Hyper-responsiveness of adrenal gland to vasopressin resulting in enhanced plasma cortisol in patients with adrenal nodule(s)

Clinical, pathophysiologic, genetic and therapeutic progress in Primary Bilateral Macronodular Adrenal Hyperplasia

Patients with primary bilateral macronodular adrenal hyperplasia (PBMAH) usually present bilateral benign adrenocortical macronodules at imaging and variable levels of cortisol excess. PBMAH is a rare cause of primary overt Cushing's syndrome, but may represent up to one third of bilateral adrenal incidentalomas with evidence of cortisol excess. The increased steroidogenesis in PBMAH is often regulated by various G-protein coupled receptors aberrantly expressed in PBMAH tissues; some receptor ligands are ectopically produced in PBMAH tissues creating aberrant autocrine/paracrine regulation of steroidogenesis. The bilateral nature of PBMAH and familial aggregation, led to the identification of germline heterozygous inactivating mutations of the ARMC5 gene, in 20-25% of the apparent sporadic cases and more frequently in familial cases; ARMC5 mutations/pathogenic variants can be associated with meningiomas. More recently, combined germline mutations/pathogenic variants and somatic events inactivating the KDM1A gene were specifically identified in patients affected by GIP-dependent PBMAH. Functional studies demonstrated that inactivation of KDM1A leads to GIP-receptor (GIPR) overexpression and over or down-regulation of other GPCRs. Genetic analysis is now available for early detection of family members of index cases with PBMAH carrying identified germline pathogenic variants. Detailed biochemical, imaging, and co-morbidities assessment of the nature and severity of PBMAH is essential for its management. Treatment is reserved for patients with overt or mild cortisol/aldosterone or other steroid excesses taking in account co-morbidities. It previously relied on bilateral adrenalectomy; however recent studies tend to favor unilateral adrenalectomy, or less frequently, medical treatment with cortisol synthesis inhibitors or specific blockers of aberrant GPCR.

[Immunohistochemical study on the expression/hyperexpression of aberrant/eutopic receptors in patients with bilateral macronodular adrenal hyperplasia]

Bilateral macronodular adrenal hyperplasia (BMAH) is a rare cause of Cushing's syndrome. In this case cortisol production can be regulated by both genetic factors and various molecular mechanisms. The presence of aberrant or overexpression of eutopic receptors on the membrane of adrenal cortex may lead to activation of cAMP/PKA signaling pathways and consequently, pathological stimulation of steroidogenesis. Since proving the effectiveness of unilateral adrenalectomy in BMAH by achievement of stable remission, preoperative clinical and laboratory tests (ligand-induced tests) are no longer of relevant. Nevertheless, in the absence of normalization of the level of cortisol in the postoperative period or its recurrence, subsequent specific targeted medical options can be offered only if expression/hyperexpression predominance of one or another receptor. Their detection becomes possible using more reliable diagnostic methods such as polymerase chain reaction (PCR) and immunohistochemical studies (IHC) than clinical laboratory tests. At the moment, PCR has gained a wider application. This article summarizes data on the use of immunohistochemical study in BMAH.

Aberrant G-protein coupled hormone receptor in adrenal diseases

The regulation of cortisol or aldosterone production when ACTH of pituitary origin or the renin-angiotensin systems are suppressed in primary adrenal Cushing's syndrome or in primary aldosteronism is exerted by diverse genetic and molecular mechanisms. In addition to recently identified mutations in various genes implicated in the cyclic AMP or ion channel pathways, steroidogenesis is not really autonomous as it is frequently regulated by the aberrant adrenocortical expression of diverse hormone receptors, particularly G-protein coupled hormone receptors (GPCR) which can substitute for the normal function of ACTH or angiotensin-II. In addition, paracrine or autocrine production of ligands for the aberrant GPCR such as ACTH or serotonin is found in some adrenal tumors or hyperplasias and participates in a complex regulatory loop causing steroid excess. Targeted therapies to block the aberrant ligands or their receptors could become useful in the future, particularly for patients with bilateral source of steroid excess.

Adrenal Cushing's syndrome due to bilateral macronodular adrenal hyperplasia: prediction of the efficacy of beta-blockade therapy and interest of unilateral adrenalectomy

Bilateral adrenalectomy is the standard treatment for Cushing's syndrome (CS) related to ACTH-independent bilateral macronodular hyperplasia (AIMAH), although it imposes life-long adrenal insufficiency. This study reports a clinical case in order to discuss the clinical interest of pharmacological beta-blockade of illegitimate membrane receptors and unilateral adrenalectomy as alternatives to bilateral adrenalectomy for treatment of CS due to AIMAH. Evidence for cortisol stimulation by upright posture and insulin-induced hypoglycemia in a patient with CS related to AIMAH led us to try beta-blockers as a therapeutic test and then as a first line treatment. Thus, a 3-day beta-blocker test (320 mg/d propranolol) induced normalization of cortisol secretion, with return of hypercortisolism at the end of the test. A long term treatment with 320 mg/d propranolol allowed sustained normalization of cortisol secretion and progressive disappearance of Cushingoid features but after 8 months the patient complained of Raynaud's syndrome and fatigue. Lowering propranolol dosage or switching to atenolol was less efficient to reduce cortisol levels. Unilateral adrenalectomy was then performed as a second line treatment, leading to normalisation of the 24h urinary cortisol without adrenal insufficiency. Long term control of blood pressure and glycemia were observed during a 7-year follow-up without beta-blocker. In conclusion, a 3-day propranolol test may identify patients with AIMAH who can benefit from a long term beta-blocker treatment. In case of intolerance to beta-blocking agents, unilateral adrenalectomy may allow for long term control of Cushing's syndrome related to AIMAH without adrenal insufficiency.

A possible association between aldosterone response to vasopressin and circadian change of aldosterone in the patients with aldosterone-producing adenoma

Vasopressin was reported to stimulate secretion of both cortisol and aldosterone through eutopic V1a receptors in adrenal gland. Recently, adrenal hyper-responsiveness of plasma cortisol to vasopressin with eutopic overexpession of V1a receptors has been reported in Cushing's syndrome, such as a majority of cases of ACTH-independent macronodular adrenal hyperplasia and some cases of Cushing's adenomas. There were a few reports regarding the aldosterone response to vasopressin in aldosterone-producing adenoma. The aim of our study was to investigate the aldosterone response to vasopressin and its pathophysiological roles in the patients with aldosterone-producing adenoma. Vasopressin-loading test was performed in 10 patients with aldosterone-producing adenoma, and in 16 patients with non-functioning adrenal tumors. The roles of the aldosterone response to vasopressin were analyzed in terms of hormonal secretion and the expression of V1a receptor mRNA on the operated adrenal gland in aldosterone-producing adenoma. We found that (1) a varying aldosterone response to vasopressin was observed, (2) absolute response of plasma aldosterone in aldosterone-producing adenoma was significantly higher than that in non-functioning tumor, (3) aldosterone response rate to vasopressin was significantly and negatively correlated with the decline rate (%) in plasma aldosterone from morning to evening in aldosterone-producing adenoma, (4) V1a receptor mRNA was expressed at various values in aldosterone-producing adenoma, and (5) surgical removal of aldosterone-producing adenoma eliminated the aldosterone response to vasopressin observed in patients with aldosterone-producing adenoma. These findings indicated that vasopressin might be involved in the coordination of aldosterone secretion through eutopic expression of V1a receptor in aldosterone-producing adenoma.