Low thyroid, technically known as hypothyroidism, is a condition that can develop in any dog but is most common in mid-sized and large breed dogs between four and ten years of age. In hypothyroidism, the thyroid gland does not produce enough thyroid hormones to properly regulate the dog's metabolism. This is usually the result of autoimmune destruction of thyroid gland tissue but can be caused by cancer or other diseases. It can be related to the use of certain medications as well.
The symptoms that cause a dog owner to suspect a potential problem are most often physical changes. Excessive shedding or hair loss, a very dry quality to the coat, changes in skin color and weight gain without cause can all signal hypothyroidism. Another unusual characteristic is that some dogs with the disease become intolerant to cold temperatures.
Hypothyroidism appears to be more common in some breeds. Large breeds such as Doberman pinschers, Irish setters, golden retrievers and Airedale retrievers have a propensity for the condition. While small breeds are not typically at risk, hypothyroidism has been found to be prevalent in cocker spaniels, dachshunds and miniature schnauzers.
Another symptom of this disease commonly noticed by owners is that a dog may seem lethargic in comparison to its typical energy level, often appearing dull, bored or just plain tired. While lethargy is a symptom associated with many conditions and illnesses, when seen together with the already noted physical changes, it is best to consult a veterinarian for a proper diagnosis.
A veterinarian who suspects hypothyroidism will order a series of diagnostic blood tests. In hypothyroidism, thyroid levels are low, blood cholesterol is usually high and anemia may be present. The dog may also have a low heart rate upon exam. If the veterinarian determines that your dog has hypothyroidism, it will be prescribed thyroid medication, dosed according to the dog's thyroid level, size and weight. This treatment must continue for the duration of the dog's life.