Feline hyperthyroidism is a disorder of older cats caused by a benign adenoma tumor growing on the thyroid gland.
- Onset of this disorder can be gradual and may not be recognized until symptoms are far advanced. A cat with this disorder may have weight loss, increased appetite, increased thirst, increased urination, nervousness and vomiting. The cat should be taken to the veterinarian and the owner should ask for a complete blood panel, including a thyroid test. The blood panel will also rule out other disorders such as diabetes and kidney disease.
- Cats left untreated often die of heart failure, since the disease makes the heart beat faster and can cause a thickening of the heart wall. Fluid builds up in the chest and the cat begins wheezing and coughing. Treating the hyperthyroidism may resolve the heart issues, but the cat may also need heart medication until the heart is healthier.
- Treatment of the disorder depends on the cat. The preferred treatment is iodine radiotherapy for cats who are otherwise healthy. The cat is injected with radioactive iodine isotopes that hone in on the enlarged thyroid gland and destroy it. This resolves the problem completely. This method is very expensive, though, and requires at least a 72-hour hospitalization.
- Surgery that removes about three-fourths of the thyroid gland can also be done. Enough of the gland is left to produce the necessary hormones, but not enough to overproduce them. This is also done in relatively healthy cats. The disadvantages are that the cat may have too much thyroid removed, necessitating a treatment for low thyroid, or there may be some thyroid tissue elsewhere in the body that could overproduce the hormones.
- Oral medication is the third treatment of choice. This is used for older animals, those that might not survive surgery or have other health issues. Since the overproduction of the thyroid hormone increases the blood flow to the kidneys, enabling them to work better, the iodine treatment or surgery may aggravate kidney disease, and the cat may become ill again.
Oral medication enables a veterinarian to reduce the thyroid hormone to make the cat feel better, but keeps enough of the hormone in the cat's system to assist the kidneys. Most cats do tolerate the medication well in the long term, which makes it a desirable treatment.
- An owner should ask for a thyroid panel for cats over age 8 when the cat goes in for his yearly check-up. A careful owner will make note of any change in bladder or bowel habits, or in eating habits, and will seek treatment for his cat immediately.