Hyperthyroid Disease In Cats | Pets and Animals

By Dr.AndrewJones,DVM
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Older cats that have been losing weight but have an increased appetite should be checked for hyperthyroidism.

Hyperthyroid disease exists when overproduction of thyroid hormone is made by the thyroid gland. It occurs mostly in older cats, with the average age of about 13. Approximately 5% of hyperthyroid cats are younger than 10.

In hyperthyroid disease, one (or both) of the thyroid glands in the neck enlarge and produce too much thyroid hormone. It's more common for both glands to be actively overproducing thyroid hormone.

Although there are common signs, since the thyroid hormone affects the function of most of the organs in the body, the signs can be quite variable. Some of the common signs include weight loss, increased appetite, elevated heart rate, increased restlessness, and aggressive behavior (overly 'cranky'). Additional signs include increased water consumption, increased urination, occasional vomiting, increased size of stool (or diarrhea), poor hair coat, difficulty breathing, or occasionally weakness and depression.

When diagnosing the disease, the first thing your Vet may do is to palpate the thyroid glands in the neck of your cat to see if the glands are enlarged. Actual diagnosis of the disease is made if thyroid hormone is found in increased levels in blood tests. Diagnosis is usually straightforward, as most cats with hyperthyroid disease will have very high levels of the hormone. But occasionally cats will have the signs of hyperthyroid disease but show normal or only slightly increased levels of thyroid hormone in the blood. When testing, thyroid hormone levels can vary over time, so it may be necessary to check blood levels several times.

An effective conventional treatment is with Radioactive Iodine Therapy. Radioactive Iodine is given by injection, and it destroys abnormal thyroid tissue without harming the other organs. Treatment will require one to two weeks of hospitalization at a veterinary facility that is licensed to administer radiation therapy. Because of governmental regulations regarding radioactive materials, this treatment is often limited to veterinary teaching institutions. The cost of the treatment is sometimes (although not always) more expensive than with other options.

A second traditional treatment is with Oral Medication. Administration of an oral drug, methimazole, can control the effects of the overactive thyroid gland. Some cats have reactions to the drug (approximately 20%). However, the side-effects may begin as late as six months after the beginning of treatment and can include vomiting, lethargy, anorexia, fever, and anemia. Methimazole does not destroy the abnormal thyroid tissue but rather prevents the production of excess thyroid hormone. Therefore, the drug must be given for the remainder of the cat's life. Periodic blood tests must be done to keep the dosage regulated. This type of treatment is appropriate for the cat who is a poor surgical risk due to other health problems or is exceptionally old. It may also be used for a few weeks to stabilize the cat who is at increased surgical risk because of cardiac complications.

Surgery to remove the abnormal tissue, called thyroidectomy, is another option. With surgery, however, recurrence of the disease is a possibility in some cats (it is uncommon after radioactive iodine therapy). When surgery is done, recurrence is possible if abnormal thyroid cells are left in the cat. The remaining cells will likely grow causing the disease to recur. However, this occurs less than 5% of the time and usually after 2-4 years. Another possibility for disease recurrence is that one lobe of the thyroid gland was normal at the time of surgery so it was not removed. Then, months or years later, it became abnormal.

Bugleweed (Lycopus Europeus) and Melissa (Melissa Officinalis) can be used as an alternative treatment. These two herbs have been used in combination successfully in some cats to combat the effects of hyperthyroidism. In testing, bugleweed itself has been shown to decrease thyroid hormone levels in rats 24 hours after administration. Standard dose of the tinctures is 1 drop per lb of body weight given twice daily.

Another alternative treatment is Carnitine, an amino acid nutritional supplement. Carnitine is an ammonium compound normally synthesized within the body from the amino acids lysine or methionine, primarily in the liver and kidneys. Given as a supplement, this has been found to be effective in reversing the signs of hyperthyroid disease in people. The starting cat dose is 250 mg per day.

Hyperthyroid disease in cats is a very serious disease. It is a very common endocrine disorder. About 2% of all cats greater than the age of 10 will contract hyperthyroidism. However, the disease is relatively easy to diagnose and correctly administered treatment has a quite high success rate. Cats who have been treated for the disease are able to lead healthy, normal lives.

About the Author

Question what your Vet tells you! Avoid medication side effects with holistic cat health remedies. Dr. Andrew Jones, a practicing veterinarian, has a special focus on alternative pet health.

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