Hypothyroidism in Dogs – Causes, Symptoms and Treatment!
Hypothyroidism in dogs is one of the most common endocrine diseases in dogs. Unfortunately, this is a difficult disease to prevent, as it is believed that the causes are predominantly due to a genetic predisposition to hypothyroidism.
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If your dog has recently been diagnosed with this disease or if you are simply curious to know more about it, YourCatCareguide has prepared this article with everything you need to know about hypothyroidism in dogs – causes, symptoms and treatment !
Hypothyroidism in Dogs
The thyroid gland is largely responsible for regulating the dog’s metabolism. Sometimes due to an anomaly in this gland, sufficient amounts of necessary hormones are not produced in the dog causing the so-called hypothyroidism. Hypothyroidism can arise from any dysfunction of the hypothalamic-pituitary-thyroid axis.
We can thus describe hypothyroidism as an endocrine disease characterized by a decrease in the production of thyroid hormones . The thyroid gland is responsible for producing the hormones T3, called triidotironine and T4, called tetraiodothyronine. A low production of these hormones gives rise to this problem so common in dogs.
Primary hypothyroidism in dogs
The primary hypothyroidism is by far the most common in dogs. The origin is usually directly a problem in the thyroid gland, usually the destruction of it. The two most common histopathological patterns are lymphocytic thyroiditis (a process in which the thyroid is infiltrated by lymphocytes, plasma cells and lymphocytes) and idiopathic thyroid atrophy (a process in which the gland loses its parenchyma which is replaced by adipose tissue) .
Secondary hypothyroidism in dogs
Secondary hypothyroidism is characterized by dysfunction of the pituitary cells themselves, causing a decrease in the production of the hormone TSH . This hormone is responsible for stimulating the thyroid to produce hormones and so is called “secondary”. There is progressive atrophy of the gland, due to the absence of this hormone, decrease in TSH production and consequently of T3 and T4.
There are different processes that can lead to this secondary hypothyroidism, namely  :
- Pituitary tumors
- Congenital malformation of the pituitary gland (common in races such as the German Shepherd )
- TSH deficiency
- Surgical treatments or medications such as glucocorticoids
- Secondary to hyperadrenocorticism
Tertiary hypothyroidism in dogs
Tertiary hypothyroidism in dogs arises as a consequence of insufficient production of TRH, the hormone that releases thyroxine and stimulates the production of TSH in the anterior pituitary. That is, the problem is located in the hypothalamus , which produces TRH.
This disease is extremely rare and there are virtually no reports of this disease in dogs.
Congenital hypothyroidism in dogs
Congenital thyroid defects are very rare in dogs. However, sometimes they can occur and we could not fail to mention them. This type of disease is reported in puppy puppies and is usually fatal .
One of the most documented causes of this type of hypothyroidism is the low intake of foods rich in iodine . In addition, it may be due to a defect in the proper organization of iodine, called dysthymiogenesis or thyroid dysgenesis.
Symptoms of Canine Hypothyroidism
The clinical signs of this disease arise by turns from 4 to 10 years of age. The breeds with a greater predisposition for this disease are, among others, Boxer, Poodle, Golden Retriever , Doberman Pinscher , Miniature Schnauzer and Irish Setter. According to some studies, there is no sexual predisposition to this problem, that is, it can affect males or females alike  .
The main clinical signs of this problem are:
- Weight gain and obesity
- Intolerance to physical exercise
- Zonas sem pelo (alopecia)
- Dry skin
- Sebaceous skin
In any case, the clinical signs of this disease are very varied and can range from dermatological, as described, to neuromuscular, reproductive and even behavioral. The thyroid gland intervenes throughout the dog’s metabolism, hence the great complexity of this problem.
Diagnosis of Canine Hypothyroidism
Although veterinary medicine is not as advanced as human medicine with regard to this disease, there are different alternatives to study the functioning of the thyroid gland and confirm if the dog does indeed have a hypothyroidism problem.
Your veterinarian will rely on clinical signs, thyroid function tests and hormone replacement therapy to definitively diagnose the disease  .
To correctly diagnose this problem it is necessary to measure the hormones in the dog’s blood (mainly t4). The measurement alone of the levels of this hormone in the blood are not enough. However, if the values are normal or elevated, hypothyroidism can be excluded from our list of differential diagnoses. For this reason, this is one of the first tests to be performed when your veterinarian suspects this problem.
If we prove that t4 levels are low, it does not necessarily mean that we have a hypothyroidism problem, it will be necessary to perform another test called the thyrotropin stimulation test (TSH) to confirm the definitive diagnosis.
In addition to these tests, conducting may be required other evidence as the specific case of the animal. In particular:
- Nuclear scintigraphy (to determine the absorption of radioactive iodine)
- Measurement of antibodies
- Ultrasound to the thyroid.
- X-ray (if thyroid tumor is suspected, to see if there are metastases)
Hypothyroidism in dogs – treatment
After the diagnosis is made, the veterinarian may prescribe hormonal supplementation . Some veterinarians also use this method as a diagnosis, assessing the response to treatment. The treatment of choice is based on levothyroxine sodium, synthetic T4.
In cases where dogs suffer from secondary or tertiary hypothyroidism it may be necessary to prescribe glucocorticoid and cobalt therapy.
Generally, at the end of a week of treatment the animal begins to show improvements, increased appetite and general well-being.
It is very important to respect the dates of reassessment and visits to the veterinarian . Animals with this problem should be closely monitored since sometimes the veterinarian needs to readjust the doses of the treatment, depending on the animal’s response.
This article is purely informative, in YourCatCareguide.com.br we do not have the capacity to prescribe veterinary treatments nor to make any type of diagnosis. We suggest you bring your pet to the veterinarian in case of any type of condition or malaise.
If you want to read more articles that may be updated, please let us know. , we recommend that you enter our section on Other health problems .