The thyroid gland performs a number of important functions, but it is mostly known for regulating the metabolism. When the thyroid malfunctions by not producing enough of the thyroid hormone, this can result in a disorder called hypothyroid and is often called low thyroid. While hypothyroid is easily treatable, a dog may suffer for years with this disorder before it is diagnosed. In this article, we'll take a look at how low thyroid is caused, which breeds are usually affected, and what treatment is available.
What causes low thyroid?
When the production of the thyroid hormone is impaired or reduced, the result is a disorder called hypothyroid. This hormone is produced in coordination between the pituitary gland, the hypothalamus and the thyroid gland, but 95% of cases of hypothyroid occur because of a breakdown in the thyroid. There are two causes of the disease in the thyroid: either the dog's immune system is attacking the thyroid, or the thyroid tissue atrophies because of fat infiltrating the tissue. This disease usually develops in dogs that are between four and ten years of age.
Which breeds are susceptible?
Hypothyroid usually occurs in mid to large sized dogs, and toy breeds and other small breeds are very rarely affected. Some breeds that seem to be susceptible to developing the disease are Golden Retrievers, Doberman Pinschers, Irish Setters, Miniature Schnauzers, Dachshunds, Cocker Spaniels, and Airedale Terriers. Dogs that are mixed breeds and German Shepherds seem to have a reduced risk of developing the disease.
Unfortunately, because the loss of the thyroid hormone can affect all bodily organs, there are not clear cut symptoms that point in the direction of low thyroid. However, some symptoms, when found together, may indicate to a veterinarian that a malfunction of the thyroid may be the cause. These can include lethargy, obesity, hair loss, dry skin, excessive shedding and high blood cholesterol.
Diagnosis and Treatment
There are several tests that can be performed by a veterinarian to diagnose low thyroid, although which one the veterinarian chooses to use will depend of availability and symptoms. The most commonly used test is the Baseline T4 Test, which is a blood test that determines the level of the T4 thyroid hormone in the blood system. A similar test is the Baseline T3 Test, which determines the level of the T3 thyroid hormone, but it isn't as effective in diagnosing low thyroid, so it is often used in conjunction with another test. The TSH Stimulation Test is the most definitive test in diagnosing low thyroid. A Thyroid Stimulating Hormone (TSH) is injected and a blood sample is taken six hours later. Dogs with low thyroid will still have a low level of T4 in their system.
Luckily, low thyroid is very easy to treat, by way of a thyroid hormone replacement. The dose and frequency will vary according to the dog and the severity of the disease, and the dog will have to take this medicine for the rest of his life, but his quality of life will vastly improve, and many of the symptoms seen before treatment will usually improve as well.