Thyroid Cancer in Dogs

Thyroid Cancer in Dogs

The thyroid is one of the most important endocrine glands that animals and humans are equipped with. This gland is in charge of producing the thyroid hormone, which regulates how the body uses the energy it gets from food and also its reactions to any other hormones.

Although less common compared to other types of cancer, thyroid tumors can occur in some dog breeds. In today’s article, we’re looking at the clinical signs, treatment, and prognosis of thyroid cancer in our canine friends.

Are Some Dogs More Prone to Getting Thyroid Cancer?


Some studies have found that Beagles, Golden Retrievers, as well as Boxers are much more exposed to this disease compared to other dog breeds. Siberian Huskies are also on this list.

What’s interesting about this type of cancer is that dogs almost always develop the malignant form, but it is non-functional, which means that it doesn’t cause the gland to secrete more thyroid hormone. So while the gland does grow in size and the tumor can spread to other organs, dogs do not develop hyperthyroidism.

Cats, on the other hand, are more likely to have the benign form of thyroid cancer, which means that the neoplasm will not spread to other organs. However, almost all cats that have thyroid cancer suffer from hyperthyroidism, so the gland becomes overactive.

Another aspect worth noting about this type of cancer is that some dogs and cats can have thyroid tissue in other areas of their bodies besides the physiological location of the thyroid gland (meaning right over the trachea). Some locations can be baffling — some dogs can have ectopic thyroid tissue next to their hearts. Worst of all, these ‘remnants’ can also develop tumors.

Symptoms and Diagnosis

Besides a local mass, most dogs end up not showing any particular clinical signs, which makes it harder for their owners to tell whether it’s time to go to the animal hospital or not.

Those that do develop symptoms can show different ones depending on how much of the thyroid gland was affected or not. Some can develop hyperthyroidism while others can develop hypothyroidism, so they’ll become lethargic, experience hair loss, and be exhausted all the time.

In most cases, though, dog parents can notice a significant change in their pet’s voice as they bark, changes in their water and food consumption (the gland might push against the esophagus and make swallowing difficult), and sometimes, even breathing difficulties (since the gland can also apply pressure to the trachea).

How is this Disease Diagnosed?

Well, a clinical examination is never enough for a disease as serious as cancer. Sure, the animal’s medical history along with the anamnesis (what you tell your vet about the symptoms) are both important, but a complete blood count, biochemistry tests, as well as a thyroid gland ultrasound and hormone blood tests can be far more useful.

A local x-ray might also be necessary to determine just how much the tumor has spread. Sometimes, thyroid cancer can reach the lungs. A biopsy is, more often than not, necessary to establish the exact type of cancer the dog has and the stage it has reached (malignancy wise).

How Can Thyroid Cancer Be Treated?

Less than 50% of the patients diagnosed with this type of cancer go into surgery for it. The fact is that most cases are diagnosed too late in their development, which makes surgery somewhat useless. Radiation therapy does prove its worth in most situations, but frequent treatments have to be administered for a longer duration.

Chemotherapy seems to be quite effective in treating thyroid tumors, so it is a therapy to consider.

What Is the Prognosis for a Thyroid Cancer Canine Patient?

The prognosis is variable depending on the stage the tumor has reached, whether it has spread to other organs or not, how large it is, if it can be surgically removed, and a variety of such factors.

If the tumor is smaller than 4-5 cm and hasn’t spread anywhere else, an operation can be performed for its removal. Chemotherapy might be recommended following surgery as combination therapy is frequently effective, especially in treating adenocarcinomas.

As for life expectancy, it can be different from one animal to the next. If the pet is fairly young and has a healthy immune system and a form of thyroid cancer that isn’t particularly aggressive (or that was diagnosed early), they have a fairly good chance of living for at least three years following the operation.

Dogs that are diagnosed later in life and have other chronic health issues and a less capable immune system have a shorter life expectancy — sometimes just one year.

Final thoughts

When it comes to thyroid cancer (or any other type of cancer, for that matter), early diagnosis is the most important thing that pet owners can ensure for their dogs.

If your pet is older than 5-6, we strongly advise you to take them to the vet hospital for a check-up twice a year instead of one. Unfortunately, cancer has begun to show up in younger dogs, and early diagnosis can make a significant difference in treating this disease.

Although some dogs can be completely asymptomatic, there could be something happening inside your pooch’s body. Even standard blood tests can reveal certain abnormalities that can lead to a cancer diagnosis, so taking Fido to the vet twice a year is the best way of going about things.



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