Diagnostics before I131 treatment

o   In order for us to determine if your patient is a good candidate to undergo I131 therapy, we request the following work-up:

  1. Current full chemistry panel, including a total T4
  2. Current complete blood count (CBC)
  3. Current urinalysis (including urine specific gravity)
  4. 2-view thoracic radiographs. The thoracic radiographs will need to be submitted for radiologist review (via DVMInsight or using our radiographic case submission form).

o  The patient’s total T4 must be higher than the lab’s reference range to be considered for I131 treatment.

o   Please send the completed request form and the work up result to us (VDIT) at or fax to 512-585-1721.

o Once we have received your patient’s information, Dr. Kunze or Dr. Lo will review the work-up information. When we have determined that your patient is eligible for I131 treatment, we (VDIT) will contact your client to set up a consultation appointment. We currently partner with the internal medicine specialists at Austin Veterinary Emergency and Specialty Center (AVESC) for I131 consultation appointments. The consultation appointment will be with one of the AVESC internal medicine specialists (Dr. Duffy). During this appointment (with client as well as the patient), the AVESC internal medicine specialist will discuss pertinent information about the I131 treatment, possible outcomes, safety concerns and future monitoring. They will also conduct a physical exam of the patient.

o In some patients, further diagnostics (such as an echocardiogram or an abdominal ultrasound) may be necessary before treatment. In other patients, it may be appropriate to treat with methimazole prior to I131 treatment. This will be discussed on a case-by-case basis with the owners.

o The I131 treatment will be conducted at Austin Veterinary Emergency and Specialty Center (AVESC). The patient will stay in the hospital for a week (generally Monday to Friday). No visiting will be allowed as the patient will be in isolation.

o Upon discharge, the patient will be excreting very low levels of radioactivity, and there are safety precautions that the owners will have to practice for 3 weeks after the patient is discharged (details will be discussed with the owner during the consultation appointment and upon discharge).”

o We ask that a recheck total T4 and renal panel be performed 1 month after treatment. Please forward results to


What is hyperthyroidism?
This is a common endocrine (hormonal) disorder in which too much thyroid hormone is produced. The majority of hyperthyroid patients have overactive gland tissue rather than a tumor.

What are the available treatments for hyperthyroidism?
o   Medical – methimazole is a drug that stops production of thyroid hormone. This is typically an oral medication, but it can be formulated to be a topical cream. This medication is given every day and is a life-long treatment.

o   Surgery – complete removal of the thyroid glands.  However, this procedure requires general anesthesia and may lead to deficiency of parathyroid hormone (parathyroid glands small glands that are embedded within the thyroid gland).

o   Radioactive iodine – specifically I131.

How does radioactive iodine work?
The iodine is naturally absorbed and concentrated by the thyroid gland. The radioactivity will kill the overactive thyroid cells.

Is my cat a good candidate for treatment?
We will work with your veterinarian to determine if your cat is a good candidate for I131 treatment. The pre-treatment diagnostics will include blood work (chemistry panel, complete blood count), urinalysis and chest x-rays.  For some patients, further diagnostics (such as an echocardiogram or abdominal ultrasound) may be needed prior to treatment.

What will happen during the initial consultation?
We will discuss the details of treatment (what actually happens during treatment, treatment outcomes, etc.). We will also perform a physical exam of your cat during the appointment.

What actually happens during treatment of my cat?
Your cat will receive an injection of the I131, and he/she will be hospitalized from Monday to Friday. Your cat will be hospitalized for the week in order for most of the radioactive iodine to be excreted, and it is safe for him/her to go home.

Can I visit my cat during his/her hospital stay?
No, your cat will be radioactive. We are regulated by law to limit access to trained personnel only.

What happens after my cat comes home from treatment?
Your cat will still be excreting low levels of radiation. We will discuss specific safety precautions to take when we have the consultation.

How do I schedule an appointment for treatment?
Please have your veterinarian contact us and send us the necessary information. We will then contact you to schedule an appointment.