Hypothyroidism in dogs: causes, symptoms, diagnosis and treatment

One of the most interesting and not fully studied topics are hormones. Since they affect almost all processes occurring in the human or animal body, the importance of these substances is difficult to underestimate. The more dangerous are the disorders associated just with hormonal pathologies. For example, hypothyroidism in dogs.

What it is?

Hypothyroidism is a fairly common disease in dogs. It is accompanied by disorders in the thyroid gland. The latter has many different functions, but its main "occupation" is the regulation of metabolism, which is carried out due to the work of specialized hormones. Thus, hypothyroidism is a pathology characterized by a decrease in the synthesis of essential thyroid hormones.

Like all pathologies of this type, this disease can be accompanied by a huge number of symptoms, but is often suspected in dogs experiencing obesity problems. In addition, this disease is often found in animals suffering from hair loss and skin problems. Hypothyroidism is easy to diagnose by just having a complete blood count in a good veterinary clinic. During this study, specialists will check the level of thyroid hormones and compare it with the norm characteristic of animals of the same breed and age. In most cases, the disease is incurable, but sick pets live well if they are given synthetic hormones on time.

Clinics in large cities generally believe that at least 20-30% of old dogs suffer from chronic problems caused by low levels of hormones over the years. If your dog has persistent skin problems, or the dog has a tendency to turn into a bun, the animal may suffer from hypothyroidism.

What causes hypothyroidism?

The thyroid gland is a small organ located close to the larynx. Its activity is regulated by the pituitary gland of the brain. For this purpose serves ... correctly, a special stimulating hormone. Thus, the scheme is quite entertaining: the pituitary gland synthesizes a hormone that causes the thyroid gland to increase the production of its own hormone. Thus, the performance of the thyroid gland directly depends on its condition, since it will not work without “supervisory supervision”. But the disease described by us in many cases begins in dogs, the pituitary gland of which is in excellent condition. Why is this happening?

Approximately 95% of cases of hypothyroidism are "background", developing due to diseases accompanied by processes of destructive changes in the thyroid gland. It is far from always the essence of these processes that can be found out. Veterinarians suggest that autoimmune diseases, in which the body begins to destroy itself, are probably to blame. Hypothyroidism can also be the result of atrophy of the tissue of the thyroid gland, which often happens with severe obesity or cancer.

In addition, pathology can develop against the background of infectious and parasitic diseases, the uncontrolled intake of certain hormonal drugs leads to the same outcome. Rare cases of congenital hypothyroidism are also detected from time to time. It is already more or less accurately known that a serious helminthic invasion, in which a large amount of toxins were released into the animal's body for a long time, can also cause damage to the thyroid gland (and other organs, by the way).

Predisposed breeds

As a rule, clinical signs are diagnosed with equal success in pets of different ages, sex and breeds, but most often symptoms of hypothyroidism in dogs are detected in animals aged four to ten years. It is noted that 70% of cases are detected in dogs of large and giant breeds, while "babies" are sick much less often. The statistics accumulated by veterinarians all over the world indicate that representatives of breeds most often fall ill:

  • Golden retriever.
  • Doberman Pinschers.
  • Irish Setters.
  • Schnauzers.
  • Dachshunds.
  • Cocker Spaniels.
  • Airedale Terriers.

Most likely, the long-suffering German shepherd dogs, already prone to numerous genetic pathologies, and to hypothyroidism are also very sensitive. Most likely, there is no gender dependence in normal conditions, but bitches who have had their ovaries removed are still more likely to get sick. But they are removed to prevent breast cancer, so in this situation, hypothyroidism seems to be the preferred option. In any case, mortality from this pathology is ten times lower.


Thyroid hormones are essential for normal metabolic function. The lack of these substances affects all organs and systems. As a result, the symptoms are changeable and vague. There is no specific symptom that is diagnostic for hypothyroidism. However, there are several symptoms that occur in 90% of cases when the functionality of the thyroid gland is somehow affected. For convenience, we have grouped them into a simple table:


There are several different tests used to diagnose hypothyroidism in a dog. Their choice depends on the financial capabilities of the owner of the dog, and on the availability of the necessary equipment and / or reagents in the clinic. Since the signs of hypothyroidism in a dog are very vague, they cannot do without professional clinical diagnosis.

The most common test is testing for free thyroxine (T4). This substance is synthesized exclusively in the thyroid gland, and therefore, with a low content in the bloodstream, the presence of the disease can already be suspected. But it must be remembered that there are other reasons for the decrease in thyroxine in the bloodstream, and therefore, in any case, you should focus on other diagnostic methods.

It should be remembered that thyroxine is present in the general bloodstream in two forms. The “bound” form is attached to proteins in the blood and is unable to penetrate into the cells. “Free” T4 is not attached to proteins; it can penetrate into cellular structures and fulfill its function. Free T4 is usually present in very small amounts. It is his (!) Volume fraction that is used in the diagnosis.

If a dog has a low T4 level, a thyroxin test can be tested, which is based on the action of special medications. A small amount of synthetic pituitary hormone is administered intravenously. Six hours after this procedure, blood is taken, the T4 level is checked. If the dog has hypothyroidism, the level of the hormone in the blood will be normal or close to normal. In a healthy animal, the level of this substance will go far beyond the upper limits of the norm.

How is hypothyroidism treated?

What is the treatment for hypothyroidism in dogs? It is, and, moreover, very effective. Therapy consists in the introduction of synthetic thyroxine (levothyroxine). To date, the global pharmaceutical industry produces many varieties of this drug, differing only in registered names. The dose and frequency of administration of this drug vary depending on the severity of the disease and the individual response of the animal to therapy.

Usually, a standard dose is first introduced, a blood test is taken in a day, the hormone level is checked, and then the treatment is adjusted according to the situation. Depending on which system of the body reacts most difficult to the disease, appropriate symptomatic and supportive treatment is prescribed. If you start therapy on time and not start the disease, then in most cases everything ends well. By the way, this distinguishes this pathology from hyperthyroidism, which is much more difficult and more difficult to treat.

Watch the video: Understanding Canine Hypothyroidism (February 2020).