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Hyperthyroidism – Cats

Hyperthyroidism is the second most common condition of the older cat (10 years and older). Uniquely, all cats have 2 thyroid glands near their voice box in their neck, which get bigger and produce large amounts of the thyroid hormone. This over production of thyroid hormone, which controls the body’s metabolic rate, causes a range of symptoms which include;

  • Increased appetite
  • Weight loss
  • Vomiting
  • Diarrhoea
  • Anxious, irritable, unable to settle
  • Unkempt, tatty coat appearance

As metabolism affects all parts of the body, muscles, gut system, urinary, nervous and cardiac symptoms can all be present. Typically, our veterinary examinations will reveal high heart rates, often with murmurs, a ‘pointy face’ due to the weight loss, a palpable swelling in the neck (a goitre), and a grumpy cat who might start panting and be very agitated. If we check our cats regularly throughout their lives, these symptoms are easier to suspect and detect.

We always confirm this condition with a blood test, ideally checking more than just the thyroid hormone and assessing the ‘knock on’ effects of the cat’s metabolism being deranged.

There are now 4 treatment options for this condition and these should be discussed with your veterinary surgeon. Not all cats are suitable for all of these treatments and should be selected for on a case by case basis. All options require monitoring examinations and blood tests for the rest of the cat’s life.

Tablet medications
These are drugs to turn down the thyroid hormone production and therefore the metabolic rate. These are life-long treatments and are still the most commonly used treatments

There is a unique formulation of a diet (called Hills Y/D) which if fed EXCLUSIVELY will decrease the thyroid levels. It does require NO OTHER food to be given. It works by having no iodine in it, an element which is crucial to thyroid hormone production. Iodine is very common in all meats especially fish and present in all pet foods.

Once stabilised with tablets, we can perform a surgical removal of the affected gland(s). As with all surgeries, there are risks involved with this treatment, and it can need to be repeated.

Radioactive Iodine
This is a unique treatment. We need to refer these patients to specialised hospitals where the cats stay for several weeks. The treatment involves giving radioactive iodine which targets and destroys the thyroid glands.

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