Hyperthyroidism in Cats
This is a very common disease of the middle aged to older cat. A tumor (97% are benign) on the thyroid gland starts producing too much thyroid hormone. Symptoms are usually weight loss in spite of eating well and vomiting. Other signs you might see are diarrhea, a dull and flaky hair coat, and personality changes. This disease usually can be easily diagnosed with a blood test, although occasionally we need a special test called a technesium scan to diagnose the early, borderline cases.
There are three basic methods of treatment: radioactive iodine, surgery, or an oral medication called methimazole (Tapazole). For most cats, the best treatment is radioactive iodine. In 97% of the cases, it is a one -time treatment. The biggest disadvantage is that the treatment needs to be done at a special facility, and the cat needs to be hospitalized for usually 5 to 10 days. In the past, surgery was a common treatment, but it is performed less frequently as the problem seems to recur on the other gland. Treating with Tapazole is also common, but has the disadvantage that it is life long and the cat needs blood tests to monitor the thyroid level and to check for adverse effects.
The disease of hyperthyroidism can actually help the kidneys. If the cat has both kidney disease and hyperthyroidism, it is not a candidate for radioactive iodine and the dose of Tapazole may need to be adjusted. Kidney tests are also monitored when a cat is being treated for hyperthyroidism.