Thyroid Treatment in Cats

Significance

• Hyperthyroidism is seen largely in older cats. It's practically nonexistent in canines. According to 2ndchance.info's Ron Hines, D.V.M., the average age of onset in cats is 13. The vast majority of cats who exhibit the disorder are older than age 10. The disorder doesn't tend to target a particular breed or favor one gender over the other. However, it does seem to be on the rise in the past couple of decades, probably because of feline diets and environmental factors, says PetEducation.com, but no one knows for sure.

Features

• Hyperthyroidism is most commonly caused by cells multiplying somewhat out of control in the thyroid gland. This is considered a noncancerous growth of cells. Eventually, these cells form small nodules, or adenomas, on the thyroid gland itself. The cat's thyroid gland has two lobes, or sides, unlike the single-lobed human organ. Many adenomas can attach to a single lobe. Both lobes are affected in roughly 70 percent of cases, however. Cancer presents as a cause of hyperthyroidism in only 1 percent to 2 percent of cases, reports PetEducation.com.

Signs and Treatment

• A hyperthyroid cat will exhibit weight loss while at the same time eating more. Other signs include increased activity and panting. Along with a cat's symptoms, elevated hormone levels and an enlarged thyroid tell the veterinarian that hyperthyroidism is the likely culprit.

  The current approach to treatment provides three options, depending on the individual cat. There's a drug regimen that commonly employs methimazole, the antithyroid medication. Veterinarians will sometimes remove the gland. Treatment with radioactive iodine is another option.

Methimazole

• Administered in pill form on a daily basis for the life of the cat, the antithyroid drug methimazole (brand-name Tapazole), is actually a human preparation. It works by inhibiting the thyroid's production of T-4. Methimazole does not cure hyperthyroidism, it's difficult to administer to some cats, and it can cause vomiting and lethargy. However, the drug does not harm the parathyroid glands, which control the body's use of calcium and phosphorus, in a way that other treatments can; and it's relatively inexpensive.

Surgery and Radioactive Iodine

• A thyroidectomy is a surgical procedure that completely removes the cat's thyroid, thus providing a cure. It's commonly performed in animals well enough to undergo anesthesia and surgery. A big risk during surgery is the inadvertent removal of the parathyroid glands. Other potential complications include laryngeal paralysis due to nerve damage and hypothyroidism (insufficient T-4 hormone production).

  Radioactive iodine therapy is a straightforward, safe and proven method for eliminating hyperthyroidism. However, it costs about $1,000. Radioactive iodine is administered via injection, which quickly becomes concentrated in the thyroid gland itself. The out-of-control cells are then destroyed. The parathyroid glands are unaffected. The cat remains with the vet until dangerous radioactive emissions subside, often for two days to a week.