A dog resting on a couch in a watercolor painting.

What is Hypothyroidism in Dogs?

What is it?

Hypothyroidism is a common endocrine disorder in dogs that occurs when the thyroid gland does not produce enough thyroid hormone. This can be caused by a variety of factors, including autoimmune disease, congenital defects, or certain medications. Hypothyroidism can lead to a range of health problems for dogs, so early detection and treatment are essential.

How is it Treated?

The treatment for hypothyroidism in dogs typically involves daily thyroid hormone replacement therapy, which can be administered orally or by injection. The goal of treatment is to restore normal thyroid hormone levels and improve symptoms, such as weight gain, lethargy, and skin problems. It’s important to monitor your dog’s hormone levels and adjust the medication dosage as needed to ensure optimal management of the condition.

Breed Predispositions

Golden Retrievers Doberman Pinschers Dachshunds Irish Setters Boxers Cocker Spaniels Great Danes Miniature Schnauzers Bulldogs


When Sarah began to notice that her normally active and cheerful Greyhound, Max, had become lethargic and was gaining weight despite no change in his diet, she grew concerned. Additionally, Max’s once-shiny coat had become dull and thin. Seeking answers, Sarah took Max to their trusted veterinarian for a thorough examination. After running several tests, the vet diagnosed Max with hypothyroidism, a condition that Sarah had never encountered in her previous experiences with dogs.

Hypothyroidism in dogs is an endocrine imbalance characterized by the thyroid gland’s inadequate production of thyroid hormones, which are crucial for controlling the dog’s metabolism. These hormones are instrumental in numerous physiological functions, including maintaining healthy skin and coat, overseeing growth and development, and regulating energy levels.

This thyroid disease, known as primary hypothyroidism, considerably impacts various bodily systems and can dramatically alter your canine companion’s overall health and vitality. This disorder is typically prevalent in middle-aged to older dogs and is commonly observed in certain breeds such as the Golden Retriever, Doberman Pinscher, and Cocker Spaniel. The management of this condition predominantly involves administering lifelong medication to supplement the deficient thyroid hormone levels.

What is a Thyroid Gland in Dogs?

The thyroid gland in dogs is a small, butterfly-shaped gland near the trachea or windpipe in the neck. Despite its small size, the thyroid gland plays an incredibly critical role in the overall health and function of a dog’s body.

The primary role of the thyroid gland is to produce and secrete thyroid hormones, namely triiodothyronine (T3) and thyroxine (T4). These hormones are essential for regulating the dog’s metabolism – the process by which the body converts food into energy. In addition, the thyroid hormones influence virtually every organ system in the body. For example, they control the rate at which cells burn fuel from food, affect heart rate, regulate body temperature, and contribute to the growth and development of the nervous system.

A dog’s thyroid gland operates in a feedback loop with the brain. The hypothalamus and the pituitary gland in the brain release hormones that instruct the thyroid when to produce and release T3 and T4. This balance is crucial for maintaining the dog’s health and overall metabolic function.

When the thyroid gland is not functioning correctly, such as in hypothyroidism, where it is underactive and doesn’t produce enough thyroid hormones, it can lead to various health problems. These can include lethargy, weight gain, skin and coat issues, and other symptoms. Conversely, an overactive thyroid gland, a condition known as hyperthyroidism, can also cause various health concerns, such as weight loss, increased heart rate, and hyperactivity.

Causes of Hypothyroidism in Dogs

Hypothyroidism in dogs, often signified by a low thyroid hormone concentration, typically arises from one of two primary conditions – lymphocytic thyroiditis or idiopathic thyroid gland atrophy.

Lymphocytic Thyroiditis

Lymphocytic Thyroiditis is an autoimmune disease where the dog’s immune system erroneously targets its thyroid gland, triggering inflammation and subsequent gradual destruction of the thyroid tissue. This process ultimately leads to decreased thyroid hormone production. The exact catalyst behind this autoimmune reaction remains unclear, but genetic factors are suspected to play a part.

Idiopathic Thyroid Gland Atrophy

On the other hand, Idiopathic Thyroid Gland Atrophy involves the gradual replacement of functional thyroid tissue with fatty tissue over time. The cause of this condition, aptly named “idiopathic” – meaning of unknown origin – is not yet fully comprehended; much like lymphocytic thyroiditis, idiopathic thyroid atrophy results in diminished production of thyroid hormones.

Hypothyroidism in dogs can also stem from less frequent causes, such as certain medications, dietary complications, and exposure to toxins. Surgical removal of thyroid tumors or the entire gland can also induce hypothyroidism. Furthermore, it’s notable that while hypothyroidism can manifest in any dog breed, medium to large-breed dogs shows a higher incidence rate, hinting at a potential genetic predisposition.

The thyroid gland’s critical role in a dog’s body is to generate hormones regulating metabolism. Consequently, when these hormone levels decline, multiple body systems are affected, resulting in symptoms observed in a hypothyroid dog, such as skin infection and thickening skin.

Symptoms of Hypothyroidism in Dogs

The clinical signs of hypothyroidism in dogs can vary significantly, mirroring the extensive impact of thyroid hormones on various body systems. These symptoms often start subtly and gradually intensify, sometimes making the disease difficult to detect.

hypothyroidism in dogs
  1. Affected dogs may display unexplained weight gain, which occurs despite no significant changes in diet or exercise. Alongside this, they may show signs of lethargy and decreased activity levels – symptoms that are too common when thyroid function in dogs is compromised.
  2. Alterations in the dog’s coat and skin may also indicate hypothyroidism. This could manifest as thinning hair, dryness, or recurrent skin infections. Cold intolerance, where the dog seems more sensitive to lower temperatures than before, can also be a telltale sign.
  3. Reproductive issues may emerge in dogs where hypothyroidism occurs. This could include testicular atrophy in males, whereas females may experience irregular estrous cycles.
  4. In some instances, the destruction of the thyroid gland may lead to neurological problems. As a result, dogs may display various issues ranging from seizures to changes in temperament or behavior.
  5. Other symptoms suggesting hypothyroidism include a slower heart rate, increased cholesterol levels, anemia, and constipation. Some dogs may also develop a puffy or swollen facial appearance, often called a “tragic face” expression.

Remember, the symptoms mentioned above and treatment options should always be discussed with a veterinarian, as hypothyroidism can greatly affect a dog’s health.

How to Diagnose Hypothyroidism in Dogs?

Diagnosing hypothyroidism in dogs entails a series of tests to eliminate the possibilities of other ailments and confirm the diagnosis of canine hypothyroidism. Hypothyroidism’s effects can mimic other conditions, so a holistic approach is essential for a definitive diagnosis.

Complete Blood Count (CBC) and Biochemical Profile

This preliminary blood work offers general data about the dog’s health status and can assist in excluding other conditions that may be responsible for the dog’s symptoms. Nevertheless, these tests are insufficient for diagnosing hypothyroidism independently.

Thyroid Function Tests

These tests, crucial in diagnosing hypothyroidism, evaluate the concentrations of various thyroid hormones in the dog’s blood, including T3 and T4. A low T4 level, for instance, could suggest an underactive thyroid gland. The Total T4 concentration serves as the initial screening test for hypothyroidism and holds a high diagnostic sensitivity (~90%), albeit a low specificity (~50%).

Thyroid-stimulating Hormone (TSH) Test

In certain instances, a TSH test may also be performed. For example, middle-aged dogs suffering from hypothyroidism often exhibit elevated TSH levels as the pituitary gland produces more TSH to stimulate the thyroid gland.

Thyroid Scintigraphy

This advanced imaging method utilizes radioactive isotopes to visualize the thyroid gland. It can yield detailed data about the gland’s size and function. Still, it’s generally employed for complicated cases because it demands specialized apparatus and expertise.

Autoantibody Tests

Some dogs with hypothyroidism generate autoantibodies against their thyroid hormones or thyroid tissue. These can be detected with particular blood tests and could indicate autoimmune thyroiditis, a frequent cause of hypothyroidism in dogs.

It’s important to note that testing for hypothyroidism should ideally be done progressively. Therefore, the dog’s thyroid levels should be evaluated and monitored over time, especially since other diseases can mimic hypothyroidism, creating complexities in the diagnosis.

Treatment of Hypothyroidism in Dogs

a vet and a dog with addison disease

Hypothyroidism management in dogs typically comprises medication, regular monitoring, and supportive care. The central objective of treatment is to restore the balance of thyroid hormone production, thus alleviating symptoms and enhancing the dog’s quality of life.

Thyroid Hormone Replacement Therapy

The mainstay of treatment for hypothyroidism in dogs is hormone replacement therapy. The dog is given a synthetic form of thyroxine, the hormone that the thyroid gland normally produces. The following are considered the best treatment options:

  1. Levothyroxine: This synthetic form of thyroxine (also known as T4) is the most common treatment for canine hypothyroidism. Levothyroxine (L-thyroxine) is frequently used for this purpose. It is usually given orally once or twice daily, and the dose is tailored to each dog’s individual needs based on weight, severity of symptoms, and response to the medication. Regular blood tests are needed to ensure the dose remains appropriate and the dog is not receiving too much or too little medication.
  2. Liothyronine: In some cases, dogs might not respond adequately to levothyroxine. In such situations, the veterinarian might consider using liothyronine, a synthetic triiodothyronine (T3), another hormone the thyroid gland produces. This medication is usually reserved for cases where the dog’s body is not converting T4 to T3 efficiently.

Following initiating thyroid hormone replacement therapy or thyroid supplementation, it’s crucial to keep regular veterinary appointments to track the dog’s response to the treatment. This typically includes routine blood tests to assess the thyroid level and tweak the thyroid medication dosage as required. Doing so ensures that the thyroid-stimulating hormone is kept within an optimal range, which is crucial for effectively treating hypothyroidism.

Preventing Hypothyroidism in Dogs

Hypothyroidism in dogs is predominantly seen in middle-aged to older dogs, often triggered by an autoimmune process that is not preventable. Nevertheless, dog owners can undertake several measures to support overall health and mitigate the risk of hypothyroidism.

  • Frequent Vet Check-ups – Regular visits to the vet can aid in the early detection of various diseases, including suspicion of hypothyroidism. Always communicate any noticeable changes in your dog’s behavior, energy level, or physical appearance to your vet.
  • Nutritious Diet – Supplying your dog with a balanced diet is crucial for their health. Ensure your pet’s meals include the nutrients vital for a healthy thyroid, such as iodine.
  • Weight Management – Obesity can initiate or amplify numerous health complications in dogs, possibly hypothyroidism. Regular physical activity and portion control are paramount in maintaining a healthy weight.
  • Minimize Toxin Exposure – Some research points to a potential correlation between certain toxins and hypothyroidism in dogs. Therefore, please keep your pet’s exposure to harmful chemicals to a minimum in their food and environment.
  • Vaccination and DewormingRegular vaccination and deworming contribute to maintaining overall health, which can reduce the risk of hypothyroidism.

It’s important to remember that while promoting overall health, these measures do not guarantee against hypothyroidism. As hypothyroidism cannot be fully prevented due to many of its causes not being fully understood or beyond our control, regular veterinary care remains the optimal approach to detect and manage this disease early. While managing this condition may be for the rest of the dog’s life, it’s important to remember that hypothyroidism is treatable, and many dogs with this condition go on to live normal, healthy lives.

Frequently Asked Questions

The life expectancy of a dog with hypothyroidism is generally not significantly affected by the condition itself if properly managed. It’s important to work closely with a veterinarian to establish an appropriate treatment plan and ensure regular monitoring of thyroid hormone levels to maintain the dog’s overall health and well-being.

Avoiding certain food items can help prevent problems associated with hypothyroidism. The following list includes some common foods that dogs with hypothyroidism should avoid.

  • Dairy products include milk, cheese, yogurt, ice cream, butter, sour cream, cottage cheese, and other dairy products. Milk contains calcium, but too much calcium can lead to kidney stones. Cheese can contain lactic acid bacteria that can upset the stomach, and yogurt contains live cultures that can make pets sick.
  • Meat – Eating meat, dogs often develop diarrhea because they do not digest proteins properly. They also tend to become overweight because they cannot burn fat efficiently.
  • Eggs – Egg yolks contain cholesterol, which can increase the risk of developing plaque buildup in arteries.
  • Wheat – Wheat contains gluten, which can trigger inflammation in the intestines. Gluten sensitivity can result in vomiting, diarrhea, and abdominal pain.
  • Corn – Corn is high in starch and can cause intestinal gas.
  • Fruits – Some fruits like apples, pears, peaches, plums, apricots, cherries, grapes, melons, and bananas contain natural sugars that can cause diarrhea.
  • Beans – Beans contain lectins, which can irritate the digestive tract lining. Lectin sensitivity can cause loose stools, bloating, and flatulence.

When it comes to dogs with thyroid problems, a balanced and nutritious diet is crucial. Ideally, the diet should consist of high-quality, easily digestible protein sources, healthy fats, and moderate levels of carbohydrates. It is generally recommended to feed dogs with thyroid problems a commercial dog food specifically formulated for thyroid health or hypoallergenic diets free from common allergens like wheat, soy, and corn. Additionally, including ingredients rich in omega-3 fatty acids, such as fish oil or flaxseed, can support thyroid health. However, consulting a veterinarian for personalized dietary recommendations based on your dog’s specific condition and needs is important. Regular monitoring of thyroid function and follow-up visits with the veterinarian is also essential to ensure the dog’s thyroid health is properly managed.

If left untreated, hypothyroidism in dogs can lead to various health issues and complications. The dog’s metabolism and various bodily functions can be disrupted without the proper amount of thyroid hormone. Common symptoms of untreated hypothyroidism include weight gain, lethargy, hair loss, skin problems, cold intolerance, muscle weakness, and behavioral changes. Over time, the condition can progressively worsen, resulting in more severe complications such as heart problems, infertility, and neurological issues. Additionally, untreated hypothyroidism can compromise the dog’s immune system, making them more susceptible to infections and other diseases. Therefore, it is important to seek veterinary treatment if hypothyroidism is suspected of properly managing the condition and preventing potential long-term health consequences.

While it’s important to consult with a veterinarian for proper diagnosis and treatment of thyroid conditions in dogs, some natural approaches can complement conventional treatments. These include:

  1. Balanced diet: Provide a nutritionally balanced diet appropriate for your dog’s specific needs, which may include high-quality protein sources, essential fatty acids, and antioxidants.
  2. Herbal supplements: Some herbal supplements, such as kelp, ashwagandha, and licorice root, are believed to support thyroid health. However, it’s crucial to consult with a veterinarian or holistic practitioner before adding supplements to your dog’s regimen.
  3. Exercise and weight management: Regular exercise and maintaining a healthy weight can help support overall wellness, including thyroid function.
  4. Stress management: Minimize stress in your dog’s environment, as stress can impact hormonal balance. Provide a calm and comfortable living space, regular exercise, and positive reinforcement training techniques.

Remember, natural remedies should not replace veterinary care and medication a professional prescribes. Always consult a veterinarian who can provide appropriate guidance and treatment options based on your dog’s condition.

Hypothyroidism itself is not typically considered a life-threatening condition in dogs. However, if left untreated, it can lead to various health issues and complications affecting the dog’s quality of life. For example, untreated hypothyroidism can result in weight gain, lethargy, skin problems, hair loss, muscle weakness, and other symptoms that can significantly impact the dog’s well-being. 

Hypothyroidism in dogs can sometimes contribute to changes in behavior, including increased irritability, aggression, and other mood changes. However, it’s important to note that aggression can have various underlying causes, and hypothyroidism is just one potential factor. Other factors such as genetics, environment, training, socialization, and medical conditions can also influence a dog’s behavior.

Hypothyroidism is relatively common in dogs, especially in certain breeds. It is estimated to affect about 1-2% of all dogs. However, the prevalence can vary among breeds, with some breeds being more predisposed to the condition.

Hypothyroidism in dogs can cause various symptoms, and excessive panting can be one of them. However, panting can also be attributed to other factors such as heat, anxiety, or physical exertion. Therefore, while hypothyroidism can contribute to panting in dogs, it is important to consider other potential causes and consult a veterinarian for a proper diagnosis. Other signs of hypothyroidism in dogs may include weight gain, lethargy, hair loss, cold intolerance, changes in skin or coat, and behavioral changes. A thorough veterinary examination and blood tests are typically required to confirm a diagnosis of hypothyroidism and determine the appropriate treatment plan.

Yes, hypothyroidism in dogs can cause various skin problems. The thyroid hormone is crucial in regulating dogs’ skin and coat health. Insufficient thyroid hormone production can lead to changes in the skin and coat, resulting in dryness, flakiness, hair loss, and poor hair regrowth. In addition, the skin may become thickened, darkened, or have a greasy appearance. Dogs with hypothyroidism may also be prone to skin infections, itchiness, and increased susceptibility to external parasites. 

Yes, hypothyroidism in dogs can contribute to urinary incontinence. Reduced thyroid hormone levels can affect the urinary system’s normal function, leading to problems such as decreased muscle tone in the bladder or weakened sphincter control. This can result in involuntary urine leakage or difficulty in controlling urination.

Hypothyroidism in dogs is more commonly associated with weight gain rather than loss. This is because dogs with hypothyroidism often have a decreased metabolic rate, which can lead to weight gain and difficulty in losing weight. However, it’s important to note that weight loss can occur in some cases of hypothyroidism, especially if other underlying factors are involved. Therefore, if your dog is experiencing weight loss, it is essential to consult with a veterinarian to determine the underlying cause and develop an appropriate treatment plan.

Autoimmune hypothyroidism in dogs, also known as autoimmune thyroiditis, is a condition where the immune system mistakenly attacks and damages the thyroid gland. This immune response leads to inflammation and destruction of thyroid tissue, resulting in decreased production of thyroid hormones. It is believed to be the most common cause of hypothyroidism in dogs. The exact cause of autoimmune hypothyroidism is unknown, but genetic factors are believed to play a role. Dogs with autoimmune hypothyroidism may experience a range of symptoms, including weight gain, lethargy, hair loss, skin problems, and changes in behavior.

Hypothyroidism can start at any age in dogs but is more commonly seen in middle-aged and older dogs. The condition is typically seen in dogs between 4 and 10 years old. However, it can also occur in rare cases in younger dogs or even puppies. In addition, hypothyroidism in dogs is often progressive, developing gradually over time. 

Yes, a veterinarian should regularly monitor dogs on thyroid hormone replacement therapy. Monitoring is necessary to ensure the prescribed thyroid hormone medication is appropriate for the dog’s needs. Over time, the veterinarian may need to adjust the dosage based on the dog’s response and bloodwork results. Regular blood tests, including thyroid hormone level checks, are commonly conducted to assess the dog’s thyroid function and make necessary dosage adjustments. Monitoring also allows the veterinarian to evaluate the dog’s overall health and address any potential complications or side effects associated with the medication.

Disclaimer: The information provided on this veterinary website is intended for general educational purposes only and should not be considered as a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a licensed veterinarian for any concerns or questions regarding the health and well-being of your pet. This website does not claim to cover every possible situation or provide exhaustive knowledge on the subjects presented. The owners and contributors of this website are not responsible for any harm or loss that may result from the use or misuse of the information provided herein.

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