AVP and inappropriate ADH syndrome: However, regarding hyponatremia in these patients, it can be caused by other conditions that need to be investigated and differentiated, like syndrome of inappropriate secretion of anti-diuretic hormone (SIADH), due to ectopic ADH secretion from malignancy, other drugs, acute illnesses, etc. Finally, in the most severe form of PAI, adrenal crisis, clinical picture is characterized by hypovolemic shock with fever, generalized abdominal pain, and vomiting up to confusion/coma [10].