Treating Hyperthyroidism in Cats

By none

Dear Dr. Shawn:

My cat was recently diagnosed with hyperthyroidism. Her doctor recommended radioactive iodine therapy, but this sounds drastic. What do you recommend for your feline patients with this problem?


Hyperthyroidism occurs when the cat’s thyroid gland produces excessive amounts of thyroid hormone. This occurs due to enlargement of the gland, formation of benign thyroid tumors, or very rarely as the result of a malignant thyroid tumor. (Unlike cats that develop hyperthyroidism, dogs develop the opposite problem—too little thyroid hormone, or hypothyroidism, due to immune destruction of the thyroid gland.)

Clinical signs of hyperthyroidism include weight loss despite a ravenous appetite and hyperactivity; though it's rare, some cats develop the opposite signs (lethargy and lack of appetite).

Left untreated, hyperthyroidism can result in heart failure and death. Diagnosis is confirmed by finding an elevated T4 value on a blood test. While natural therapies such as administration of herbs may help in mild cases, I usually recommend more definitive therapy for my more severe cases.

Radioactive iodine sounds risky but is actually the safest therapy. It is also the only therapy that can cure the disease. The main drawback is cost (usually about $1,000). However, administration of medication—a drug called methimazole—actually costs more for most cats, as blood must be drawn frequently (every 3 to 6 months) for the life of the cat to make sure the drug does not cause side effects. Side effects of the drugs can include liver disease or bone marrow disease.

Some cats cannot be treated with radioactive iodine; most commonly these cats also have kidney disease, which may become worse with iodine therapy. Surgery can be done to remove the affected thyroid gland, but this has fallen out of favor as iodine or methimazole is much easier on the pet.

In addition to treatment with either iodine or methimazole, a general holistic protocol to ensure health of the pet is needed. This can include a natural diet and supplements for the thyroid, heart, and liver; these organs are secondarily affected by excessive thyroid hormone levels. A health maintenance formula to support the immune and digestive systems is also recommended.

Finally, I stop vaccinating these older cats with hyperthyroidism as I don’t want to upset their systems once the disease is under control.

Fortunately, hyperthyroidism is one of the few diseases of older cats that we can not only treat but actually cure. Regular veterinary visits can allow early diagnosis, treatment, and cure.

Dr. Shawn

By none| December 29, 2008
Categories:  Nest

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