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Everything you need to know about hypothyroidism in dogs

By Daniel Mar Journalist

Updated on the

Hypothyroidism in dogs can be common in certain dog breeds. This disease is a result of a malfunction of the thyroid gland. It does not have a cure

The thyroid is a very important gland that human beings possess. Dogs, like humans, can develop a thyroid disease. One of the most common ones is hypothyroidism. This is an endocrine disease that is a consequence of a deficiency of thyroid hormones. Hypothyroidism in dogs can cause a decreased metabolic rate and it can lead to many systemic complications. Identifying this disease is difficult. Hence, regular thyroid checks should be part of your dog’s vet routine check.

What is hypothyroidism in dogs?

Canine hypothyroidism is a disease caused by an irregular functioning of the thyroid gland. “In mammals, the thyroid gland is found in the neck area. The dog's thyroid is divided into two lobes that lie on either side of the trachea (windpipe) below the larynx (voice box). The lobes look a bit like small deflated balloons, but they have a large role in regulating the body's metabolism”, said Jenna Stregowski, RVT. It is regulated by the pituitary gland which uses a hormone called thyroid-stimulating hormone (TSH). When TSH reaches the thyroid gland, it produces T4 (thyroxine) and T3 to regulate metabolic processes, growth, and development.

Veterinarians have discovered two types of thyroid problems. The first, hyperthyroidism, when the gland produces too much thyroid hormone. The second, hypothyroidism, when the gland doesn’t produce enough. Many diseases can result as a consequence of hypothyroidism in dogs. The most common ones are lymphocytic thyroiditis, congenital hypothyroidism, and Cushing’s Disease.

Which dog breeds need to watch out?

This disease mostly affects middle-size to large dogs. However, don’t ignore the possibility that it can affect any dog. Here you have a list of the breeds most prone to getting hypothyroidism:

  1. Boxers
  2. Irish Setters
  3. Cocker spaniels
  4. Doberman
  5. Rottweilers
  6. Labrador retrievers

It needs to be duly noted that hypothyroidism is very common in retrievers. Up to 80% of this breed can show signs of hypothyroidism.

Causes of hypothyroidism in dogs

“There are a number of potential causes of hypothyroidism in dogs, and the exact cause usually cannot be determined. Most commonly, canine hypothyroidism is immune-mediated”, said Dr Stregowski. Nevertheless, it is not always clear what causes hypothyroidism in dogs.

Vets do agree that some breeds are already predisposed, so by carrying extra weight and having a sedimentary lifestyle, chances are increased. Furthermore, dog owners should also consider the dog’s environment. Exposure to toxins, vaccines and medications (like corticosteroids) can put your dog’s thyroid gland at risk.

Unfortunately, diet is closely linked to this disease. A poor quality diet made up of highly processed dog foods is bad for dogs. Canned food can contain chemical additives that your dog doesn’t need.

Truth is that, whatever is the cause, this disease can affect any dog at any age (mostly from four to ten). Gender is not a factor when evaluating this disease. However, when it comes to females, evidence has shown that “(…) the disease can occur more commonly in spayed females than intact females”, said Dr Stregowski.

In rare cases, the disease might be congenital. Your puppy can actually have this disease since day one. This is very harmful and could be deathly.

Symptoms of hypothyroidism in dogs

Since this disease is mainly a deficiency of the thyroid gland, it can affect all the organs in the body. Likewise, the symptoms can be varied. As a matter of fact, the symptoms can point out towards another non-thyroidal disease.

It is very important to know your dog’s routine. This can help you to catch the signs of this illness early. Here you have a list of the most common symptoms:

  • Weight gain
  • Depression
  • Lethargy
  • Decreased heart rate
  • Intolerance to cold
  • Dry and brittle coat
  • Hair loss
  • Flaking and other skin infections
  • Otitis
  • Behavioural changes

“Less common but potentially serious complications of hypothyroidism include vestibular dysfunction (vertigo) and other neurological disorders, heart problems, and various health issues associated with obesity”, said Dr Stregowski.

Diagnosing hypothyroidism in dogs

For a proper diagnose of this disease, you must take your dog to the vet. He will perform a complete physical examination of your dog. This includes a series of blood tests to determine the levels of thyroid hormone in the blood. Firstly, your vet will test T4 levels. “In theory, a low T4 indicates hypothyroidism, but the diagnosis is not always this simple. Sometimes the T4 can fall in a grey area, and further testing is necessary”, said Dr Stregowski.

Afterwards, your vet can also measure the TSH levels. High levels of TSH also indicate hypothyroidism in dogs. This is so because the pituitary gland will be forced to produce excess TSH.

Treatment for this disease

As of now, there is no cure for hypothyroidism in dogs. “The good news is this disease isn’t life-threatening. Plus, it’s fairly easy and inexpensive to treat”, said Dr Amy Flowers, DVM. Usually, vets will prescribe synthetic T4 which is applied orally one or two times daily. This drug is called levothyroxine or L-thyroxine. Also, vets can prescribe liothyronine (T3) to dogs that can’t convert T4 into T3.

“Your dog will have to take oral drugs daily for the rest of his life”, said Dr Flowers. Even though the costs of thyroid supplements are low, it can add up over time. Nonetheless, don’t attempt to treat hypothyroidism in dogs with alternative methods. “There are no herbal, homoeopathic or home remedies that are effective as alternatives to synthetic thyroid hormone supplements”, said Dr Stregowski.

If your dog has hypothyroidism, then you must prepare your new responsibilities. Caring for your dog’s health is very important when dealing with this disease. Be sure to keep track of changes in his health appearance and behaviour. Lastly, always keep your vet nearby.

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