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Hypothyroidism in dogs: symptoms, causes, treatment and prevention

Hypothyroidism can affect both male and female dogs. However, this endocrine disorder mainly affects dogs between the ages of 3 and 8, and some breeds of dogs are more prone to it than others. There are different forms of hypothyroidism: primary, secondary, tertiary, lymphocytic thyroiditis and idiopathic atrophy. Depending on its form, different symptoms can alert the dog's owner. It is essential to consult the veterinarian so that it can be diagnosed reliably and the animal can be treated appropriately. Let's take stock of this serious disease for which there is no way to prevent it.

What is hypothyroidism and what causes it?

The thyroid gland is one of the most important glands in the body, both in dogs and humans, as it regulates the metabolism. It is the pituitary gland that controls the thyroid gland. But the hypothalamus can also have an impact on the proper functioning of endocrine glands such as the pituitary and thyroid. The hypothalamus is located in the heart of the brain. It is involved in many vital functions that it regulates, such as sleep, hunger, thirst, and stimulates endocrine secretions.

Hypothyroidism is therefore an endocrine disease. It is manifested by a decrease in the thyroid hormone. The metabolism is slowed down, which also leads to a slowing down of all body functions.

There are different forms of hypothyroidism, namely:
  • Primary hypothyroidism: the thyroid gland no longer secretes hormone. This primary form is frequently due to a dysfunction of the immune system. It is asymptomatic, meaning that it does not cause any symptoms.
  • Secondary hypothyroidism: the pituitary gland no longer secretes sufficient Thyroid Stimulating Hormone or TSH, so that the thyroid is no longer stimulated,
  • Tertiary hypothyroidism: the hypothalamus no longer secretes thyrotropin-releasing hormone (THR), which results in a disturbance of the pituitary gland and thus a deregulation of the thyroid.
Two other forms of thyroid dysfunction are more rarely observed. These are :

  • Lymphocytic thyroiditis, which occurs when the animal's body produces antibodies leading to the destruction of thyroid cells. The disease progresses over 12 to 36 months, and it is only when the gland is completely destroyed that the symptoms of hypothyroidism are revealed.
  • Idiopathic atrophy, the cause of which is still unknown at this time. In these rare cases, fat cells gradually replace the thyroid cells.

Symptoms of hypothyroidism in dogs

A dog with hypothyroidism may have some of the following symptoms:
  • A change in the appearance of the coat and hair loss,
  • A build-up of lipids in the cornea,
  • A change in voice,
  • Edema of the face,
  • Hyperpigmentation of the skin,
  • Breathing difficulties,
  • Scaling of the skin,
  • A slowing of the heart rate,
  • Unusual coldness,
  • Behavioral problems,
  • Weakness in the hind legs,
  • A great fatigue,
  • A weight gain that can go as far as obesity, while the dog's appetite remains the same as before, or even decreases.
We can see that a dysfunction of the thyroid gland can completely disrupt daily life. Of course, the dog may not have all these symptoms. In any case, the change in his condition warrants a quick visit to the veterinarian.

Canine Hypothyroidism: Treatments

To make a diagnosis, the veterinarian needs to do a blood test to check hormone levels, cholesterol and triglyceride levels. In some cases, a CT scan, ultrasound or other imaging test is necessary.

If there is no doubt that the dog has hypothyroidism, then a treatment protocol is put in place to correct the hormonal deficiency with a synthetic hormone. This is essential to rebalance the dog's metabolism.

The treatment of hypothyroidism must be continued throughout the dog's life. Regular monitoring of the animal is necessary as well as a blood test so that the dosage can be revised up or down depending on its health and the results of the analyses. It is therefore a case-by-case treatment. Encouraging improvements are obtained as the clinical signs fade over time until they disappear. The treatment of the animal must always be considered in the long term, but the prognosis is very good.

Dog breeds most at risk for canine hypothyroidism

Some dog breeds are more prone to hypothyroidism than others. These include the Golden Retriever, Poodle, Beagle, Doberman, Dachshund, Irish Setter, Chow-Chow, Shetland Sheepdog, Airedale Terrier, Pomeranian, English Bulldog and Shar-Pei.

The owner of one of these dogs must therefore be vigilant and regularly take his little companion to the veterinarian to have a health check-up. This allows for the early detection of congenital hypothyroidism and the early management of the dog. In this way, it is sometimes possible to prevent certain irreversible damage to the central nervous system.