Hyperthyroidism is the most common hormonal abnormality affecting cats. Most frequently afflicting cats eight years of age or older, it is a multisystemic metabolic disorder caused by high circulating levels of thyroid hormones. As a result, the body's systems begin working at an accelerated rate that can cause them to function abnormally. Most often, cats that develop this condition have hyperfunctional thyroid gland nodules. In rare cases, malignant thyroid tumors can lead to hyperthyroidism.
The elevated levels of thyroid hormones associated with hyperthyroidism cause many of the body's functions to run much faster than normal. Thyroid hormones affect the musculoskeletal, cardiovascular, gastrointestinal, liver, urinary, nervous, and behavioral systems. Common complications resulting from hyperthyroidism include heart muscle enlargement, high blood pressure, kidney function impairment, and intestinal problems.
