title: Vasopressin responsiveness of subclinical Cushing's syndrome due to ACTH-independent macronodular adrenocortical hyperplasia.
abstract: OBJECTIVE
  Vasopressin (AVP) is reported to be an important factor for regulating cortisol secretion in patients with Cushing's syndrome due to ACTH-independent macronodular adrenocortical hyperplasia (AIMAH). Recently, there have been several case reports of subclinical Cushing's syndrome due to AIMAH, in which the pathophysiological role of AVP has been unknown. The aim was to conduct an extensive investigation of AVP in the autonomous secretion of cortisol in subclinical Cushing's syndrome due to AIMAH.
  
  
  METHODS
  Five cases of AIMAH with subclinical Cushing's syndrome underwent prospective study including physical examination, imaging (MRI, CT and 131I-adosterol scintigraphy) and endocrinological evaluation that comprised basal plasma cortisol levels and urinary excretions of steroid metabolites, a dexamethasone suppression test and an AVP stimulation test. In case 1, left adrenalectomy was performed and the pathological diagnosis of AIMAH was established. An in vitro experiment using the cultured AIMAH adrenal cells was conducted to investigate cortisol secretion and expression of the V1-AVP receptor, mRNA by RT-PCR.
  
  
  RESULTS
  All five cases were discovered incidentally to have bilateral adrenal nodules. Imaging by MRI and CT revealed large multinodular lesions in both adrenal glands, which showed positive uptake on 131I-adosterol scintigraphy. Although the basal values of plasma cortisol and urinary excretions of steroid metabolites were within normal limits, autonomous secretion of cortisol was assumed to occur because of lack of suppression during dexamethasone suppression. The five patients had no overt signs of Cushing's syndrome, and they were therefore diagnosed with subclinical Cushing's syndrome due to AIMAH. In all five patients, AVP stimulated cortisol secretion in vivo, whereas desmopressin acetate failed to affect cortisol secretion. In case 1, AVP stimulated cortisol secretion from cultured AIMAH adrenal cells, but this secretion had no relationship with cAMP production. In addition, over-expression of V1-AVP receptor mRNA in AIMAH tissue was determined by RT-PCR.
  
  
  CONCLUSIONS
  Patients with subclinical Cushing's syndrome due to AIMAH commonly exhibit cortisol responsiveness to AVP, and this is probably mediated through activation of overexpressed V1-AVP receptors.
authors.affiliation: Department of Clinical Cell Biology, Chiba University Graduate School of Medicine, Chiba, Japan. ichiro-tatsuno@faculty.chiba-u.jp
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tatsuno
authors.forename: Daigaku
authors.initials: D
authors.lastname: Uchida
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tanaka
authors.forename: Hisashi
authors.initials: H
authors.lastname: Koide
authors.forename: Azusa
authors.initials: A
authors.lastname: Shigeta
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Hironobu
authors.initials: H
authors.lastname: Sasano
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Saito
mesh_terms: D000302:Adrenal Cortex / Q000473:pathology*; D001127:Arginine Vasopressin / Q000097:blood; D002478:Cells, Cultured; D003480:Cushing Syndrome / Q000097:blood* / Q000209:etiology; D003907:Dexamethasone; D005260:Female; D005938:Glucocorticoids; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D006965:Hyperplasia / Q000150:complications; D033162:Incidental Findings; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012333:RNA, Messenger / Q000032:analysis; D017483:Receptors, Vasopressin / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013268:Stimulation, Chemical
chemical_list: D005938:Glucocorticoids; D012333:RNA, Messenger; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D003907:Dexamethasone; D006854:Hydrocortisone