Hyperthyroidism is the most common endocrine system disorder in cats.
It is seen most frequently in cats with an average age of 13 years. This can be caused most frequently by a benign tumor on one or both of the lobes of the gland. Because this condition, when left untreated, can cause severe damage to a cat's metabolism and heart, early detection, as in most disease processes, is crucial. The onset of symptoms of hyperthyroidism can be slow and gradual, thus more difficult for the owner to detect until the disease has progressed. Because the metabolism has been accelerated, weight loss is quite common even though the cat displays a ravenous appetite.