Hyperthyroid cats: brochure and FAQ
Tip: First, review the brochure Radioiodine Therapy in Hyperthyroid Cats.
Frequently asked questions about the treatment of hyperthyroid cats
Are there reasons why my cat should not be treated?
- Isn't my cat too old for treatment?
- How long beforehand should the regular medication be stopped?
- Where does the cat stay during hospitalization?
- Can I come and visit my cat?
- What after the therapy, once the cat is back home?
- Are there reasons why my cat should not be treated?
- Can I be kept informed during my cat's stay?
- The radioprotection brochure states that children should not come in contact with the cat after treatment, but what about the age of the children?
- What about other pets?
- What are the success rates?
- What if a cat already has kidney problems?
- How long should the cat be hospitalized?
- Are there side effects of the iodine treatment itself?
- What are the effects of radiation on humans?
- How long does it take for the treatment to work?
- What is the long-term prognosis?
Isn't my cat too old for treatment?
Hyperthyroidism is a condition typically found in older animals. Especially if your cat has no other major health problems, there is no reason not to have him/her treated. The age of patients we have already treated ranges from 9 to 18 years.
How long beforehand should the regular medication be stopped?
Thyroid inhibiting medication can affect our radioiodine therapy The thyroid medication should be stopped in most cats 10 days before radioiodine therapy. Exceptionally, this can be shortened to 3 days. We advise on this when you make the appointment and we have all the cat's details.
If the cat is taking other medication, for example heart medication, we will give specific advice when you make the appointment.
Where does the cat stay during hospitalization?
The cat hospitalization is located in a new, separate part of the Nuclear Veterinary Department. Here the cats have a separate, quiet room, each with its own spacious pen. They can hear each other but cannot see each other to avoid problems with any runaways. Several times a day the veterinary assistants come by and the litter box is changed, water changed and food (and some attention) given, and medication administered if necessary. Although it is an adventure for the cats, after a day most cats are used to the new environment and therefore seem to experience little inconvenience from their stay.
Since radioactive materials are handled, visits are not legally allowed. The 4 days of hospitalization are usually more difficult for the owner than for the cat. We assure you that your cat will be surrounded with the best possible care.
What after the therapy, once the cat is back home?
Read the brochure (at the bottom of this page) carefully. You can read the guidelines and aftercare in the section 'Follow-up after radioiodine therapy'.
Control blood tests can be done at your own veterinarian, you do not need to come to the Faculty of Veterinary Medicine again. However, we urge you to keep us informed about the further follow-up of your cat. This can be done by e-mail (katomic@ugent.be) or post (Faculty of Veterinary Medicine, Nuclear Medicine, Salisburylaan 133, 9820 Merelbeke).
Are there reasons why my cat should not be treated?
If the cat has another condition at the same time, for example kidney failure or diabetes (diabetes mellitus), or the cat is clinically unstable (e.g. prolonged poor appetite) for whatever reason, we recommend a consultation with the Endocrinology / Internal Medicine department first. A treatment decision is made on the basis of the preliminary examinations already done at your veterinarian. So it is important to provide us with all the data in advance so that we can make the best choice and give your cat the best care.
Although it is rather rare, there are cats that do not qualify, which is why it is important to detect underlying or concomitant diseases or problems as much as possible. Indeed, once the animals are treated with radioactive iodine, examination options are temporarily (3-4 weeks) limited.
Can I be kept informed during my cat's stay?
We will keep you informed how the treatment went and regularly inform you how the cat is doing during the hospitalization. If specific questions arise, you will of course be contacted immediately.
Legally, we speak of children up to 16 years of age, the youngest being the most sensitive. Therefore, contact with young children during the first two weeks after the cat comes home is not permissible. The same applies to women who are pregnant. Unborn children and growing children are more sensitive to radiation, and then contact with the cat (and the litter box) is best avoided, no matter how low the radiation from the cat may be.
Also, women who are trying to get pregnant or may be pregnant at the time the cat is being treated are best to temporarily transfer the care of the cat to someone else for a while. Although again the chance of harmful effects of the radiation is very small, it is better to take precautions whenever possible.
It you are taking care of the cat, it is not a problem for you as an adult to have contact with children and pregnant women.
In principle, there is no problem with other pets, as long as they are adults who are not pregnant. Using the same litter box also poses little problem. We do recommend that you wash your hands thoroughly even after petting the other animals, for example, if two cats were to wash each other, some contamination of the coat of the non-treated cat could possibly occur. The easiest way to avoid this is to keep the animals separate. If this is not possible, then wash your hands a little more often. Also try to change the litter box on a regular basis: possibly clumping cat litter can help with this to reduce the amount of litter you need to collect.
For animals that do not seek contact with each other, there is no problem (adult animals that are not pregnant).
If you wish to breed with one of your other animals in the near future, it is recommended to avoid contact with the treated cat for the first two weeks after returning home as well.
The majority of treated cats become euthyroid after treatment, that is, the thyroid gland returns to normal function.
A small number of cats will produce too little thyroid hormone after treatment (= hypothyroidism). This may be temporary and transient after treatment, but it can sometimes take several weeks to months before thyroid function is restored. Hence the long period of follow-up (12 months). In some females, however, there is not enough normal thyroid tissue left after radioiodine treatment, and they will remain hypothyroid. If that happens, the hormone deficiency can be supplemented by giving pills. These are very well tolerated by cats. Hormone supplementation is also recommended if kidney function is compromised, in order to provide some support to the kidneys.
Some cats remain hyperthyroid after treatment. In certain cases, namely when the thyroid gland is very enlarged, we can estimate this somewhat, and you will be informed of this. We can only determine this after the diagnostic scan, and we will then treat the cat anyway but with an adjusted dose. In other cases, it cannot be predicted. A second treatment may then be necessary. Relapse after a first successful treatment is also possible, sometimes even after several years, and then it is more common in cats where only 1 thyroid gland is initially affected. We cannot guarantee that the other thyroid will never be affected, but there is nothing we can do about this preventively.
What if a cat already has kidney problems?
If the initial blood test shows that the kidney values have already risen (even with a high TT4), we recommend a trial period with thyroid inhibitors. That way the thyroid hormone can normalize, and we can monitor how the kidneys evolve when there is no more excess thyroid hormone.
If the kidneys remain stable, or only get worse to a mild degree, and the cat shows no symptoms of kidney failure clinically, then iodine treatment can still be performed. Of course, it remains important to monitor the evolution of the kidneys. Possibly, supporting measures can already be taken for the kidneys, such as an adapted diet (kidney diet).
If the kidney values deteriorate sharply after the trial period with thyroid inhibitors or if the kidney function was already poor at the time of the diagnosis of hyperthyroidism, it may be better to abandon iodine treatment and try to control the thyroid gland with medication. Too low an amount of thyroid hormone should be avoided. Of course, supportive therapy for the kidneys should also be instituted at this time.
How long should the cat be hospitalized?
The cats stay with us for 4 days, that is, you bring them in on Tuesday morning, and may pick them up again on Friday morning (the time of pick-up is done in consultation with the veterinary assistants). In exceptional cases, such as an animal that refuses to eat, the owner is informed and we look for another solution. During this period, the cats are in a quiet and specially equipped hospitalization room. Of course, they are not left to their own devices during these days. They are visited several times a day by their caretaker, and the veterinarians also visit regularly. Moreover, the cats also go to the litter box several times during this period, which already leaves a lot of radiation with us: in fact, the main way they get rid of their radiation is through urine.
Are there side effects of the iodine treatment itself?
The treatment itself has few side effects. The radioactive iodine is specifically going to be absorbed by the thyroid gland, and exerts its effects there locally. There is no hair loss or skin damage. However, as a result of the radiation in the thyroid gland, an inflammation may develop ("radiation-induced thyroiditis"), which may cause mild discomfort in some cats. This is then manifested by a more husky voice, or they stretch the neck a bit more when eating. This is seen rather rarely, and disappears spontaneously after 1-2 days. If necessary, a light painkiller can be given.
What are the effects of radiation on humans?
For the first two weeks after the treatment, we give you strict instructions (see Practical Info - Aftercare). Herein we explain what is and is not allowed, and how best to handle the cat. The main thing is to avoid intense contact with the cat. This means that you do not hold the cat on your lap, do not let it sleep on your bed or in the bedroom, and certainly do not let it near pregnant women and children. Note: this does not mean that you should not visit someone who is pregnant!
The radiation emitted from the cat is minute, but we know that there is still some radiation. If you follow our measures, then having the cat back home will not be a problem. In fact, the presence of the cat in the house alone will not cause any problems, but it contributes to the totality of radiation that you receive throughout your life. You can minimize this by keeping your distance from the cat (minimum 1 meter), and keeping the time of more intense contact (e.g. once a stroke or a hug) as short as possible.
How long does it take for the treatment to work?
This depends from cat to cat. Some cats show change very quickly, even after just a few weeks, while others need 2 - 3, sometimes even 6 months. Treatment will address the thyroid gland working too fast, but it may take several weeks before normal levels of thyroid hormone are reached. This will also manifest itself in the behaviour of your cat, who will gradually become calmer, less food-obsessed, and at the same time regain some weight. We cannot predict how quickly this happens.
What is the long-term prognosis?
As mentioned, one treatment with radioactive iodine is sufficient for the majority of patients.
If hypothyroidism (thyroid hormone deficiency) does occur, it still need not be a problem. Usually the cat is not affected by this, and nothing needs to be done. Only when clinical symptoms appear (reduced appetite, less active and alert, ...) or the kidney function deteriorates, then it is best to supplement thyroid hormone. This medication is given daily and is very well tolerated by cats (far fewer side effects than thyroid inhibitors!).
Preliminary blood tests and any probation usually give us an idea about the condition of the cat's kidneys. However, it remains important to follow them up - even long after treatment. Kidney problems are frequent in older cats, and while they cannot be cured, we can support kidney function, helping the cat to hopefully live a long life.
Persistent hyperthyroidism or relapses occur in a very small percentage of treated cats. A second treatment is always possible. For this, it is best that you or your veterinarian contact us first.
| Attachment | Size |
|---|---|
 Radiojoodtherapie bij hyperthyroïde katten - brochure | 687.91 KB |