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Treating Hyperthyroid Cats With Just One Shot


Pet Column for the week of September 7, 2009

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Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Ashley Mitek
Information Specialist

Source - Thomas K. Graves, DVM, MS, PhD, DACVIM
Although injecting a cat with radioactive material might sound like it would do more harm than good, it's the best treatment option for cats with an overactive thyroid gland. The disease, which is common in middle-aged cats, causes several symptoms such as: weight loss, hyperactivity, anxiety, vomiting, increased thirst and urination, along with an increased appetite. Once diagnosed, there are three treatment options: radioiodine therapy, surgery, and lifelong oral medication.

"Radioiodine therapy is arguably the safest and most effective treatment," explains Dr. Thomas Graves, a veterinary internal medicine specialist and endocrinology expert at the University of Illinois Veterinary Teaching Hospital in Urbana. Surgical removal of the thyroid glands can cause laryngeal paralysis, as well as other complications, such as hypocalcemia (low calcium levels). Lifelong oral administration of methimazole, an anti-thyroid drug, also carries risks and can be expensive long-term.

Although the thought of injecting your cat with radioactive material may cause concern, it does not seem to bother cats or cause any discomfort. In fact, the procedure is incredibly simple. The cat arrives at the Veterinary Teaching Hospital and a catheter is placed. One injection of radioactive material is given, and then the patient relaxes in a special room until being released from the clinic.

Some owners grow concerned that leaving their beloved cats in the hospital for five days is too traumatic. However, Dr. Graves mentions that, "Over the years I don't know how many hundred cats I've treated with radioiodine therapy. I've never had a patient that did not easily acclimate to hospital life." In short, cats residing in the hospital after treatment have a good quality of life.

Because all hospitals, both human and veterinary, that administer radioactive treatment must follow extremely strict guidelines established by each individual institution, feline patients must be kept as "in patients" for approximately five days after their injections. This precaution is in place so that when cats return home they give off only minimal amounts of radiation.

It's interesting to note that in human medicine, radioiodine therapy for people with hyperthyroidism is an outpatient procedure. Even though humans receive much higher doses of radiation than cats, a recently treated person who is still radioactive could be standing in line behind you at the grocery store because doctors can explain to humans certain restrictions to follow.

For example, the American Association of Clinical Endocrinologists recommends that patients sleep alone for the first few days after treatment to avoid radiating your significant other. They also mention that women who hope to get pregnant should refrain from conceiving for at least six months after treatment.

Dr. Graves gives similar instructions to clients who come to pick up their feline friends who received radioiodine therapy. "I usually recommend that clients refrain from sleeping with their cats for the first few days, and contact with pregnant women or small children should be minimized," he notes. But besides that, cats are very safe to be around.

If you have questions about radioiodine therapy, contact your local veterinarian.