title: Resistance to vasopressin action on the kidney in patients with Cushing's disease.
abstract: OBJECTIVE
  To assess the plasma levels and action of arginine vasopressin (AVP) in patients with Cushing's disease. There are many reports that patients with Addison's disease have increased AVP levels associated with hyponatraemia and hypoosmolality, but none on the dynamics of secretion of this neurohormone during osmolality-based stimulation in patients with chronic hypercortisolism.
  
  
  METHODS
  The plasma AVP concentration and the urinary and plasma osmolality after a 7.5-h water deprivation test (WDT) were evaluated in 13 patients with Cushing's disease and 15 normal (control) individuals. In patients with Cushing's disease we also assessed the urinary osmolality in response to 10 micrograms i.v. desmopressin (DDAVP) administered at the end of the WDT.
  
  
  RESULTS
  At the end of the WDT, urinary osmolality was significantly lower in patients with Cushing's disease (511.5 +/- 148.5 mOsm/l) than in the normal subjects (981.1 +/- 107.1 mOsm/l, P < 0.001), whereas plasma osmolality did not differ between the two groups. Consequently, the urine/plasma osmolality ratio (Uosm/Posm) was lower in patients with Cushing's disease than in normal individuals (1.8 +/- 0.5 compared with 3.4 +/- 0.4, P < 0.001). The AVP concentration also was greater (7.3 +/- 3.1 pmol/l) in those with Cushing's disease than in the controls (3.9 +/- 2.3 pmol/l, P < 0.005). After administration of DDAVP to the hypercortisolaemic patients, the urinary osmolality attained (718.0 +/- 200.0 mOsm/l) was still lower than that in the normal group at the end of WDT (P < 0.005).
  
  
  CONCLUSIONS
  Patients with Cushing's disease presented higher AVP levels and smaller Uosm/Posm ratios than normal subjects. After DDAVP, the patients with Cushing's disease were unable to concentrate the urine adequately. These data suggest that the kidney shows resistance to the action of both endogenous and exogenous AVP in patients with Cushing's disease.
authors.affiliation: Endocrine Service, Hospital das Clinicas FMUSP, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Knoepfelmacher
authors.forename: M J
authors.initials: MJ
authors.lastname: Pradal
authors.forename: R D
authors.initials: RD
authors.lastname: Dio
authors.forename: L R
authors.initials: LR
authors.lastname: Salgado
authors.forename: M
authors.initials: M
authors.lastname: Semer
authors.forename: B L
authors.initials: BL
authors.lastname: Wajchenberg
authors.forename: B
authors.initials: B
authors.lastname: Liberman
mesh_terms: D000328:Adult; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000097:blood / Q000502:physiology*; D001769:Blood / Q000378:metabolism; D003480:Cushing Syndrome / Q000097:blood / Q000188:drug therapy* / Q000652:urine; D003894:Deamino Arginine Vasopressin / Q000627:therapeutic use*; D004351:Drug Resistance; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D007668:Kidney / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D012016:Reference Values; D014556:Urine / Q000737:chemistry; D014868:Water Deprivation
chemical_list: D001127:Arginine Vasopressin; D003894:Deamino Arginine Vasopressin