Understanding Cat Hyperthyroidism

Cat hyperthyroidism is one of the more common endocrine disorders in cats. Hyperthyroidism typically occurs in cats over the age of 13; with only 5% of cases occurring in cats younger than 10 years old. Whereas the exact cause is unknown, the condition is well understood. Because hyperthyroidism can cause various other conditions in your cat, treatment is important.

What Is Cat Hyperthyroidism?

There are two thyroid glands in cats: the left and the right. They produce a hormone called thyroxine. Thyroxine controls the speed of all processes in the body. When the thyroid glands overproduce thyroxine, it is called hyperthyroid. The overproduction of thyroxine is caused when one or both of the thyroid glands become enlarged. An increase in benign, non-cancerous cells in the thyroid is the most common cause of enlargement.

Signs of Cat Hyperthyroidism

The thyroid regulates the speed of every chemical process in the body. Your cat's kidneys, liver, heart, muscles, nervous system and digestive system are all being over stimulated. Because hyperthyroidism usually happens over a period of time, symptoms may start out gradual and escalate in their severity.

  • Weight loss
  • Increased appetite
  • Increased activity or restlessness
  • Vomiting 
  • Poor hair coat
  • Fast heart rate
  • Increased drinking
  • Increased urination
  • Diarrhea
  • Weakness
  • Tremors
  • Difficulty breathing

Diagnosing Hyperthyroidismin in a Feline

A simple blood tested is used to confirm hyperthyroidism. When a cat is hyperthyroid, the level of thyroid hormone in their blood increases. Because thyroid levels may vary over time or increase as the condition progresses, several blood tests may be needed before an accurate diagnosis can be made.

If testing is not conclusive by blood tests alone, a nuclear medicine scan may also be performed. A nuclear medicine test will consist of your cat ingesting a small amount of radioactive compound. The compound will travel through the blood and to the thyroid gland. At that point, a scan can be performed to check for abnormal appearances of the thyroid.

How Can Hyperthyroidism Effect Your Cat

Because the thyroid controls every process in the body, overstimulation can harm other organs. Heart disease and high blood pressure are common ailments found in cats with untreated hyperthyroidism. Also, it causes the heart to beat faster and more forcefully. When the heart is over worked, fluid can build up around the heart and the lungs. Additionally, hyperthyroidism can cause the pressure of blood in the body to be increased. High blood pressure can cause vessels in the eyes, the brain and the kidneys to burst.  

Treatment of Hyperthyroidism in Cats

There are three options for treatment of hyperthyroidism in your cat: life long oral anti-thyroid medications, surgical removal of thyroid glands and treatment with radioactive iodine.

An oral anti-thyroid medication is a hormone used to slow the natural processes of the thyroid. This can help your cat to return to normal thyroid levels. Administering medication will require annual blood tests to ensure that it is still effective. Because the thyroid will not return to a normal state on its own, medication is life long.

In lieu of giving daily medication, pet owners can choose either surgical removal or radioactive iodine treatment. Both of these options will kill the thyroid and stop its function. However, these procedures are initially more expensive than medication.

If your cat suffers from heart disease or another ailment due to their hyperthyroidism, both conditions will need to be treated. However, with successful treatment of the thyroid, heart disease and other ailments can be reversed.