Cat hyperthyroidism is a common disease among senior cats. This occurs when one or both of the cat's thyroid glands (located in the cat's neck) produce hormones affecting general metabolism and organ functions.
   When too many hormones are produced by a cat's thyroid glands cats can have ravenous appetites but loose weight at the same time. Hyperthyroidism can cause cats to have rapid or irregular heartbeats. It can also cause diarrhea and vomiting.
   Veterinarians usually diagnose cat hyperthyroidism by taking a blood test. Treatment of cat hyperthyroidism can include prescription medicine or actually removing the overactive tissue by surgery or radiation.