Specialty Teams

Monday-Friday: 8:00 am-6:00 pm
Saturday-Sunday: Closed

Emergency & Critical Care

Open 24/7

1515 Lake Pointe Pkwy,
Sugar Land, TX 77478

Radioiodine (I-131)

Feline Hyperthyroidism

Feline Hyperthyroidism is a disease of the thyroid gland that affects older cats of all breeds. The symptoms are due to excessive secretion of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) which affect several body systems by increasing their metabolic rate. Hyperthyroidism is now one of the most frequently diagnosed diseases in cats.

A common symptom is weight loss in spite of a normal or ravenous appetite. Most cats are hyperactive, restless, anxious and easily stressed. Cardiopulmonary signs can include, tachycardia, heart murmurs, congestive heart failure, panting and difficult breathing. Vomiting is more often seen than diarrhea. Simultaneous kidney disease is often present.

Left untreated, hyperthyroidism can result in severe debilitating disease and death. Appropriate and effective treatment, on the other hand, can prevent and resolve these symptoms. A diagnosis of hyperthyroidism is made by history, recognition of clinical signs, and thyroid function tests: increased total T4 and/or free T4. Additional tests are sometimes needed to evaluate the heart, kidneys and gastrointestinal tract.

FAQ About I131


Recovery from hyperthyroidism without treatment does not occur. If left untreated, hyperthyroid cats will progress to emaciation, severe metabolic and cardiac disease, and death. In hyperthyroid cats that are medically stable, radiotherapy with the radioisotope Iodine-131 is the safest and most effective method of treatment.

A simple injection of a small volume of iodine-131 is made under the skin. The I-131 is specifically metabolized by the thyroid tissue and destroys the abnormal thyroid cells without damage to other tissues. Because the patient is radioactive after this injection, state law requires special hospitalization under strict confinement for 3 to 5 days, until the radioactivity is measured below acceptable patient release levels.

Consent to Treatment

Who & Where?

I-131 treatment requires a special isolated and radiation-shielded treatment and hospitalization room. The radioiodine treatment room at Sugar Land Veterinary Specialists is specifically designed for the purpose of radiation safety and patient comfort. The 6 cat cages are glass-backed and positioned against windows that provide a view of the landscaped exercise yard through 1 ½” thick plate leaded glass.

I131 administration and care is spearheaded by our Internal Medicine Team and our Diagnostic Imaging Team.

Your cat will have their medical care overseen by the internists and day to day care will be taken care of by our Diagnostic Imaging team.

To set up an appointment for your pet to see the internists, ask your veterinarian to submit a referral.

Referral Form