Thyroid Newsmakers

One last "tail"

Thyroid disease in humans is the primary focus of this book. However, some readers, especially pet owners, might find it interesting that animals, particularly cats and dogs, develop thyroid disease, too. Cats are more likely to develop hyperthyroidism, and dogs are more prone to develop hypothyroidism.

According to Dr. Brian Poteet, a veterinary radiologist, the cause of hyperthyroidism in cats is unknown. However, the typical hyper­thyroid cat is an older cat (fourteen years or older) with a toxic multinodular goiter. Symptoms include weight loss of up to half their body weight in two to three months, ravenous appetite, intermittent vomiting and diarrhea, increased urination, restlessness, dull coat, increased shedding, and patchy loss of hair. Approximately 30% of hyperthyroid cats become apathetic and do not want to eat.

Owners sometimes do not notice any changes in their cats, and, if they do, they may attribute the cat's symptoms to advancing age. There­fore, many cats are diagnosed only when they have a geriatric feline profile, routine blood work that is done annually in cats twelve years and older. Although measurement of T 4 is part of this profile, there is no TSH for cats.

To confirm a diagnosis of feline hyperthyroidism, a veterinarian will usually order a thyroid scan. Thyroid images with radioactive materials for cats are the same as thyroid scans for humans with one exception. Since cats are unlikely to lie still while the gamma camera scans them, they are put under general anesthesia for about ten minutes.

The treatment options for feline hyperthyroidism are the same as for humans-radioactive iodine, anti­thyroid drugs, and surgery. Treating cats for hyperthyroidism can be costly, but it can be done effectively, especially when radioactive iodine treatment is chosen. According to Dr. Poteet, "the success rate of radiaoctive iodine treatment is close to 100%." He also pointed out that unlike humans, "Cats almost never become hypothy­roid after treatment."