Characterizing the Origins of Primary Aldosteronism

Background: Renin-independent aldosterone production in normotensive people increases risk for developing hypertension. In parallel, normotensive adrenal glands frequently harbor aldosterone-producing micronodules with pathogenic somatic mutations known to induce primary aldosteronism (PA). A deeper understanding of these phenomena would inform the origins of PA and its role in hypertension pathogenesis.

Methods: Prospectively recruited normotensives underwent detailed characterization of PA features via the following: oral sodium suppression test to evaluate renin-independent aldosterone production, dexamethasone suppression and adrenocorticotropic hormone-stimulation tests to evaluate adrenocorticotropic hormone-mediated aldosterone production, and 24-hour ambulatory blood pressure monitoring. The magnitude of renin-independent aldosterone production was defined via using tertiles of 24-hour urinary aldosterone production during the oral sodium suppression test to create unbiased categorizations of the magnitude of PA. Serum aldosterone, serum 18-hybrid steroids, urine tetrahydroaldosterone (biomarkers of aldosterone synthase activity), urinary potassium, and blood pressure (biomarkers of mineralocorticoid receptor activation) were evaluated across tertiles.

Results: There was a spectrum of autonomous, nonsuppressible, and renin-independent production of aldosterone, 18-hybrid steroids, and 24-hour urinary tetrahydroaldosterone (P-trend <0.01). Correspondingly, there was a continuum of adrenocorticotropic hormone-mediated aldosterone production and 18-hybrid steroid production that also paralleled renin-independent aldosterone production. The spectrum of PA pathophysiology was associated with higher ambulatory daytime systolic BP (P-trend <0.05), even within the normotensive range, and greater urinary potassium excretion (P-trend <0.05), indicating a continuum of mineralocorticoid receptor activation.

Conclusions: The pathophysiologic continuum of PA, characterized by renin-independent and adrenocorticotropic hormone-mediated aldosterone production, and enhanced aldosterone synthase and mineralocorticoid receptor activity, is evident in normotensive people. These findings provide mechanistic explanations to implicate PA in the pathogenesis of a substantial proportion of hypertension.