Pet Corner: Diagnosing, treating hyperthyrodism in cats

Published 2:42 pm Wednesday, September 12, 2018

Cats are the top dog today. Today’s column is for all the cat lovers who may feel cats don’t get as much attention as dogs.
I want to talk about hyperthyroidism, or high thyroid, in cats.

Hyperthyroidism is a condition when the thyroid glands are overactive and produce excess amounts of thyroid hormone.

Hyperthyroidism is a fairly common disease in older cats.

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There is no known cause or reason for this condition except it is commonly a result of the aging process.

There are two thyroid glands in the body located in the neck on each side of the trachea or windpipe. The thyroid glands play a vital role in regulating the body’s metabolism. It actually either directly or indirectly affects almost every organ in the body.

With hyperthyroidism, the thyroid glands become enlarged. However, the enlargement is generally benign. The normal thyroid glands are tiny so enlarged glands are even most often undetectable by feeling for them.

On occasion, your veterinarian may be able to feel enlarged glands but would still need additional diagnostics to confirm hyperthyroidism.

There are no known specific cat breeds affected more often and investigations have failed to correlate any environmental or dietary risk factors leading to hyperthyroidism.

Therefore, any cat who lives past middle age, about 7 or 8  years old, has the possibility of developing this condition.

One major organ affected by overactive thyroid glands is the heart. The heart is stimulated to beat harder and faster than normal, which causes an abnormal enlargement of the heart. Consequently, high blood pressure develops in many cats with hyperthyroidism, which also leads to other unwanted medical conditions.

On physical exams, many affected cats will have a distinct heart murmur that can be heard with a stethoscope.

The classic case of hyperthyroidism is a cat who is approximately 10 years or older and has been losing significant weight. Generally, these cats will eat extremely well and still continue to lose weight. Their metabolism has been greatly increased to the point of not being able to maintain their weight, no matter how much they eat.

Sometimes, the weight loss is so gradual the owners may not really notice it until it has progressed severely.

Other symptoms that may or may not occur in cats with hyperthyroidism are drinking a lot of water, urinating a lot, periodic vomiting or diarrhea and their fur may appear unkempt. These symptoms are also signs of lots of other illnesses.

Hyperthyroidism can be diagnosed fairly easily with a simple blood test to measure the levels of your cat’s thyroid hormone. An in-house blood machine can determine if your cat has high thyroid hormones in a matter of 30 or 40 minutes.

Other blood tests as well as a physical exam, urinalysis, EKG and heart ultrasound can be helpful to evaluate the effects of hyperthyroidism and the overall health of your cat.

Fortunately, most cases of hyperthyroidism are treatable with favorable results.

There are three basic ways to treat this condition.

The first method is very effective by using radioactive iodine injections to destroy all abnormal thyroid tissue. The problem is the treatment requires one or two weeks of hospitalization at a veterinary hospital licensed to administer radiation therapy. This treatment protocol is also expensive.

Secondly, surgery may be performed to remove one or both of the thyroid glands. This treatment is also expensive and must be performed by a veterinarian surgery specialist. Most hyperthyroid cats are older and may be at greater risk during anesthesia.

The third method of treatment involves an oral medication to control the effects of the overactive thyroid gland. The medicine blocks the production of excess thyroid hormone instead of destroying the abnormal thyroid tissue.

This method usually works well as long as the owner is able to administer the medicine to their cat orally every day. More blood tests can be performed to measure the amount of thyroid hormone, effectiveness of the medication and whether or not the dosage is correct.

Another option is a transdermal gel which is administered by rubbing the gel on the skin on the inside of your cat’s ear. The problem with this medication is some cats will immediately rub it off by rubbing their ear on the floor or against the furniture. Sometimes, this medication will cause irritation and inflammation of the skin at the site of application.

If you have an older cat that begins to show any symptoms of hyperthyroidism, contact your veterinarian as soon as possible to ensure your cat lives a long, healthy and happy life.

Dr. Jeff Castle is a veterinarian at Clark County Veterinary Clinic.