Hypothyroidism in Dogs

Rhodesian Ridgeback outside looking past camera.
Rhodesian Ridgebacks are one breed that are at a higher risk of developing hypothyroidism than others.

Getty Images/Elizabeth Dorovskikh / 500px

Hypothyroidism is a common disease in people, but dogs can also develop it. Some breeds are more likely to get it than others; however, it can still affect any dog. Thankfully though, this condition is usually easily diagnosed and treated by your veterinarian but as a dog owner, it's important that you be able to recognize the potential signs or symptoms of this endocrine disease.

What Is Hypothyroidism in Dogs?

Hypothyroidism is a condition that occurs when your dog's thyroid gland does not produce enough thyroid hormones. It is the opposite of hyperthyroidism, which is very rare in dogs and more common in cats. The thyroid gland is located in the neck of your dog, and the hormones that it naturally produces play important roles in many bodily functions. One of these bodily functions is your dog's metabolism. Without adequate amounts of thyroid hormones, your dog may be unable to properly absorb or metabolize the nutrients it gets from the food it eats so various symptoms will be seen as a result.

Symptoms of Hypothyroidism in Dogs

Signs of Hypothyroidism in Dogs

  • Weight gain
  • Lethargy
  • Excessive hairloss or thin coat
  • Dry and dull hair coat
  • Increased skin pigmentation
  • Cold intolerance
  • Recurrent skin or ear infections
  • Difficulty regrowing hair after being shaved

While the signs of hypothyroidism in dogs may not be sudden or obvious at first, if you're looking for them, you'll notice. Dogs with hypothyroidism are lethargic and gain weight. They also experience hairloss so there may be bald patches or an overall thin coat. The hair coat that remains is drier and not as glossy as it normally is and the skin becomes darker due to an increase in pigmentation. If a hypothyroid dog's hair is shaved, it may also not regrow or regrow extremely slowly. Finally, dogs with hypothyroidism may be more sensitive to the cold and may easily get skin or ear infections.

Causes of Hypothyroidism in Dogs

The majority of hypothyroidism cases are caused by one of two things:

  • Lymphocytic thyroiditis - This is thought to be an immune-mediated or degenerative disease that may also be genetic.
  • Idiopathic thyroid gland atrophy - Fat tissue replaces thyroid tissue in this disease but no one really knows why.

If the cause of your dog's hypothyroidism is not due to one of the aforementioned reasons, cancer of the thyroid gland or other rare diseases may be the cause.

Diagnosing Hypothyroidism in Dogs

If vet suspects your dog has hypothyroidism, they will recommend some bloodwork after a full physical examination. Thyroxine (T4) is the thyroid hormone that is most commonly tested either through a total T4 test or free T4 test but triiodothyronine (T3), thyroid stimulating hormone (TSH), and anti-thyroglobulin antibodies (TgAA) may also be checked. A diagnosis is made after taking all the symptoms and various test results into consideration.

Treatment of Hypothyroidism in Dogs

Most cases of hypothyroidism are able to be managed with a medication called levothyroxine. Levothyroxine is sold under many brand names, including Thyro-Tabs. There is no cure for the disease, but levothyroxine can be easily administered in a daily pill for the rest of your dog's life. Thyroid hormone blood levels will need to be routinely checked to ensure the proper amount of levothyroxine is being administered but otherwise the treatment of hypothyroidism is fairly inexpensive and easy.

How to Prevent Hypothyroidism in Dogs

Because no one really knows what causes the two main reasons why dogs develop hypothyroidism, it is impossible to prevent it. The best thing you can do to prevent a dog from developing hypothyroidism is to ensure that dogs that have been diagnosed with it are not used for breeding. This may help prevent the offspring from carrying a genetic predisposition to the disease.

At-Risk Dog Breeds

Since hypothyroidism may have a genetic component to it, dog breeds that are predisposed to developing hypothyroidism include the English setter, Rhodesian ridgeback, giant schnauzer, hovawart, old English sheepdog, boxer, Doberman pinscher, Gordon Setter and the beagle. These dog breeds may benefit from routine thyroid hormone level screening during their annual veterinary exam, even if you don't see any symptoms of the disease.