Radioiodine (I-131)

Our Nuclear Medicine Department at Valley Central Veterinary Referral and Emergency Center is designed exclusively for the treatment of cats with hyperthyroidism. We are fully licensed by the Nuclear Regulatory Commission for the administration of this treatment to cats.

Our Nuclear Medicine Department is comprised of a board-certified internist, a health physicist, and a specifically trained and licensed nursing staff. Our Nuclear Medicine Department has your cat's best medical interests in mind. When you arrive for your consultation, your cat's medical history will be reviewed, and the specialist will examine your cat and discuss your cat's medical case with you. Sometimes it is necessary to perform further testing; this may delay your planned treatment date. Occasionally, cats need to be mildly sedated in order to be given the injection without any harm to themselves or our staff. Every effort is made to administer the therapy without sedation.

A Nuclear Medicine staff member will be available during normal business hours to inform you on the condition of your cat and when your pet will be ready to be discharged.

Your cat will be discharged when their radiation levels have decreased enough to comply with the Nuclear Regulatory Commission standards. At this time, you will receive your cat's discharge instruction packet.

We look forward to working with you to restore your cat to good health. Please notify us of any questions or concerns you may have.

Frequently Asked Questions

Nuclear medicine is an area of medicine that uses radioactive isotopes to safely diagnose and treat many diseases. Here at Valley Central, we use I-131 (radioactive iodine) for the treatment of feline hyperthyroidism.

This is a disease that affects older cats, where an excess of thyroid hormone is being released from the thyroid gland. Most of the time, this is due to a benign growth on the thyroid gland. This condition severely accelerates the cat's metabolic rate putting stress on all the organs, especially the heart. If left untreated, this disease could be fatal. In rare cases (less than 1% of all hyperthyroid cats), the growth on the thyroid gland is cancerous, or malignant.

Signs of the disease include weight loss, increased appetite, vomiting, diarrhea, excessive thirst and urination, high blood pressure, and heart disease that can lead to heart failure and fatal arrhythmias.

Physical examination findings that raise suspicion for hyperthyroidism include weight loss, poor body condition, or hair loss. Many times an enlarged thyroid gland or heart murmur is detected by your veterinarian. You may also observe aggressive behavior at home.

There are three: medical, surgery and radioactive iodine therapy.

Medical therapy does not cure hyperthyroidism; it only suppresses the excessive release of thyroid hormone, requiring lifelong oral medication to be administered to the cat, usually several times a day. This medication can result in gastrointestinal upset, liver toxicity, skin irritation, or more severe reactions such as bone marrow failure.

Surgery may result in a cure; however the risk of anesthesia is a concern. Virtually all hyperthyroid cats have some alterations in their heart muscle due to the disease. There is also a risk of removal of too much, or not enough tissue, resulting in complications or treatment failure. Most cats treated surgically need to have thyroid supplementation for the rest of their life.

Radioactive iodine therapy is a form of radiation therapy that does not have the above mentioned disadvantages. After one injection, more than 96% of the cats with hyperthyroidism are cured. There is no anesthesia required, and there are no oral medications to give. Plus, there are virtually no side effects.

Radioactive iodine is a radioactive form of the mineral iodine. Dietary iodine that is ingested is concentrated into the thyroid gland to make thyroid hormone, an essential hormone for normal body function. Because of this, we are able to administer radioactive iodine, and we know that the drug will be concentrated only in thyroid tissue. There it will destroy the abnormal cells that are overproducing thyroid hormone, sparing normal cells in the thyroid gland, as well as the rest of the normal cells in the body. This is why the treatment works so well.

I-131 is prepared by the nuclear pharmacy in liquid form and given intravenously or subcutaneously. The cat will receive one injection and will board with us until the radiation has been metabolized and we can release your cat to you safely.

The Nuclear Regulatory Commission regulations are such that the length of boarding usually varies from 96 hours to 14 days. You will be contacted every weekday with an update on your cat.

Once your cat is released, you will receive complete discharge instructions and your veterinarian will be contacted by fax. A case summary will also be sent to your referring veterinarian. Blood tests to check the thyroid level and general metabolism are required at three weeks and three months post therapy.

You can make an appointment for consultation by calling the nuclear medicine department at 610-435-1553.