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Hyperthyroidism in Cats

Understanding a common feline hormone disorder

Reviewed by Dr. Peter Kintzer, DVM, DACVIM on Monday, August 3, 2015
Posted October 21, 2011 in Cat Diseases & Conditions A-Z

Hyperthyroidism is the most common hormonal disorder diagnosed in cats. It occurs when the thyroid glands, located in your cat’s neck, produce an excess of thyroid hormone.

Thyroid hormone helps regulate and control normal bodily processes. Think of it as an engine gauge: in simple terms, it controls how fast or slow the body functions. When a cat’s thyroid gland becomes overactive and produces too much thyroid hormone, the engine gauge is turned up too high, leading to an increase in the body’s metabolism. While this may sound like a great way to shed a few extra pounds, the impact of hyperthyroidism on our cat friends can be dangerous. Over a long period, the overproduction of thyroid hormone can have a negative impact on the heart, kidneys, and other organs.

Cat on floor

The exact cause of hyperthyroidism is not known. This disease typically affects cats aged 7 years or older, and both male and female cats can become hyperthyroid.

What should you keep an eye out for if you suspect your pet is hyperthyroid? The most common symptoms are weight loss despite a desire to eat more than normal, and restlessness. Additionally, some cats may look unkempt, vomit, drink more, urinate more, become cranky, and breathe more rapidly.

In some cases, you can even feel the thyroid glands on your cat's neck because they sometimes become enlarged. This is called a goiter.

So what do you do if you suspect your cat is hyperthyroid? Contact your veterinarian. She/he can run some simple tests to determine if your cat has this disorder.

These may include:

  • Chemistry tests to evaluate kidney, liver, and pancreatic function, as well as sugar levels
  • A complete blood count to rule out blood-related conditions
  • Electrolyte tests to ensure your cat is neither dehydrated nor suffering from an electrolyte imbalance
  • One or more thyroid tests, which determines if the thyroid gland is producing too much thyroid hormone
  • A urinalysis to rule out urinary tract infection and to evaluate the ability of the kidneys to concentrate urine

Additional tests may be added on an individual basis. Your veterinarian will recommend the right course for your feline friend.

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