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Natural Living


If your cat is more than 10 years old, there’s a good chance he has developed hyperthyroidism (an overactive thyroid gland), one of the most common endocrine diseases affecting older cats.

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How to recognize the signs, and natural ways to manage symptoms

It is estimated that 35 million or so U.S. households are home to one or more cats. If yours is one of them, chances are your feline friend has also taken up residence in your heart. As our pets become a part of our family, keeping them healthy throughout their lives becomes a priority.

If your cat is more than 10 years old, there’s a good chance he has developed hyperthyroidism (an overactive thyroid gland), one of the most common endocrine diseases affecting older cats. If not, hyperthyroidism is a condition cat owners should be aware of. Most cats are diagnosed with hyperthyroidism at around 13 years of age, yet cases have been reported in cats ranging from 4 to 22 years. Early diagnosis can prevent serious or irreversible health repercussions.

Hyperthyroidism means that thyroid cells are developing at a faster rate than normal and producing excess thyroid hormone. Thyroid hormones are essential to the maintenance of the body’s metabolism, as their role is to increase the natural chemical processes that occur inside all cells. However, when thyroid hormones are excessively produced, cellular metabolism functions at an abnormally fast rate which causes the clinical signs of hyperthyroidism.

Signs and Symptoms

There are also several symptoms you might observe. They can range from mild to severe. These include:

  • Vomiting
  • Diarrhea
  • Increased appetite
  • Increased water consumption
  • Increased urination
  • Unkempt appearance
  • Thickened nails
  • Weight loss
  • Weakness
  • Difficulty walking
  • Unusual aggression
  • Increased vocalization
  • Restlessness

Note: Hyperthyroidism is also not to be confused with hypothyroidism, which is an underproduction of thyroid hormone. Frequently diagnosed in older dogs, hypothyroidism is much less common in cats. That being said, hypothyroidism does sometimes develop in cats—after thyroid surgery, as a result of overmedication with drugs used to control hyperthyroidism, or after radioactive iodine treatment.

What You Can Do

When symptoms of hyperthyroidism become apparent, pet owners usually seek a consultation with a veterinarian for a diagnosis. Some cat owners don’t wait to see symptoms, but instead schedule annual diagnostic blood and urine testing in order to catch the disease (or any other disease aging cats are prone to) early.

As cats age, or if clinical signs are present, some owners choose to have other diagnostic techniques, such as X-rays or ultrasound, performed on their cats to fully evaluate the thyroid gland and help determine the best strategy for treatment beyond medication.

From a medical perspective, the most common methods for managing feline hyperthyroidism are medication, surgery, or radioactive iodine. Each of these approaches has pros and cons.

The medication, called Methimazole (Tapazole) doesn’t cure hyperthyroidism, but blocks the production of thyroid hormones. Cat owners who struggle to get their cats to take pills or liquids can choose a transdermal gel that is applied to the skin on the inside of the ear.

Surgery does cure the disease, but can cause a cat to be hypothyroid and require daily thyroid hormone supplementation.

Radioactive iodine is the most curative treatment for feline hyperthyroidism, but also can be the costliest. And, as with surgery, this treatment may also lead to hypothyroidism, although it’s less likely than with surgery.


In addition to medical intervention, there are natural alternatives to support cats suffering from hyperthyroidism or from side effects associated with treatment. Natural approaches in the form of supplements and diet can help to ease some of the stress on the feline body caused by the excessive production of thyroid hormones.


Certain supplements, such as omega-3 fatty acids, phytonutrients, and glandular extracts can be beneficial. Omega-3 fatty acids have a natural anti-inflammatory effect that benefits many organ systems. Fish oil is a great source of omega-3s because it provides preformed, long-chain polyunsaturated fatty acids that are easily absorbed.

Supplements specially formulated for cats containing phytonutrients (nutrients found in plant foods, such as green foods) and glandular extracts promote better immune system function and organ detoxification. Supplements that have an anti-inflammatory effect (such as omega-3 fatty acids) help cool some of the heat and inflammation associated with hyperthyroidism. Additionally, feline-appropriate vitamins, minerals, and antioxidants support basic cellular function that’s put into an overly active state in the face of thyroid-hormone overproduction.

Phytonutrients are often deficient in the feline diet or included in synthetic forms that are less efficiently absorbed. As for glandular extracts, if cats were eating freshly killed prey as they did before they were domesticated, they would consume many body parts, including glandular tissue. This tissue contains substances vital to whole body function that can be deficient in commercial diets.


What you feed your cat is critically important throughout its life. Because cats require a moisture-rich diet, canned foods are better than dry food (kibble) and are closer to a cat’s natural diet. When looking for a canned cat food, strive to find a food packaged in BPA-free cans. Additionally, avoid foods having meat and grain “meals and by-products,” artificial colors and flavors, and chemical preservatives (BHA, BHT, etc.).

Additionally, pieces of the cooked meat or fish you enjoy in your meals can be provided as a staple of your cat’s diet or as a snack. Doing so should be paired with a reduction in your cat’s regular food portion to ensure that daily calorie requirements are not exceeded.

Since feline hyperthyroidism prevention isn’t clear-cut and the disease can ultimately be fatal, the goal is to diagnose the disease before significant symptoms develop. In addition to giving your cat a solid foundation through a healthy diet and appropriate supplements, regular check-ups, coupled with knowing the symptoms of this disease and watching for them, are the best way to ensure a long and healthy life for your cherished cat.

Patrick Mahaney VMD, CVA, CVJ is an accomplished veterinarian known for his writing, public speaking,
media appearances, and social media presence. As both a veterinarian and certified veterinary acupuncturist, he has a patient-care approach that powerfully integrates Western and Eastern medical perspectives. Mahaney has his own house call practice, California Pet Acupuncture and Wellness, based in Los Angeles.