Hyperthyroidism is a disease of middle-aged to older cats.  It results when excess thyroid hormone is produced by a thyroid tumor (usually benign).  The high hormone levels increase the body’s metabolic rate dramatically and create extra work for all the body organ system.  Increased appetite, thirst or urination, weight loss, vomiting, diarrhea or irritability are some of the signs commonly seen.  Heart failure, seen as increased respiratory effort or rate, depression, or loss of appetite, can occur due to the extra work.  Liver disease, seen as jaundice, loss of appetite, depression or vomiting, can also develop.  While this illness can cause serious problems, proper timely treatment can be very effective in controlling the disease.

Treatment consists of controlling the thyroid levels.  Initially, oral medication is used.  Side effects of the medications occur occasionally and can include loss of appetite, depression, blood disorders and liver insult.  Development of these side effects may necessitate dosage reduction or alternative treatment.  After the thyroid level is reduced with medication, surgery or radiation can be used to “cure” the problem and obviate the need for further Tapazole.  The abnormal thyroid gland may be identified and destroyed using radiation treatment.  This is theoretically an ideal treatment as only the abnormal tissue is destroyed.  The drawbacks include cost and the need for a hospital stay.  Surgical removal of the affected gland is another option.  In most cases only one side of the gland is affected.  This can be identified during surgery and only the affected side is removed, leaving some healthy tissue.  In some unusual cases, both sides are affected or the patient has previously had one side removed and the disease has recurred in the remaining gland.  If no healthy tissue is left after surgery, lifelong thyroid and calcium supplementation may be necessary.

In some patients, heart disease, liver disease, or significant debilitation are present and additional therapy is required.  These problems will discussed on an individual basis.  Once your pet is home on medication, periodic rechecks are needed to evaluate the efficacy of the drug and to check for the development of side effects.