Radioactive iodine is one of three treatments for hyperthyroidism in cats. Hyperthyroidism is most often caused by the thyroid gland producing too much of the hormones triiodothyronine and thyroxine. Older cats are the most likely candidates for the illness, and a link may exist between the disease and cats who eat canned food. Symptoms include weight loss, hair loss, stomach upset and nervousness/hyperactivity. Diagnosis generally includes taking a medical history, a physical exam and laboratory testing.
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Treatment
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Radioactive iodine is given to cats in an injection under the skin. The radioactive iodine is absorbed into the cat's bloodstream and the diseased thyroid tissue. In the thyroid, it stops the portion of the thyroid gland that is over-producing.
Advantages
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Treating with radioactive iodine doesn't require the cat to be anesthetized and no daily medication is required following the therapy. It generally returns the thyroid to normal within one month.
Disadvantages
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The law requires that cats treated with radioactive iodine be hospitalized in isolation until their radioactivity falls to a certain level. This usually takes between three and 10 days.
Side Effects
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Side effects from radioactive iodine treatment are few and rare. A few cats develop temporary or permanent hypothyroidism, which is then controlled by supplementation. For 2 to 3 percent of treated cats, the single injection may not cure the condition and a second treatment may be required.
Home Care
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Once your cat is released from the hospital, you must follow certain precautions for an additional ten days to three weeks. These include keeping the cat indoors, wearing disposable gloves when changing the litter box, disposing of litter daily in an outside plastic bag, not allowing children to handle the cat, now allowing the cat to sleep with people, and washing your hands after handling your cat, her food bowls or her litter box. Your veterinarian will re-check your cat's thyroid hormone and kidney blood values three weeks following the radioactive iodine treatment.
Other Options
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Hyperthyroidism is also treated using methimazole, which is given daily throughout the cat's life. The medication doesn't cure the disease but reduces the production and release of the thyroid hormone. The medication can cause side effects in some cats, including vomiting, anorexia, fever, anemia and lethargy.
Surgery is also sometimes performed to treat the disease. Surgery generally is a permanent cure. The biggest risk factor to the surgery is the possibility of damaging the parathyroid glands, which are close to or inside the thyroid gland and are necessary to maintain stable blood-calcium levels.
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