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Hypothyroidism in Cats

Added on 14 July 2017

Hyperthyroidism in Cats

Hyperthyroidism n cats is caused by an increase in production of thyroid hormones from the thyroid glands which are situated in the neck. It is a condition most commonly seen in older cats and symptoms can be mistaken for old age.

Symptoms on Hyperthyroidism in Cats

  • Despite a good or increased appetite there will be weight loss
  • Increased thirst
  • Cats can become hyperactive, restless and prone to being irritable An increased heart-rate
  • Poor coat condition
  • Diarrhoea and/or vomiting

Complications of hyperthyroidism in cats

Uncontrolled hyperthyroidism has important consequences on the heart, causing increased heart rate but also changes in the muscular wall of the heart that will eventually cause heart failure if untreated.

Hypertension (high blood pressure) is another potential complication of hyperthyroidism, although seen less commonly, and this can cause damage to several organs including the eyes, kidneys, heart and brain. If Hyperthyroidism in catshypertension is diagnosed along with hyperthyroidism, drugs will be needed to control the blood pressure.

Kidney disease (chronic kidney disease) does not generally occur as a direct effect of hyperthyroidism, but the two diseases often occur together because they are both common in older cats. Care is needed where both these conditions are present, as managing hyperthyroidism can sometimes have adverse effects on kidney function.

A vet may be able to feel enlarged thyroid glands but blood tests will confirm the diagnosis. Additional blood tests and investigations may also be carried out in order to rule out any additional issues such as concurrent kidney and/or heart disease.
There is a variety of treatment options for cats with hyperthyroidism and successfully treated cats, irrespective of what treatment is used, will usually have complete reversal of all the signs of hyperthyroidism.
Treatment options include:
Medical management (anti-thyroid drug therapy). These drugs are available in tablet form and they reduce both the production and release of thyroid hormones from the thyroid gland. They do not provide a cure for, but they do allow either short-term or long-term control of hyperthyroidism. However, to maintain control of the disease medication has to be given at least on a daily basis (and often twice daily).
Surgical removal of the thyroid glands (thyroidectomy). Generally, this is very successful and can produce a longterm or permanent cure in most cats. However, occasionally signs of hyperthyroidism develop again at a later time if previously unaffected thyroid tissue becomes diseased. The major risk associated with the surgery itself is inadvertent damage to the parathyroid glands – these are small glands that lie close to, or within, the thyroid glands themselves, and have a crucial role in maintaining stable blood calcium levels.
Radioactive iodine therapy. Radioactive iodine is an effective treatment for hyperthyroidism. It has the advantage of being curative in most cases with no ongoing treatment. The radioactive iodine is administered as a single injection, usually simply given under the skin. There are no significant side-effects with this treatment, but because cats are temporarily radioactive they have to be kept hospitalised for a period after treatment as a precaution. Unfortunately, because this treatment requires handling of radioactive drugs it is also only available at certain centres. A single injection of radioactive iodine is curative in around 95 per cent of all hyperthyroid cats, but following treatment occasional blood tests are recommended to ensure normal thyroid hormone levels are being maintained.
Dietary treatment. A diet that contains a restricted amount of iodine will prevent the body from producing excessive thyroid hormone. By exclusively feeding a special diet hyperthyroidism can be controlled in some cats. The pitfalls of this approach are that many cats will eventually refuse to eat the special diet (if they start eating it at all!) and many will source food from elsewhere allowing the signs of hyperthyroidism to return. When it does succeed it is an elegant way of treating the condition.


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Eastcott Veterinary Clinic & Hospital
Edison Business Park
Hindle Way, Off Dorcan Way,

Telephone: 01793 528341
email: enquiries@eastcottvets.co.uk