Hyperthyroidism in cats can be a serious health concern and is relatively common, especially in older felines. Recognizing the symptoms early can help cat owners give their pets proper care right away to manage or cure the condition and keep their cat comfortable and healthy.

What Is Hyperthyroidism?

Also called thyrotoxicosis, hyperthyroidism is having an overactive or “hyper” thyroid, a pair of glands in the neck, one on either side of the windpipe. These glands produce hormones that regulate a cat’s energy, drive, and enthusiasm. When overactive, the excess hormones give the cat too much energy that increases metabolism and can cause a variety of troubling symptoms.

Hyperthyroidism in cats can be caused by several conditions, most commonly a benign tumor such as a thyroid adenoma. Only 1-2 percent of cases are actually cancerous. Hyperthyroidism is the most common hormone-related problem in cats, with one in five felines over the age of 10 developing the condition.

Symptoms of Hyperthyroidism in Cats

The most common hyperthyroidism symptoms cats show are a dramatic increase in appetite coupled with weight loss due to the increased thyroid hormone’s impact on the cat’s energy levels. At the same time, the cat’s behavior may change and become more agitated and irritable, though some cats show signs of apathy or depression.

Other symptoms that indicate hyperthyroidism include:

• Faster than normal heart rate and respiration
• Increased meowing or yowling
• Increased thirst
• Poor coat condition with matted or greasy fur
• General restlessness
• Diarrhea or vomiting
• Increased urination, potentially with accidents

Because many of these symptoms might first go unnoticed or could be attributed to other illnesses or conditions, it may be challenging to recognize hyperthyroidism. A clear diagnosis can only be confirmed through a blood test that will measure hormone levels.

If left untreated, hyperthyroidism in cats can lead to a very weak and emaciated animal, with complications such as heart disease, high blood pressure, kidney disease, blindness, or strokes. Because any of these effects can be extremely serious, it is important to treat hyperthyroidism as soon as possible.

Treatment Options

There are several treatment options available for cats with hyperthyroidism, though the best treatment will vary depending on when the condition is detected, how severe the symptoms are, temperament issues, the cat’s age and overall health, and the facilities available at the preferred veterinary hospital.

• Oral Medication – A pill given 1-2 times daily can help with mild hyperthyroidism, but may not be the best choice for a cat that won’t tolerate being given medication or that has very finicky taste preferences. With this option, periodic blood tests are essential to monitor the effectiveness of the medication, which can be troublesome for a cat that is not good with visiting the veterinarian.
  
  
• Special Diet – A special prescription diet that is very low in iodine (which is part of the hormone the thyroid controls) can help manage hyperthyroidism, but the diet has to be very strict with no extra treats at all. This can be difficult for pet owners if they have multiple cats or even other animals and the cat may steal food or break into food containers. Cats that have very delicate tastes may also not like the prescription food, and proper nutrition then becomes a concern.
  
  
• Surgery – Removal of the thyroid (one of the glands if only one is affected, or both if necessary) is a permanent cure for hyperthyroidism, but it does come with the associated risks of anesthesia and recovery. This can be especially concerning because hyperthyroidism is most common in older cats that may not tolerate the stress of surgery as safely. Surgery is also a more costly treatment option, but in the long term, it is a permanent solution that will not require ongoing checkups or special diets.
  
  
• Radioactive Iodine Treatment – This specialist, advanced treatment can cure hyperthyroidism in as little as 1-2 weeks depending on the state of the glands, and involves intravenous or subcutaneous injections and very close monitoring at an appropriate facility, which not every veterinary hospital is equipped to do. The cat may need to remain hospitalized for a few days or up to two weeks, and the treatment is expensive, but without the anesthesia risks of surgery. While the logistics of radioactive iodine treatment can be tricky, it is a very effective option.

Which treatment will be best for an individual cat is a decision the owner and veterinarian need to discuss carefully, choosing the most effective and practical option. It can be frightening for an older, beloved pet to develop hyperthyroidism, but the right treatment can also be very successful at managing or curing the condition and ensuring the animal has a healthy, happy life in its senior years.