Hyperthyroidism is when the thyroid gland produces an excessive amount of thyroid hormone.
Diagnosis is made on the basis of clinical signs and history, palpation and blood tests. The thyroid gland regulates many organ systems in the body, so when it begins to produce too much hormone, multiple clinical signs can develop. If the hyperthyroidism is not treated, the cardiac disease that develops can result in death. Since the clinical signs are not specific for hyperthyroidism, a blood test is needed to confirm the presence of elevated T4 hormonal blood levels. Most cats that are affected are middle-aged and older and it is the most common endocrine disease diagnosed in this age bracket.