KINDNESS ANIMAL HOSPITAL

Iodine-131 Therapy

Feline Hyperthyroidism

Cats and people have a gland called the Thyroid gland which regulates the bodies metabolism.  The gland consists of two parts one located on each side of the neck.   Sometimes thyroid tissue can also be located near the chest and this is called ectopic thyroid tissue.  Feline Hyperthyroidism is a disease of the thyroid gland resulting in the excessive production of thyroid hormone (hence the term "Hyper" thyroidism).  It is the result of a tumor growing on the thyroid gland and in 98% of the cases the tumor is benign.  The excessive production of thyroid hormone speeds up the metabolism and causes a number of problems.  Some of the more common signs include behavior changes, weight loss, excessive eating, excessive drinking and urination, rapid heartbeat, shedding of fur and vomiting.  Prolonged Hyperthyroidism can cause kidney problems,  heart murmurs as well as irregular heart beats.  Gone untreated, the condition can result in kidney failure and heart damage and eventual death.  It most commonly occurs in older cats (cats greater than 8 years old). 

If your cat has been diagnosed with Feline Hyperthyroidism, there are three treatment options available and these are (1) medical therapy, (2) surgical removal of the thyroid gland and (3) radiation (I-131) therapy.  The radiation therapy is the most effective, safest and in the long run the least expensive option. 

I-131 Therapy

I-131 is a radioactive form of Iodine and is used to treat hyperthyroidism in both people and animals.  The treatment, in cats, consists of injecting a single dose of radioactive iodine into the cat.  When absorbed in the body, Iodine is concentrated in the thyroid gland and those cells that are most active (i.e. thyroid tumor cells) will absorb most of the radiodine.  Therefore, the radioactive iodine preferentially enters the tumor cells in the thyroid gland and the radioactivity kills these cells while doing very little damage to the normal thyroid cells.  Through normal bodily processes, the radioactive iodine is removed from the body and is lost in the urine and feces.  There is no anesthesia and the success rate is approximately 95%.  Bloodwork needs to be performed prior to treatment to rule out any other medical problems.  The main drawback is that the cat will have to stay at the our hospital until the levels of radioactivity have dropped to below the levels set by the State and the Federal Government.  This may take as little as four days or as much as a week.