Radioiodine (I-131)



Radioiodine is a very specialized treatment for cats with hyperthyroidism. Referred to as I-131, it is the only treatment option currently available that completely cures this condition.

Here at NorthStar VETS, we are experts in using I-131, with a successful track record of curing hundreds of cats with hyperthyroidism. You can feel confident that your pet will receive the best possible care from our veterinary specialists.

What Is Hyperthyroidism?

Hyperthyroidism occurs when the thyroid gland, which regulates metabolic rate, develops a tumor (98% are benign) that causes an overproduction of thyroid hormone. This condition over-stimulates many organ systems and causes abnormalities, including:

  • Changes in behavior
  • Decreased or excessive appetite
  • Hyperactivity or lethargy
  • Weight loss
  • Fever
  • Rapid heartbeat
  • Increased water consumption and litter box output
  • Shedding of fur
  • Diarrhea

Prompt diagnosis and treatment of hyperthyroidism are critical because, if left untreated, the condition can be fatal.

What Are the Treatment Options for Hyperthyroidism?

There are three options for treating hyperthyroidism. Here's an overview of the risks and benefits of each one:

  • Medical Treatment with an Anti-Thyroid Drug (Tapazole)
    Medication typically causes side effects such as nausea, vomiting, loss of appetite, lethargy, hair loss and facial scabbing. Regular follow-up is needed, including blood tests to monitor thyroid hormone levels. Medication and monitoring will be constant expenses for the duration of your cat's life. In addition, your pet may experience the loss of white blood cells and blood clotting abilities, in addition to long-term liver and kidney damage. This treatment does not cure hyperthyroidism.
  • Surgery
    Many hyperthyroid cats have heart problems and therefore are at higher risk of complications from anesthesia during surgery. It is often difficult to identify and remove the entire thyroid tumor, and 80% of cats will develop another tumor within 1 1/2 years of surgery. There is increased risk of hypocalcemia after surgery and many cats still require post-surgical Radioiodine I-131 therapy.
  • Radioiodine (I-131)
    This treatment can completely cure hyperthyroidism by destroying the thyroid tumor without harming adjacent healthy tissue or causing side effects. It is administered through a simple, single subcutaneous injection. Over 94% of cats treated never need further treatment. Because it takes a few days for the radioactivity of the treatment to dissipate, by law your cat must remain hospitalized for three* days after treatment (we promise to provide plenty of love and care during this time). Your cat's thyroid function should return to normal within 4 weeks.

For your peace of mind - and the comfort of your cat - we have a specially designed room where your pet will stay during the three days following I-131 treatment. This room has large windows so you can see your pet and he/she can see you when you visit.

*NorthStar VETS has been authorized by the New Jersey Department of Environmental Protection to discharge cats after 72 hours if radiation levels have been met.

The Advantages of Radioiodine (I-131)

  • Daily pilling eliminated
  • More cost-effective
  • No anesthesia required
  • Normal thyroid tissue not affected
  • Destroys thyroid tumors regardless of location
  • Thyroid function returns to normal, usually within 4 weeks

For More Information about Radioiodine (I-131) Treatment at NorthStar VETS
Simply call us at 609.259.8300.

Beverly Starr

Beverly Starr - Client Liaison

Pet owners: Contact Beverly Starr at 609-259-8300 x1202 or at bstarr@northstarvets.com to schedule your appointment and get all pre-consultation paperwork set up.

Veterinarians: Contact Beverly with questions about in-hospital cases, or to discuss a pending case. You can also refer a case online.

If you are a veterinarian who would like to refer a feline patient for I-131 treatment, please visit the Referral Checklist page for details on the information we need to know prior to treatment