A case of ACTH-independent macronodular adrenal hyperplasia: simultaneous expression of several aberrant hormone receptors in the adrenal gland.

ACTH-independent macronodular adrenal hyperplasia (AIMAH) is a rare cause of Cushing's syndrome. Recently, aberrant expression of adrenal receptors for various hormones and/or cytokines has been identified in several cases with AIMAH, which may act as a pathogenetic factor for the disorder. We report here an AIMAH patient with a Rathke's cleft cyst. Endocrinological examinations revealed that the pituitary cyst had no hormonal secretion. Administrations of either AVP or isoproterenol provoked cortisol production in the patient, whereas DDAVP, mosapride or endogenous LH induced by GnRH did not. Reverse transcriptional-PCR analysis of total RNA obtained from the patient's adrenal tissue revealed the expression of mRNA of receptors for V1a, V1b, V2, and LH/hCG. Three of these receptors except for V1a receptor were not expressed in normal adrenal tissue. Hyperosmolar saline infusion promoted the patient's cortisol secretion through the increase in endogenous AVP (peak plasma AVP level reached 90.4 pg/ml during the test). These results suggest that endogenous AVP and catecholamines are involved in the pathophysiology of the patient. Further study will be necessary to clarify the molecular mechanisms that regulate tissue-specific expression of these receptors and their role in the overgrowth of adrenal in AIMAH.