New Diet for Hyperthyroid Cats

Pet Tales

by Barry B. Burtis D.V.M.


Maisy is a 17 year old silver grey and white domestic short-haired cat. She had enjoyed good health and had not been seen by a veterinarian for several years before her visit to an animal hospital recently. Her owner was concerned that she might have a mouth problem. She had lost some weight and now only weighed 2.5 kg (5.5 lbs). Her appetite had waned over the last few months and she was now reluctant to eat any dry food. A check-up, given by her examining veterinarian determined that indeed Maisy did have mild dental disease. However, in order to be sure it would be safe to address those issues and to be sure there were no other complicating health concerns, it was recommended some blood and urine tests be performed. The results of those tests showed that Maisy, with one exception, had essentially normal findings for a cat of her age. She had a mildly elevated thyroid hormone level that suggested she did have  hyperthyroidism. It was recommended to Maisy's owner that this problem should be addressed first before treating her dental problems.


Hyperthyroidism is a disease that often affects cats. It is the most common hormonal disease in cats. Untreated hyperthyroidism can lead to congestive heart failure, intractable diarrhea, kidney damage, retinal detachment and death. Until recently there have been only three ways to treat the disease. There are antithyroid drugs that can be given to counter-act the harmful effect of increased thyroid activity. These medications need to be given by mouth daily and are not without potential side effects. The surgical option for treatment of hyperthyroidism is to perform a thyroidectomy, removal of the thyroid gland. Finally, the best, but also the most expensive treatment, is to administer radioiodine therapy. Now, for cats like Maisy, another treatment method can be considered.


Hill's Pet Nutrition now produces a food, Prescription Diet y/d Feline Thyroid Health, that may transform the management of feline hyperthyroidism. The food comes in both dry and wet formulations. It has been 10 years in development and during that time the special diet has been used to manage 150 hyperthyroid cats, says S. Dru Forrester, DVM, MS, Dipl.ACVIM, director of scientific and technical communication at Hill's Pet Nutrition. The daily nutrition method of managing feline hyperthyroidism works by limiting dietary iodine intake and reducing thyroid hormone production.


It is important that a cat with hyperthyroidism being treated with Prescription Diet y/d, eat this food exclusively. The patient must be willing to transition to the new food. There can be no other treats or people food snacks given. It might be more difficult to achieve this requirement if the cat lives in a multi-cat household, where other foods are available. It is also best if, as with Maisy, the cat has no other diseases or health issues. The taste and texture of the diet food seems to be no problem and the new food seems to be well accepted by cats. It is, of course, a balanced and nutritionally complete diet that meets all the other nutritional needs for an adult cat.


Meanwhile Maisy has changed her diet and is doing well with it. In a few weeks she will have some repeat blood tests done to check her thyroid levels. Her weight now should stabilize. Then Maisy can plan for the dental care that will improve her quality of life and allow her to enjoy her golden years. Ask your veterinarian if you have questions about feline hyperthyroidism and Prescription Diet y/d Feline. Barry Burtis is a local companion animal veterinarian. Past Pet Tales can be found at www.baycitiesanimalhospital.ca.