Radioiodine Service

Hyperthyroidism is caused by overactive, and often, enlarged thyroid glands in the neck that produce excess hormones. 

The condition leads to a range of clinical signs including weight loss, increased appetite and thirst, poor coat condition, hyperactivity and increased blood pressure. There is also a significant risk of stroke or heart failure, due to the increased strain on the heart. Cats identified at increased risk can be further assessed by our Cardiology service when indicated. 

Hyperthryoidism is a common disease of middle-aged and older cats, affecting around 12 per cent of the UK cat population. The condition is fatal is left untreated. 

At the Hospital for Small Animals, we offer all four main treatment options for hyperthyroidism. Each has specific advantages and disadvantages:

• Medication with an oral thyroid supplement, or gel applied to the ear, doesn’t cure the cat from hyperthyroidism, but will prevent the thyroid gland from overproducing hormones. While dosing is readily adjustable, some cats can experience side-effects from the medication, and some owners find it challenging to give cats medication 
• A low-iodine diet can control hyperthyroidism by limiting the thyroid from producing hormones, however some cats may refuse to eat it. Another disadvantage is that cats prescribed this diet must eat it exclusively. Eating table scraps, other cat food or hunting will compromise the effectiveness of treatment 
• Thyroidectomy surgery can be performed to remove the thyroid gland(s). This can resolve the hyperthyroidism permanently. However, this is invasive, and there are risks associated with older cats and anaesthesia, with some cats being poor surgical candidates due to the extent of their diseased thyroid tissue.
• Radioiodine treatment (I-131 treatment) is seen as the treatment of choice for cats with hyperthyroidism. It is a painless process that usually involves a single dose of radioactive medication. Cats need to stay at the veterinary centre for several days to allow radiation levels to fall to acceptable limits, before they are discharged. However, only some veterinary centres can offer this type of treatment.

The radioiodine (I-131) is given as a single dose either by injection or oral capsule. The iodine concentrates in the thyroid gland, where it emits beta-radiation, killing the over-functioning cells. 

This treatment is extremely effective as all thyroid tissue, even overactive thyroid tissue in the chest that cannot be removed surgically, is treated. However, cats need to spend time in an isolation facility before returning home. 

We cannot accept self-referrals to the Hospital for Small Animals. If your cat has hyperthyroidism and you are interested in radioiodine (I-131) treatment, please contact your usual veterinary surgeon in the first instance and they can contact us.

If you have a feline patient with hyperthyroidism you would like to refer for I-131 treatment, please email us at Hfsareception@ed.ac.uk. We are happy to assess cases at the Hospital for suitability and then see the patient back for a separate treatment appointment. 

We are also happy for you to perform the pre-treatment assessment for suitability and send these details to us for appraisal. If there are no issues or concerns, we can book a treatment appointment.