Radioactive Iodine Treatment - (I131 for hyperthyroid cats)
Hyperthyroidism is the clinical syndrome that exists when there is overproduction of circulating thyroid hormone, which is the hormone that regulates the body’s metabolism. Hyperthyroidism is a common condition in older cats. Hyperthyroid cats have very high metabolism. Because the thyroid hormone affects the whole body’s metabolism and body systems, if this disease goes untreated multiple organ systems may be affected and damaged. Most hyperthyroid cats will have some degree of hypertrophic cardiomyopathy, which is a condition where the heart muscle becomes thickened. Most hyperthyroid cats will have increased heart rates and irregular heart rhythm. The majority of these cats will have abnormalities on routine chemistry panels (blood analysis) reflecting damage to the liver, kidneys and muscle. Veterinary Imaging Center specializes in treatment of Feline Hyperthyroidism with radioactive iodine treatment.
Radioactive iodine treatment is the therapy generally considered the optimum choice of therapy in hyperthyroid cats, as this not only treats the condition, but cures it. A single injection of I131 cures 97-99% of the cats treated at our facility. Radioactive iodine works to cure hyperthyroidism because this therapy uses the physiology or way the body works to treat the disease. Thyroid tissue normally uses iodine to manufacture thyroid hormone, and when radioactive iodine is administered to a hyperthyroid cat, the radiation emitted from the I131 will actually destroy the abnormal thyroid tissue (because the normal tissue is usually not working in hyperthyroid cats, it is not affected).
All cats treated with radioactive iodine at VIC will have a thyroid scan prior to I131 therapy. This scan is important as it documents the thyroid disease, shows which thyroid tissue is overactive, shows how overactive the thyroid tissue is and shows detail of the overactive thyroid tissue or signs of benign versus malignant disease. These details are important as this allows Dr. Voges to determine the appropriate dose of I131 to administer in each individual patient. In some cats, we also perform a nuclear glomerular filtration rate (GFR) to determine the kidney function prior to therapy and insure that treating the thyroid disease will not cause kidney failure.
Cats treated with I131 at Veterinary Imaging Center will remain hospitalized at our facility for several days until a large amount of the radioactive iodine has been eliminated from their body. Average hospitalization is 3 to 5 days. After this treatment, the cats should be “normal”, and the only follow up required is a blood test at a later date to insure the thyroid hormone levels are normal. Please read our brochure on feline hyperthyroidism for more information, or contact our office for specific questions.
Click here for hyperthyroidism brochure (pdf).