Participants then undergo clinical studies of antidiuretic function. A standard fluid deprivation-vasopressin challenge is performed with timed measurements of osmolality, electrolytes, creatinine, and vasopressin. The next day, blood pressure, plasma cyclic AMP, GMP, von Willebrand Factor, Factor VIII, and urine osmolality are measured during a water load desamino-D-arginine vasopressin (dDAVP) infusion test.