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The Ups And Downs Of Thyroid Disease

Every year Veterinary Pet Insurance publishes the top 10 most common medical diseases they received claims for from the previous year. This year thyroid disease was listed in the top 10 for both dogs and cats. These statistics certainly ring true from my experience, I deal with thyroid disease daily. As a vet student, I was taught the saying, “Cats are not small dogs.” Meaning, cats get different diseases and respond to medications differently. This is especially true when it comes to thyroid disease. In fact, cats are completely opposite. Dogs develop underactive thyroid function or hypothyroidism. Cats, however, develop overactive thyroid glands, or hyperthyroidism.

Feline hyperthyroidism is a fairly common disease of older cats- Number 4 on the top 10 list! The thyroid gland enlarges and overproduces thyroid hormone and is a benign change (not cancerous) 98% of the time. The specific cause of the thyroid enlargement isn’t clear, there is thought there might be some relation to genetic predisposition and iodine levels in the diet. The typical cat with hyperthyroidism averages 12 years old and there is no increase in disease in one sex over the other. The cat’s symptoms include weight loss in spite of an increased and perhaps ravenous appetite. They often are drinking and urinating more. On exam, we can frequently feel enlarged thyroid glands in the neck and many cats will also have a fast heart rate. Increased thyroid hormone increases a cat’s metabolic rate; this causes the heart to pump faster and stronger. Many cats with hyperthyroidism also have hypertension (high blood pressure.) Stress on the heart and hypertension can cause serious complications. These problems are potentially reversible with treatment. It takes simple lab work to diagnose hyperthyroidism. Hyperthyroidism responds very nicely to therapy, and there are multiple treatment options. Methimazole is an oral medication that blocks the production of excess thyroid hormone. This is not a cure and requires lifelong medication. It is effective and has a low risk of side effects, but the major downside is trying to get the medication into your cat once to twice daily. A onetime treatment with radioactive iodine (I131) is less work for the owner, but the initial cost can be a challenge. Radioactive iodine therapy destroys the thyroid gland tissue without endangering other tissues. A brand new treatment option is a prescription low iodine diet which shows some promise for controlling hyperthyroid disease. Because it is brand new, I would say we aren’t sure exactly how well it will work. The bottom line for cats with thyroid disease is that the right treatment is the one that will work best for the owner’s situation. It’s our job to help you make the best decision.

Hypothyroidism (underactive thyroid function) is number 10 on the top 10 diseases reported in dogs. The majority of thyroid disease in dogs is caused by the immune system attacking the gland or the thyroid gland being replaced with fat tissue. Symptoms include weight gain in face of normal appetite, decreased activity, heat seeking (gets cold easily), thinning hair, increased pigmentation of the skin, ear infections and failure of hair growing back after being clipped. Another classic symptom is a “tragic facial expression” secondary to thickening of the facial skin. Again, this is a disease diagnosed by blood testing. Sometimes blood testing isn’t straightforward and additional blood testing is necessary. Once diagnosed, the treatment is much simpler than cats. Hypothyroid dogs need thyroid supplement medication. And for most dogs, treating them is easier. Most dogs love getting pills, either with peanut butter, cream cheese or a pill pocket makes it a great treat.

Follow up testing and lifelong therapy is necessary when on oral medication for both cats and dogs. Treatment makes a great difference in the pet’s life, improving the quality of life and for cats, prolongs their lives. Thyroid screening is often part of wellness blood testing, often discussed during annual exams. Remember if you have any questions feel free to contact me or visit our Facebook page.