I-131 Radioactive Iodine Therapy

Treating Feline Hyperthyroidism with I-131

Radioactive iodine, known as I-131, is a revolutionary treatment option for cats with hyperthyroidism (overactive thyroid), a common feline endocrine disorder. Oradell Animal Hospital is the exclusive provider of this highly effective therapy in the greater Paramus region.

Treatment involves a single subcutaneous injection of I-131, which has been proven to cure over 98% of affected cats.

Understanding Hyperthyroidism in Cats

Hyperthyroidism occurs when an enlarged thyroid gland over-produces thyroid hormone. Symptoms can include:

  • Excessive thirst
  • Hyperactivity
  • Increased appetite
  • Unkempt appearance
  • Weight loss

How Radioactive Iodine Therapy Works

Radioactive iodine therapy uses a form of iodine that’s radioactive. When administered, this iodine is taken up by the thyroid gland and selectively destroys the hyperactive thyroid cells, shrinking the gland back to its normal size and reducing its hormone production.

The Benefits of Radioactive Iodine Therapy

The benefits of I-131 therapy are substantial:

  • It has a remarkable success rate, effectively curing the condition in most cases
  • It’s exceptionally safe with minimal side effects—particularly important for older cats or those with multiple health issues
  • It involves a simple one-time injection (cats can have a second injection, if needed), making it an easier, more comfortable option than surgery or a lifetime of daily pills

What’s Involved in Radioactive Iodine Therapy

Here’s an overview:

  • First, your cat will need a comprehensive health evaluation to ensure they’re a suitable candidate for I-131 therapy. This typically includes blood tests, a physical exam, and sometimes imaging tests to assess the thyroid gland.
  • After the I-131 injection is administered, your cat must, by law, stay in a special isolation ward at our hospital for a few days because they’ll be emitting low levels of radiation. Our veterinary staff will monitor them and make sure they’re comfortable.
  • Once your cat comes home, we recommend precautions to limit your exposure to any radiation for a specified period, usually just 1 to 2 weeks—we’ll provide detailed instructions tailored to your cat’s individual situation.
  • After this period, your pet can generally resume their normal activities.
  • A few weeks after I-131 therapy, we’ll do a follow-up exam and blood work to measure your cat’s thyroid levels, which by now should be in the normal range. In rare cases, some cats may require a second injection or medication.
  • Long-term care after radioactive iodine therapy is minimal. We recommend regular check-ups by your primary care veterinarian to monitor your pet’s overall health, including their thyroid levels, but recurrence of hyperthyroidism after I-131 therapy is extremely rare.

Get to Know Your Cat's I-131 Therapy Team

John Lucy, DVM, DACVIM (SAIM)

Reena Shah, DVM

Questions?

We’re here to help. Call us at 201-262-0010 or visit our FAQ page for quick answers to common pet owner questions.

If you are a veterinarian and would like to refer a patient, please visit our referral portal.

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