The thyroid gland secretes hormones that your dog needs for body metabolism and cell development. When the thyroid gland is underactive, your dog does not get these hormones at normal levels, which brings about a host of health problems.
An underactive thyroid may be atrophied or diseased. Pollution or chemicals can damage it. Sometimes the dog's own immune system attacks the thyroid gland.
Your hypothyroid dog gains unexpected weight. Its skin becomes flaky and hair becomes dry. The dog is easily tired and sleeps long hours.
An underactive thyroid is diagnosed by a blood test. This test measures thyroid hormones in the blood. The results are compared to the desired thyroid level for your dog's breed.
A dog with an underactive thyroid will need replacement hormones such as thyroxine or a similar drug given twice daily.
A dog will improve rapidly with thyroid medication, and its energy level will return quickly. With good diet and exercise, excess fat is gradually replaced with muscle, and the coat and skin improves in three to four months.
A hypothyroid dog requires thyroid medication for the rest of its life. With regular thyroid tests, however, it should have a normal and healthy life.