Thyroid Hormone Deficiency in Dogs

Picture of a Chow in the field

Thyroid disease is diagnosed in dogs more often than you might think. The thyroid glands are located in the neck and they play the role of producing hormones that have an impact on a variety of body parts. Usually, cats suffer from an overproduction of thyroid hormones whereas dogs are typically diagnosed with thyroid hormone deficiency.

It’s very rare that dogs are diagnosed with an overactive thyroid gland and if that does happen, this type of medical problem is usually associated with cancer. Hypothyroidism in dogs can be caused either by the shrinkage of the gland or by inflammation. Fortunately, thyroid cancer isn’t very common in our canine friends.

Let’s look at some facts about thyroid hormone deficiency in dogs that you might want to know, especially if you’ve recently become a dog parent.

What Breeds Are More Exposed to This Issue?

Many studies have found that hypothyroidism is a more common medical problem diagnosed in medium to large breed dogs. Also, it traditionally affects dogs that are at least middle-aged. The breeds that are predisposed to developing thyroid hormone deficiency are Irish Setter, Golden Retriever, and Doberman Pinscher, but it has also been found to affect Cocker Spaniels, Miniature Schnauzers, and Airedale Terriers.


Some of the common clinical signs that a pet parent can notice in a dog that suffers from this disease range from exercise intolerance and mental dullness to lethargy, obesity, weight gain without any particular change in appetite, as well as an intolerance to the cold.

Some dogs develop thickening of the skin and will manifest various reproductive disturbances despite being otherwise healthy. There is another somewhat classic symptom that can be seen in patients and it consists of modifications in their skin and coat condition – hair loss or thinning or increased shedding. Some dogs can even have alopecia (total hair loss) in some areas except the head and legs but that can be seen on the dog’s trunk, for example.


If you notice any of the symptoms that we have described earlier, it is a good idea to take your Fido to the veterinarian as soon as possible. If thyroid hormone deficiency is suspected, the vet will perform a series of tests. However, the problem with this disease is that it is often over-diagnosed as many other medical conditions have similar clinical developments or will cause lower production of thyroid hormones.

Fortunately, careful diagnostic testing along with a thorough clinical examination can reveal the issue. Blood tests can be extremely valuable as they can show whether your dog exhibits any abnormalities that are associated with the medical problem. Another way of telling whether the dog is suffering from this disease is by monitoring his or her thyroid hormone levels over the course of a set time span.

A test of your dog’s T4 concentration can also be performed and while it is good enough, your vet might recommend that several other tests are done.

Treating Hypothyroidism in Dogs

Hypothyroidism is completely treatable, but what you should know is that in many cases, you will have to give your dog pills for the remainder of his or her life. The substance that you will have to administer is thyroxine, which is a replacement hormone compound.

The dosage of the medication naturally depends on your dog’s thyroid levels, but also on your dog’s age and weight. Keep in mind that you should take your canine friend to the clinic every year or so as he or she ages. Most dogs have to be retested once or twice per year so that the dose is adjusted.

Autoimmune Thyroiditis

Although it is somewhat rare compared to thyroid hormone deficiency, autoimmune thyroiditis is a type of disease that produces hypothyroidism. Therefore, what is otherwise a disease is, in this case, a symptom of another illness.

Autoimmune thyroiditis can affect Doberman Pinschers, Beagles, Akitas, and Golden Retrievers more than other breeds. Its only clinical manifestation is usually thyroid hormone deficiency, but it shows up in other disorders such as pan-endocrinopathy or systemic lupus erythematosus.

What about Hyperthyroidism?

As stated at the beginning of the article, hyperthyroidism isn’t something that can be considered a common medical issue in dogs. However, there are cases where a dog could produce too much thyroid hormone, in which case his or her metabolic rate could reach dangerous levels.

Thyroid carcinoma causes hyperthyroidism and since it is a form of cancer, the type of treatment must be chosen according to your dog’s age, the size of the tumor, the stage of the disease, as well as whether any of the nearby tissue was affected, as well.

Fortunately, there are many options when it comes to treating thyroid carcinoma nowadays. Surgery is one of them, but there are also radiation treatments, as well as chemotherapy. Picking the right type of treatment must always be made based on the dog’s health status.

The clinical signs of hyperthyroidism are the exact opposite of those that characterize hypothyroidism. Therefore, a dog suffering from this hormone imbalance or thyroid disease will exhibit weight loss, increased thirst, urination, and an increased appetite, as well as hyper-excitability.

In some dogs, an enlargement of the thyroid gland is visible, too. Other symptoms typical of this medical condition are tachycardia, heart murmurs, or cardiomegaly, as well as shortness of breath. In some cases, congestive heart failure can happen, especially if the cardiac symptoms aren’t noticed in due time.



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