Medical Jargon Explained: Hypo- versus Hyperthyroid

Endocrine glands: Thyroid

Endocrine glands are hormone-producing organs that regulate various functions in the dog's body, such as metabolism, growth and sexual development. Disturbances in production and release of these hormones lead to serious imbalances.

The thyroid gland is located in the neck and produces hormones that regulate growth, metabolism and affect the function of a number of systems in a dog's body.

Hypothyroid versus Hyperthyroid

When the thyroid isn't functioning properly, either too much or not enough thyroid hormone is released, which leads to serious health problems.

Knowledge and awareness are important to be able to detect early signs of hypo and hyperthyroidism. The longer these conditions remain untreated the more profound impact they might have on your dog's overall health.


Hypothyroid, or an under-active thyroid, is a deficiency condition in which the thyroid gland doesn't release sufficient amounts of its hormone into the bloodstream. This can lead to a number of health problems. For example, under-active thyroid has been linked to conditions such as arthritis and ligament injuries and seizure disorders.

The good news is, that once hypothyroidism is diagnosed, treatment is relatively simple and usually very successful. Conventional treatment involves oral supplementation with synthetic thyroid hormone. The only downside is that your dog will have to receive the hormone supplement for the rest of his life.

Alternative modalities, such as holistic or Traditional Chinese medicine, may offer treatments to stimulate the thyroid function. This might work for marginally low thyroids.

Although it can be caused by other factors, the most common cause of hypothyroidism in dogs seems to be the result of an autoimmune disease.

Recognizing symptoms of hypothyroidism in your dog can be quite challenging. Jasmine eventually got diagnosed based on a symptom completely unrelated to her hypothyroid, when we were trying to determine a cause of her panting and pacing episodes.

Some of the common symptoms of hypothyroidism in dogs are
  • lethargy
  • listlessness
  • unexplained weight gain
  • cold intolerance
  • exercise intolerance
  • personality changes
  • coat and skin changes
  • poor growth in puppies
Hypothyroidism in Dogs


Hyperthyroid, or over-active thyroid, is an excess condition. Overproduction of the thyroid hormone can lead to a number of serious health problems.

Fortunately, hyperthyroidism is rare in dogs.

The most common cause of hyperthyroidism in dogs is a cancer of the thyroid gland. Unlike with hypothyroidism, treatment is much more invasive and difficult.

Some of the symptoms of hyperthyroidism in dogs are
  • unexplained weight loss
  • increased appetite
  • excessive thirst
  • diarrhea
  • hyperactivity
  • heat intolerance
  • nervousness
  • coat changes
It is important to be sensitive to potential signs of disease in your dog. The longer these conditions remain untreated the more profound damage they will cause.

In this series:
Hypothermia vs Hyperthermia
Hypothyroid vs Hyperthyroid
Addison's vs Cushing's
Hypoglycemia vs Hyperglycemia