Hypothyroidism in Dogs: A Comprehensive Guide

By Chelsea Hunt-Rivera / April 9, 2018
hypothyroism in dogs

Pet owners know first hand just how many diseases and ailments can affect their beloved furry companions. It can be a bit terrifying when your dog isn’t acting like themselves. You can’t exactly ask them and receive an answer. Knowing your pet’s usual mannerisms and behavior is the first step in being able to pinpoint that something is “off” … but then what? Thyroid conditions such as hyper or hypothyroidism are among the more common ailments that can affect your dog. Knowing the clinical signs and protocol for such conditions can make a world of a difference for your pup.

dog with hypothyroidism

What is Hypothyroidism in Dogs?

Hypothyroidism, also referred to as underactive thyroid disease, is a common disorder in which the thyroid gland doesn’t make enough thyroid hormone. Hypothyroidism disrupts the normal balance of chemical reactions in the body.

What is the Thyroid

thyroid in dogs

In order to fully understand thyroid disease, it’s important to know about a few things about the thyroid.

The thyroid is a butterfly-shaped, essential gland that is part of the endocrine system. The thyroid has two side lobes that connect in the middle. If the thyroid is its normal size, you won’t be able to feel it.

What Does the Thyroid Do

An essential gland in the body, the thyroid produces the hormone thyroxine (T4), liothyronine (T3), as well as several other important hormones that are necessary to regulate the metabolism. The metabolism is responsible for turning food into energy. The thyroid hormones control the development and maintenance of carbohydrate, protein, and lipid metabolism.

When these hormones are not produced at appropriate levels, major problems can develop. You may hear the thyroid being referred to as the thermostat of the body for the number of functions its responsible for.

The metabolism affects the body’s heartbeat, temperature, and the rate at which you burn calories. When the thyroid is overactive or underactive, the entire body is thrown off course.

Where is the Thyroid Located

The thyroid is located in the front lower part of the neck below the larynx (voice box). Dogs have two sets of thyroid glands, one on each side of the windpipe in their neck.

Hypothyroidism in Dogs

Hypothyroidism in dogs is a clinical condition that results from a lower release of T4 hormones which control the metabolism.


Some breeds are at a higher risk of developing hypothyroidism than others. Middle-aged (4-10 years old), medium and large-sized dogs are more predisposed to the condition along with the following breeds:

  • Doberman pinschers
  • Irish setters
  • Golden retrievers
  • Great Danes
  • Old English sheepdogs
  • Dachshunds
  • Miniature Schnauzers
  • Boxers
  • Poodles
  • Cocker spaniels

Additionally, neutered males and spayed females are at a higher risk of developing hypothyroidism, although veterinarians are unsure why.

Symptoms of Hypothyroidism / Low Thyroid Symptoms *

symptoms of hypothyroidism in dogs

* Just a heads up, these terms are interchangeable, and your veterinarian may use both.

Early clinical signs of hypothyroidism are often non-specific. Non-specific means that they are symptoms of a large number of common ailments. Therefore, hypothyroidism is often misdiagnosed, causing the dog to suffer and, at times, additional issues to develop. Low thyroid levels affect all of the organ systems.

The following symptoms are telling signs of hypothyroidism, although you will see that many are also symptoms of other conditions:

  • Lethargy
  • Overall body weakness
  • Sluggishness or lack of desire to do things that once were enjoyed
  • Depression
  • Weight gain
  • Alopecia (hair loss)
  • Extreme hair shedding
  • Weak hair growth
  • Dry skin and coat
  • Flaky skin
  • Recurring skin infections
  • Black patches on skin
  • Intolerance to cold
  • Slowed heart rate
  • Toenail infections
  • Ear infections – typically bacterial staph infections
  • Seizures (uncommon)
  • Heart and blood vessel problems (uncommon)
  • Infertility (uncommon)

What to Expect

Hypothyroidism in dogs most often begins with generalized weakness and lethargy, followed by alopecia. The hair loss is usually on the trunk, back of the rear legs, and tail. While your dog’s coat will be flaky and thin, it is less common for it to be inflamed or itchy, which are usually signs of a bacterial infection. Dogs also may have a darkening of their skin, primarily around the armpits and groin area.

These initial clinical signs are then followed by weight gain, infections, and intolerance to cold.

Pet owners may also see slight changes in their dog’s face. For example, the brows may be furrowed or you may see a cleft above the eyes. Leading veterinary specialist, Dr Dodds, suggests regularly taking photos of your dog so that you can see any changes that may occur.

It’s important to note that studies show that if these clinical symptoms are present, the thyroid may already be up to 70% damaged.

Behavioral Issues

behavioral issue in dogs with hypothyroidism

Additionally, behavioral issues are being tied to dogs with hypothyroidism more and more often. An overly snappy dog doesn’t seem like it would be associated with hypothyroidism, so it is often overlooked.

Pet owners who once had mild natured pups may find that their dog has suddenly become aggressive. It’s not uncommon for the thyroid to go without testing if no other symptoms are present. However, hypothyroidism is to blame.

The more ya know!

Additional Symptoms of Thyroid Problems

While we have covered the symptoms of hypothyroidism, additional signs exist if a tumor is present or if a different thyroid condition is the issue at hand.

Thyroid Tumor

The additional symptoms of thyroid tumors include:

  • Hoarseness
  • A noticeable change in your dog’s bark
  • Coughing
  • Round mass projecting from the throat area
  • Loss of appetite

If your dog is diagnosed as having a thyroid tumor, a few factors come into play. The removal of the tumor is based on whether it is benign or malignant as well as how close it is the esophagus and other major arteries. Treatment is commonly a biopsy and surgical removal followed by chemotherapy or radiation.

It is important to mention that these symptoms, as well as the general symptoms of hypothyroidism, worsen over time.

It is imperative for pet owners to be aware of their dog’s behaviors and habits so that if a change does occur, they can act quickly and appropriately.


Goiter in dogs is an additional thyroid condition. This dysfunction causes the thyroid gland to swell and become enlarged. Goiters are benign conditions that occur when the thyroid is not operating correctly. They can also occur when the pituitary gland does not produce the right signals for the thyroid.

Enlarged Thyroid Symptoms

An enlarged thyroid doesn’t always mean cancer. Iodine deficiencies, too much iodine, eating goitrogenic foods, or inherited conditions can all cause a goiter to form.

While goiters in dogs are a benign condition, they tell your veterinarian that there is another underlying issue.

Also, while goiters are not generally harmful, you may be surprised at the size of them. Whenever there’s swelling in your dog’s neck, it should be taken seriously. You’ll want to see your veterinarian to diagnose and treat the underlying thyroid condition that is causing the goiter.

Symptoms to look out for:

  • Shortness of breath during activities
  • Shortness of breath while resting
  • Wheezing while breathing
  • Difficulty swallowing
  • Lack of appetite
  • Extreme weight loss

What Causes Hypothyroidism?

Thyroid conditions are not uncommon in dogs. In order to know exactly how to proceed in treatment and adjusting your pup’s lifestyle, pet owners should be familiar with the main causes of the disease.

Immune Problems

Over 80% of hypothyroidism cases are due to autoimmune destruction of the thyroid gland, also referred to as autoimmune thyroiditis. Autoimmune thyroiditis (also called lymphocytic thyroiditis) is a dysfunction in the immune system in which the body mistakenly sees the thyroid gland and hormones as foreign and abnormal. Therefore, in order to get rid of the “threat,” the body creates the antibodies to attack the thyroid, resulting in the loss of thyroid function.

Commonly, thyroiditis will affect multiple areas of the body, including the skin and the digestive system along with the thyroid.

Thyroid Gland Atrophy

The remaining 15-20% of hypothyroid conditions are caused either by familial, genetic patterns (in which there’s really not much pet owners can do) or idiopathic thyroid atrophy.

Idiopathic thyroid atrophy means that the thyroid is gradually demolished by a cause that is not entirely known. Veterinarians do know that fat is replacing the thyroid gland but don’t completely understand why. Through biopsies, veterinarians have found that as the normal thyroid tissue diminishes, instead of new, healthy thyroid tissues reforming, fat tissues form in its place. This also classifies idiopathic thyroid atrophy as a degenerative disease.


medications can cause hypothyroidism in dogs

Additionally, while some breeds are more prone to hypothyroidism, environmental factors also serve as triggers.

Some of these environmental triggers include:

Furthermore, certain medications can decrease the production of the thyroid hormone. In fact, the corticosteroid medication that is often used for allergic reactions and skin irritations can cause hypothyroidism. Additionally, a common drug used to treat seizures in dogs called phenobarbital can block the production of thyroid hormone.


Medications are chemically produced and, therefore, flood the body with toxins. When the dog’s body is unable to process and rid itself of the toxicity for one reason or another, the toxins will often elicit an autoimmune reaction.

Additionally, toxins such as household cleaners, pesticides in the yard, and preservatives found in food only add to toxicity levels on a daily basis. That’s why it’s good to do a detox on occasion!

Dog Collars

Another cause of extensive damage to the thyroid is tight or pronged collars, especially for dogs who pull. In fact, if the collar causes substantial damage from the amount of pressure day in and day out, inflammation will naturally occur.

The inflammation from the constant pressure can trigger your dog’s immune system to eliminate the inflamed thyroid cells, thus resulting in hypothyroidism. With that said, wearing a harness is the safer method for walking your pup.

Excessive Inbreeding

Researchers believe that excessive inbreeding, as well as line-breeding, leads to hypothyroidism. Breeders breed in order to get very specific behavioral and physical traits. However, the selective breeding also means passing down less desirable traits, including hypothyroidism.

Lack of Exercise

A lack of exercise can lead to hypothyroidism in dogs as it lowers the production of the thyroid hormone.

While possible, hypothyroidism is rarely caused by cancer or congenital defects.

Secondary Hypothyroidism

Secondary hypothyroidism involves three glands: the hypothalamus, thyroid, and pituitary gland.

These three glands need to work in conjunction with one another in order to carry out various functions. The pituitary gland creates TSH (thyroid stimulating hormone) which tells the thyroid to function. However, the pituitary gland secretes the TSH after hormones released by the hypothalamus stimulates it.

In short, if one of the glands isn’t functioning properly, none of them function properly, therefore resulting in secondary hypothyroidism.

Hyperthyroidism vs Hypothyroidism

We have discussed that hypothyroidism is when the thyroid is not producing enough hormones in order to function properly.

Conversely, dogs with hyperthyroidism have a thyroid that produces too much thyroid hormone. The overactive thyroid causes a constant state of metabolic hyperactivity.

Hypothyroidism is a common condition while hyperthyroidism is relatively rare.

Hyperthyroidism Symptoms

hyperthyroidism symptoms in dogs

Symptoms of hyperthyroidism include:

  • Weight loss
  • Increased appetite
  • Increased thirst
  • Excessive urination
  • Elevated heart rate
  • Diarrhea
  • Vomiting
  • Breathing difficulties
  • Hyperactive behavior
  • Restlessness
  • Dull coat

Hyperthyroidism Treatment

Treatment options for hyperthyroidism include radioactive iodine, radiotherapy, chemotherapy, or anti-thyroid medication.

After treatment, regular testing will be necessary to monitor the thyroid levels.

Hyperthyroidism in dogs is quite rare, although it does occur.

Diagnosing Hypothyroidism

Diagnosing hypothyroidism can prove to be incredibly challenging. This is due to the number of other diseases mimicking the symptoms of hypothyroidism. In fact, The Merck Veterinary Manual explains that hypothyroidism is one of the most misdiagnosed diseases in dogs. These other diseases affect or involve the thyroid, but they are not hypothyroidism.

To diagnose thyroid conditions, your veterinarian may have to perform several tests. The testing first determines the level of thyroid hormone. Further testing may be necessary to evaluate tumors or abnormal tissues.

Typical diagnosis is as followed:

  1. Evaluation – Blood tests such as a chemistry profile, a complete blood count (CBC), and a urinalysis may be performed in order to rule out any other conditions. As previously mentioned, the early signs of hypothyroidism in dogs are non-specific. For this reason, full evaluations are necessary.
  2. Thyroid Scanning or Imaging – In order to see the how much of the thyroid is affected, X-rays and diagnostics may be necessary. It will also locate the infected tissues and tumors if they are present.
  3. Biopsy- Biopsies are determined based on the size and location of the tumors.

Hormonal testing

The right kind of testing is critical for the diagnosis of hypothyroidism. Vets may only request a T4 count, but that’s rarely enough for an accurate diagnosis because of how many other factors can affect it, such as medications and diet.

It is important to get a full thyroid antibody profile.

Total T3: Measures the T3 hormone levels.

Total T4: Measures Thyroxine. Conditions such as age, breed, size, and medications can affect the T4 levels.

Free T4: Considered a more accurate depiction of the thyroid issues and activity. It is important that this test is also included.

TSH: Measures thyroid-stimulating hormones but often results are inaccurate.

Other Diseases Mimicking Hypothyroidism

One of the main reasons hypothyroidism is so over and misdiagnosed is that so many other ailments share symptoms.

Cushing’s Disease

Cushing’s Disease is one of the ailments that shares very comparable symptoms as hypothyroidism. Also referred to as hyperadrenocorticism, Cushing’s disease occurs when the adrenal glands produce excess amounts of hormones.

Nearly every symptom of Cushing’s disease is also a symptom of hypothyroidism. However, these two diseases require very different treatment methods.

Medical Treatment for Hypothyroidism

While hypothyroidism disease looks and sounds pretty scary, it’s not life-threatening and is very treatable.

Hormone Replacement

The conventional, clinical treatment of hypothyroidism is synthetic thyroid replacement medication to offset the dog’s low thyroid function.

This treatment method entails oral medication, every day, for the rest of your dog’s life.

The medication is a synthetic (man-made) thyroid hormone called levothyroxine or L-thyroxine.

The dosage depends on your dog’s size and thyroid levels and may have to be adjusted over time. Making sure your dog is receiving the right dosage is important. If it’s too high, they can begin showing signs of hyperthyroidism or lead to a thyroxine overdose.

Pet owners usually start seeing results after a month or two on the medication.

Hypothyroidism won’t go away on its own and if left without treatment, it will negatively affect your dog’s life.

Natural Treatment for Hypothyroidism Disease

If medication every day for the rest of your pup’s life sounds a bit tragic, you may be in luck. There are quite a few natural treatments that you can try before resorting to a synthetic thyroid hormone replacement.

You may also want to combine a natural treatment along with herbs that help ease symptoms.

It is absolutely necessary to consult with your holistic pet wellness doctor to decide on an appropriate treatment plan.

Natural Thyroid Extract

Natural thyroid extract is made from bovine or porcine thyroid glands. Adjusting the dosage will be necessary, as some of the products contain both T4 and T3 hormones, all which aren’t necessary.


Kelp is rich in iodine as well as other minerals and nutrients. The herb regulates the glandular systems, including the thyroid.

Licorice Root

Licorice root not only restores and supports the entire body, but also stimulates an unproductive thyroid gland.

Astragalus or Siberian Ginseng

Individuals use these herbs to prevent thyroid atrophy.


As with any diseases, diet can be everything. Making sure that you are feeding your dog a minimally processed, species-appropriate diet is key. If you’re able to, a raw food diet is optimal for health.

It is also important to have balanced levels of iodine. Pet owners may accidentally give their pet too much iodine which ultimately aggravates the thyroid.


If the hypothyroidism is due to the autoimmune dysfunction, autoimmune thyroiditis, it is also important that you pay attention to your dog’s intestinal health. A daily probiotic (especially after giving medication) can be valuable.


Turmeric, fish oil, and other anti-inflammatory herbal supplements can be very effective in reducing inflammation.

Preventing Hypothyroidism

Unfortunately, unlike some diseases such as diabetes, there really isn’t a specific way to prevent hypothyroidism in dogs from developing.

One thing that pet owners can always take note of is their pet’s diet. A proper diet, preferably a raw food diet, will always be a great way to boost the immune system and keep your pup feeling good.

Additionally, pet owners should be hyperaware of the influx of environmental toxins in the dog’s life.

The high toxicity levels will only worsen preexisting conditions and have the potential to create additional ailments for your dog.

Managing the Thyroid = One Happy Pup

one happy pup

At the end of the day, while hypothyroidism is not life-threatening, it can really bum out your dog. Once an energetic, flower sniffing, ball of life can quickly become a couch potato who can’t muster up the energy for a walk.

Hypothyroidism is a very common disease that is often the cause of such changes in your beloved pup. However, hypothyroidism is often misdiagnosed or a diagnosis comes when substantial damage has been done.

Pet owners knowing the signs of hypothyroidism and perhaps, more importantly, knowing the natural ins and outs of their dog, can prove to be incredibly significant. The majority of the time, if unexplainable changes occur, something is probably up.

Don’t wait to get your dog in to see their veterinarian. Hypothyroidism won’t get better on its own. The sooner you receive a proper diagnosis, the sooner you’ll get your happy pup back.


Which breeds are high risk for developing hypothyroidism?

What are the signs of hypothyroidism in dogs?

Why did my dog get hypothyroidism?

What’s the difference between hypothyroidism and hyperthyroidism?

Can I treat hypothyroidism in dogs naturally?


Natural Treatments For Hypothyroidism In Dogs


Top 5 Things You Need To Know About Hypothyroidism and Your Dog




Thyroid Disease in Dogs

What You Need to Know About Thyroid Problems in Dogs



About the author

Chelsea Hunt-Rivera

Chelsea Rivera is a Dedicated Pet Parent who loves to create amazing content for pet owners and is helping change pet wellness as the Head of Content for Honestpaws.com.