Ectopic expression of vasopressin V1b and V2 receptors in the adrenal glands of familial ACTH-independent macronodular adrenal hyperplasia

Objective: ACTH-independent macronodular adrenal hyperplasia (AIMAH) is a rare and unusual cause of Cushing's syndrome, characterized by bilateral nodular adrenocortical hyperplasia and hypersecretion of cortisol. Familial AIMAH has rarely been reported. Recently, the aberrant expression of adrenal receptors for various ligands in AIMAH patients has become important in explaining the pathogenesis of AIMAH. In this study, we present the cases of two sisters who were affected with AIMAH. Patients and Measurements: Two sisters, aged 46 and 58, respectively, at the time of diagnosis, were found to have Cushing's syndrome due to AIMAH. We performed provocation tests with various materials and reverse transcription polymerase chain reaction (RT-PCR) with their resected adrenal tissues to examine the hyperresponsiveness to steroidogenesis and the overexpression of related receptors, respectively. Results: Provocation tests in vivo indicated that arginine vasopressin (AVP) promoted cortisol secretion through vasopressin V1a as well as V1b and V2 receptors. RT-PCR analysis revealed an abnormal cDNA expression of vasopressin V1b and V2 receptors, none of which is known to be normally expressed in the adrenal glands. Conclusion: The expression of ectopic vasopressin V1b and V2 receptors may be involved in the aetiology of AIMAH, at least in the case of the sibling patients presented here.