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Autoimmune Thyroiditis in Dogs

The thyroid is a small, butterfly-shaped gland situated at the base of the front of your neck, just below your Adam's apple. It is a part of the endocrine system which is responsible for coordinating many of your body’s activities. It basically controls the metabolism in the body. Now, this gland can undergo some issues which can lead to over or under production of hormones, which is called hyperthyroidism and hypothyroidism respectively. And when such a problem occurs, it leads to irritability, fatigue, weight loss, weight gain, and more. So thyroid is an important part of the body. We humans are not the only ones with the gland. Our beloved doggy friends are also blessed with it.Just like humans, the thyroid gland is located in your dog's neck, where it produces the hormone thyroxine, along with several other important thyroid hormones. These hormones play an important role in his/her metabolism and can cause major problems when they are not produced at normal levels. There are several diseases and complications that can affect this gland of theirs. Hypothyroidism is the most common one in middle-aged dogs of either sex. And just like people, dogs tend to be lethargic and gain weight.

Autoimmune Thyroiditis

If your thyroid becomes inflamed, you have thyroiditis. And the surprising part is that it’s not an external agent causing this but your own immune system. What happens is, at times your body makes antibodies that attack your thyroid by mistake. This results in a leak in the gland which then ends up producing excess thyroid hormones (hyperthyroidism) and thus inflammation. But over time, inflammation prevents the thyroid from producing enough hormones (hypothyroidism). This condition is called autoimmune thyroiditis, chronic lymphocytic thyroiditis, Hashimoto’s thyroiditis, or Hashimoto’s disease.

Thyroid problems in Dogs

Thyroid diseases are a relatively common problem in dogs. There are 3 major problems that can occur in the thyroid gland of the dog.

  • Hyperthyroidism

  • Hypothyroidism

  • Auto-immune thyroiditis

Auto-Immune Thyroiditis in Dogs

There are dogs, a very small proportion though, which are affected by this disease called autoimmune thyroiditis. The disease is the same as found in humans where the body’s own immune system attacks the gland. The consequences are nothing but eventual hypothyroidism. but autoimmune thyroiditis can also be a symptom of another disorder, such as systemic lupus erythematosus, or pan-endocrinopathy. This makes it important for pet owners to get a thorough test done for detecting hypothyroidism.

Signs and Symptoms of Autoimmune Thyroiditis in Dogs

The symptoms of Autoimmune Thyroiditis will be the same as those of hypothyroidism, which can include –

  • Lethargy

  • Exercise intolerance

  • Mental dullness

  • Weight gain without a change in appetite

  • Obesity

  • Cold intolerance

  • Shedding, hair thinning, and hair loss

  • Thickening of the skin

  • Reproductive disturbances

Lethargy and weight gain are the most common symptoms which will be found as the metabolism is directly related to both of these symptoms. Apart from these, there can be some other signs as well in some cases. These include –

  • Thickening of the facial skin making a ‘tragic facial expression’

  • Non-painful lameness, dragging of feet, lack of coordination, and a head tilt

  • Loss of libido and infertility in intact males

  • Lack of heat periods, infertility, and abortion (miscarriage) in females

  • Fat deposits in the corneas of the eyes

  • Dry eyes due to lack proper tear production

Causes of Autoimmune Thyroiditis in Dogs

Lymphocytic thyroiditis or idiopathic thyroid gland atrophy are the two main reasons causing hypothyroidism in dogs. Lymphocytic thyroiditis is nothing but the same as auto-immune thyroiditis and is the most common reason for hypothyroidism in dogs. This happens when the immune system decides that the thyroid is abnormal or foreign and attacks it. The reason for the same is yet unknown but genetics have been found as a culprit in most cases. This means that this condition is mostly inherited from the parents.

On the other end, the other cause for this condition, idiopathic thyroid gland atrophy occurs when normal thyroid tissue is replaced by fat tissue. This condition is also poorly understood. There can be a third reason as well for the complications in the thyroid gland. That is a cancer of the thyroid gland. But it only appears as a reason in 5% of the affected cases.

Dog breeds more prone to Auto-immune thyroiditis

All breeds and mixed breeds are affected at the same levels but there are some breeds for whom the hereditary condition is more prevalent. These include –

Diagnosis of Auto-immune Thyroiditis in Dogs

A blood sample would be taken by the vet and tested for total thyroxin (TT4) levels, which is the main thyroid hormone. A low level of total thyroxin, along with the presence of clinical signs is suggestive of hypothyroidism. If the observations are inconclusive, then a free T4 by equilibrium dialysis or a thyroid panel that assesses the levels of multiple forms of thyroxin is performed.

Treatment of Autoimmune Thyroiditis in Dogs

The consequence of Auto-immune thyroiditis, hypothyroidism is treatable but not curable. In case of any visible signs, you should be heading to the vet as soon as possible. Your veterinarian will probably give your dog a prescription for thyroxine, a replacement hormone compound, to offset your dog’s low thyroid function. The dose will depend upon the dog’s weight, size, and severity of the thyroid condition. This condition usually takes 1-2 months before it improves, so your vet might change the dosage over time. And as this disease is not completely curable, you will have to take your dog for testing the thyroid levels again once or twice every year.


Autoimmune Thyroiditis or lymphocytic thyroiditis is a disease of the thyroid gland caused by the dog’s own immune system affecting the production of thyroid hormones which regulate the metabolism in the body. It is not fatal but however can have some serious symptoms which are needed to be attended to at the earliest. As a responsible and caring pet owner, you should be consulting your vet at the sight of any of the signs or symptoms. Also read about Epilepsy In Dogs, Fever In Dogs & Swelling In Dogs

Happy Mood and Health to your Dog and lots of Love and Licks to you!


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