HYPOTHYROIDISM IN DOGS

Hypothyroidism in dogs is a problem where the thyroid glands do not create enough thyroid hormones. Thyroid hormones regulate metabolism, how much energy the body uses for everyday functions (like eating and digesting), skin health and general bodily functions.

As thyroid hormone levels decrease, a dog’s metabolic rate decreases; this leads to an assortment of behaviors and physical characteristics that can be seen by veterinarians. The typical age affected by hypothyroidism is middle aged to old and it typically develops over time. It is quite common for a case of hypothyroidism to go undetected until the clinical signs begin to become apparent. With appropriate medical treatment, most dogs will have a normal quality of life.

Causes

Most cases of hypothyroidism occur due to some type of injury or failure of the thyroid gland to produce sufficient amounts of thyroxine.

The most common cause is immune mediated destruction. This occurs when the immune system of the dog progressively destroys parts of the thyroid gland, eventually decreasing the amount of thyroxine produced.

There are other possible causes for hypothyroidism, including: congenitally defective thyroid glands, atrophy of the thyroid gland with no known reason, tumors of the thyroid gland and damage to the thyroid gland from surgical procedures or radiation therapy.

Symptoms

• Low energy
• Weight gain
• Reduced interest in exercise
• Dry, flaky skin and poor coat quality
• Hair loss
• Recurrent skin infections
• Cold intolerance
• Slow heart rate
• Thickened or darkened skin in some areas

Risks and Complications

Hypothyroidism, if left untreated, can gradually affect a dogs overall health and quality of life. A slowdown in metabolism could result in obesity, loss of energy and muscle weakness. Changes in skin health and immune function can increase susceptibility to recurrent skin infections. In addition, high cholesterol levels may occur and can be detected through blood testing. Dogs with advanced untreated disease may experience neurological or behavioral issues as well. Although it is not typically an immediate threat to their lives, untreated disease over a period of time can severely diminish their quality of life.

Diagnosis

The diagnosis of hypothyroidism is primarily based upon clinical evidence supported by laboratory results from blood testing. The initial assessment by a veterinarian would include the presence of the aforementioned symptoms, including weight gain, changes in coat condition and lethargy. Diagnosis requires interpretation of thyroid hormone testing together with clinical signs because other illnesses can also cause low thyroid hormone levels.

Common diagnostic tests used to diagnose thyroid function:

• Total T4
• Free T4
• Thyroid stimulating hormone (TSH) test
• Blood lipid profiles, which provide information about total cholesterol levels.

Treatment

Hypothyroidism is an easy to manage medical condition requiring lifelong management and care.

Hormone Replacement Therapy

Daily administration of levothyroxine (synthetic thyroid hormone replacement) is the standard treatment. THR allows for normalization of thyroid hormones and subsequently improves metabolic function, energy and skin health.

Over time, THR dosing will need to be adjusted based on how well the dog responds to the medication or the results from subsequent blood draws.

Supportive Care

While the use of THR is the mainstay of treatment, additional supportive care measures can support improved recovery:

• Controlled diet to manage weight
• Regular exercise suited to energy levels
• Treatment of skin infections if present
• Routine monitoring through veterinary checkups

Most dogs start showing significant improvements in their energy levels and coat quality within a few short weeks of initiating THR therapy.

Prevention

Due to genetic influences or autoimmune diseases, it may not be possible to prevent all instances of hypothyroidism; however, early diagnosis can significantly limit the long term consequences of hypothyroidism.

Owners need to schedule regular veterinary appointments, particularly for middle aged and senior dogs, so as to monitor for potential indicators of hypothyroidism, including but not limited to unexplained weight gain, changes to the skin, decreased physical activity, etc. Additionally, maintaining a healthy lifestyle can contribute to overall thyroid and metabolic health.