What Is Hypothyroidism In Dogs?

Here’s what to know about hypothyroidism, according to a vet.

dog with clipboard

If your dog’s been gaining a little bit of weight lately, you might think more exercise is the solution. But that’s not always the case.

One cause of weight gain in dogs can actually be hypothyroidism, which is a serious health condition that needs to be treated by your vet. So how can you tell the difference?

We reached out to Dr. Aliya McCullough, Fetch by The Dodo’s on-staff vet, to find out all about hypothyroidism in dogs and how to tell if your pup has it.

What is hypothyroidism?

Hypothyroidism occurs when the thyroid gland doesn’t produce enough of the hormone thyroxine, which controls metabolism. The low amount of thyroxine slows down your dog’s metabolism and causes weight gain.

Hypothyroidism is actually pretty common in dogs. And while any dog can get it, it’s more prevalent in medium- and large-sized dogs and certain breeds, such as Doberman pinschers, golden retrievers, miniature schnauzers, cocker spaniels, Airedale terriers and Irish setters. It also occurs most often in middle-aged dogs.

Causes of hypothyroidism in dogs

The most common cause of hypothyroidism in dogs is lymphocytic thyroiditis, which is an immune-mediated disease. With lymphocytic thyroiditis, your dog’s immune system confuses the thyroid gland for a foreign object and attacks it.

Another common cause is idiopathic thyroid gland atrophy, which occurs when thyroid tissue gets replaced with fat. Idiopathic means it happens spontaneously and without a known cause.

Other less common causes include pituitary gland tumors or congenitally (meaning the dog was born with it) abnormal thyroid.

Symptoms of hypothyroidism in dogs

According to Dr. McCullough, the most common symptoms of hypothyroidism in dogs include:

  • Weight gain without increased appetite
  • Lack of appetite
  • Lethargy or not wanting to exercise
  • Coat changes, such as dull coat, thin hair and increased shedding
  • Skin changes, such as dark skin
  • Hair loss
  • Weakness
  • Abnormal heart rate and rhythm
  • Gastrointestinal upset

In more severe cases, your dog’s facial skin can thicken as a symptom, making his face look puffy or his eyelids look droopy.

Dogs who are born with an underactive thyroid gland can have dwarfism because the thyroid’s important for skeletal growth and development.

Hypothyroidism in dogs treatment

Luckily, hypothyroidism is pretty easy to manage.

“Hypothyroidism is managed by administering a synthetic thyroid hormone, called levothyroxine, to dogs,” Dr. McCullough told The Dodo. “Hypothyroidism is a chronic condition that cannot be cured; therefore, treatment is lifelong.”

While your pup might have hypothyroidism for the rest of his life, it’s not life-threatening.

“Dogs receiving appropriate therapy for hypothyroidism have an excellent prognosis and have a normal life expectancy,” Dr. McCullough said.

But since your pup will need to have lifelong treatment, the costs can add up, so it’s a good idea to get pet insurance to help you cover the costs. Plus, if he’s diagnosed with the disease before you buy insurance, it’ll be considered a pre-existing condition and won’t be covered.

If you're looking for pet insurance, you’ll want to check out Fetch by The Dodo because it's made by and for adoring pet parents, and it's the most comprehensive coverage in the U.S. and Canada, covering things that other providers don't or charge extra for, like holistic services, prescribed supplements for conditions they’re covering, and breed-specific conditions.

If your pup gets diagnosed with hypothyroidism, don’t panic. It’s easily treatable and not fatal, so as long as your dog gets treatment, he’ll live a normal life.