Hyperthyroid Cat Questions and Answers
2. The “gold standard” and accepted way to CONFIRM hyperthyroidism is with a diagnostic thyroid scan. Although there are other less accurate and more expensive methods (T3 suppression test), the thyroid scan is quick and 100% accurate in confirming or denying feline hyperthyroidism. The thyroid scan is also a good predictor as to whether the hyperfunctional thyroid gland is also aggressive in its appearance, which is suggestive of a thyroid adenocarcinoma (actual thyroid cancer). Patients with thyroid adenocarcinoma typically have a poor prognosis as this cancer is very aggressive and tends to metastasize readily. In fact, it is standard protocol in all Veterinary Schools and Universities in the United States that ALL cats undergo a diagnostic thyroid scan prior to the administration of radioiodine in order to confirm the patient is truly hyperthyroid AND to confirm that the gland does not appear to be aggressive. Clinics that have chosen to NOT thyroid scan ALL cats prior to radioiodine administration do so simply because they do not own a gamma camera (the piece of equipment necessary to do a thyroid scan) and thus are settling for less than the “standard of care”. Inevitably, the clinics that have chosen to NOT perform routine thyroid scans on ALL cats will without a doubt treat a fair number of cats that are not really hyperthyroid and will also inject radioiodine into a small percentage of cats that may have a malignant, aggressive thyroid adenocarcinoma.
3. Pre-treatment with methimazole (Tapazole) is recommended in cats with any signs of renal disease (elevated creatinine, lack of ability to concentrate urine, etc) in order to see if the subsequent lowering of the circulating thyroxin will cause the renal disease to worsen. If the cat’s thyroid levels lower into the normal range while at the same time, the renal enzymes do not elevate, they should be a good candidate for radioiodine therapy. If the patient can not tolerate the potentially serous side effects of methimazole (Tapazole) then the only viable option may be low dose radioiodine therapy.
4. In all cases, methimazole (Tapazole) should be discontinued a few days prior to administration of radioiodine (the exact number of days is controversial, but we recommended 5-7 days).
5. Radioactive licenses vary from one institution to the next, and as such, the isolation period in which these patients must be hospitalized may vary as well. In our case, most cats are hospitalized for 3-5 days. During this time, they are closely monitored and are released as soon as legally possible. During this period of time, the cats are NOT ignored and are tended to regularly by authorized, properly trained personnel. Unfortunately, the State prohibits owner visitation during this short period of time.
6. It is NOT against State regulations to administer needed medication during this period of time (antibiotics, insulin, etc), however, the medication can only be administered by properly trained, authorized personnel.
7. The success of radioiodine therapy for nearly all cats with confirmed, non-aggressive hyperthyroidism is nearly 100%. In rare cases, a second dose of iodine is needed. If this is the case, our practice will not charge an additional fee for the second dose of iodine or any other ancillary items (it’s FREE). Also, we have a policy that if your cat’s hyperthyroid condition recurs in the future (very rare but possible) we will also re-treat for no charge.
8. Personal items (beds, baskets, toys, t-shirts) are permitted, however, they are closely monitored for any evidence of contamination with radioiodine, and if they are contaminated, we can not return these items.
10. At the time of discharge from the hospital, you will receive special instructions on how to handle you cat properly for the next week or so. Isolation is not necessary.
11. If you, the owner of a hyperthyroid cat, is pregnant or may be pregnant, you should inform the radiologist of this at the time of the initial appointment. We generally must keep the cat for an additional period of time to allow the radiation levels to drop even more than required by law in order to make this procedure as safe as possible. If you have small children, they should be kept away from the litter box and your cat for at least 10 days.
12. The radiologists at GCVS have successfully treated well over 3,000 cats in the Houston area over the last 15 years. We have authored several scientific papers, text book chapters and numerous presentations at nationally recognized meetings on all forms of nuclear imaging and radioiodine therapy. We have more experience in treating hyperthyroid kitties than anyone in the Houston area and probably all of Texas.