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Hyperthyroidism in Cats

General Information

Hyperthyroidism is a disease of older cats, caused by excessive production of thyroid hormones. The usual cause for increased hormone production is a tumor of the thyroid gland. These tumors may be benign (non-cancerous) or malignant. The reason these glands develop tumors is not known.

Signs of excessive thyroid production include weight loss despite a ravenous appetite, frequent bowel movements, increased thirst and urination, restlessness, frequent crying or vocalizing, neglect of normal grooming, and rapid heart beat. The effects on the heart may be severe and result in congestive heart failure.

Surgical removal of the thyroid gland or treatment with radioactive iodine are the recommended treatments. Surgery, in this clinic is usually done in two parts. The total cost for this mode of treatment is about $300 to $450. Radioactive Iodine would have to be done at a referral facility. This treatment is currently being done in Greenville (SC) by Radiocat at Upstate Referral Services. The cost of this mode of treatment is about $1200. If the gland is totally removed, replacement thyroid hormone is sometimes given for life though in our experience this has not normally been needed. Long-term medical therapy is often not recommended because the underlying tumor may be malignant and because the drugs can have serious side effects when used for long periods. That said, we have had patients that have treated the condition medically that have been happy with the treatment. When necessary "compounded" medication can make giving the medication easier. When serious heart disease has already occurred, medical treatment is used until the pet is healthy enough to undergo surgery. Some animals that are treated for hyperthyroidism will have problems with kidney function after treatment. We attempt to predict which animals will have problems with kidney function based on their laboratory results but we cannot alway be sure about this. Sometimes treating with medication and the reevaluating kidney function can be helpful.

Important Points in Treatment

1. A complete examination, including blood tests and radiographs (x-rays), is performed before surgery to be sure the tumor, of present has not already spread and to evaluate the condition of the heart and other internal organs.

2. Thyroid hormone levels are checked after surgery and during drug therapy to determine the proper replacement dose.

3. Medication must be given as directed. Call the doctor if you cannot give the medication.

Notify the Doctor if Any of the Following Occur:

* Your pet has trouble breathing or swallowing.

* Your pet's signs continue or worsen.

* Your pet does not gain weight.

* Your pet's general health declines.

Larry Tilley's Recommended Info site (www.VetMedCenter.com)