As we and our pets age, a variety of medical problems await them and us, with new ones seeming to be discovered almost daily. Hyperthyroidism is a medical condition in which the thyroid gland produces too much of the hormones that regulate the body’s metabolism and affect every system in the body. This is a condition that is rare in dogs but has become quite common in cats. Hyperthyroidism in cats has been steadily increasing for the past 25 years and no one is sure why. What is known is that the condition is rarely caused by cancer (1-2% of cases) and that it usually occurs in older cats over 8 years in age, with 13 being the median age at which it appears.

The most common cause of hyperthyroidism is an increase in the number of abnormal but benign cells in the thyroid gland. Groups of these abnormal cells form small nodules on the thyroid gland called adenomas. The thyroid gland is a small organ found in the neck, consisting of two lobes, one on either side of the trachea. This gland produces two hormones, T4 and in smaller amounts, T3. When the thyroid produces too much of the hormone T4 the condition known as hyperthyroid exists. The most common symptoms of this condition are weight loss along with increased appetite. A cat will seem constantly hungry and will demand or beg for food, and at the same time will be losing weight. Eating will often be followed by vomiting, then seeking more food. Another sign is increased water intake along with increased urine output. You may see increased activity and behavioral changes, which may include trying to steal food from you as you prepare it or even as you eat. The hormones are causing the cat to be constantly hungry.

Some of the symptoms resemble those of other medical conditions, including diabetes, so the vet will test blood and urine to diagnose the problem. Elevated levels of T4 will confirm that it is hyperthyroidism, and if that is all it is, the problem can be corrected.

The two most common ways of treating this problem are with medication, which can often control the problem, or by surgery to remove the thyroid gland, which cures the condition. While both treatments will work, there are drawbacks to each of them.

Medication – the drug Methimazole reduces the amount of thyroid hormones that are produced, allowing the cat’s condition to improve. The cost is nominal, about fifty cents a day, but in some cases will not have an affect. When it does work it is not a cure; it merely controls the symptoms. The adenomas on the gland may continue to grow and become more of a problem. Many vets consider medication a temporary solution to be followed by surgery. It is frequently used with a cat that is a poor candidate for surgery until the cat’s condition improves.

Surgery – removal of the thyroid gland will solve the problem, but there are caveats. As mentioned before, the thyroid is a small gland in the neck consisting of two lobes, one on either side of the trachea, the windpipe. Within the thyroid is an even smaller but equally important organ, the parathyroid gland, which controls the calcium and phosphorus levels in the body. The parathyroid must be separated from the thyroid and left in the body. Inadvertent removal of this organ would lead to a life-threatening condition called hypocalcemia, or low blood calcium.

People with older cats should be aware of the signs and see a vet if they appear. The sooner treatment is begun, the better the chance of a full recovery. Waiting may allow the adenomas to increase and grow to a point where surgery is more difficult or impossible, and medication will not be effective.

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