Causes and Symptoms of Feline Hyperthyroidism

As I mentioned in the previous post on this subject, hyperthyroidism in cats has been associated with the feeding of a canned commercial diet. Although no one knows why the two are correlated, some postulate that allergies to additives may be to blame. Another theory is that multiple vaccinations over the course of a cat's lifetime may cause the immune system to either shut down or turn against the body itself. The one common thread here, of course, is the role of the immune system in this disease.

Thyroid hormones, mainly thyroxin, have a direct impact on body metabolism. When something causes the thyroid gland to overproduce this hormone, metabolism speeds up and does not modulate. Why does this happen? Often, a tumor growing on the gland will cause this, possibly as a result of suppressed immune function. Too little iodine in the diet can cause enlargement of the gland, hence hyperthyroidism. Richard Pitcairn, DVM, believes that the gland becomes hyperactive due to attack by the immune system brought about by over-vaccination.

The effects of this disease on a cat's health will be noticeable as the body reacts to the increased metabolic rate. The animal will lose weight despite a voracious appetite. Diarrhea, sometimes bloody, is almost always present, and vomiting is common. The fur will look dirty since over-active oil glands make the coat greasy. Increased thirst and urine output will also be present. Personality changes occur as well, such as nervousness, hyperactivity and constant crying for attention (and food). A higher body temperature may cause the animal to pant and/or look for cool places to stay.

As you can see, this disease causes a whole palette of other health problems. Since food is passing through the digestive tract too quickly to allow for adequate absorption of nutrients, the animal will eventually become nutritionally deficient. Another side effect of hyperthyroidism is high blood pressure, which in itself can cause many problems, not the least of which is heart disease.

Left unchecked, this disease will be fatal, possibly in a matter of weeks or months. What should you do if your cat starts exhibiting the above symptoms? Treatment options do exist, and I'll discuss some of them tomorrow.
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