Hyperthyroidism is the most common hormonal disorder diagnosed in cats. It occurs when a tumor develops in the thyroid gland, located in your cat’s neck, and causes an excessive production of thyroid hormone.  In some cases, this tumor may be cancerous and can spread to other areas in the body.

Thyroid hormone helps regulate and control normal body metabolism. 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 it causes 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. Untreated, the overproduction of thyroid hormone has a negative impact on the heart, kidneys, and other organs.

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

The most common symptoms are weight loss despite an increased appetite and restlessness or hyperactivity.  Some cats may look unkempt, vomit, drink more, urinate more, be irritable, and breathe more rapidly.  In some cases, you can feel the thyroid gland tumor on your cat’s neck.

So what do you do if you suspect your cat is hyperthyroid? Contact your veterinarian. They 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
  • A thyroid test, 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.

If your cat is diagnosed with hyperthyroidism, your veterinarian will discuss which treatment options are best for him and for you.

The two most commonly recommended treatments are:

  • Oral medication: the generic name for this medication is methimazole and it will help reduce the production of your cat’s thyroid hormone, helping your cat’s metabolism return to normal. This medication doesn’t reduce the size of your cat’s thyroid gland tumor; it disrupts the production of the hormone itself. It will have to be given for the rest of your pet’s life and is often administered twice a day. If you and your veterinarian decide that medication is the right option for your pet, follow-up tests are needed to ensure that your cat is on the correct amount of medication and there are no adverse side effects.
  • Radioactive iodine therapy is considered a safe and effective treatment for cats, offering a permanent cure. The treatment can be expensive and your pet will require special care while being treated.  But once the treatment is done, your cat will not require medication or further treatment. Radioactive iodine therapy also has the advantage of treating all thyroid tumor cells, so if the tumor is cancerous and has spread, this treatment will kill all cancer cells around the body. Your veterinarian will discuss with you whether or not your cat is a good candidate for this treatment.