Info on overactive cat thyroid?

My cat has an overactive thyroid and is on medication. Please can you explain this condition and prognosis please.

  • Vetinfo

    By: Rebecca Osterfund El Segundo, CA

    Replied on 04/19/2011

    Hyperthyroidism is a condition that affects many older felines. It is caused by cancer cells growing in the thyroid gland. These cells overproduce thyroid hormone, which results in the symptoms of hyperthyroidism. These symptoms include weight loss, increased drinking and urination, and vomiting. There are three treatment options for hyperthyroidism: medication (methimazole), radioactive iodine therapy and surgery. The prognosis of the disease depends on how well your pet responds to therapy. Sometimes the treatment of hyperthyroidism can worsen underlying kidney disease which is also common in older felines. Many times when cats are diagnosed with hyperthyroidism the disease has already caused irreversible damage to the heart. Hyperthyroidism can also cause increased blood pressure which can lead to retinal hemorrhage and subsequent blindness. Speak with your veterinarian at your pet's future followup visits as to how your pet is responding to medication and if radioactive iodine therapy would be an option for your pet. If your pet's kidney values remain normal after being started on methimazole, you may want to consider radioactive iodine. It is more expensive than medication, but the procedure completely eliminates the cancer cells from your pet's body and you will not have to give him or her medication for the rest of his or her life.

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