Feline Hyperthyroidism: Over Active Thyroid

Hyperthyroidism is a common condition in older cats where excessive levels of thyroid hormones are produced from the thyroid. Learn more about the clinical signs and treatment options.

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This is a common condition in older cats where excessive levels of thyroid hormones are produced from the thyroid. It is a slowly progressive disease where cats generally maintain a good to excellent appetite and are active for their age (indeed sometimes even hyperactive).

These clinical signs often make many owners feel that their cat is exceptionally well, until weight loss and other problems become evident.

What Clinical Signs Should I See?

  • Increased appetite
  • Increased urination/thirst
  • Weight loss
  • Vomiting/diarrhoea
  • Hyperactivity
  • Poor coat quality/over grooming

Occasionally some cats can show inappetance and decreased activity but this is much less common.

How Will I Know If My Cat Is Hyperthyroid?

Often the clinical exam and history are highly suggestive of the condition, but a blood sample is required to confirm it.

Treatment Options

Initial Therapy

Initially cats are stabilised with treatment designed to normalise the thyroid levels. This can come in the form of medication or even a low iodine diet (Hills prescription Y/d diet). A blood test (and urine sample in some cases) are often performed after at least three weeks to confirm good thyroid control and check for no adverse effects.

It is also often useful to check the blood pressure, as this can sometimes be high in these cases. Feline hyperthyroidism can certainly be a risk factor. High blood pressure (hypertension) can be highly damaging to the heart, eyes and brain but can be easily treated by extra medication once detected.

Long Term Therapy

If initialisation therapy has been successful then longer term management can be considered. This can take two forms. Either maintenance therapy or curative treatment.

  1. Maintenance Therapy

    Often if the medical or dietary management is successful then this can be carried on for life. Regular health-checks are performed in many cases to confirm good thyroid control and make sure that there are no adverse effects.

  2. Curative Therapy:

    There are treatments available to potentially cure the overactive thyroid. This involves removing excess thyroid tissue by an operation (surgical thyroidectomy) or by radioactive means (radioactive iodine therapy).

Radioactive iodine therapy has become the gold standard as this mainly selects the overactive thyroid tissue and destroys it without surgery. Often this can be curative with just one treatment with fewer risks involved compared to surgical management.

If you suspect that your cat may have hyperthyroidism, please contact the practice and we can carry out a test, and discuss the treatment options available to you and your cat.

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