Radioactive Iodine Therapy

Veterinary Referral Hyperthyroid TreatmentHyperthyroidism (overactive thyroid gland) is a common problem in middle-aged to older cats. Clinical signs of hyperthyroidism include weight loss, increased appetite, increased urination, increased water intake, vomiting, diarrhea, restlessness or hyperactivity and poor, dull hair coat. Some affected cats may also have a noticeably enlarged thyroid gland, an increased heart rate, an irregular heart rhythm or high blood pressure.

Treatment of hyperthyroidism is always recommended, even in cats without any symptoms. When recognized early and treated appropriately, affected cats have a good prognosis. In some cases, depending on treatment, hyperthyroid cats can be cured.

Normal thyroid glands use iodine to produce the thyroid hormone. In Radioactive Iodine Therapy the radioactive form of iodine is absorbed by the thyroid gland; it then destroys the overactive cells that cause hyperthyroidism. This treatment does not damage the normal parts of the thyroid glands, nor does it affect the parathyroid glands.

The radioactive iodine is given through an injection under the skin similar to a vaccination. After the injection is given the patient remains hospitalized for 2 to 7 days, until the radioactivity counts have fallen to a safe level. The radiation is excreted through urine and feces, which must be handled and disposed of in accordance with state and federal safety regulations.

At the Fox Valley Animal Referral Center, Radioactive Iodine Therapy is provided by our Radioactive Iodine Therapy Coordinator, Judy Freeman, CVT, VTS (ecc) and by Dr. Lisa Peters, Dr. Terri Cole and Dr. Elizabeth Breuhl.

For more information please contact Radioactive Iodine Therapy Coordinator Judy Freeman by email at

Information for Clients

Client Information (PDF | DOC)

What to Expect at Your Appointment (PDF | DOC)

Discharge Instructions (PDF | DOC)

Information for Veterinarians

Information for Referring Veterinarians(PDF | DOC)