Animal Emergency and Referral Center of Minnesota’s treatment facility for cats who suffer from hyperthyroid disease is the premiere facility for cat comfort and owner access in the Midwest.

Our caring healthcare team will welcome your cat into a luxurious, window-side cat condo, complete with separate sleeping, eating, and bathroom areas.


Hyperthyroidism is a common endocrine disease in middle-aged and older cats. It is a multi-system disorder caused by an increase in the amount of thyroid hormones (called T3 and T4) produced by the thyroid gland. Hyperthyroidism was first documented in cats in the early 1980s. Although the disorder is caused by a tumor in the thyroid gland, it is generally a benign (non-cancerous) adenoma.

The most common signs of hyperthyroidism in cats include weight loss, increased appetite (although some patients have decreased appetite), vomiting, increased thirst and urination, hyperactivity, and diarrhea. The high levels of thyroid hormones can cause heart disease, so cats may also have a heart murmur, difficulty breathing, or a high/irregular heartrate. If your cat has a murmur, or your primary care veterinarian has identified one in the past, we recommend your cat have an echocardiogram prior to I-131 treatment.


In about 95% of patients, a single dose of radioactive iodine (I-131) destroys the tumor within the thyroid gland, eliminating hyperthyroid disease. Once the tumor is destroyed, the normal thyroid tissue begins to produce hormone at more normal levels. It can take several months before the thyroid hormone returns to regular levels; however, most cats show improvement almost immediately with a decrease in thirst and appetite, as well as a return to regular activity. Up to 95% of cats will have normal thyroid levels within three months following treatment.


If your cat is currently being treated for thyroid disease, he/she will need to stop taking thyroid medications two weeks prior to the date of treatment. If he/she currently eats Hill’s Y/D diet, you’ll need to feed a different food starting one week prior to the date of treatment. Speak to your primary care veterinarian prior to withdrawing medications or changing food.

Current state health regulations require patients to remain hospitalized for 10 days following injection, and they may be released once radioactive emissions have reached safe levels. Being away from your cat for that long can be difficult; we understand! We’ll send you daily text updates, and our team will provide clean food and water and clean the litterbox regularly. Your cat will be in a nice, quiet space that is for cats only, with a window for natural light, and quiet classical music playing. Each kitty gets an individual cozy, cat condo.

You’re encouraged to bring your cat’s own food to prevent the tummy upset that can come from a sudden diet change. You can also bring something that smells like home to help your cat feel comfortable. Keep in mind that this item will not be returned, so leave favorite blankies and toys at home! The cost of treatment includes day-of-admittance diagnostics, chest x-rays, 11-14 days of hospitalization, and the I-131 injection itself.

For more information on I-131 treatment, please contact us at (651) 501-3766 and ask for the Internal Medicine Department.