Radioactive iodine treatment is a therapy that your veterinary surgeon may recommend if your cat is diagnosed with hyperthyroidism. Hyperthyroidism, or an overactive thyroid, is a common disease of older cats. Affected cats produce too much thyroid hormone. Thyroid hormone regulates the metabolic rate of an animal. Too much of this hormone can lead to problems including weight loss despite an increased appetite, excessive drinking, an unkempt hair coat, and a fast heart rate. If your veterinary surgeon suspects your cat may be hyperthyroid they will recommend tests including a blood test to diagnose the condition. Fortunately, there are now a range of treatment options – some of which are completely curative. Read on for more information!

If the condition is confirmed most cats will initially be started on a course of tablets or liquid medication to try and reduce the levels of thyroid hormone in their blood. Most cats will need their medication dose to be adjusted a few times, especially in the first few months, and regular blood tests are usually necessary. This kind of treatment may be continued for life, or other treatment options might be considered. Alternative treatment options include a prescription low iodine diet, surgery or radioactive iodine treatment. Each treatment option has advantages and disadvantages.

Radioactive iodine therapy 

This is a treatment that involves injecting affected cats with radioactive iodine. This is absorbed into the bloodstream and then taken up by the thyroid gland. The radioactive iodine destroys the diseased thyroid tissue and results in a reduction in thyroid hormone levels. For most cats it is a very effective and safe treatment and offers the potential of a true cure.

There are however some drawbacks to this type of treatment. 

As the therapy involves radioactive materials there are very strict regulations involving its use in the UK. This means that only a limited number of centres, fifteen in the UK, are able to offer this option. Following the injection of radioactive iodine, your pet will emit radioactive material for a short time afterwards. For this reason they have to be isolated for a period of time in order to protect humans from contamination. 

There are two phases to this quarantine, for the first period they must be very strictly isolated with minimal handling. This is one of the reasons that most centres carry out strict screening procedures to ensure treated patients are unlikely to become ill over this period and need medical intervention which would be difficult to give. During the second period the isolation is less strict but waste and bedding still need to be carefully disposed of, and treated cats should be kept away from pregnant women and very young children who may be more susceptible to the effects of any residual radiation. The length of time these isolation periods are for vary from centre to centre, and in some cases the second period may be carried out at home if certain strict criteria are met.

There are a small number of cats that standard radiation treatment does not work for.

These are often cats suspected of suffering from a more malignant form of hyperthyroidism caused by a thyroid carcinoma or cancerous growth. In these cases the standard doses are often not strong enough. There are however some centres who are licensed to give higher dose treatments. These are more likely to be effective against this form.

Conversely there are a small number of cats for whom the treatment is too effective.

This results in them becoming hypothryoid, in other words they don’t produce enough thyroid hormone. Affected cats will need thyroid supplementation in the form of tablets or liquid. This is usually temporary or but in rare cases may be lifelong.

Taking this into account, it’s clear that this treatment won’t be right for every cat, but here are a number of cats that are particularly suited to this treatment.

Younger cats faced with lifelong treatment, cats suffering side effects of other treatments, cats where other treatments have failed and in some cases cats that are hard to medicate, although it should be remembered that a small number of cats may still need medication of some sort.

Cats that are less suitable for treatment may include very elderly cats, cats that live a long way from a centre and are not good travellers, cats with other underlying health conditions or those that may become stressed by a period of isolation.

Radioactive iodine is a great option for many cats affected by hyperthyroidism. It can seem expensive but often when compared to a lifetime of blood tests and medication, the costs are actually very reasonable. It won’t be right for every cat, but your veterinary surgeon is the best person to help you decide whether it might be the right choice for your precious pet. 

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