Hypothyroidism in Dogs: Symptoms, Diagnosis & Treatment

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If your dog has been extremely tired lately or has been having issues with their skin or hair, they could have hypothyroidism. Thankfully, thyroid problems in dogs are easy to diagnose and manage. While the exact cause of thyroid dysfunction in our canine companions isn't clear, we do know how hypothyroidism affects dogs and how to treat it.

What Is the Thyroid?

The thyroid, in dogs and in humans, is a butterfly-shaped gland located in the neck, right next to the windpipe. As part of the endocrine system, the thyroid gland makes the hormones necessary for cells to function normally. The thyroid affects the body's metabolism.

If a dog produces too much thyroid hormone, they can develop signs of hyperthyroidism, including diarrhea, increased heart rate, anxiety and hyperactivity. If the thyroid gland doesn't secrete enough thyroid hormone, you get the exact opposite — hypothyroidism, the most common thyroid problem in dogs.

Risk Factors for Hypothyroidism in Dogs

Hypothyroidism is most often diagnosed in dogs between 4 and 10 years old. In most cases, an autoimmune disorder that shrinks or inflames the thyroid tissue causes hypothyroidism in dogs. There are no known genetic causes. However, according to the American Kennel Club, medium to large breeds are at greater risk than toy and miniature breeds. The cocker spaniel, miniature schnauzer, dachshund, Doberman pinscher, golden retriever, Airedale terrier and Irish setter also appear more likely to develop the disease. While rare, dogs can also develop hypothyroidism due to cancer of the thyroid gland. Spayed and neutered dogs seem to have increased risk; however, the many benefits of spaying and neutering may outweigh this suspected risk.

Airedale terrier close-up lying down, staring straight ahead.

Signs of Hypothyroidism in Dogs

Hypothyroidism in dogs affects every system of the body, including the gastrointestinal system, the nervous system and the circulatory system. If a dog hasn't been spayed or neutered, hypothyroidism can also affect the reproductive system.

The most common signs of low thyroid problems in dogs include:

  • Excessive tiredness
  • Mental dullness or depression
  • Weight gain
  • Skin infections
  • Cold intolerance
  • Skin and coat changes, such as hair loss, excessive shedding, excessive dandruff, a dry or dull coat and hyperpigmented skin.
  • Excessively long heat cycles in female dogs who haven't been spayed
  • Generalized weakness and other neuromuscular problems
  • A stiff walk or loud breathing due to laryngeal paralysis (loss or normal function of the larynx)

How It's Diagnosed

The good news is that, unlike human thyroid problems, thyroid problems in dogs are usually easily diagnosed and managed. If you suspect your dog might be suffering from a thyroid problem, make an appointment with your pet's veterinarian. During the visit, the vet will ask you some questions, conduct an exam and will likely ask to run some lab tests — probably blood work and urine testing.

High blood cholesterol is a common indicator of hypothyroidism in dogs. Most clinics can also test for thyroid hormone levels in dogs with a simple blood test.

All this information together will build a picture for your vet so that they can determine whether or not your dog has hypothyroidism.

Treatment for Hypothyroidism in Dogs

If your dog is diagnosed with hypothyroidism, don't worry! Even though you can't cure hypothyroidism in dogs, it's usually easy and relatively inexpensive to manage with an oral thyroid supplement. The supplement mimics the effect of thyroid hormone on the body. If it's successful, your dog will regain their energy, lose weight, have a brighter attitude and stop shedding hair.

The key thing to remember when treating thyroid problems in dogs is the importance of balance. If your dog takes too much thyroid supplement, they can develop signs of an overactive thyroid, which is the opposite of what you want. If the vet prescribes your dog a thyroid supplement, it's important to follow all dosing instructions — don't change the dosage without talking to the vet.

After starting your dog on a thyroid supplement, the vet will likely ask you to return in a couple of weeks to get a follow-up blood test to make sure your dog's thyroid hormone levels are appropriate. Once their hormone levels are stabilized, the vet will probably want to check them once or twice a year.

Nutrition for Dogs With Hypothyroidism

Providing proper nutrition to a dog with hypothyroidism is an important part of supporting overall thyroid health. Dogs with hypothyroidism need to be supported by food that contains balanced levels of amino acids, iodine, probiotics for gut health, antioxidants and the right amount of calories that contribute to a healthy weight. Ask your vet for nutritional recommendations for your dog.

Low thyroid problems in dogs are common and can be easily managed. Even with a diagnosis of hypothyroidism, your dog can live a long, healthy and happy life.

Contributor Bio

Dr. Sarah Wooten

Dr. Sarah Wooten

Dr. Sarah Wooten graduated from UC Davis School of Veterinary Medicine in 2002. A member of the American Society of Veterinary Journalists, Dr. Wooten divides her professional time between small animal practice in Greeley, Colorado, public speaking on associate issues, leadership, and client communication, and writing. She enjoys camping with her family, skiing, SCUBA, and participating in triathlons.

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