Feline-Hyperthyroidism

Questions and Answers:

Feline Hyperthyroidism

Q: What is hyperthyroidism?

The thyroid gland is a small gland located on either side of a cat’s trachea. It produces thyroid hormones to regulate metabolism and help organ function. In hyperthyroidism, the gland produces excessive hormones.

Q: How does hyperthyroidism develop?

The excessive hormone comes from a tumor, called an adenoma, which forms on the thyroid gland.

Q: What are symptoms of hyperthyroidism?

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Weight loss

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Increased appetite without weight gain

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Ravenous appetite or demanding food

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Increased thirst

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Increased urination

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Vomiting

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Diarrhea

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Vocalization

Q: How is hyperthyroidism diagnosed?

It is usually diagnosed with a blood test for thyroxine (T4). Sometimes a more sensitive blood test may be required, thyroxine by equilibrium dialysis (T4-ED). High T4 or T4-ED levels are indicative of hyperthyroidism. Remember that your veterinarian may also want to get other diagnostics to look for health issues associated with hyperthyroidism.

Q: What are disease conditions often associated with hyperthyroidism?

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Hypertension

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Kidney disease

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Retinal detachment

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Hypertrophic cardiomyopathy

Q: How common is hyperthyroidism in cats?

It is one of the most significant endocrine diseases affecting older cats today.

Q: What are the treatment options for hyperthyroidism?

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Surgical removal (controversial)

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Suppressive (anti-thyroid) medications

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Radioactive iodine treatment

Q: What suppressive medication is used to treat hyperthyroidism?

The drug methimazole (Tapazole) is used as an anti-thyroid drug. It is inexpensive and non-invasive. It is usually the owner’s first choice for treatment. It does not cure the hyperthyroidism. It is a medication that has to be continued for life.

Q: What is radioactive iodine treatment?

This is a treatment which will resolve the hyperthyroid condition. The cat is injected with one-time shot of iodine I-131. It goes to the thyroid and destroys the part that is not functioning properly. The healthy thyroid tissue remains undamaged. The draw back to this treatment is that it can be costly and it has to be administered by special licensed veterinarian. The cat becomes radioactive for about one week and must stay isolated in a special facility.