HYPERTHYROIDISM IN CATS

Hyperthyroidism is a common multisystemic disease of older cats. The disease is most often caused by a thyroid gland adenoma, or hyperplasia, that produces excessive amounts of thyroid hormones. The most common clinical signs are weight loss, hyperexcitability, and increased appetite. Hyperthyroidism can cause hypertrophic cardiomyopathy, which is usually reversible after resolution of hyperthyroidism. Hyperthyroidism is often diagnosed by detecting increased serum levels of thyroxine (T4); in some hyperthyroid cats, however, the serum T4 level fluctuates into the normal range, thereby making diagnosis difficult. Hyperthyroidism can be treated with antithyroid drugs, surgery, or radioactive iodine therapy. Thyroidectomy is an effective, practical treatment. Hypoparathyroidism and subsequent hypocalcemia are potential postoperative complications if the function of at least one parathyroid gland is not preserved. Radioactive iodine therapy is recommended for cats with metastatic or intrathoracic disease.