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FELINE HYPERTHYROIDISM
This information is designed to help you understand your cat's hyperthyroidism so that you can make important decisions about the sort of treatment you would like your cat to receive.
What is Hyperthyroidism?
Hyperthyroidism is a very common disease of older cats.
Unlike most diseases in cats of this age it is relatively easy to treat.
The most common symptoms are:
· weight loss despite a good or even voracious appetite
· increased drinking
· poor coat condition (including matting and even increased shedding)
· changes in behaviour or character (they are often restless and
more grumpy)
· occasional vomiting and diarrhoea
Sometimes affected cats may have a poor appetite and more persistent sickness.
In the past this disease has sometimes been overlooked because the changes have been dismissed as the cat "just getting old". It is important to realise, however, that by treating this disease you can not only significantly improve your cat's quality of life but also extend his or her life expectancy.
Hyperthyroidism is caused by a benign (i.e not malignant)
tumour of the thyroid gland which produces excessive amounts of thyroid
hormone. The thyroid gland is situated in the throat region and the hormone
it produces is important in regulation of the body's metabolism. Increased
amounts of the thyroid hormone increases the metabolic rate of tissues
of the body so that the energy from food is burnt off much more quickly,
hence weight loss with a good appetite.
There are other very important effects of the increase in this hormone
which develop over a period of time. The most important is over-activity
of the heart muscle which causes a heart disease called hypertrophic cardiomyopathy.
The heart beats excessively fast and is less effective at pumping blood
around the body. This in turn causes high blood pressure and damage to
the kidneys and eyes, and ultimately heart failure.
Animals with heart failure, kidney failure and an overactive thyroid gland
are very unlikely to respond well to medical treatment and are poor candidates
for surgery or radioactive iodine treatment so it is important to treat
the underlying thyroid disease early to prevent this from happening.
What happens if we suspect your cat may be Hyperthyroid?
We will normally take a blood sample to measure thyroid levels which we can test at our surgery. We may also test your cat's kidney and liver function and its blood sugar level in a separate profile as there are other diseases that can cause similar signs. Also, as mentioned earlier, cats with kidney failure as well are poor candidates for treatment for hyperthyroidism and other medication may be more appropriate.
What are the options for treating a cat with Hyperthyroidism?
1. MEDICATION
Tablets to suppress the thyroid's production of hormone. These will be given three times daily initially and then decreased to once or twice daily depending on the results of regular blood tests and weight checks.
The advantages are that the tablets are relatively cheap costing a few pence each and for many cats this provides very good control of the condition.
The disadvantages are:
· Some cats will not take tablets readily.
· Some cats require multiple blood samples before the right level of medication is reached.
· Some cats develop an intolerance to the medication over time. These cats will show reduced appetite, sickness and depression.
· Medication and monitoring are required for life.2. SURGERY
The thyroid glands are surgically removed. This is a relatively straightforward procedure in most cats requiring a short anaesthetic and 1-2 days of hospitalisation. Medication is normally given for 2-4 weeks before the operation to stabilise the animal and improve heart function
The advantage is that this normally provides a cure and removes the need for medication and monitoring for the rest of the cat's life.
The disadvantages are:
· An anaesthetic is required which involves a small risk to an elderly patient. We try to minimise this risk by fully assessing and treating as necessary the heart and kidney problems that may occur with this disease.
· The thyroid gland is very closely associated with the gland responsible for controlling the level of calcium in the blood. Surgical removal of the thyroid gland may cause lowering of blood calcium levels. This can cause poor appetite, incoordination and trembling as calcium is very important for muscle function. This is treatable and usually only temporary but to monitor for this we will hospitalise your cat for 1-2 days following surgery.
· Occasionally there is some thyroid gland tissue away from the neck, in the chest, and for this reason very rarely the hyperthyroidism will recur. If this happens one of the other options for treatment will be necessary.3. RADIOACTIVE IODINE TREATMENT
This is a very successful therapy for most hyperthyroid cats but not all. The thyroid hormone is dependant on an element called iodine so it tends to accumulate in that gland. In this treatment a small amount of radioactive iodine is injected into the cat, This will have no other effect except to destroy the affected thyroid tissue.
The advantage of this treatment is that it involves a minimum of stressful procedures for the cat, no anaesthetic and it is a cure for life.
Disadvantages of this treatment are:
· It is only available at the University of Glasgow Vet School and cats MUST be hospitalised for 1 month after treatment because of the radioactive risk.
· It is expensive, mainly because of the cost of hospitalisation, but may end up being comparatively similar in price for some cats to lifelong medical therapy and blood tests, or surgery and aftercare.
· In a small number of cats with extremely high values a second injection may be necessary.
· Glasgow University will not accept cats with pre-existing kidney trouble or other serious diseases, or if they are positive for any of the major feline viruses (Feline leukaemia, Feline AIDS or Feline coronavirus). We will test your cat for these problems before referring you to Glasgow to make sure your cat would qualify.We hope that this information will help you to understand your cat's problems and the options available to treat him or her. Please feel free to give us a ring if you have any more questions.
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INFORMATION COMPILED BY MRS PATRICIA MacFADYEN
FOR BLACKNESS VETERINARY SURGERY
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