie were also waiting in cages.

I had mentioned my occupation as a cat writer to Carol, and Dr. Melinda readily gave permission for me to photograph the examination and parts of the facility. Because of state laws governing radioactive material, I was not allowed to set foot past the threshhold of the door to the combination treatment/recovery room, for safety reasons, but I was able to take photos of the equipment. Carol then took my camera into the room and took a few photos of kitties in cages who are in various stages of "de-radiation."

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