Our Pets often suffer from “human” diseases, and it is these pathologies that include hypothyroidism in dogs — a disease that occurs as a result of a decrease in the level of hormones produced by the thyroid gland.
Scientists attach great importance to hormones, which are involved in almost all metabolic processes occurring in the body, and affect the work of all organs. Based on this, we can conclude that the correct hormonal background is one of the factors of good dog health.
Let’s look at why dogs suffer from hypothyroidism, consider the methods of its diagnosis and treatment.
How does hypothyroidism occur?
The main cause of the disease is a “breakdown” in the thyroid gland, which is located in the larynx of dogs and has the appearance of a butterfly consisting of two lobes. The pituitary gland directs the activity of the thyroid gland with the help of special hormones. They “force” the thyroid gland, in turn, to produce its own hormones triiodothyronine (T3) and thyroxine (T4), which regulate the functioning of all organs.
It would seem that failures in the functioning of the thyroid gland should be manifested in problems with the pituitary gland, since without its “guidance” it will not be able to work. But veterinary practice shows that thyroid diseases occur in dogs with absolutely healthy pituitary gland. Why do they get hypothyroidism?
Types and causes of the disease
There are several types of this disease in dogs:
- Primary hypothyroidism, in which the thyroid gland stops producing enough hormones.
- Secondary hypothyroidism that occurs against the background of reduced stimulation of the thyroid gland by the pituitary gland.
- Tertiary hypothyroidism, manifested as a result of a lack of hypothalamus neurohormones.
In dogs, more than 90 % of cases are diagnosed with primary hypothyroidism. Almost half of them are autoimmune diseases — chronic thyroiditis. At the same time, the dog’s own immune system attacks the thyroid gland and causes it to produce more and more hormones.
This increased activity of the gland quickly depletes it and there is a lack of thyroid hormones, that is, hypothyroidism. The remaining 50 % of cases of primary hypothyroidism belong to such variants of the development of the disease, when the thyroid atrophy occurs for unknown reasons.
Hypothyroidism can be congenital and inherited in dogs, but the percentage of this method of occurrence of the disease is very small.
Another cause of this pathology may be infectious diseases and the presence of endoparasites. Currently, veterinarians have information that if a dog is infected with worms for a long time, the toxins produced by parasites can affect many organs, including the thyroid gland.
If the dog undergoes long-term and uncontrolled treatment with hormonal agents, this can also cause a malfunction of the thyroid gland.
How the disease manifests itself
Given the fact that the lack of thyroid hormones has a significant impact on the work of all organs of the dog, then the signs of hypothyroidism will be diverse. Moreover, it is necessary to take into account that the symptoms of hypothyroidism are often mistaken for other diseases.
However, there are classic manifestations of the disease that indicate problems with the thyroid gland:
- increase in dog weight by 15-20%;
- lethargy and apathy in the animal;
- the appearance of dandruff and areas of baldness;
- the problems with digestion.
Signs of hypothyroidism grow quite slowly over a long time and at first do not alarm the dog owner at all, he may take them for age-related changes or another disease. What symptoms should the owner pay more attention to in order to start treating the pet in time?
First of all, you should focus on the mood and behavior of your pet. If you notice that the dog has become sad and lethargic, reluctant to walk, plays less and sleeps more, then this is a reason to watch it more closely.
With hypothyroidism, a disturbed metabolism leads to a change in the function of thermoregulation in the animal, so the dog begins to freeze quickly on the street, and at home it settles in the warmest place.
When the power mode is saved, your pet suddenly gained weight or has swelling on the muzzle? This may also indicate a thyroid disease.
A characteristic symptom of hypothyroidism is problems with hair. The dog may have dandruff and areas of baldness.
If you notice similar symptoms in your dog, contact a competent veterinarian so that the diagnosis is correct and the treatment started is adequate.
In addition to the symptoms that are considered “mandatory” for hypothyroidism, there are a number of non-specific signs:
- Ophthalmology. With hypothyroidism, the amount of lipolysis products in the blood increases, which are later deposited in places of small corneal lesions and lead to its dystrophy. Less often, corneal ulceration or inflammation of the vascular network of the eye may occur.
- Cardio-vascular system. Lowering the level of thyroid hormones can lead to bradycardia, arrhythmia, and other heart disorders.
- Neurology. Hypothyroidism gives various manifestations that affect the functioning of the Central and peripheral nervous system. In 70 % of sick dogs, this is expressed in apathetic or uncharacteristic behavior, and problems with the vestibular apparatus may also occur. Often, hypothyroidism may cause paresis or paralysis of the facial/trigeminal nerve.
- Dermatology. Dermatological manifestations of hypothyroidism most clearly indicate the dog owner to have a problem. The pet begins to develop foci of baldness, first affecting the back of the nose and the surface of the tail, and then they spread to the groin, armpits, and abdomen. The animal does not itch, meaning the hair falls out on its own. On bald areas, the skin pigmentation changes, and it becomes drier, since hypothyroidism atrophies the sebaceous glands and the production of secretions decreases.
- Reproductive system. Bitches with hypothyroidism lose the ability to fertilize or can not bear full-fledged offspring due to miscarriages. In addition, the period between estrus increases up to 10 months or they stop altogether, and male sexual desire decreases.
For an accurate diagnosis of hypothyroidism, it is necessary to consider the results of tests in conjunction with the classic symptoms of this disease. At the moment, the equipment of many veterinary clinics does not allow for a complete analysis of thyroid hormones. The main method is to determine the concentration of total T4 in the blood plasma, and in some cases, an analysis for TSH or thyroid-stimulating hormone is added.
But the level of TSH and T4 in General in a dog is influenced by many factors and their deviation from the norm, can not 100% talk about the incidence of hypothyroidism. For example, certain medications and anesthesia used less than 48 hours before the analysis are affected.
Infectious diseases, oncological tumors, and chronic liver or kidney diseases can significantly change the level of T4A.
For a more accurate diagnosis, it is necessary to know the level of free T4, which is determined in the blood of a dog only by the method of equilibrium dialysis. Other methods do not allow you to estimate this indicator correctly.
To complete the picture, it is better to conduct additional research:
- General and biochemical blood analysis;
- Ultrasound of the heart.
It is very difficult to assess the function of the thyroid gland only on the basis of laboratory tests, so the veterinarian is faced with the task of correctly “reading” the results of tests and comparing them with the symptoms of the disease that appear in the dog.
Ultrasound and analysis of thyroid cells is justified only if the animal is suspected of having a tumor of this organ. in hypothyroidism, these methods are not sufficiently informative.
How to treat
After the diagnosis is established, the veterinarian prescribes treatment, which will consist in taking hormone-substituting drugs. The hormone levothyroxine is usually used. With the right dose and proper medication, the symptoms of the disease disappear quite quickly.
But canine hypothyroidism has its pitfalls. So, if the veterinarian incorrectly diagnosed the disease and prescribed levothyroxine to a dog that does not have hypothyroidism, then after a while the dog may lose some of the symptoms of the disease, but this improvement will be temporary. With such incorrect treatment, precious time may be lost for the treatment of another disease.
The initial dose of levothyroxine is 10-12 micrograms/ kilogram of dog weight twice a day. During treatment, a blood test is periodically performed to monitor the course of treatment, and if necessary, adjust the dose of medication and bring the T4 level to normal.
Taking medication in a dog with hypothyroidism will last a lifetime, but their survival prognosis is very good. After starting treatment, the main symptoms of the disease soon disappear — the dog becomes cheerful, active, bald spots begin to overgrow. It may take 3-4 months to fully restore the coat.
If the drug is overdosed, the dog has symptoms that are the opposite of those that were during the illness. She can become nervous, aggressive, lose weight, and feel very thirsty. In this case, you should visit a doctor to adjust the dose of the medication you are taking.
We wish your dogs good health, and you can always count on our help!
Hi, my name is Mike Fletcher. I am 36 years old and a veterinarian at a veterinary clinic in Granby Colorado. And this is my blog about Pets. I hope I can answer your questions here.