Veterinarians tell us that hyperthyroidism is very common type of hormonal disorder seen in older cats, and even some middle aged cats. This occurs when the thyroid glands began producing large amounts of thyroid hormones. Often this happens as a result of a benign thyroid tumor (adenoma); however, vets do not know what causes the tumor to develop in cats.
For informational purposes, thyroid glands are paired glands located in the neck and they secrete thyroid hormone. Thyroid hormone is important because it controls metabolic rate of an animal. Cats with hyperthyroidism have an increased metabolic rate, and thus they tend to use up excessive amounts of energy within their bodies.
This means that your cat may be eating more and always hungry, but still seems to be losing weight. This is one of the most common clinical signs of hyperthyroidism. Some other signs may include a patchy hair coat and hyperactivity. The onset of this disease is usually very slow, and signs are usually not recognized until they are severe. Sometimes, the hyperthyroid state can exist for months to years before becoming severe enough for the owner to recognize the clinical signs.
Many times, a veterinarian can feel a nodule in your cat’s neck where the thyroid gland is located. This is usually indicates your cat has hyperthyroidism. The diagnosis can be confirmed by testing the T4 (thyroid hormone) levels in your cat’s blood.
If your cat is diagnosed with hyperthyroidism, there are a few treatment options: There is medical treatment, surgical removal of the thyroid, or radioactive iodine treatments.
With medical management, this consists of the administration of anti-thyroid hormone drugs. However, this will not cure the disease but will provide for long term control of the disorder. These drugs will probably have to be administered twice daily for the rest of your cat’s life.
With surgical thyroidectomy, this involves the removal of the affected parts of the thyroid glands, and this can result in a permanent cure–but there can be complications. As with any surgery, there is always a risk with anesthesia. Hyperthyroidism can recur if some of the remaining thyroid tissue becomes hyperactive. A common secondary complication of surgery is accidental removal of part or all of the parathyroid glands which are small glands sitting next to the thyroid glands; and this results in a hypo-parathyroid state. This can result in transient hypocalcemia that may need to be treated for a few weeks or months.
Radioactive iodine is the last treatment option. This works because the thyroid gland takes up the iodine whereas no other body tissue does this; and the iodine kills all of the affected thyroid tissue. All other body tissues are spared and this can be a cure as it does not have any major side effects for the cat. Note, however, this must be performed in a facility licensed to handle radioactive substances. A university teaching hospital is a common place to perform this. Also, an extended hospital stay for your cat is usually required. Most of the excess radioactive iodine is eliminated in the cat’s urine. The cat is kept in isolation until most of the radioactivity has been eliminated.
