Clinical signs of Addison's disease are usually vague and non-specific. Pets suffering from Addison’s disease may show symptoms of lethargy, diarrhea, vomiting, increased thirst, increased urination, and unplanned weight loss. Intermittent shaking episodes are sometimes seen. The symptoms may grow and wane.
Addison’s disease is primarily caused by an immune –mediated destruction of adrenal tissue. Less commonly, the adrenal glands may be damaged by trauma or infection. Addison’s disease can also occur following treatment of Cushing’s disease (hyperadrenocorticism), in which too much cortisol and aldosterone are produced. If the medication used to treat Cushing’s disease inadvertently suppresses too much adrenal gland activity, deficiency of cortisol and aldosterone may result.
A secondary form of Addison's disease can result from a tumor or defect in the pituitary gland, which is an important hormonal regulator located in the brain. Secondary Addison's disease can also develop if a pet has been treated with long-term steroids for any reason and the medication is abruptly stopped. This last condition is known as iatrogenic hypoadrenocorticism and is generally temporary.
Certain breeds seem to be at increased risk for developing Addison’s disease. These include, but are not limited to: Portuguese water dog, bearded collie, standard poodles, Nova Scotia duck tolling retrievers, Leonbergers, and Labrador retrievers.
Once diagnosed, most dogs with Addison’s disease can be successfully treated with injectable medication.