Hyperthyroidism, the overproduction and overabundance of thyroid hormones, is relatively common in older cats, both male and female. In fact, it’s the most common hormonal abnormality there is. In a cat with hyperthyroidism, the elevated levels of thyroid hormones, which normally work to regulate the metabolic processes, speed up the metabolism and cause many of the body’s functions to run much faster than normal.

This can lead to a number of complications, including enlargement of the heart muscle, high blood pressure, kidney function impairment, and intestinal problems. Hyperthyroidism can be caused by thyroid cancer, but it is generally caused by benign nodules of tissue in the thyroid that hyperproduce—work too hard and produce too much hormone.

There is no way to prevent hyperthyroidism, but you can catch it early by bringing your cat to the veterinarian for regular checkups and keeping a close eye on his health. As your cat gets older, watch him for the symptoms of overactive thyroid: weight loss, hyperactivity, and an increased appetite. Other common symptoms include vomiting, unkempt fur, patches of hair loss, and increased water intake and urination.

The good new is that hyperthyroidism is usually not difficult to diagnose or treat. Veterinarians can generally diagnose the disorder through a physical exam and routine blood test. Hyperthyroidism can be treated with medication, by surgically removing thyroid tissue, or by destroying thyroid tissue through radioactive iodine therapy. Treatment is often very successful.

Copyright © 2009, American Animal Hospital Association

Reprinted with permission from the American Animal Hospital Association.