Hypoadrenocorticism in dogs, or, as it is known in people, Addison's disease, is an endocrine system disorder that occurs when the adrenal glands fail to produce enough hormones for normal function. The adrenal glands secrete glucocorticoids such as cortisol and mineralocorticoids such as aldosterone; when proper amounts of these are not produced, the metabolic and electrolyte balance is upset. Mineralocorticoids control the amount of potassium, sodium, and water in the body. Hypoadrenocorticism is fatal if left untreated. The most common cause of inadequate adrenal production is idiopathic adrenocortical atrophy. All causes for hypoadrenocorticism are not yet known. The usual causes are genetic, often related to autoimmune disorders, where the body attacks and kill its own tissue ("immune mediated destruction"). Other cases are caused by various disease processes, including failure of the pituitary gland to secrete ACTH, the hormone which stimulates the adrenal production of cortisol. Hypoadrenocorticism is more frequent in dogs than in humans; in fact, it may occur one hundred times more often in the canine population. It mostly affects young to middle-aged female dogs, as the average age at diagnosis being four years old (although it has been found in puppies and dogs up to twelve years old). About seventy percent of dogs that are diagnosed with hypoadrenocorticism are female. Hypoadrenocorticism is still relatively uncommon or underdiagnosed in dogs. Statistics gathered from a large veterinary hospital placed the number at 0.36 dogs per 1000. For an average veterinary practice with two veterinarians and 1500 canine patients, this would mean an average of one diagnosis of the disease each year. Signs and symptoms The most common clinical manifestations are related to mental status and gastrointestinal function; they include lethargy, anorexia, vomiting, weight loss, and weakness. Additional findings may include dehydration, bradycardia, weak femoral pulses, abdominal pain, lack of appetite, tremors or shaking, muscle weakness, low body temperature, collapse, and pain in the hindquarters. Polyuria and polydipsia, diarrhea, and shivering are occasionally reported. Hypoglycemia can also be present, and initially may be confused with a seizure disorder or an insulin-secreting pancreatic tumor (insulinoma). Hypoadrenocorticism may also be misdiagnosed as food poisoning, parvovirus enteritis, gastric volvulus, or spinal/joint problems, earning this disease nicknames like "the Great Mimic" and "the Great Imitator". It is possible not to see any signs of the disease until 90% of the adrenal cortex is no longer functioning. Addisonian crisis If hyponatremia (low sodium) and hyperkalemia (high