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Hypothyroidism in Dogs: Symptoms, Causes, and Treatment

In this blog post, we’re going to give you the 411 on hypothyroidism in dogs - what it is, why it happens, and how to treat it.

Written by Raquel Astacio. Published in May 2023.
Hypothyroidism in Dogs

If your dog is experiencing unexplained weight gain, hair loss, and skin issues, hypothyroidism may be the underlying cause. Fortunately, this condition is not typically life-threatening and can usually be managed with medication once diagnosed.

But what exactly is the thyroid, and why is it so important? We’re glad you asked! 

In this blog post, we’re going to give you the 411 on hypothyroidism in dogs - what it is, why it happens, and how to treat it. Plus, we’re going to discuss the tell-tale signs of this common condition before answering some of the internet’s most frequently asked questions. Let’s get started! 

What is Hypothyroidism in Dogs?

Hypothyroidism in dogs is a common hormonal disorder caused by an underactive thyroid gland. This gland plays a crucial role in the regulation of metabolism, which is why hypothyroidism can lead to a wide range of symptoms.

For many dogs, hypothyroidism will cause weight gain, lethargy, hair loss, and skin problems. It can also affect behavior, causing them to be less active or more irritable. In more serious cases, it can even lead to other health problems such as high cholesterol or heart disease.

It's important to note that hypothyroidism can affect dogs of any breed, age, or gender. However, it is more common in middle-aged dogs and medium-to-large breeds, such as Golden Retrievers, Miniature Schnauzers, and Dobermans. 

Fortunately, hypothyroidism in dogs is treatable with medication that replaces the missing thyroid hormone. With proper treatment, most dogs can live happy, healthy lives. But to fully understand why it’s so imperative to regulate an underactive thyroid, we must first understand what function the thyroid serves and why it’s so important. Let’s take a closer look. 

What Does the Thyroid Do?

The thyroid is a small, butterfly-shaped gland in the neck responsible for producing hormones that regulate metabolism and other important functions. In both dogs and humans alike, the thyroid gland plays a vital role in maintaining overall body health.

Thyroid hormones affect almost every organ and tissue in a dog's body, including the brain, heart, digestive system, and skin. In addition to controlling metabolism, the thyroid gland also plays a crucial role in regulating body temperature, heart rate, and energy levels. 

This gland is also responsible for maintaining healthy skin and coats and ensuring that our furry friends maintain a healthy weight. However, when the thyroid gland is not functioning properly, it can lead to a range of health issues. 

Hypothyroidism in Dogs Symptoms

Dogs with hypothyroidism may show one or more of the following clinical signs: 

  • Weight gain with no obvious cause
  • Lethargy or laziness (preferring to sleep and lie around all day rather than run and play)
  • Heat-seeking behavior (dogs with hypothyroidism constantly run a little cold, so they may prefer to lie near the fireplace or on the heat vent to stay warm)
  • Chronic skin and ear infections (as a result of reduced immunity)
  • Dry, brittle hair with a thinning hair coat
  • Increased pigmentation of the skin
  • Inability to regrow hair after it’s been shaved

Less common symptoms include reproductive problems, nerve pain, hind leg dragging, small, white fat deposits on the surface of the eyes, dry eye, and even thickening of facial skin that causes the muscles of the face to droop.

What Causes Hypothyroidism in Dogs?

The two most common causes of hypothyroidism in dogs are:

  1. Inflammation of the thyroid gland (lymphocytic thyroiditis)
  2. Degeneration of the thyroid gland (idiopathic thyroid gland atrophy)

While the exact reason that this occurs in some dogs but not others is unknown, experts believe a genetic predisposition is involved. There is no evidence suggesting that hypothyroidism is linked to diet or lifestyle. 

In rare cases, hypothyroidism in dogs can also be caused by cancer or thyroid gland trauma, but these instances are (thankfully) few and far between. Most cases of canine hypothyroidism are inflammatory or degenerative in nature - both of which can be treated with medication. 

Diagnosing Hypothyroidism in Dogs

Hypothyroidism in dogs can be diagnosed with a simple blood test called a “Total Thyroxine Level” (Total T4 or TT4). This test determines the dog's main thyroid hormone level, and if it is low and the dog is showing clinical signs of hypothyroidism, this is suggestive of a diagnosis. However, to confirm the diagnosis, veterinarians may run additional blood tests, such as a free T4 level or a full thyroid panel.

At times, dogs might exhibit low total T4 levels without actually developing hypothyroidism. On the flip side, some dogs may show total T4 levels that fall within the normal range but still have hypothyroidism. Confirmatory tests like free T4 or a full thyroid panel can be especially helpful in such cases.

Hypothyroidism in Dogs Treatment

Hypothyroidism is a condition without a cure, but it can be well managed. Typically, this is done using an oral medication called Levothyroxine, which is a synthetic form of the thyroid hormone that your dog's body lacks.

It's essential to note that dogs with hypothyroidism will need to take their thyroid replacement hormone for life. The dosage of the medication is based on the dog's weight and T4 levels, which will be determined by your veterinarian. In most cases, your veterinarian will also want to re-check your dog's bloodwork after one or two months to ensure that no dose adjustments are required.

Untreated hypothyroidism can have a significantly negative impact on a dog's quality of life. Nearly every organ in the body is affected by thyroid hormone, and a lack of it in dogs can lead to high cholesterol, decreased immune function, a slowed heart rate, and neuromuscular symptoms such as unsteadiness, a head tilt, and even seizures. 

Natural Remedies for Hypothyroidism in Dogs

Effective treatment for hypothyroidism requires supplementation of the missing thyroid hormone, which can only be done with medication. However, certain vegetables, such as asparagus, green beans, beetroots, broccoli, brussels sprouts, carrots, celery, lettuce, mushrooms, and spinach, can support thyroid function when added to your pet’s daily diet. 

Long-Term Management and Prevention of Hypothyroidism in Dogs

Over time, your pup’s tolerance to thyroid replacement hormone may change, which may require a dose adjustment. That’s why regular monitoring of thyroid hormone levels is crucial to ensure that your dog is receiving the appropriate dose of medication.

It's recommended to have your dog's blood thyroid levels checked every 6-12 months to avoid administering too much or too little thyroid hormone in the long term.

Once a dog's thyroid levels have been restored to normal, they should experience notable improvements in their body condition, energy levels, and hair coat. 

Since hypothyroidism is a genetic condition, it can not be readily prevented. However, consider the potential for this condition when adopting your next pet, as it primarily affects middle-aged dogs of medium-to-large breeds. 

FAQs About Hypothyroidism in Dogs

“Hypothyroidism in dogs' life expectancy?”

Hypothyroidism is a treatable condition in dogs, and with proper management, affected dogs can live normal, healthy lives. While the condition is not curable, it has an excellent prognosis, and patients generally respond well to treatment. Medically managed patients have a normal life expectancy.

“What happens if hypothyroidism is left untreated in dogs?”

If not treated promptly, hypothyroidism can have a negative impact on a dog's health and demeanor and even shorten his lifespan! Nearly every organ in the body is affected by thyroid hormone and metabolism, so dogs with untreated hypothyroidism may develop high cholesterol, decreased immune function, a slowed heart rate, and neuromuscular symptoms.

“Is hypothyroidism curable in dogs?”

There is no cure for hypothyroidism in dogs, but it can be effectively managed with daily medication. 

“Is hypothyroidism genetic in dogs?”

According to Dr. Jerold Bell of the Veterinary Information Network, “... almost all primary hypothyroidism in dogs is caused by thyroiditis (autoimmune destruction of the thyroid gland), and that this is a genetic disorder.”

So yes, the large majority of hypothyroidism cases are believed to be genetic. 

“Can hypothyroidism cause excessive thirst in dogs?”

Yes, hypothyroidism can cause excessive thirst and urination in pets, known in the veterinary world as PU/PD or Polyuria/Polydipsia. If your pet displays these symptoms, thyroid disorders and other common ailments like kidney disease are among the leading suspects.

“How common is hypothyroidism in dogs?”

According to a 2008 study performed by the Canadian Veterinary Journal, “​​Reported prevalence of hypothyroidism in dogs is 0.2% to 0.8%, with a mean age at diagnosis of 7 years.”

Conclusion

Hypothyroidism is a common endocrine disorder that mainly impacts middle-aged dogs of medium-to-large breeds. It can trigger a gamut of unpleasant symptoms, but fortunately, it can be easily treated with daily medication. While frequent vet visits and blood tests are essential for the long-term management of this condition, dogs that receive proper treatment can look forward to a long and happy life.

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