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Hypothyroidism in Dogs

Chandramita Bora
Hypothyroidism is a disease caused by the deficiency of the thyroid hormone. This usually occurs due to a malfunctioning or underactive thyroid gland. Find out more about this condition, and its causes and treatment through this story.
The thyroid gland is located near the base of the neck, and is responsible for producing thyroxine, a hormone that regulates the metabolic processes of the body. Hypothyroidism is a disease that is caused by the insufficient production of the thyroid hormone. It is a common health problem that can affect both male and female dogs equally.


It is usually caused by a malfunctioning thyroid gland, which fails to produce and release adequate amounts of hormones required to carry out the metabolic processes. Sometimes, the immune system of the dog can also attack and damage the thyroid gland. This condition is known as autoimmune thyroiditis.
Sometimes, hypothyroidism in dogs can be caused by the atrophy of the thyroid tissues, and the consequent invasion of these tissues by fats. The production of the thyroid hormones depends on other glands, like the pituitary and the hypothalamus. Therefore, diseases or disorders of these glands can impair the production of thyroid hormones.


Dogs suffering from this condition may exhibit several vague symptoms. A deficiency of the thyroid hormones can produce symptoms, like hair loss, obesity, anemia, lethargy, a slow heart rate, and skin problems like hyperpigmentation, especially black pigmentation of the skin near the groin.
The level of blood cholesterol can increase if the level of thyroid hormone decreases in the body. Apart from these, an increased sensitivity to cold, edema, and toenail and skin infections are commonly observed in dogs suffering from this condition.

Diagnosis and Treatment

This condition is usually diagnosed with the help of blood tests that can determine the levels of T4 and T3 thyroid hormones. Initially, the blood is tested for checking the level of T4 hormone. If the level of T4 is low, it can indicate a malfunctioning thyroid gland. But this is not a definitive test, as sometimes factors other than a malfunctioning thyroid gland can reduce the level of T4 hormone.
Therefore, if the level of T4 is low, then another blood test is carried out to determine the level of T3 hormone. However, this may not be an accurate test for diagnosing the disease in the early stage. The test that is used for a confirmed diagnosis is known as the TSH (thyroid-stimulating hormone) test, which is performed if the levels of T4 and T3 hormones are found to be low.
In the TSH simulation test, a small dose of thyroid-stimulating hormone is administered into a vein of the dog, and then the blood is tested to determine the level of T4 hormone. If the dog is suffering from hypothyroidism, then there won't be any change in the level of T4 hormone.
However, if the level of T4 increases in blood in response to TSH, then it indicates that factors other than an underactive thyroid gland, may be responsible for an insufficient production of T4 hormone.
This condition can be easily treated by administering the hormone thyroxine, which helps maintain the normal rate of metabolism. However, the treatment has to be continued for lifelong. It is important to administer this hormone in the appropriate dosage.
It has been observed that middle-aged dogs are commonly affected by this disease. This condition is also common in mid to large dog breeds, but quite rare in small breeds. Labradors, Golden Retrievers, Doberman Pinschers, Dachshunds, Cocker Spaniels, Airedales, and greyhounds are found to be more likely to develop this condition.
Untreated hypothyroidism can lead to several complications. So, if your dog is exhibiting symptoms, like sudden weight gain, hair loss, skin disorders, laziness, and reduced mental alertness, consider to consult a veterinarian.
Disclaimer: This story is for informative purposes only, and should not be treated as a substitute for the medical advice of a veterinarian.