How Many Ways Can the Thyroid Malfunction?

June 21, 2012

The thyroid gland sits in the neck of dogs and cats, just below the voice box, and controls metabolic functions. Most of the time, a routine physical examination cannot detect the organ if it is normal. Last week, my patient list ran the gamut of thyroid dysfunction. Here is a sampling:

A Tail of Two Thyroids

Some days, strange coincidences happen in the waiting room. Today it was two dogs, both with thyroid cancer. Although measuring 15 centimeters in length, Beckey’s thyroid tumor had been surgically removed. The biopsy showed her tumor trying to escape into the lymph vessels and she was waiting her turn for chemotherapy, administered to halt the spread. Her treatment involves intravenous administration of two different chemotherapy agents and Beckey so far has sailed through the treatment with flying colors.

As Beckey was leaving the waiting room, Henry entered. A CT scan showed his thyroid tumor had already spread to the lymph nodes in his neck, precluding surgical removal. He was in for a check-up following completion of four radiation therapy treatments. Careful measurement of his tumor with calipers showed no increase in tumor size. The radiation treatment arrested tumor growth but had given him a sore esophagus. I had warned the owners about this type of side effect before we started treatment and told them to expect it to start resolving about two weeks after he completed his treatment. Henry did not disappoint us. Through telephone triage, we had already rearranged his medications to make his throat less painful. Henry spends summer in the country but in the fall he will come back to The AMC for measurement of the tumor and a chest x-ray.

Old Patient, New Problem

Otra’s family was worried. This cute kitty had completed chemotherapy for intestinal lymphoma about a year ago, but suddenly her weight plummeted. I could see from the look on their faces they were sure the cancer was back. Auscultation of Otra’s heart discovered a very elevated heart rate, prompting a test of her thyroid levels. Overactive thyroid glands ramp up the cat’s metabolism and they lose weight despite eating well, have a high heart rate, and are very peppy. An abdominal ultrasound showed no evidence the lymphoma had recurred and blood tests showed the thyroid was overactive. I sent thyroid-suppressing medications home with the relieved family and planned to reassess the thyroid hormone levels in two weeks.

Porterhouse to Pork Chop

Every time I saw Mango to follow up on a skin tumor that had been completely removed via surgery, she had gained another pound. This 60-pound Portuguese Water Dog should have weighed 50 pounds. The owners took her swimming, fed her diet food from feeding toys, and still she gained two more pounds. During an evaluation for a urinary tract infection, we noted her thyroid hormone levels were borderline low. When we retested the levels three months later, we confirmed diagnosis of hypothyroidism. Low thyroid function, the opposite of Otra’s problem, can cause weight gain. Since she started treatment with thyroid supplementation, Mango has lost nearly 6 pounds and gone from a 20-ounce porterhouse to a 4-ounce pork chop over the past few months!

There you have it, thyroid malfunction runs the gamut of disease: overactive, underactive, and two different tumors, all in one tiny organ.


I am glad I just learned the word "auscultation" this morning through Word A Day prior to reading your article--but thanks for the variations on the thyroid. I've had four hyperthyroid cats over the years, none with tumors, though the disease affected each of them differently.

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