DIETARY THERAPY FOR HYPERTHYROIDISM
As you may recall from earlier sections, thyroid hormone is made with iodine. It should not be too surprising that the production of excessive amounts of thyroid hormone requires excessive amounts of iodine. Since iodine comes from the diet, it turns out that it is possible to create a diet that is restricted enough in iodine to preclude production of excessive amounts of hormone yet not so restricted that an iodine deficiency results. Hills Pet Nutrition has developed such a diet and it has been available as an alternative to the more traditional therapies since mid-October 2011. An FAQ has been assembled and will be modified as information becomes available. The diet is called “Y/d” diet and is available in both dry and canned formulations.
HOW LONG DO YOU HAVE TO FEED THE DIET FOR THE CAT NOT TO BE HYPERTHYROID ANYMORE?
Several studies have been performed and hundreds of cats evaluated. Many cats will have normal thyroid levels in the first 2 months of diet use; however, full response can take up to 12 weeks. By 12 weeks on the diet, 90% will show normal thyroid levels. The diet is ineffective in approximately 10% of cats where it is used.
CAN THE CAT HAVE ANY TREATS WHILE ON Y/D DIET?
Unfortunately, there are no acceptable treats. Feeding ANYthing other than the therapeutic diet could interfere with effectiveness of treatment. Foods or treats meant for other pets in the home should be kept away from a cat on this form of therapy. It should also be noted that hyperthyroid cats who roam outside may be eating any number of things out in the world. It is unlikely that their diet can be controlled enough for this form of therapy to be effective. In fact, if the cat on Y/d diet is still hyperthyroid after 8 weeks, it can be assumed that the cat is finding another iodine source. The cat might simply be cheating on the diet, getting extra iodine in a medication or in drinking water, or even from the surface of a food bowl.
CAN OTHER CATS IN THE HOUSEHOLD EAT THIS DIET SAFELY?
CAN A CAT BECOME HYPOTHYROID ON THIS DIET?
None of the hyperthyroid cats tested become hypothyroid after eating this diet. In fact, hyperthyroid cats fed diets vastly more restrictive on iodine than this still did not become hypothyroid.
WHAT KIND OF FOLLOW-UP TESTING IS APPROPRIATE FOR A CAT ON THIS DIET?
Hills recommends taking a week to transition the cat from its normal food to Y/d diet, not because of the iodine issue but because it is always a good idea to avoid an abrupt food change. After the transition is complete, Hills recommends a thyroid level, kidney parameters, a recheck exam and a urine specific gravity (test for urine concentration) after 4 weeks and 8 weeks on Y/d diet. If the cat is still not showing a normal thyroid level in 8 weeks, it is worth going out to 12 weeks and evaluating one more time. After the cat has achieved a normal thyroid level, an exam and blood work should be performed every 6 months.
In cats with concurrent kidney disease, lab work is recommended after 2 weeks, 4 weeks, and 8 weeks on the diet and then every 3-4 months thereafter.
WHAT ABOUT SWITCHING A CAT ON METHIMAZOLE OVER TO THE DIET?
Hills recommends simply switching from medication to diet directly with no transitional period. Simply, discontinue the medication and start the diet.
Methimazole, surgery and radiotherapy are well-reviewed effective therapies for feline hyperthyroidism. Where this diet fits in this picture and whether it should replace traditional therapy or be considered an acceptable last resort remains to be seen over time.
Page posted: 10/15/2011