Hypothyroidism is the most common endocrine disorder in dogs and our canine companions seem to be the pets most often afflicted with this disorder; it's quite rare in cats. This disorder affects the thyroid gland, which is made of two small, connected lobes in the neck, on either side of the windpipe, that together are shaped like a butterfly. It is a very important gland because it has quite a number of functions, but one of its most important ones is the regulation of metabolism; it does this through a chemical messenger, or hormone, called thyroid hormone. The word hypo means below normal, and so hypothyroidism means a below normal activity of the thyroid, and more specifically, a below normal secretion level of thyroid hormone. With not enough thyroid hormone, your German Shorthaired Pointer's metabolic rate will slow down.
In the majority of cases, hypothyroidism develops because your dog's own immune system short-circuits and starts attacking the tissues and cells of his own thyroid gland. When the dog's body realizes what's going on, it at first attempts to counteract the death of the cells by over-secreting thyroid hormone, but it eventually is overwhelmed and can no longer compensate for the lack of the hormone. This is when the dog truly develops hypothyroidism and the symptoms associated with the disorder. As usual, doctors aren't completely sure about what triggers the immune system to attack its own cells (there are a variety of mysterious auto-immune disorders), but most agree that it's a combination of genetic predisposition and environmental triggers such as allergies and/or pollutants.
Symptoms of hypothyroidism can vary and most dog fanciers agree that you should take your German Shorthaired Pointer to the vet if you see he gains weight with very little food intake; some insist that ANY overweight dog should be checked. Other signs include the development of lethargic behavior; this means that your GSP starts becoming disinterested in playing, he takes frequent naps and gets tired much quicker when walking or performing any routine activities. Some dogs with hypothyroidism develop bacterial skin infections and/or dry skin, while others start losing hair, especially on their tails. You'll see a much lower threshold of cold tolerance and their heart rate may slow. Some dogs will develop chronic ear infections and their overall behavior may change, with some becoming aggressive, anxious, or even depressed.
Most often, dogs between 4 and 10 years of age develop the condition. Your vet can diagnose hypothyroidism by performing blood tests aimed at detecting the level of thyroid hormones secreted by the gland. If your GSP is found to have hypothyroidism, he most likely will be given synthetic thyroid medications for the rest of his life; this will usually resolve all symptoms. While a mild case of hypothyroidism is not an emergency (many dogs live for years with undiagnosed mild hypothyroidism), you should have your dog checked; providing medication will improve his quality of life.