Q. What happens to a cat with hyperthyroidism?

Elaine Wexler-Mitchell, D.V.M., says: Hyperthyroid cats produce too much T4, the active hormonal product of the thyroid gland. Thyroid hormone does not have one specific function but it interacts with other hormones and organs to regulate general metabolism. When cats have excessive levels of T4, they tend to have increased heart rates, act more restless and hyper, and lose weight. They usually have good or increased appetites and occasionally experience vomiting or diarrhea. Uncontrolled thyroid disease leads to high blood pressure (hypertension) and heart disease.

Hyperthyroidism is typically found in cats nine years and older. Your veterinarian can diagnose the disease through a blood test or a thyroid scan. Cats who have clinical signs consistent with the disease and normal T4 levels need to have an additional test called T4 by equilibrium dialysis performed. Hyperthyroidism is one of the most treatable and even curable diseases in older cats. There are three treatment options: long-term medication with methimazole given twice daily, surgical removal of the glands, or selective destruction of the overactive tissue with a special form of radiation called I-131. Cost, overall patient condition, ease of medicating, and owner preference are all factors in determining which treatment option to pursue.

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