Hyperthyroid Disease in Cats

Hyperthyroid disease is the most common endocrine disease seen in older cats. Fortunately, it can be diagnosed with routine blood work and it is a manageable disease. Hyperthyroid cats tend to display certain tell-tale warning signs that they may be affected by the disease. In the following article, I will discuss the signs you may notice at home as well as how to diagnose and treat the disease.

Hyperthyroid cats tend to have a ravenous appetite. Despite this, they continue to lose weight. If it seems like you are filling the food bowl more often than in the past but your cat is getting thinner, they may have hyperthyroid disease. In addition, cats are fastidiously clean creatures. In contrast, hyperthyroid cats may have unkempt hair coats. Hyperthyroid cats also tend to vomit more frequently and may eliminate outside of the Litterbox. Finally, some hyperthyroid cats will be more vocal, particularly at night.

If your cat is getting older and displaying all or even some of those signs, testing and treatment is imperative. If left untreated, hyperthyroid disease is fatal. Treatment can also help ameliorate clinical signs you are noticing at home. To diagnose hyperthyroid disease, routine blood work that looks at levels of thyroid hormone in the blood (T4) will tell your veterinarian if your cat has the disease. Hyperthyroid cats will have elevated T4 levels.

There are many treatment options for hyperthyroid disease. The most common medication dispensed is called Methimazole and it comes as a liquid or a tablet. Methimazole is a drug which helps prevent the thyroid gland from overproducing thyroid hormones. Most cats are started on an initial dose and blood work is re-checked one month later. Since each cat will respond to the medication differently, recheck blood work can help your veterinarian make adjustments to your cat’s dose. In addition, monitoring of weight changes, appetite, and energy level is recommended.

Some cats will just not tolerate being given a pill or a liquid twice daily (you know if you have one of these cats). For these patients, other treatment options are available. There is a prescription diet that contains no iodine (Y/D) and may be used as a treatment for hyperthyroid disease. Cats on the Y/D diet cannot eat anything else and it’s imperative that cats who do not have the disease do not eat a strictly iodine-free diet. Additional treatments include a paste which is applied to the inside ear flap (transdermal) and even radiation therapy to the thyroid gland. Most cats who undergo radiation therapy will no longer require daily treatment but special care must be given to handling their litter for several weeks after the treatment.

Untreated hyperthyroid disease will ultimately cause heart disease and cardiac failure. For this reason, it is important that all cats who develop the disease be diagnosed and managed. This is also a key reason for having your senior cat’s blood values checked routinely once a year. If you suspect your cat has hyperthyroid disease, I recommend calling a member of our Veterinary Hospital who can help schedule an appointment for your cat to be evaluated by a veterinarian and tested for hyperthyroid disease. With a few blood tests and one of many available treatment options, hyperthyroid cats can continue to live long and happy lives.

Jeffrey Stupine VMD

Medical Director

World of Animals Veterinary Hospitals