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Hyperthyroid Disease In Cats
Any older cat that has been losing weight, while perhaps eating more, should be checked for hyperthyroidism.
Any older cat that has been losing weight, while perhaps eating more, should be checked for hyperthyroidism.
Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone. It occurs mostly in older cats (and is rare in dogs). The average age of cats with hyperthyroid disease is about 13 - only around 5% of cats with hyperthyroidism 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.
There are several common signs of the disease. But since thyroid hormone affects the functioning of all of the bodily organs, signs may be variable. More common signs will include losing weight, increased appetite, increased restlessness, elevated heart rate, and aggressive behavior. Other signs can include increased urination, increased water consumption, difficulty breathing, vomiting, bigger stools, diarrhea, poor haircoat, and weakness and depression.
The first step is correct diagnosis. The first examination will be to palpate the thyroid glands in the neck and see if they are enlarged. Diagnosis of this disease is made when the level of thyroid hormone is found in increased levels in the blood. Most hyperthyroid cats have very high levels of hormone, so it is usually very straightforward. But some cats will have signs of hyperthyroidism with normal or only slightly increased levels of thyroid hormone. And, thyroid hormone levels may vary over time, so it might 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.
Another conventional treatment is Oral Medication. The orally administered drug methimazole can control the effects of the overproducing thyroid gland. Around 20% of cats treated with this medication may have reactions to the drug. The side effects may not begin until six months after the start of treatment, and the effects can include anemia, vomiting, anorexia, lethargy, and fever. This medication does not destroy the abnormal tissue but rather it prevents the overproduction thyroid hormone. So if used, the drug will have to be given for the rest of the cat’s life. Blood tests must be done periodically in order to keep the dosage regulated. Methimazole treatment is usually appropriate for cats with other health problems, who are poor surgical risks, or if they are very old.
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.
One alternative treatment would be with Bugleweed (Lycopus Europeus) and Melissa (Melissa Officinalis). These are two herbs that have been used in combination to combat the effects of hyperthyroid disease. Bugleweed has been shown to decrease thyroid hormone levels in rats 24 hours after administration. The standard dose is 1 drop per lb of body weight of the tinctures given twice daily.
An additional alternative treatment is with Carnitine, an amino acid health supplement. Carnitine is normally synthesized within the body, primarily in the liver and kidneys, from the amino acids lysine or methionine. When given as a nutritional supplement, Carnitine has been found to be quite effective in reversing signs of hyperthyroidism in people. Starting cat dose of the supplement 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.