One of the youngest and rapidly developing branches of medicine is endocrinology. However, in veterinary practice, the diagnosis of most endocrine disorders is currently in an embryonic state. Nevertheless, animals are sick, and the task of specialists is to correctly diagnose and, if necessary, correct disorders of the endocrine system.
One of the most common such diseases is hypothyroidism in dogs. Photos of animals, causes, symptoms and methods of treating this disease, we will present to you in this article. Diagnostic methods will also be considered.
Hypothyroidism in dogs: a description of the disease
This disease is accompanied by disorders in the activity of the thyroid gland, which has many different functions. Hypothyroidism is a pathology characterized by a decrease in the amount of synthesized thyroid hormones.
Types of disease
Specialists distinguish two types of this disease - primary and secondary. Acquired (primary) hypothyroidism is an inflammation of the thyroid gland called Hashimoto's disease, or other processes that destroy the organ. Sometimes hypothyroidism in dogs provokes a lack of iodine in the diet of an animal, infection, thyroid tumor. In any case, the affected organ is unable to produce the required amount of hormones.
Secondary hypothyroidism in dogs, the signs of which can occur at an early age of the animal, has a destructive effect on the growing organism. Thyroid hormones are necessary for the development of the central nervous system and bones, their lack can cause dwarfism of animals. Secondary hypothyroidism in dogs manifests itself with congenital thyroid dysfunction or a tendency to form tumors. As a result, the process of hormone production is disrupted.
Secondary hypothyroidism sometimes develops after improper treatment with glucocorticoids or with an unbalanced diet.
Stages of the disease
In the process of developing hypothyroidism in dogs, the symptoms are also different. At an early stage of the disease, the amount of tyrosine in the thyroid gland decreases, provoking an increased production of other hormones. Thus, in the body the hormonal balance is leveled. In very rare cases, the body can recover on its own, but much more often the disease goes into a late stage.
In this case, the level of tyrosine decreases significantly and very sharply, while the alignment of the balance is impossible. The thyroid gland receives serious damage, which leads to a significant deterioration in the general condition of the animal.
Like most endocrine pathologies, hypothyroidism in dogs can have various symptoms. Most often, overweight, obesity indicates the development of the disease. In addition, this disease is often diagnosed with loss of coat and skin problems.
How is dog hypothyroidism detected? Diagnosis is possible only in a good veterinary clinic after a complete blood test of the animal. The analysis result will allow you to compare the data with the norm, which is typical for animals of the same age and breed.
Causes of the disease
The thyroid gland is a small-sized iron located in the larynx. Her work is regulated by the pituitary gland of the brain. For its normal activity, a special stimulating hormone is needed. The pituitary gland synthesizes such a hormone, and it causes the thyroid gland to intensively produce its own. The efficiency of the gland depends on its condition.
However, hypothyroidism in dogs often develops in animals, the pituitary gland of which is in a normal state. Why is this happening? About 95% of cases are “background”, they develop due to diseases that accompany the processes of destructive changes in the thyroid gland. Unfortunately, it is not always possible to find out the essence of these processes.
Veterinarians believe that autoimmune disorders are to blame for this, in which the animal's body begins to destroy itself. Hypothyroidism, the cause of which may be different, is often the result of atrophy of the thyroid gland. This is especially evident in the last stages of obesity and oncology.
What else can cause hypothyroidism? The reason may be hiding in the presence of parasitic and infectious diseases. An uncontrolled intake of hormonal drugs can lead to a similar result. Cases of congenital hypothyroidism are periodically detected. Veterinarians claim that serious helminthic invasion can provoke hypothyroidism in dogs. The reasons are obvious - a huge amount of toxins are released into the body of the animal, which affect the thyroid gland.
Species predisposed to hypothyroidism
Hypothyroidism in dogs, symptoms (photos you can see in our article), clinical signs can be diagnosed in animals of different sex, age and breed. Although, over the course of many years of observation, it was found that the symptoms of this disease are more often detected in animals under the age of ten years. In 70% of cases, they appear in dogs of large and very large breeds, and small animals get sick much less often.
The statistics accumulated by experts all over the world indicate that representatives of the following breeds are much more likely to get sick:
- Doberman Pinscher;
- Golden retriever;
- Schnauzer
- Irish Setter
- Cocker Spaniel;
- dachshund;
- airedale.
The German Shepherd is predisposed to numerous genetic pathologies (including hypothyroidism). Under normal conditions, there is no gender dependence, however, bitches with removed ovaries suffer from this disease quite often. But such an operation is necessary to prevent breast cancer, therefore, in this situation, hypothyroidism is a more preferable choice: mortality from this disease is tens of times lower than from cancer.
Symptomatology
Thyroid hormones are necessary for the normal metabolic function of the animal’s body. Their lack affects almost all organs and systems. In this regard, hypothyroidism in dogs can manifest itself in different ways. Symptoms and treatment of the disease are determined by the veterinarian based on clinical studies. However, there are several signs that can clearly occur in 90% of cases when the thyroid gland is disrupted.
The clinical picture of the disease can only be considered in a comprehensive manner, since individually some symptoms indicate the presence of another ailment. Dog owners should contact a veterinary clinic if the following signs appear in the animal:
- Differences in behavior (excessive aggressiveness or, conversely, timidity).
- Violation of concentration (apathy, floating eyes).
- Nervous problems (fatigue, overweight, intolerance to heat and cold, sudden mood swings).
- Significant deterioration in the condition of the skin and coat (dandruff, dryness, focal hair loss, abnormal pigmentation, keratinization of the skin).
- Problems with the reproduction of offspring (a small or too large interval between estrus, poor libido, weak or dead offspring, false pregnancy).
- Disturbances in the work of the heart and blood vessels, as well as the hematopoietic system (bradycardia, arrhythmia, decreased platelets, as well as white blood cells, low hemoglobin, bleeding).
- Changes in the digestive tract (diarrhea, vomiting, constipation).
- Eye problems (conjunctivitis, dry eyes, corneal fat, eye infections).
Other serious symptoms are gait, paralysis, sagging eyelids, and problems with touch. Often, symptoms appear only at a late stage, as they develop gradually. Clinical signs, in general, may not appear for several weeks, or be so weak, “blurred” and periodic that the owners do not immediately pay attention to them.
There is another important aspect - this is the pathology of the thyroid gland. Often, after the dog has undergone an intensive course of treatment with strong drugs, the organ can weaken. When examining the animal’s medical records, the attending physician must take this fact into account, otherwise the diagnosis may be made incorrectly. Diseases of the kidneys, liver, diabetes mellitus and other diseases provoke pathological thyroid syndrome.
Diagnosis of the disease
Hypothyroidism in dogs is diagnosed based on the results of several tests. Their choice depends on the financial capabilities of the owners of the animal, the availability of modern equipment and the necessary reagents in the clinic. Since the symptoms of this disease are rather vague, professional clinical diagnostics cannot be dispensed with.
The most common test is a thyroxine (T4) test. This substance can only be synthesized by the thyroid gland. Therefore, with its low content in the bloodstream, we can assume the presence of this serious disease. However, it should be borne in mind that there are a number of reasons that provoke a decrease in thyroxine in the blood, therefore, other diagnostic methods must be considered.
Thyroxine can be present in the bloodstream in two forms. The bound form attaches to the proteins and does not penetrate the cells. Free T4 is not bound to proteins, it is able to penetrate into cellular structures and, as a rule, is present in small amounts in them. Its volume fraction is taken into account when making a diagnosis.
If the dog has a low T4 level, a thyroxin test can be done based on the effects of special medications. In this case, a small amount of pituitary synthetic hormone is administered intravenously. Six hours after the procedure, blood is drawn from the dog and the T4 level is checked. If the animal confirms hypothyroidism, the level of the hormone in his blood will be close to normal. In a healthy dog, the level of this substance will significantly exceed the upper limits of the norm.
Routine studies that are conducted during a clinical examination can provide valuable information. To do this, carry out the following:
- biochemical blood test with determination of the level of triglycerides and cholesterol and general clinical;
- urinalysis (general);
- echocardiography;
- electrocardiogram.
Hematologic studies
Based on data collected by veterinarians, approximately thirty percent of dogs with hypothyroidism develop non-regenerative anemia. In addition, evidence has been obtained that hypothyroidism in dogs often causes pathological hemostasis or provokes bleeding.
In the blood serum of a sick animal, the concentration of triglycerides and cholesterol increases significantly. Hyperlipemia is a fairly common complication of hypothyroidism. Hypertriglyceridemia is much less common. Sometimes in the blood serum there is an increased content of liver enzymes and azotemia, from mild to moderate.
Treatment
Each year, the study of hypothyroidism in dogs, specialists are able to identify new data that affect the methods and methods of treating this ailment. Today, a treatment regimen has been developed that includes an attempt to eliminate the cause of the disease and symptomatic treatment.
If the doctor was able to diagnose thyroid inflammation at an early stage (Hashimoto's disease), it is very important to eliminate it in order to prevent hypothyroidism in dogs. Treatment consists of administering doses of a synthetic thyroid hormone, thyroxine (Levothyroxine). It should be administered daily. Combination therapy involves frequent blood tests to adjust the dosage of the drug.
Today, global pharmaceutical companies produce many varieties of this drug, which differ only in registered names. The dose of the drug depends on the stage of the disease and the reaction of the animal to therapy. First, a standard dose is administered, a blood test is done a day later, the hormone level is checked, after which the treatment is adjusted in accordance with the result. The doctor determines which system of the body reacts particularly hard to the disease and prescribes supportive and symptomatic treatment.
Patient follow-up and further prognosis
Two weeks after the start of treatment, the concentration of T4 in the blood plasma is checked. Typically, a peak concentration is recorded six to eight hours after taking the drug. During this period, the concentration of thyroxine should be as close to normal as possible.
Before the introduction of the drug, the content of T4 in serum should be at the lower limit of normal. A low concentration of T4 before and after taking the drug indicates an unreasonably low dose. This can be caused by a violation of the absorption of the drug in the intestine, an incorrect schedule of administration or administration of the drug.
The need to adjust the dose of the drug is indicated by the persistent symptoms of thyroid insufficiency, or, on the contrary, overdose symptoms. The prognosis for adult animals with primary hypothyroidism that undergo appropriate replacement therapy is positive.
If the administration of thyroid hormones after long-term use is discontinued, it may take several weeks, and sometimes months, to restore the connection between the thyroid hormones and the pituitary gland. Such recovery, as a rule, occurs without consequences for the health of the animal.