Hypothyroidism in Dogs: Symptoms & Treatment

Dr. Jason Gagné, DVM, DACVIM
By Dr. Jason Gagné, DVM, DACVIM
Updated: 5/20/20242-4 minutes
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The thyroid is an important gland located in your dog’s neck, close to the windpipe. Although its size is quite small, it has a big role to play. The thyroid produces hormones used in many processes throughout the body. Its function is key to the health and well-being of your pet.

This important gland can sometimes stop working properly, however, leading to thyroid problems in dogs. One of the most common issues is called hypothyroidism. Fortunately, while symptoms can be concerning, the condition is often treatable with help from your veterinarian.

Here’s what you need to know about hypothyroidism in dogs, including causes, symptoms, and how to care for your pet if they’re diagnosed with this problem.

What is Dog Hypothyroidism?

Hypothyroidism refers to a health issue where abnormally low levels of thyroid hormones are produced by the thyroid glands in a dog’s neck. The condition can affect multiple systems in the body that rely on these hormones to function normally. The problem can often be managed with special medication.

What Are the Symptoms of Hypothyroidism in Dogs?

If your dog has hypothyroidism, their metabolism will slow down. You’ll probably notice changes in their behavior and routines. The signs of hypothyroidism in dogs can vary from pet to pet, but here are the most common symptoms to watch for: 

  • Reduced activity 
  • Lethargy 
  • Weight gain 
  • Hair loss (which is often symmetrical) 
  • Lack of interest in daily walks 
  • Feeling cold 
  • Skin issues 
  • Diminished coat quality

What Causes Hypothyroidism in Dogs?

The most common causes of hypothyroidism include lymphocytic thyroiditis, a disorder where the immune system attacks the thyroid gland, and idiopathic atrophy of the thyroid gland. The latter occurs when normal thyroid tissue is replaced with fatty tissue. Unfortunately, the condition is still poorly understood.

However, the symptoms and treatment of canine hypothyroidism are normally similar regardless of the underlying cause.

Are Certain Dogs More Prone to Hypothyroidism?

Medium and large dog breeds tend to be more vulnerable to hypothyroidism, and it typically develops between 4 and 10 years of age. These breeds are more commonly affected:  

If you’re concerned about hypothyroidism because of your dog’s genetics, remember that breed doesn’t guarantee a diagnosis. Also, regardless of breed, it’s always a good idea to watch for any signs that your pet’s metabolism is slowing down, such as weight gain and lethargy.

How is Hypothyroidism in Dogs Diagnosed?

Diagnosing hypothyroidism can be challenging, as there are many other health issues that share the same symptoms. Additionally, low levels of thyroid hormone can be caused by diseases other than hypothyroidism.

If your veterinarian suspects hypothyroidism, they will likely test your dog’s blood to detect the level of thyroid hormones. Based on these results, your dog’s symptoms and medical history, and potentially other tests, your veterinarian can make a determination about their condition.

Can Hypothyroidism in Dogs Be Treated?

While a hypothyroidism diagnosis can be worrying for pet owners, the good news is the condition can be managed. Your veterinarian will often recommend oral medication that your dog will need to take for the rest of their life. This will help restore thyroid hormones to their normal levels.

Follow your veterinarian’s guidance and make sure your dog doesn’t miss their daily medication. Hypothyroidism in dogs is not a fatal disease, but it can have serious health consequences if left untreated.

Although the medication for dog hypothyroidism starts working quickly, it can take a few weeks before you notice visible improvements in your pet’s energy levels or the health of their coat. 

Prognosis for Hypothyroidism in Dogs

Dogs with hypothyroidism generally have a good prognosis, provided they receive treatment. The disorder isn’t curable but, with the help of medication, they can enjoy a normal life expectancy.

Any condition that negatively affects your dog’s health is scary. Fortunately, while hypothyroidism is serious, you can minimize its impact and help your canine companion live a happy, healthy life.

For more expert tips on how to keep your canine companion healthy, check out our collection of dog health articles.

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