Feline Hypothyroidism FAQs ~ Pawprints and Purrs, Inc.

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Any health care links located here are NOT to replace a veterinarian visit; please take your cat to a vet immediately at any sign of odd behavior or any symptoms of illness or injury. Call your vet and describe your cat's symptoms with any of your concerns about the cat's well-being. Your veterinarian may discover changes in your cat's health that you have overlooked. It is always better to err on the side of caution.

Hypothyroidism

The thyroid gland consists of two lobes located near the larynx (Adam's apple) in the cat's neck along side the windpipe. The thyroid gland combines the amino acid tyrosine and iodine to manufacture the thyroid hormone. The pituitary gland exerts control over the thyroid gland. TSH from the pituitary stimulates the thyroid gland to produce its hormone, thyroxine. Thyroxine is the hormone that controls metabolic and activity levels. The thyroid gland also secretes another hormone, calcitonin, which is necessary for proper calcium metalbolism.

In layman terms, the above paragraph simply means the thyroid gland controls the cat's metabolism. The thyroid gland produces the thyroid hormones that are critical to maintaining the cat’s normal metabolic rate. This is the speed at which the body converts nutrient energy into energy fueling the body. If the thyroid gland degenerates or becomes inflamed, it can no longer produce sufficient quantities of hormones. As a result, cells don’t convert the nutritional energy it needs into biologically usable fuel as fast as usual.

Feline hypothyroidism is rare in cats, though hyperthyroidism is much more common. Hypothyroidism occurs when there is too little thyroid hormone in the cat's blood - an underactive thyroid gland. If thyroid hormones are given to test whether it is the problem, the cat may show hair growth even though hypothyroidism may not be the problem. This is because the hormones generally stimulates the body. If it is overactive, the metabolism speeds up and is called hyperthyroidism.

Elderly cats (after age 10) often become overweight without a change in their regular diet. Unexplained weight gain can be a sign of a medical problem such as hypothyroidism. Hypothyroidism isn’t life threatening, but it does diminish quality of life. Once diagnosed, however, the disorder is relatively easy to treat.

The cat will gain weight because of increased appetite, increased thirst, excessively groom himself (often to the point of pulling his fur out in clumps), and his coat may be extremely dry, itchy, and flakey with excessive dander. The coat may look dull and feel greasy with frequent matting of the hair. The cat may become lethargic and mentally dull. Hair-producing cells slow down, so there is less hair growth and more hair loss. Skin producing cells slow down, so there is more wrinkling and seborrhea (dandruff). Also, the cat may suffer an increased propensity to joint disease, especially ligament damage.The cat may often soil or urinate indoors. Don't assume that your cat is being lazy or obstinate if he fails to use his litter box; it may be a sign of an underlying health or behavior problem. Punishing your cat will have no effect on this behavior except perhaps to make it worse.

Veterinarians will order a blood chemistry panel as well as a thyroid hormone (T4 test) level in cats suspected of being affected by this disease. It is important to evaluate the health of the other major organs, including the kidneys and heart in these patients.

Veterinarians treat hypothyroidism by prescribing supplemental thyroid hormone, which the guardian must administer to the cat orally once or twice a day. These medications are initially prescribed according to the cat's weight. Your veterinarian will closely monitor your cat in the initial stage of treatment by retesting the thyroid level (T4) to make sure the cat is getting the appropriate dosage. Too little hormone won’t alleviate the signs, while too much can cause a cat to develop hyperthyroidism (excessive thyroid hormone causing agitated and overactive behavior, weight loss, excessive drinking, and excessive urination). Once thyroid hormone levels have stabilized within a normal range, your veterinarian will likely check the levels every six months to year.

Once treatment begins, most hypothyroid cats are increasingly active and show fewer behavior problems within a week. Hair growth typically accelerates in about a week, too, although bare spots may take months to fully grow in. Most cats begin to lose excess weight within 2-4 weeks of starting treatment.

Some veterinarians also suspect a link between behavior problems and hypothyroidism. Increased aggression is the most commonly suspected behavior change, but some veterinarians speculate that a few hypothyroid cats may develop anxiety related or compulsive behaviors. If your pet develops a sudden behavioral change, have your cat's thyroid status examined.

While all guardians should be on the lookout for changes in their cat’s appearance or behavior that suggest hypothyroidism, guardians of middle-aged and elderly cats should be especially watchful. If you notice any signs, consult your veterinarian. By simply taking a sample of your cat’s blood, it can be determined if the cat has hypothyroidism. Many veterinarians are recommending testing as part of the senior cat health examinations.

If you suspect hypothyroidism, consult your veterinarian. The treatment for hypothyroidism is straightforward, and the medication is relatively inexpensive.

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Resource Reference:
The Cat Owner's Health Manual, Stillman, John D., DVM