Fig. 2.23 
The water deprivation test used in the diagnosis of hypopituitarism. 
(a) The sequence of events during normal testing. (b) The hypopituitary response to this test. The patient with ADH deficiency fails to concentrate unne in the presence of a nsing plasma osmolality until desmopressin is given. Normally, the peak urine osmolality exceeds twice that of urine before desmopressin administration.