Hyperthyroidism Radioactive Iodine treatment FAQs

Radioactive iodine treatment is a simple and effective option for treating hyperthyroidism in cats. Your cat will be given a single capsule of radioactive iodine (I-131), which is absorbed into its system. The iodine travels directly to the thyroid gland, where it targets and destroys the overactive, abnormal thyroid tissue.

The best part is that the iodine focuses on the abnormal tissue, leaving the normal thyroid tissue unharmed. Since the thyroid gland uses iodine to produce hormones, it’s the only part of your cat’s body that is affected by the treatment. This makes it a safe and precise way to treat hyperthyroidism.

Radioactive iodine (I-131) is a simple, safe, and effective way to treat hyperthyroidism without the hassle of daily medications, their side effects, or the need for an iodine-restricted diet. It also eliminates the risks that come with surgery and anesthesia.

The best part? This treatment can cure hyperthyroidism in most cats! Within just 4 weeks, 80% of cats have normal thyroid hormone levels, and by 6 months, 95% are back to normal. It’s a great long-term solution to help your cat feel better without the ongoing need for medication.

We offer consultations on Mondays and Tuesdays to assess your cat’s suitability for iodine treatment. If these days don’t work for you, just give our reception a call, and we’ll be happy to help find a solution.

Since hyperthyroidism usually affects older cats, it’s important to check for other health conditions, like kidney disease, that may affect whether iodine treatment is right for them. Cats should undergo basic screening tests before their appointment, including blood work, chest X-rays, and possibly an abdominal ultrasound or heart scan.

Your regular vet can perform these tests and send us the results at least 7 days before your cat’s appointment. Alternatively, we can carry out the pre-screening at CSS before treatment. Once we’ve confirmed your cat is safe for treatment, the radioactive iodine will be administered on a Wednesday or Thursday.
Please note that any anti-thyroid medications (like carbimazole, methimazole, or Hills y/d) need to be stopped 14 days prior to treatment.

The night before treatment, your cat will need to fast, and we’ll give them an anti-nausea medication (maropitant) to help prevent any vomiting of the radioactive iodine capsule. Upon arrival, your cat will receive a thorough physical exam, including a body weight check, before being admitted into the special radioactive iodine unit.

Once ready, your cat will be given the radioactive iodine capsule orally and will stay in the radiation suites for about 5-7 days.

Rest assured, we always aim to administer the safest and most effective dosage tailored specifically to your cat’s needs.

Handling and giving radioactive iodine to cats requires special licensing, hospital equipment, and careful adherence to state radiation laws (like those from Queensland Health).

After receiving radioactive iodine, cats will continue to excrete small amounts of radioactivity in their urine, stools, and saliva for about 2-4 weeks, depending on the dosage.

The radioactivity reduces significantly within the first 5-7 days, and most cats can go home after that, but they must stay indoors for another two weeks to ensure safety.

This treatment is highly safe for both cats and their owners. Keep your cat indoors for those two weeks and avoid direct contact with its saliva, urine, stools, or vomit. If these simple steps are followed, the risk of radiation exposure to humans is minimal.

In our radioactive iodine suites, your cat will be cared for by a dedicated, highly trained feline nurse, under the supervision of a specialist feline veterinarian.

Every day, your cat will receive fresh food, water, and clean litter, along with close monitoring to ensure their radioactivity levels are decreasing safely for discharge.

When your cat is ready to go home, they may stay in our comfortable medical boarding suites until it’s time for you to pick them up.

After receiving radioactive iodine treatment, your cat will excrete small amounts of radioactivity in their urine, stools, and saliva for about 2-4 weeks. To ensure everyone’s safety, your cat must stay indoors for two weeks after discharge, and you’ll need to avoid contact with their saliva, stools, vomit, or urine.

Here are some tips to follow during this period:

• Limit direct contact: It’s okay to pick up your cat for short moments, but try to avoid letting them sit on your lap for extended periods or sleep in your bed.
• No face-to-face contact: Avoid letting your cat lick or groom you.
• Wash your hands: Always wash your hands after petting your cat.
• Handle waste carefully: Keep litter trays in an unoccupied area, use a waterproof liner, and wear gloves when cleaning. Dispose of all waste in a sealed rubbish bag.

By following these steps, the radiation risk to humans is minimal.

Follow up blood tests are recommended between 6 and 12 weeks after treatment to assess kidney function and thyroid hormones levels. Thyroid hormone levels are within normal range in 80% of cats by 4 weeks and 95% of cats by 6 months.

These tests can be performed at your local vets and forwarded to us and we will help with any follow up required.

We’d be delighted to have your cat stay with us for the two-week period in our medical boarding suites. These suites are designed to be cozy and welcoming, with plenty of direct sunlight and multiple shelves for lounging. Plus, your cat will get to enjoy time in one of our fun themed playrooms—Star Wars, Harry Potter, or Lord of the Rings!

Our highly trained staff, supervised by specialist feline veterinarians, care for the cats daily. The suites are right across from our offices, so when we have a bit of free time, we love to pop in for some extra playtime and grooming. Trust us—we adore cats!

You can visit during visiting hours.

We suggest keeping your cats separate for the 2 weeks after your cat returns home and avoiding them sharing a litter box and coming into contact with urine or stools.

Unfortunately, you won’t be able to visit your cat while they’re in the radioactive iodine unit. This treatment requires special licensing and equipment, and we must follow strict state radiation laws (like those from Queensland Health). Rest assured, we’ve made every effort to ensure your cat is as comfortable as possible and will enjoy a quiet, relaxing week.

As for something from home, absolutely! You can bring along a small item like a t-shirt or pillowcase that smells familiar to them. Remember that these items can’t be returned after their stay, as they must be safely disposed of to meet radiation guidelines.

Absolutely. You are welcome to provide your cat’s own food supply. We keep many cat food brands in the hospital; however, it always helps to have your cat’s favourite.

Hyperthyroidism often affects older cats who love their naps! To keep them comfortable and entertained, we’ve ensured each cat has access to plenty of cozy sleeping spots, direct sunlight, ramps for exploring, toys, and a lovely garden view. Plus, we’ve got “cat TV” set up in every suite! This plays different programs at various times throughout the day to provide fun enrichment and keep your cat entertained between naps.

Side effects from radioactive iodine treatment are very rare, but one possibility is hypothyroidism, which happens when the thyroid becomes underactive and doesn’t produce enough thyroid hormone. This is more likely if a higher dose of iodine is used.

Hypothyroidism can develop weeks or months after treatment and may need to be managed with thyroid hormone supplements. It’s important to avoid hypothyroidism as it can impact kidney function and potentially shorten a cat’s life, but the good news is that using lower doses of iodine can reduce this risk.

For some cats with hidden kidney issues, bringing their thyroid levels back to normal can reveal existing kidney disease.

Hyperthyroidism masks underlying kidney disease. Approximately 15% of hyperthyroid cats have increases in kidney blood tests after treatment, however this is often not associated with a worse outcome.

About 5% of cats may not fully respond to radioactive iodine and can remain hyperthyroid. This is more common in cats with larger thyroid tumors. If your cat is still showing signs of hyperthyroidism six months after the first treatment, a second round of radioactive iodine may be an option to consider to help improve their symptoms.

Relapse of hyperthyroidism is very uncommon but is reported in approximately 5 % of cats treated. If relapse does occur it is generally after 3 or more years.

Please contact us to ask about our waiting list for Radioactive Iodine treatment.