Thyro-Cat, LLP

Full WebsiteHome

FAQs: Cat Hyperthyroidism & Treatment

Thank you for considering Thyro-Cat to be part of your cat's health care team!

The most effective health care team in the treatment of feline hyperthyroidism with RadioIodine therapy consists of a knowledgeable owner, a primary care veterinarian who works closely with the radiation oncologist, and a caring support team of technicians who monitor your cat while in our facility.

We want to make sure your cat is an appropriate candidate for I-131 therapy, and then to treat the condition and manage your pet with respect and dignity in a comfortable environment.

Commonly Asked Questions: Click to download as PDF

  1. What causes hyperthyroidism in cats?

    Feline Hyperthyroidism is a disease caused by excessive thyroid hormone. It is common in middle aged to geriatric cats, and is often caused by benign tumors of the thyroid gland. The condition can also be caused by congenital, inflammatory, toxic and/or nutritional processes.

  2. What is the best way to treat it?
    Radioactive I-131 has proven to be the preferred therapeutic regimen compared to surgery, medicine and/or diet for appropriate candidates. It is curative in more than 95% of patients.

  3. Is my cat an appropriate candidate?
    We need you and your veterinarian's help in providing us with meaningful historical information, insights into your pet's health problems, current blood work and x-rays. We need to know of any preexisting condition that will cause your cat to become progressively ill independently of how the hyperthyroid condition is treated. It may not be appropriate to proceed with I-131 therapy if certain conditions exist.

  4. What about performing additional imaging studies such as a nuclear scan, CT, MRI before proceeding with I-131?
    We have found that being selective with the use of any additional imaging studies is more appropriate than requiring them for all patients. All are appropriate under the right circumstances, but we will discuss with you and your veterinarian if it is recommended any additional diagnostic tests be pursued.

  5. What should I do if I have questions prior to, during and after I-131 therapy?
    Simply contact the Thyro-Cat main office. The office treatment coordinator is well-trained and available to answer questions, address concerns, and to keep you updated on your cat's health during his/her stay.

  6. What happens after admission?
    After the I-131 is injected, your cat will stay with us for 3 to 5 days. Each pet is monitored, fed, given fresh water and their activities are recorded on an ongoing basis every day. Cats must stay in their cages during their stay, as the amount of interaction between the pet and support staff is limited by law because of the concerns for radiation safety for the staff members. This is why your cat cannot be injected and immediately sent home with you. We provide large, clean cages with plenty of ventilated fresh air and provide cat friendly videos for your cat to enjoy.

  7. What happens if my pet needs to be treated for other conditions during his/her stay?
    Pets should be as stable as possible before receiving the therapy as federal law mandates that they cannot be removed from the room post treatment for a minimum of 72 hrs, even if they become seriously ill. We will do the best we can within the limits of the law to treat your pet as needed to assure a stable health status.

  8. Will food, medication and personal items be returned to me afterward?
    The items that were taken into the Thyro-Cat facility with your pet may have radioactivity on them. As such, we do not want to expose you or your cat to any radiation that is not absolutely necessary. What goes into Thyro-Cat, except for your pet and the carrier, has to stay in Thyro-Cat.

  9. Why do some pets stay longer than others?
    Your cat cannot be released until the amount of radiation in his/her body is below a level mandated by law. It is a minimum of three days and can take as long as 5. Factors such as family environment, pregnancy and the presence of children can require the need for the lowest level of activity detected before release.

  10. Can I board my cat at Thyro-Cat beyond the required stay if needed?
    If you bring your pet to a Thyro-Cat facility, we are a member of your health care team, and we will do all we can to meet your needs. Additional fees for extended boarding and patient management will be discussed with you if you wish to have the pet spend additional time with us.

  11. What happens if my pet becomes sick after treatment?
    Some diseases may not be apparent before I-131 therapy but progress and express themselves within a short time after the therapy. We are always available as needed to interact with you and your veterinarian to define these disease processes as they occur and make recommendations for therapy.

  12. Post-therapy monitoring
    You'll be asked to complete a survey at the end of the procedure and to provide follow-up bloodwork so we can remain updated on the health status of your cat. We are always available as needed to speak with you, your primary care veterinarian and others who are involved in the health care needs of your cat.


Victor T. Rendano Jr, VMD, MSc, DACVR, DACVR-RO
Radiation Oncology Director/Thyro-Cat