Adrenal Diagnostics: An Endocrinologist's Perspective focused on Hyperaldosteronism

Abstract

The era of sophisticated high resolution imaging with the consequent identification of previously unrecognised adrenal masses (adrenal incidentalomas), has emphasised the need for an appropriate biochemical approach to define adrenal function. The focus of this testing is on catecholamines from the adrenal medulla (testing that has been rendered relatively straightforward by plasma metanephrine measurements) and the physiological corticosteroids, cortisol and aldosterone, synthesised by the adrenal cortex. The diagnosis of hypercortisolism remains a challenge and has been extensively reviewed. In the context of hypertension and an adrenal incidentaloma, the exclusion of hyperaldosteronism has an importance beyond simple blood pressure control. This review focuses on the recommended approaches to both the diagnosis of hyperaldosteronism and the characterisation of its aetiology. Monogenetic causes of mineralocorticoid hypertension are discussed as are recent developments with respect to both the molecular aetiology and the differential diagnosis of aldosterone-producing adenomas.

Figure.

Schematic representation of the physiology of aldosterone action in a normal sodium transporting epithelial cell (upper panel) including the points at which the anti-mineralocorticoid agents amiloride and spironolactone act. The pathophysiology of the various inherited forms of mineralocorticoid hypertension are represented in the subsequent panels: GRA – glucocorticoid remediable hyperaldosteronism (or indeed in Conn’s syndrome); AME-apparent mineralocorticoid excess syndrome; MRS810L - an activating mutation of the MR and; ENaC*- Liddle’s syndrome. Adapted from Kuhnle et al. Horm Res, 2004,29 with permission from S. Karger AG, Basel.