THYROID TREATMENT: RADIOTHERAPY
IMAGING WITH NUCLEAR MEDICINE AND TREATMENT BY RADIOTHERAPY
This method of therapy is generally considered the safest and most effective method of treatment for feline hyperthyroidism. Your cat will be given an injection of radioactive iodine (iodine 131) and kept in the facility until the radiation levels have reduced adequately to allow the cat to return home (usually three to four days). Treatment is not invasive and most cats tolerate brief separation from home without significant stress.
After release, there will be a period of time (usually about a week and a half) where the cat will need confinement, flushable cat litter, and restricted human contact because he or she is still emitting low levels of radiation. After this period, the cat is back to normal without restrictions and all that is left to do is return for some follow up lab work over the next few months. The radioactive iodine injection is given under the skin similar to a vaccine and the cat is basically boarding afterwards until the radiation levels drop.
This treatment works because iodine (radioactive or otherwise) homes to thyroid tissue. Radioactive iodine emits high speed electrons which damage the thyroid tissue from within, effectively destroying the thyroid tumor. The electrons only penetrate a fraction an inch which means only the thyroid tissue is affected and the rest of the cat's body is not. Human beings with hyperthyroidism are similarly irradiated and are not confined in any way afterwards but because, in this situation, the patient is a cat, the Nuclear Regulatory Commission insists on confinement as described above. The potential for side effects with this therapy is very very low and it is very low stress for the cat.
THE PERTECHNETATE SCAN
In most facilities (but not all), therapy begins with a nuclear medicine scan called a pertechnetate scan. There is a much lower cost to radio iodine therapy if the scan is skipped, however, if you opt for a facility that skips the scan you should be aware of the information that is lost in doing so in order to make an informed decision.
If the scan identifies a bizarre distribution of thyroid tissue that is typical of malignancy, a different iodine 131 protocol is used. For more information on thyroid malignancy click here.
ADVANTAGES OF THIS METHOD OF TREATMENT
DISADVANTAGES OF THIS METHOD OF TREATMENT
If kidney function is not thoroughly investigated prior to this therapy, latent kidney failure may be unmasked irreversibly by this therapy. This can be avoided simply by screening potential candidates for kidney failure prior to recommending radiotherapy. Those who have possible kidney insufficiency should be treated with medication to bring the thyroid levels under control. If kidney function begins to show deterioration on this therapy, medication is discontinued and one must reevaluate the need for treating thyroid disease. If kidney function remains stable on treatment with anti-thyroid medications, then a more permanent therapy (such as radiotherapy) can proceed.
For a list of facilities known to us in the United States and Canada that can offer Radiotherapy Treatment for your cat, click here.
Page last updated: 12/1/2020