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 which indicate that they may be affected by the disease. In the following article, I will discuss the symptoms you may notice at home and how to diagnose and treat the condition.

Hyperthyroid cats tend to have a ravenous appetite. Despite this, they continuously lose weight. If it seems like you are filling the food bowl more and more often than in the past, but your cat is getting thinner, they may have hyperthyroid disease. Furthermore, 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, especially during the night.

If your cat is getting older and displaying all or some of those signs, testing and treatment are imperative. When left untreated, hyperthyroid disease is fatal. Treatment can also alleviate the clinical signs you are noticing at home. To diagnose hyperthyroid disease, routine blood work that looks at thyroid hormone levels 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 distributed is called Methimazole, which comes as a liquid or a tablet. Methimazole helps prevent the thyroid gland from overproducing thyroid hormones. Most cats start on an initial dose, and blood work is reviewed one month later. Since each cat will respond to the medication differently, rechecking blood work can help your veterinarian make adjustments to your cat’s dose. Monitoring of weight changes, appetite, and energy levels is also recommended.

Some cats will not tolerate being given a pill or a liquid twice daily (you would 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, but cats who do not have the disease do not need a strictly iodine-free diet. Some additional treatments that may be considered include a paste 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 is required for handling their litter for several weeks after the treatment has concluded.

Cat Hyperthyroid Disease 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