Hyperthyroidism is the most common hormonal disease in cats. It is due to the enlargement of one, or both, of the thyroid glands and subsequent over-production of thyroid hormone. It affects both male and female cats of middle-to-older age.

Thyroid hormone plays an important role in metabolic regulation and can negatively impact multiple organ systems if left untreated. In particular, the heart and kidneys can experience significant adverse effects when exposed to elevated levels of thyroid hormone for long periods of time.



Hyperthyroidism can be relatively easily diagnosed with a blood test for thyroid hormone. However, as the symptoms of thyroid disease mimic those of other disease processes, your veterinarian will likely recommend:


The goal of treatment is to reduce the amount of circulating thyroid hormone. This can be achieved with a medication, methimazole, or by destroying part of the overactive thyroid gland(s) with radioactive iodine therapy. Your veterinarian can best counsel you on which option will be best for you and your pet.