Cat’s weight loss a sign of thyroid trouble

Dear Dr. John,

I had two 17-year-old sister cats until one died two months ago. The remaining sister has been losing weight for a few months. I finally had my vet look at her. They took bloodwork, and the diagnosis came back as her being hyperthyroid. I was told that it was consistent with her weight loss. I was given a few options on how to treat her and I opted for using a transdermal paste because one option was too expensive and the other meant giving her pills or oral liquids and she is difficult to handle or medicate. Should this option work and what is your experience in using such a form of treatment?  B.L.

Dear B.L.,

I am sorry for your loss of one of the cats but luckily you have a diagnosis on your remaining cat that will allow you to have her for a few years to come. Cats with hyperthyroidism typically present with weight loss with a simultaneous ravenous appetite and are often found to have rapid heart rates. The excess thyroid hormone production puts their metabolism in high gear.

In the past, surgical removal of the thyroid gland was done but for the most part that is no longer done. Another option was a radioactive iodine treatment of I-131 that typically costs over $1,500. There is a dietary means of treatment with a prescription diet called Hill’s y/d and some have had success using that. Going forward, you should avoid feeding her fish foods and canned foods are better for her in providing more moisture to replace fluids lost with increased urine production as well as providing the high protein and high calorie levels that she needs. The drug of choice to treat hyperthyroidism is methimazole, either given in pill form, compounded into tuna or chicken flavored liquid form, or transdermal pastes which can be rubbed on the inside of the ears. Since you just started treatment, a follow up blood test should be done in 1-2 months to make sure that she is being dosed appropriately. After that and depending on how she is doing, checkups with bloods should be done every 6 or 12 months.

Dr. John de Jong owns and operates the Boston Mobile Veterinary Clinic. He can be reached at 781-899-9994.