Just Ask the Expert: Managing a cat with concurrent hyperthyroidism and diabetes

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Q. How do you manage a cat with hyperthyroidism that is receiving Prescription Diet y/d Feline Thyroid Health (Hill's Pet Nutrition) and is also diabetic?

A. How I would manage this case depends on which of two scenarios we are evaluating.

Dr. David S. Bruyette

In the first scenario, if the cat has recently become a diabetic and its hyperthyroidism is being well-controlled clinically and biochemically, I would have the patient stay on Prescription Diet y/d (preferably canned). I would initiate insulin therapy with glargine at 0.5 U b.i.d. along with the diet and would monitor the cat weekly for remission. If the diabetes goes into remission, I would have the owners continue to monitor the diabetes with fasting and four-hour postprandial blood glucose concentration measurements on a monthly basis. If the diabetes does not go into remission after the cat has received glargine and the canned Prescription Diet y/d for two months, I would switch the cat to a higher protein, lower carbohydrate diet and recommend that we manage the hyperthyroidism with either methimazole or radioactive iodine therapy, depending on the owners' preference.

In the second scenario, if this is a diabetic cat that has been well-controlled on insulin and its current diet for more than six months and has then become hyperthyroid, I would switch the cat to canned Prescription Diet y/d. In a cat that has been diabetic for more than six months, there is little chance that the cat will attain remission, so the diet is less important in this case as we will be able to manage the cat's blood glucose concentration with insulin. So if we can continue to control the diabetes with the current insulin protocol and also successfully manage the hyperthyroidism with Prescription Diet y/d, then we have done well by the patient and client.

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David S. Bruyette, DVM, DACVIM

VCA West Los Angeles Animal Hospital

1818 S. Sepulveda Blvd.

Los Angeles, CA 90025

Veterinary Diagnostic Investigation and Consultation

26205 Fairside Road

Malibu, CA 90256