What Causes Thyroid Problems in Dogs?

Thyroid problems in dogs occur when the thyroid glands, located in the dog's throat on either side of his windpipe, malfunction. These glands are responsible for producing thyroid hormones, which regulate important metabolic processes. There are two basic types of thyroid problems in dogs.

Types of Thyroid Problems in Dogs

There are two basic types of thyroid problems in dogs, hypothyroidism and hyperthyroidism. Hypothyroidism occurs when the thyroid glands don't produce enough thyroid hormone. Hyperthyroidism occurs when the glands produce too much thyroid hormone. Each disorder has different causes.

Causes of Hypothyroidism in Dogs

Hypothyroidism can strike your dog if his thyroid glands don't produce enough hormone. Mid-sized and large breed dogs between the ages of 4 and 10 are most vulnerable to it. Symptoms include hair loss, lethargy, cold intolerance, weight gain and lowered heart rate.

The function of your dog's thyroid glands is closely connected to the function of his pituitary and hypothalamus glands, so if anything goes wrong with one of those glands, it could cause reduced thyroid function. It's more likely, however, that your dog's hypothyroidism is the result of damage to the thyroid glands themselves. Vets believe that most cases of thyroid damage occur as an autoimmune reaction, in which your dog's own immune system attacks his thyroid glands and damages them. Cancer or other medical conditions, as well as the use of some medications, can lead to thyroid damage. Sometimes, fat deposits form in the thyroid tissue, damaging it.

In rare cases, hypothyroidism in dogs occurs as a birth defect.

Causes of Hyperthyroidism in Dogs

Hyperthyroidism in dogs occurs when the thyroid glands become enlarged and produce too much thyroid hormone. Vets don't fully understand why this occurs. Hyperthyroidism in dogs is significantly more rare than hypothyroidism, but it usually occurs in middle-aged and geriatric animals.

Hyperthyroidism can strike dogs of any breed or gender. Symptoms include increased heart rate, increased appetite accompanied by weight loss, excessive thirst and excessive urination.

Diagnosing and Treating Thyroid Problems in Dogs

Usually a simple blood test is enough to diagnose a thyroid problem in your dog. Your vet can check a sample of your dog's blood for elevated or lowered thyroid hormone levels to diagnose him with hyperthyroidism or hypothyroidism. While these disorders can both have dangerous health consequences for your dog, they are easily treated.

Hypothyroidism in dogs is usually treated with medication alone. Thyroxine, a synthetic type of thyroid hormone, can be administered daily to treat this condition. Your vet may need to adjust your dog's dosage several times before finding the right one, but once the correct dosage is determined, your dog should return to a normal state of health. Your dog will need the medication for the rest of his life, but he should enjoy a symptom-free existence.

Vets often treat hyperthyroidism with a combination of surgery and medication. Drugs can be administered to normalize your dog's thyroid hormone levels, and surgery can be done on one or both of his thyroid glands to permanently lower blood levels of thyroid hormone. There's a good chance that your dog will develop hypothyroidism after the surgery. If he does, he'll need to take thyroxine for the rest of his life.