Thyroid Disease in Dogs & Cats

Written by: Dr. Jean Hofve, Holistic Veterinarian, DVM

The thyroid gland produces hormones that affect the body’s metabolism, growth and development. The two most important hormones are tetraiodothyronine (thyroxine or T4) and triodothyronine (T3). There are two conditions caused by a dysfunctional thyroid gland – hyperthyroidism and hypothyroidism. Hyperthyroidism is more common in cats and is caused by an overactive thyroid gland with the resulting overproduction of hormones. Hypothyroidism, which is more common in dogs, is caused by an under active thyroid gland that is not producing enough hormones resulting in decreased metabolism.


Hyperthyroidism is diagnosed so often in cats that it has practically become an epidemic. It is rarely seen in dogs. It is more common in older cats, but may be seen in younger cats as well. Hyperthyroidism is generally a result of benign (non-cancerous) changes or enlargement of the thyroid gland. It seems to be more common among cats that have been fed sub-standard nutrition and food containing artificial preservatives. Some holistic veterinarians feel they have seen an increase in hyperthyroidism that corresponds to the increased vaccination rate for feline leukemia. Viral and bacterial infections can also play a role, as well as environmental toxins.

Symptoms of hyperthyroidism include:

  • Excessive thirst (in 10% of hyperthyroid cats)
  • Excessive urination
  • Increased appetite
  • Weight loss (despite increased appetite)
  • Hyperactivity
  • Irritability or Aggression
  • Vomiting
  • Diarrhea
  • Voluminous fatty feces
  • Panting, Heat intolerance
  • Skin lesions, dry, greasy, matted coat

Secondary problems include high blood pressure and heart disease. The increased metabolic activity stimulated by the excess thyroid hormones cause an increased heart rate which leads to an enlargement of the heart and thickening of the heart walls. The increased pumping pressure of the heart leads to high blood pressure.

Hyperthyroidism is best addressed with a team approach that includes you, your veterinarian and a holistic veterinarian – either in your area or via phone consultation. Some cats are excellent candidates for allopathic treatments; some cats need a strictly holistic approach; many will do best with a combination of both approaches.

The holistic methods of treating hyperthyroidism include improving the overall health of the animal through improving diet and providing proper supplements, as well as more targeted treatments such as constitutional homeopathy or Chinese herbal remedies.


Feeding the best diet possible is the place to start. Feed the freshest food you can – raw is best, freeze dried and dehydrated follow that, then canned, and lastly dry food. Dry kibble should be a minimal part of the diet for cats. Cats do not produce as much of the enzyme amylase, that digests carbohydrates, as people and dogs do, so grains and other carbohydrates are more difficult for cats to break down and digest properly. Cats need meat as the main portion of their diet. (See the articles What You Need to Know About Your Pet’s Food and All About Raw Food for additional information on appropriate diets). Hyperthyroidism commonly occurs in cats that have some form of Inflammatory Bowel Disease (IBD). Chronic vomiting and other symptoms of gastro-intestinal disorders are often resolved through diet changes as outlined above. In addition to feeding the freshest food possible, the diet should be free of common allergens such as wheat, corn, soy and dairy. See Inflammatory Bowel Disease & Other Gastrointestinal Issues for more information about treating IBD.


Carnitine is an amino acid that has been shown to prevent or reverse hyperthyroid symptoms in humans, and is often recommended for cats as well. Since hyperthyroidism tends to deplete the body of carnitine, supplementation is recommended anyway. Cats can be given 125 to 250 mg 2 times per day.

Chinese herbal formulas are frequently a part of a comprehensive approach to hyperthyroidism. Thyroid Calming by Nature’s Herbs for Pets is designed to aid in balancing thyroid function. More advanced Chinese herbal remedies may be prescribed by your holistic veterinarian.

The herbs Bugleweed and Melissa (lemon balm) are western herbs used traditionally in the treatment of hyperthyroidism in cats. These should be used under the supervision of a holistically trained veterinarian.

Constitutional Homeopathy has also been successful in reversing hyperthyroidism, particularly in the early stages. Constitutional homeopathy takes into consideration the whole patient, the totality of all symptoms including physical, mental and emotional states. A classically trained homeopath will ask many detailed questions in order to obtain a complete picture of the individual and match this to the most appropriate remedy. To find a holistic veterinarian that practices homeopathy near you, check the Academy of Veterinary Homeopathy referral directories.

Flower essences can support your pet’s emotional well-being during his treatment. Thyroid Balance Flower Essence by Pet Essences may help calm the irritability or ease depression that often occurs with hyperthyroidism.

Hyperthyroidism often masks underlying kidney disease in older cats. It is not uncommon to bring the thyroid under control only to find that the patient needs treatment for kidney disease within months. For this reason it is even more important to improve the diet as much as possible and provide daily supplements for optimal overall health including a good daily multivitamin, digestive enzymes, essential fatty acids, and vitamin C.

"Prevention of hyperthyroidism (and hypothyroidism) is the best approach through proper diet and daily supplements..."


Hypothyroidism is more commonly seen in dogs than cats. It is typically a result of physical degeneration of the thyroid gland – either from an autoimmune response or atrophy of the thyroid gland. Some holistic veterinarians believe this degeneration may be related to environmental toxin exposure, poor diet and nutrition, over-vaccination, or a combination of these factors. Some dogs have a genetic pre-disposition to the disease. Breeds that are more commonly affected include Golden Retrievers, Doberman Pinschers, Greyhounds, Irish setters, Dachshunds, and Cocker Spaniels. Hypothyroidism is rare in toy and miniature breeds of dogs.

Over 80% of hypothyroid dogs show some kind of skin abnormality such as thickening in some areas, darkening pigmentation, dry skin, or infections. Other symptoms of Hypothyroidism may include the following:

  • Lethargic behavior (lack of interest in play, frequent napping, tiring out easily)
  • Weight gain, sometimes without an apparent gain in appetite
  • Hair loss, especially on the trunk or tail (without associated itching)
  • Cold intolerance/seeking out warm places to lie down
  • Slow heart rate
  • Chronic ear infections
  • Behavioral changes such as aggression, anxiety and/or compulsivity
  • Depression

These symptoms will appear gradually, so it is not uncommon for guardians to miss the initial stage of the disorder. It is generally seen in middle-aged or older dogs.

Hypothyroidism is difficult to diagnose despite its seeming simplicity. It is not so straight forward as testing for low thyroid hormone levels and prescribing synthetic hormone replacement. There are a variety of tests available to determine the level of thyroid function and hormones available in the system. Endocrinologists may use multiple tests to make a proper diagnosis. Some veterinarians will prescribe a trial period of synthetic thyroid hormone and, if the response is positive, use this as the means of diagnosis. The problem with this method is that synthetic thyroid hormone acts as a stimulant, so most dogs will respond with increased activity and interest in life. If a dog that is not truly hypothyroid is kept on synthetic thyroid hormones for an extended period, the increased metabolic rate can tax the dog’s system - hastening the aging process and leading to other degenerative conditions. In addition, the use of synthetic thyroid hormone can hasten the degeneration of the thyroid gland. As you can see, proper diagnosis is rather important.

Since most hypothyroid dogs will retain at least some function of the thyroid gland, it may be very useful to support the function of the thyroid gland through the use of supplements, herbs and glandulars – possibly in combination with synthetic thyroid hormone depending on the stage and severity of the issue.

Again, diet is the place to begin (see above under hyperthyroid treatment). A high quality diet supports the body in managing its own endocrine system. As with treating any health issue, provide daily supplements for support of overall health including a good daily multivitamin, digestive enzymes, essential fatty acids. Essential fatty acids can be helpful in treating some of the skin abnormalities resulting from hypothyroidism.

Chinese herbal formulas can be particularly helpful in treating hypothyroidism. Thyroid Boost by Nature’s Herbs for Pets is designed to aid in balancing thyroid function. Again, more advanced Chinese herbal remedies can be prescribed by a holistic veterinarian.

Thyroid Balance Flower Essence by Pet Essences may help address any emotional and behavioral issues resulting from the thyroid imbalance.

Glandular supplements can be prescribed by a holistic veterinarian and are often helpful in supporting thyroid function.
Additional articles of interest

What You Need to Know About Your Pet’s Food

All About Raw Food

The Importance of Daily Supplements for Your Companion

Inflammatory Bowel Disease & Other Gastrointestinal Issues

Dealing with Kidney Failure in Cats and Dogs

What You Need to Know About Vaccinations


A Manual of Natural Veterinary Medicine by Dr's Susan Wynn and Steve Marsden

Herbs for Pets by Mary L Wulff-Tilford & Gregory L Tilford

The Nature of Animal Healing” by Martin Goldstein, DVM - The Pet Health Library – “Hypothyroidism in Dogs” by Wendy C. Brooks, DVM, DipABVP

Dr. Pitcairn’s Complete Guide to Natural Health for Dogs & Cats by Dr. Richard Pitcairn