Hyperthyroidism in cats: cause, symptoms and treatment

Hyperthyroidism in cats: cause, symptoms and treatment

Hyperthyroidism in cats

Feline hyperthyroidism or hyperthyroidism in cats is the most common hormonal disease in cats. It mostly affects middle-aged cats and older.

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What causes hyperthyroidism?

It is important to note here that hyperthyroidism in cats must be treated with the urgency required. If you suspect that your cat is suffering from it, you should visit the veterinarian as soon as possible. Do not try to diagnose and medicate your cat yourself.

Also called thyrotoxicosis, this condition happens when the production of thyroid hormones increases caused by an increase in the size of the thyroid gland in the cat’s neck. This enlargement is caused by a non-cancerous tumor called adenoma.

But the cause of hyperthyroidism in cats is not known but it could be deficiencies or excesses of certain compounds in the diet or over-exposure to thyroid-disrupting chemicals in the environment or even in the food.


The thyroid hormones affect many organs in the body; therefore, it will cause some secondary effects.

Among the most common symptoms of hyperthyroidism in cats, we find weight loss and increased appetite. Other symptoms include:

  • Excessive thirst
  • Increased urination
  • Restlessness
  • Cat may look unkempt
  • Hyperactivity
  • Panting
  • Diarrhea
  • Vomiting
  • Increased shedding

Clinical signs brought about by the condition are due to the excess production of T4 hormone in various body systems.

Hyperthyroidism can affect cats of any breed, male or female, but it is more common in older cats.  Less than 6% of cats affected are under 10 years of age. The average is placed between 12 and 13 years.


In order to confirm the diagnosis of hyperthyroidism in cats, a battery of tests must be conducted. This is because there is a host of other diseases with symptoms similar to those of hyperthyroidism.

There are usually four ways of treating the disease: medication, radioactive iodine therapy, dietary therapy, and surgery. Each one has its advantages and disadvantages.

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