Integrative Pet Vet: Thyroid disease epidemic in cats
Integrative Pet Vet
The thyroid gland is the most commonly diseased gland in cats. It is almost always overactive (hyper-), so the condition has been referred to as hyperthyroidism. Unfortunately, hyperthyroidism in cats is so common today that it is being described as an epidemic.
Feline hyperthyroidism was first reported in 1979. Prior to that, enlarged or abnormal thyroid glands and signs of thyroid illness were rarely observed. Since then, there has been a steady and dramatic increase in the number of cats affected. Along with this increase in incidence, it has become a major cause of death in cats.
In spite of numerous theories for the cause of hyperthyroidism in cats, sadly, the cause is unknown and there is no clear recommendation for prevention. The two main areas of focus are nutritional factors including excesses or deficiencies in cat food and thyroid-disrupting compounds present in the environment, drinking water or food.
In more than 95 percent of the hyperthyroid cats, the glands have benign (not cancer) changes and are overproducing hormones. In 70 percent of affected cats, both glands are involved. Less than 5 percent of hyperthyroid cats have cancer in the thyroid glands. The average age of affected cats is 13 years, but 5 percent are younger than 10.
The thyroid is a paired hormone-producing gland that is located on each side of the trachea near the throat. Hormones produced by the thyroid, mainly T4 and T3, affect nearly all organs in the body. As a result, when elevated, they can cause other problems including an elevated heart rate and heart enlargement. Over time this can lead to compromised heart function and even heart failure. Elevated blood pressure can also occur. This hypertension can cause damage to the eyes, kidneys, brain, and heart.
Indications that a cat is affected by hyperthyroidism can be mild initially and progress to severe over time. These signs include weight loss, increased appetite, increased thirst, urination, hyperactivity, diarrhea and vomiting. Often the hair coat is matted and unkempt. The heart rate may be increased and the cat may be depressed or have aggressive behavior. Some cats are restless, mentally confused and may yowl at night.
Diagnosis of hyperthyroidism typically involves measurement of the T4 hormone in the blood. However, since there are other diseases with the same signs, such as diabetes, chronic kidney failure and intestinal disease, it is valuable to perform a complete blood count, serum chemistry profile, and urinalysis. A thorough physical exam is important along with palpation for enlarged thyroid glands.
While most cats with hyperthyroidism have an elevated T4, 2-10 percent will have a normal T4, making the diagnosis more complicated. These normal T4 values in a hyperthyroid cat may be the result of mild hyperthyroidism or a concurrent illness that is suppressing the T4 levels so that they appear normal.
There are basically three accepted therapies for hyperthyroidism: oral treatment with methimazole, surgery to remove the thyroid glands or treatment with radioactive iodine. While radioactive iodine is currently considered the treatment of choice, each approach has advantages and disadvantages. These should be discussed with your veterinarian so that the appropriate therapy can be planned. The pet food manufacturer Hills has developed a Prescription Diet, y/d that has been beneficial for some cats with hyperthyroidism. Regardless of the therapy chosen, once the thyroid hormones are returned to a normal range, underlying kidney or heart disease may become apparent. The high blood flow caused by the hyperthyroidism, can mask these underlying problems.
From an integrative perspective, the organs that are stressed by the hyperthyroidism should be supported using appropriate nutritional supplements and herbs. These organs include the kidneys, heart and liver. If high blood pressure is present, supportive care for the eyes may also be beneficial in addition to controlling the blood pressure.
If you have questions about hyperthyroidism or suspect your cat may be hyperthyroid, contact your veterinarian for further information.
Ron Carsten, DVM, PhD, CVA, CCRT was one of the first veterinarians in Colorado to use the integrative approach, has lectured widely to veterinarians, and has been a pioneer in the therapeutic use of food concentrates. He has a Doctor of Veterinary Medicine, a Ph.D. in Cell and Molecular Biology, and is a Certified Veterinary Acupuncturist and Canine Rehabilitation Therapist. He practices integrative veterinary medicine in Glenwood Springs.
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