Please bring enough food for up to 5 days, as we want to maintain your cat's regular diet. We encourage you to bring one or more small personal items, such as a sock or toy, to place in your cat's cage. However, don’t bring anything of sentimental value because we cannot return these personal items, since they may become contaminated with radiation.

When you arrive at our Hypurrcat facility on the admission day, we will review the "Owner Consent" and "Release Information” forms. Once the required paperwork has been reviewed, you and your cat will meet with Dr. Mark Peterson. He will thoroughly examine your cat and review the medical records and tests performed by your regular veterinarian. He will also answer any questions you have concerning the treatment or long-term care.

If not already done, we will next collect a blood sample for determination of a complete thyroid panel (4 thyroid tests), as well as any other tests that are deemed necessary. Through the same catheter used for blood collection, we then inject the radioactive dye needed for thyroid imaging. After 1 hour, we do a thyroid scan to confirm the diagnosis of hyperthyroidism and determine the extent and severity of your cat’s thyroid tumor disease.

Based on the results of this thyroid scan, the thyroid tumor volume is determined and a proper dose of radioiodine is calculated.

Admission Day at The Hypurrcat Spa for Hyperthyroid Cats Click here to watch the video

Once we determine your cat’s radioiodine dose, it is injected in a small volume (1-ml volume) under the skin (subcutaneously), exactly like a routine vaccination. There is absolutely no discomfort associated with this injection, and the entire procedure takes less than 1 minute.

Treating a Hyperthyroid Cat with Subcutaneous Injection of Radioiodine Click here to watch the video

During your cat's stay at Hypurrcat, the clinic is staffed from 8 AM to around 7 PM by our vet assistants. No one is present overnight. Due to radiation exposure, we cannot spend an extended time in close contact with your cat. However, each cat has their own condo cameras for you, as well as by us, to view and check up on them.

During the day, we check on each hospitalized cat frequently and feed them 3 times a day, so they get plenty of attention. The cats can also view a TV playing enriching videos of birds and squirrels. At night, we turn off the lights and set the TV to turn off at roughly 9 PM. Our cat condo cameras are infrared, they will still allow you to see your cat overnight, even in the dark.

Since each cat's metabolism is slightly different, the length of stay may vary and is determined by the remaining radioactivity in your cat’s thyroid gland. State and City law requires that a cat remain hospitalized until the radioactivity has dropped to a very low level. This usually takes 4 to 6 days.

We measure the radioactivity emitted by your cat’s thyroid every day during their hospitalization to ensure that the thyroid has taken up adequate radioiodine to be effective. If a cat’s tumor fails to take up enough of the administered radioiodine dose, the treatment may not be effective unless an additional dose is given. Although rare, this is one cause for treatment failure, which we avoid by daily monitoring.

We will remain involved in your cat's recovery and long-term care, and we will review the results of all follow-up thyroid monitoring and provide your veterinarian Dr. Peterson’s interpretation and recommendations.

At Hypurrcat, we understand the special role the cat plays in the owner’s family. Our entire Hypurrcat team is committed to providing personal attention to the unique concerns of each individual cat and cat owner. We call or email each owner daily during their cat's stay.

Almost all owners would like to visit their cat during their hospitalization, but they cannot because of the potential for radiation exposure during the first few days after treatment. That’s why we offer owners and veterinarians the ability to monitor their cats live over the Internet.

Our Hypurrcat facility has private cameras installed in each of the cat condos. The web cams allow both the owner and referring veterinarian to check in on their cat, even though they cannot visit. When your cat is admitted, we will email you a “link” that you can open on your home or office computer to monitor your cat live over the internet. You can share this link with friends and family so that everyone can participate in checking in on your cat!

Once treated, cats cannot be removed from the Hypurrcat facility until the level of radioactivity has decreased to a safe level. The New York City and New York State Departments of Health and the Nuclear Regulatory Commission mandate this rule.

There are almost no side effects from radioiodine treatment. Since the radioiodine is specific in its site of action  at the thyroid tumor, there is no hair loss or increase in skin pigmentation as may be seen with other forms of external radiation therapy, such as LINAC or cobalt radiation.

Once your cat is back at home with you, there may be a period of readjustment while your cat’s thyroid returns to normal function. Your cat may be quieter and less active than “normal”. But recall that “normal” in the recent past was really hyperthyroid, not normal!

Because your cat's metabolic rate will return to normal after treatment, he or she may not need to eat as much food as before therapy. A change in voice may develop after treatment, but this is extremely rare. Rarely, a cat will develop hypothyroidism (underactive thyroid gland), which is easily controlled with thyroid hormone supplementation. Overall, side effects are very uncommon.

Radioactive iodine, despite its somewhat scary title, is considered the "gold standard" for safety and efficacy in treating hyperthyroid cats. The greatest risk is radiation exposure to the doctors and staff who work in the thyroid treatment facility on a long-term basis. However, with stringent safety regulations, protocols, and monitoring, this form of therapy is safe for both the cats and the caregivers!

Chronic kidney disease and hyperthyroidism often occur together because they are both common disorders in older cats. Hyperthyroidism tends to artificially increase the blood flow to the kidneys as well as the glomerular filtration rate (abbreviated, GFR). The GFR is a measure of how efficiently the kidney filters the blood. When it is artificially increased, it can mask renal insufficiency; blood tests on a hyperthyroid cat may appear normal despite mild to moderate kidney disease.

Treating hyperthyroidism restores the high serum T4 concentration to normal. This tends to lower kidney blood flow and GFR to normal or low levels, “worsening” kidney function tests. It is important to remember that treating hyperthyroidism itself does not cause chronic kidney disease; the kidney problem was already present before treatment. It was simply masked by the hyperthyroidism.

Chronic kidney disease is reported to be present in 8% of cats greater than 10 years of age and in 15% of cats greater than 15 years of age. In contrast, about 30% of hyperthyroid cats have chronic kidney disease. This suggests that hyperthyroidism may be initiating or worsening the chronic kidney disease in these cats. If this is true, one should always try to correct the cat’s hyperthyroidism, even if the cat has known renal disease.

In addition, reports also indicate that many untreated hyperthyroid cats develop proteinuria (ie, excessive protein in the urine), This proteinuria resolves after successful treatment with radioiodine. In addition, high levels of retinol binding protein, a marker for renal damage, have also been shown to decrease significantly after radioiodine treatment. This too suggests that hyperthyroidism can cause reversible renal dysfunction.

Therefore, it appears that leaving a hyperthyroid cat untreated (or poorly regulated with methimazole) may be detrimental to long-term kidney function. However, treating and curing hyperthyroidism may help to preserve remaining kidney function. 

We will review your cat’s kidney tests and urinalysis prior to admitting your cat to Hypurrcat. If we find any signs of chronic kidney disease, we will begin prophylactic measures to control the kidney disease while your cat is being treated. Even in cats with healthy kidneys, we always repeat kidney tests at the end of the treatment to ensure that kidney function has not deteriorated.

Again, if kidney disease does develop, it is not caused by the radioiodine. It was present before the treatment, but was masked by the hyperthyroidism.

Hyperthyroidism and Kidney Function: A Love/Hate Relationship Click here to watch the video

When you pick up your cat, we will explain in detail the radiation safety precautions that you should follow for two weeks. We will also review when your cat should be reexamined and what tests should be done at each recheck.

Absolutely. The most important factor that causes worsening of kidney disease is the development of hypothyroidism, secondary to an overdose of radioiodine. At Hypurrcat, we titrate the dose given to each cat, so that severe hypothyroidism almost never occurs. By maintaining the serum T4 value at normal levels, this helps maintain kidney function.