How is Feline Hyperthyroidism Diagnosed and Treated?

Hyperthyroidism is the overproduction of thyroid hormone by the thyroid glands. Hyperthyroidism occurs most commonly in older cats and is rare in dogs.

The average age of cats with hyperthyroidism is 13 years of age; only about 5 % of hyperthyroid cats are younger than 10 years of age. There are 2 thyroid glands located in the neck. One or both of the glands can enlarge and overproduce thyroid hormone. Involvement of both glands is more common than involvement of one gland. Thyroid hormone affects the function of most organs in the body, so the signs of hyperthyroidism are quite variable.

Signs of hyperthyroidism can include:

weight loss
increased appetite
increased activity and restlessness
aggressive or “cranky” behavior
a poor hair coat
a fast heart rate
increased water drinking
increased urination
periodic vomiting
increased amount of stool or diarrhea
occasionally difficulty breathing
occasionally weakness
occasionally depression

A diagnosis of hyperthyroidism is made when the level of thyroid hormone is increased in the blood. Most hyperthyroid cats have very high levels of hormone but some cats will have signs of hyperthyroidism with normal or only slightly increased levels of thyroid hormone. Thyroid hormone levels can vary over time so it may be necessary to check blood levels several times or perform a different test called a T3 suppression test. The enlarged thyroid gland(s) can often be felt in the neck. If the diagnosis is not obvious by blood tests, a nuclear medicine scan of the thyroid glands can be performed at certain specialty veterinary practices. The cat is given a small dose of a radioactive compound that travels by the blood to the thyroid glands. Hyperactive thyroid glands accumulate more of the compound than normal glands. After this test the cat must be hospitalized for a few days while it clears the radioactive compound from its body.

NB: As with most other potentially serious diseases, homeopathic treatment of these patients is best accomplished early in the course of the illness. Ablation of the thyroid gland with radioactive iodine is the current treatment of choice. In my experience, this increases the difficulty in management of these patients. If intervention other than homeoopathy is needed, I recommend palliation with methimazole (Tapazole®).–Dr. Jeff

Please note: The information provided here is intended to supplement the recommendations of your veterinarian. Do not disregard veterinary advice or delay treatment based on information on this site. Nothing can replace a complete history and physical examination performed by your veterinarian. -Dr. Jeff