Radioactive Iodine Therapy in Dogs

A dog’s thyroid gland is responsible for releasing hormones that control metabolic processes in the body. To do this, the thyroid gland essentially “traps” iodine already present in the dog’s food. This makes radioactive iodine therapy safe for dogs diagnosed with thyroid conditions such as hyperthyroidism and thyroid cancer. Dogs undergoing radioactive iodine treatment will need to be hospitalized for at least four days, and up to two weeks. However, radioactive iodine therapy is a safe, minimally invasive procedure that does not require the use of general anesthesia. In many cases of primary hyperthyroidism, radioactive iodine therapy is curative.

Your veterinarian will discuss dietary and medication adjustments with you before treatment begins. You should tell your veterinarian if your dog is on a special diet. It is imperative that you follow your veterinarian’s pre-treatment instructions carefully to maximize the efficiency of the treatment.

1. Prior to treatment, the veterinary specialist will evaluate the dog’s health through a physical examination and diagnostic tests, including blood work, x-rays, ultrasounds, and urinalysis.
2. The dog will be hospitalized in a specialist radiotherapy ward for at least four days, and up to two weeks.
3. On the first day of hospitalization, the specialist will perform a nuclear medicine thyroid scan to evaluate the thyroid glands.
4. Radioactive iodine treatment will begin on the following day. This will involve the administration of radioactive iodine capsules.
5. The dog’s bloodstream absorbs the iodine, which is then transported to the thyroid tissue.
6. The iodine will destroy the parts of the thyroid gland that produce excess thyroid hormones.
7. Throughout the hospitalization, the dog’s radiation levels will be closely monitored. All radioactive material will exit the body through the dog’s feces and urine.

Radioactive iodine therapy is considered a permanent solution to primary hyperthyroidism in most cases. It has a 90% success rate in dogs with hyperthyroidism. Radioactive iodine therapy may be less effective for treating thyroid cancer, and will also need to be administered in higher doses. However, it is usually combined with chemotherapy and traditional radiotherapy. The dog’s prognosis will vary depending on the condition. Thyroid cancer may recur in spite of successful treatment. Hyperthyroidism associated with thyroid cancer will usually resolve following successful cancer treatment.

Your dog will need to be confined for two weeks after treatment. You may take your dog home, but you must keep all contact to an absolute minimum. Your dog will not be allowed to sit on your lap or sleep in the same bed with you. This is due to the levels of radiation still present in the bloodstream. Dogs that have received radioactive iodine treatment are not allowed to be around children younger than eighteen or pregnant women. This is a legal requirement, and you will need to sign a form confirming this.

After the two-week confinement period has concluded, you can resume your normal routine. A follow-up appointment will be scheduled with the veterinary specialist one month after treatment has concluded. Your veterinarian will also examine your dog three months after treatment. During these appointments, the veterinary professionals will assess thyroid function. If thyroid function has returned to normal, the treatment is considered successful. Dogs diagnosed with cancer will be evaluated more often.

The cost of radioactive iodine therapy will vary based on the underlying condition, standards of living, and additional costs incurred. The average cost of radioactive iodine therapy, including lab tests and boarding fees, ranges from $1,400 to $1,800, but may be higher depending on the length of hospitalization.

Radioactive iodine therapy is safe, minimally invasive, and does not damage tissues in other areas of the body. Dogs will not typically experience side effects of radioactive iodine therapy unless it is administered in large amounts. Side effects include gastrointestinal upset and irritation of the salivary gland and bladder. These side effects occur in less than 1% of animals receiving this treatment. 

Hospitalization times are longer for dogs receiving iodine therapy than cats. Because it is rarely diagnosed in dogs, there are also additional factors to consider, which your veterinarian will discuss with you before treatment begins.

Complications of radioactive iodine therapy, although rare, may include:

• Hypothyroidism
• Treatment failure, usually due to cancer
• Renal failure or decrease in kidney function

Hypothyroidism is corrected with medication, which is discontinued once thyroid activity returns to normal, usually within three months. Treatment failure occurs in 5% of animals, and is typically attributed to cancer. Renal complications are considered extremely rare.

It is difficult to prevent hyperthyroidism and thyroid cancer in dogs. Dietary changes, particularly for dogs that are fed a raw diet, may resolve signs of hyperthyroidism. Dogs diagnosed with and treated for thyroid conditions should not be bred.