Hypothyroidism in Dogs – Causes and Treatment

Picture of a Dogtime Australian Cattle Dog

Both in humans and in many animals, the thyroid gland is in charge of regulating the body’s metabolic rate. Sometimes, it can be too active (in which case the dog can suffer from hyperthyroidism), but in other situations, it can be underactive (causing hypothyroidism).

In this post, we’ll look at what causes hypothyroidism in our canine friends, what the clinical signs of this medical condition are, how it’s diagnosed, and how it can be treated.

Are There Any Breeds More Predisposed to Hypothyroidism?

The short answer to this question is yes. Some studies have found that the Irish Setter, the Golden Retriever, and the Doberman Pinscher have a higher likelihood of developing this medical problem.

While hypothyroidism isn’t as dangerous, hyperthyroidism is most often associated with cancer. Hypothyroidism is most common in medium to large breed dogs, and it usually shows up in dogs that are middle-aged.


Hypothyroidism is typically caused by two diseases:

  • Idiopathic thyroid gland atrophy
  • Lymphocytic thyroiditis

In dogs that have idiopathic thyroid gland atrophy, their immune system doesn’t recognize the thyroid gland as a natural part of the body, which is why it starts attacking it as if it were something foreign.

Although it is still unknown why this happens, it is presumed to be a genetic problem. What is important to note here is that the two diseases that we have mentioned are at the root of more than 90% of all hypothyroidism cases in dogs, and that under 5% have cancer as their main cause.

Clinical Signs

So, what should you expect from a dog that suffers from hypothyroidism? Since this disease is associated with a lower metabolic rate, one of the first things that dog parents can notice is an inexplicable weight gain (without the presence of an increase in appetite).

Dogs that have hypothyroidism are also less likely to want to engage in strenuous exercise, and they might also be lethargic from time to time. Here are some other symptoms of hypothyroidism that show up in the first stages of the medical condition.

  • Dull hair
  • Excessive shedding
  • Dark pigmentation of the skin
  • The dog gets cold easily and seeks out warm spots in the house
  • Skin and ear infections
  • A slower heart rate than normal
  • High levels of blood cholesterol

As for the less common symptoms that you might notice, they range from a droopy facial expression to a dilatation of the esophagus, causing many dogs to regurgitate. Both males and females can suffer from fertility problems, with the latter suffering miscarriages or experiencing a complete lack of heat periods.

Some animals can experience dry eyes since their eyes don’t produce enough tears, while others might develop fat deposits in their corneas.

How Is Hypothyroidism in Dogs Diagnosed?

Blood tests are particularly effective when it comes to diagnosing this medical condition. Naturally, the veterinarian might be able to make a presumptive diagnosis based on the symptoms that we have showcased earlier, but blood tests are always necessary to confirm the presence of the disease.

Routine blood tests aren’t of any help, however, since the dog needs to be tested for his or her endocrine gland levels. The first and most important hormone level that needs to be assessed is TT4 (total thyroxine). Still, a definitive diagnosis can be made by performing a free T4 by ED (by equilibrium dialysis). This test determines the different types of thyroxine in your dog’s body.

Can Canine Hypothyroidism Be Treated?

As is the case with people who have hypothyroidism, regulating thyroid hormone levels can be done by taking medication for the rest of the animal’s life. In the first stages of the therapy, the treatment needs to be administered twice a day, but once the hormone level is improved, one daily dose of medication can be used, too.

Levothyroxine is one of the most common treatments recommended by most veterinarians, and it is basically a synthetic thyroid hormone replacement. Dogs can be given two forms of medications depending on what their bodies are capable of doing.

For example, some might receive T4, with their bodies being able to transform it into T3, and this is what happens with most hypothyroid dogs. There are some dogs that can’t make this type of conversion on their own, and these have to receive T3 medication directly.

How long does it take for your dog to get better? It varies from one dog to the other and it also depends on how severe the case of hypothyroidism is, but most pets recover in about four to six weeks.

Some will need treatment for eye and ear infections, in case they have developed one, but the majority of pets begin to look better and have a healthier coat after about a month of receiving the right treatment. Their energy levels also increase, so they are less lethargic.

Giving Your Dog the Medication

It’s crucial for you to stick to the veterinarian’s recommendations when it comes to giving your dog the appropriate medication and the right dose. If you accidentally give your dog a higher dose of the medication, he or she might experience an increase in water consumption, weight loss, hyperactivity, or lack of sleep.

Pet parents have to understand that they now have the responsibility of ensuring that their dog’s thyroid hormone levels are always on par.

It’s not uncommon for the pet to experience the same symptoms all over again if you begin to decrease the dose or forget to give your canine friend the treatment altogether. If you ever plan on leaving for a trip and there will be someone other than you caring for your pooch, make sure that they are properly informed about the medication and dose that they have to administer to your Fido while you are away.



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