OR20-3 Characterization of the Pathophysiologic Spectrum of Subclinical Primary Aldosteronism in Normotension

CONTEXT: Accumulating evidence suggests that primary aldosteronism can manifest across a broad phenotypic spectrum and that its origins can at times be detected among normotensive individuals. Herein, we conducted deep-phenotyping studies to interrogate the pathophysiologic continuum of the primary aldosteronism phenotype among normotensive participants. METHODS: Normotensive participants with obesity, metabolic syndrome, and/or high-normal untreated blood pressure underwent dietary sodium loading and restriction protocols (to maximally suppress and stimulate angiotensin II-mediated aldosterone production), dexamethasone suppression and cosyntropin stimulation protocols (to maximally suppress and stimulate ACTH-mediated aldosterone production), and 24h ambulatory blood pressure monitoring. Measurement of aldosterone and 18-hybrid steroids via LC-MS/MS was conducted to quantify the degree of dysregulated CYP11B2 expression. Urinary extracellular vesicles (uEV) were isolated to measure renal tubular protein content associated with mineralocorticoid receptor activation. In order to characterize parameters across the severity spectrum of non-suppressible and renin-independent aldosterone production, participants with suppressed renin activity were categorized by tertile of 24h urinary aldosterone production following oral sodium suppression testing. Repeated measures linear mixed models were used to analyze trends for each parameter across tertiles of autonomous aldosterone production; for ease of presentation, the mean [SD] of the first vs. third tertile are presented for selected parameters. RESULTS: Following oral sodium loading, greater non-suppressible renin-independent aldosterone production was associated with greater kaliuresis, higher daytime ambulatory systolic blood pressure within the normal range, and a progressive impairment in the ability to suppress production of serum aldosterone (P-trend=0.009), 18-hydroxycorticosterone (9.3 [5.0] vs. 19.6 [6.5] ng/dL, P-trend=0.004), 18-hydroxycortisol (45.0 [25.4] vs. 70.9 [29.9] ng/dL, P-trend=0.03), and 18-oxocortisol (1.2 [0.03] vs. 3.4 [7.2], P-trend=0.01). Similarly, following dexamethasone suppression testing, there was a progressive inability to suppress 18-hydroxycorticosterone (8.3 [5.0] vs. 15.4 [8.2] ng/dL, P-trend=0.004), 18-hydroxycortisol (6.6 [3.8] vs. 10.2 [3.6] ng/dL, P-trend=0.03), and 18-oxocortisol (1.2 [0.01] vs. 1.4 [0.6] ng/dL, P-trend=0.01) in parallel with greater renin-independent aldosterone production. In contrast, following stimulation with cosyntropin, greater non-suppressible and renin-independent aldosterone production was associated with progressively enhanced production of 18-hydroxycorticosterone (77.6 [25.4] vs. 121.1 [31.1] ng/dL, P-trend=0.004), 18-hydroxycortisol (68.5 [28.4] vs. 86.2 [26.3] ng/dL, P-trend=0.03), and 18-oxocortisol (3.2 [2.8] vs. 7.3 [3.5] ng/dL, P-trend=0.01). Excretion of uEV's of pendrin (P=0.002) and aquaporin 2 (P=0.002) all increased with greater non-suppressible aldosterone production. CONCLUSIONS: Dynamic phenotyping studies in normotensive individuals demonstrate a continuum of non-suppressible and renin-independent aldosterone production that parallels higher blood pressure, greater kaliuresis, increased 18-hybrid steroid production indicative of dysregulated CYP11B2 expression, and increased uEV excretion indicative of renal mineralocorticoid receptor activation. This pathophysiologic continuum of normotensive primary aldosteronism provides phenotypic support for histopathology studies showing ectopic CYP11B2 expression within adrenal glands of normotensive humans, and for epidemiologic studies demonstrating renin-independent aldosterone production in normotensive populations increases risk for developing hypertension. Presentation: Monday, June 13, 2022 11:30 a.m. - 11:45 a.m.