With hyperthyroidism the thyroid glands become enlarged. However, the enlargement is generally benign or non-malignant type of growth. The normal thyroid glands are extremely small so that enlarged glands are 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 no known specific cat breeds that are affected more often and investigations have failed to correlate any environmental or dietary risk factors leading to hyperthyroidism. Therefore, any cat that lives past middle age, about 7 or 8, has the possibility of developing this condition.
One major organ affected by overactive thyroid glands is the heart. The heart is stimulated to beat faster and harder 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 exam, many affected cats will have a very distinct heart murmur that can be heard by a veterinarian through a stethoscope.
The classical case of hyperthyroidism is a cat that is approximately 10 years old or older and has been losing a lot of weight. Mostly, such 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 that the owners may not really notice it until it has progressed to severe. 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. Of course, these symptoms are also signs of lots of other illnesses.
Fortunately, hyperthyroidism can be diagnosed fairly easily with a simple blood test to measure the levels of their 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 very helpful to evaluate the overall health of your cat.
Additionally, fortunate is the fact that most cases of hyperthyroidism are very 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 method is extremely expensive.
Secondly, surgery may be performed to remove one or both of the thyroid glands. Again, this treatment is very expensive and must be performed by a specialist. Also, most hyperthyroid cats are older and may be greater risk for anesthesia.
The third method of treatment involves an oral medication that can 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 treatment method usually works very well as long as the owner is able to orally medicate their cat every day. More blood tests can be performed to measure the amount of thyroid hormone and whether or not the dosage is correct.
If you have an older cat that begins losing weight despite still eating well, see your veterinarian to ensure your cat lives a long, healthy, and happy life.