Hypothyroidism in dogs

My son who is an avid watcher of Pitbulls and Parolees got me thinking this week. He was telling me about a dog on the show that they thought was fat but really had hypothyroidism.

I started thinking about how common it is in people and pets to have a symptom of a problem only to find out the problem is something entirely different.

Our greyhound that passed in September was getting very thin in the months leading up to his diagnosis. And he was ravenous. We thought we weren’t feeding him enough. Or maybe we needed to change his food. Then we found out that he had a tumor on his thyroid that was causing hyperthyroidism.

The signs of a thyroid problem can seem pretty harmless at first. Then, before you know it, your dog’s quality of life is seriously diminished.

What is hypothyroidism?

The thyroid gland is a small 2-lobe gland near the windpipe in the dog’s throat area. It regulates the body’s metabolism by producing thyroid hormones.

Hypothyroidism (underactive thyroid) is a lowered production and release of T3 (liothyronine) and T4 (levothyroxine), two of the hormones produced by the thyroid your dog needs for their metabolism to function normally.

Hypothyroidism is quite common in dogs but very rare in cats. In cats, it’s not uncommon to see hyperthyroidism (overactive thyroid). We’ll talk about that next week.

What causes hypothyroidism?

Most cases are caused by something destroying the gland.   That could be a problem with the immune system, or the destruction could be caused by atrophy of the thyroid tissue. When this happens, fat is able to infiltrate the tissue. It could also be caused by cancer that destroys the gland.

Hypothyroidism usually occurs in middle-aged dogs, between 4 and 10 years old. It’s not specific to one sex, but spayed females and neutered males seem to be more at risk than intact dogs. And although any dog can suffer from hypothyroidism, mid to large size breeds tend to be most at risk.

Here are the 10 breeds most susceptible:

Golden Retriever

Labrador Retriever



Cocker Spaniel


English Bulldogs

Great Danes

Doberman Pinscher

Mixed breed dogs tend to be less prone to this condition.

What are the signs of hypothyroidism?

Some of the symptoms of hypothyroidism seem very benign, taken on their own. But combine a few of them together, and your vet will be suspicious.

Here are the most common symptoms to watch out for:

Dark skin patches

Dry skin

Lethargy/mental dullness

Hair loss

Dull coat

Weight gain/obesity

Dry hair coat/excessive shedding

Cold intolerance

Slow heart rate

High blood cholesterol


Dogs can go on for years with undetected hypothyroidism, but at some point it will start to affect their quality of life. And that’s probably when you’ll start to take notice.

If your dog has unexplained weight gain, along with some of the other symptoms on the list like chronic skin problems, they may be suffering from hypothyroidism. Talk to your vet about it.

Hypothyroidism is easily diagnosed with blood work. Your vet may suggest additional tests if your dog has more serious but less common symptoms, like seizures or heart problems.

Can hypothyroidism be treated?

Fortunately, hypothyroidism is treatable.

If your dog is diagnosed with it the treatment is a synthetic thyroid hormone called thyroxine taken twice a day. Your dog will have to be on the medication for the rest of their life, and your vet will have to monitor the dose with regular blood tests.

The good news is that once treatment begins, most of the symptoms will start to subside in a few months.

Your vet may also suggest a reduced fat diet initially. But be sure you get the go ahead from your vet before changing your dog’s diet. You don’t want to inadvertently impact the effectiveness of the treatment.

Have you had a dog that suffered from hypothyroidism? What were the symptoms that made you suspicious that something was going on? Share your experience in the comment section above.






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