Autonomous Aldosterone Secretion as a Subclinical Form of Primary Aldosteronism: Pathogenesis and Clinical Significance

The improvement of postoperative blood pressure and associated factors in patients with hormone-negative adrenal adenoma and hypertension

OBJECTIVE

To investigate the effect of adrenal surgery on blood pressure (BP) improvements in patients with hormone-negative adrenal adenoma (HNA) concomitant with hypertension and analyze associated prognostic factors.

METHODS

We retrospectively reviewed the clinical data of patients with HNA and hypertension and patients with aldosterone-producing adenoma (APA) and hypertension who underwent adrenal surgery at our center between 2019 and 2022. Hypertension outcomes were evaluated in all patients and subjects were divided into three groups according to follow-up BP and the administration of anti-hypertensive agents: a clinical curation group, an improvement group, and a no-improvement group. Logistic regression analysis was performed to predict factors associated with clinical curation in patients with HNA post-surgery.

RESULTS

Of the 182 patients with HNA, clinical curation was achieved in 58 patients (31.9%), improvement in 72 (39.5%), and no improvement in 52 (28.6%). The clinical curation, improvement and no improvement rates in patients with APA were 64.8% (n = 118), 15.9% (n = 29), and 19.2% (n = 35). Multivariate logistic regression analysis indicated that a duration of hypertension ≤6 years and a plasma aldosterone level >160 pg/ml were both independent factors for the clinical curation of hypertension in patients with HNA after adrenal surgery.

CONCLUSION

Adrenal surgery can cure or improve hypertension in most patients with HNA, especially in a short duration of hypertension and high plasma levels of aldosterone.

Autonomous Aldosterone Secretion in Patients with Adrenal Incidentaloma

In recent years, research has emphasized the significance of mild clinical and biochemical presentations of primary aldosteronism (PA) that do not meet current diagnostic criteria of the syndrome. In this study, we assessed the prevalence of autonomous aldosterone (Ald) secretion (AAS), defined as a positive (>1.2 ng/dL/mIU/L) Ald-to-renin ratio (ADRR) combined with unsuppressed Ald (>4 ng/dL), and its associations with blood pressure (BP), cardiac function, and common carotid artery (CCA) intima-media thickness (IMT) in patients with incidentally discovered adrenal adenomas (AI), who were either normo- or hypertensive but had no other cardiovascular disease. Among 332 AI patients hospitalized between November 2018 and December 2019, 63 study participants were recruited (26 normo- and 37 hypertensive), who underwent hormonal examinations, 24 h ambulatory BP measurement, transthoracic echocardiography, and CCA IMT assessment without altering chronic medications. AAS was found in approximately 25% of subjects (seven normo- and nine hypertensive); urinary aldosterone excretion (UAldE) exceeded 10 ug/day in none of the subjects. The left ventricular mass index correlated positively with UAldE in non-diabetic patients (n = 50), and negatively with renin in those without beta blocker therapy (n = 38). The study shows that a pragmatic approach to hormonal assessment (no chronic therapy modification) may reveal patients with AAS. Screening for this subclinical PA presentation is probably more effective with a permissive ADRR than UAldE in such a setting.

Intrinsic Adrenal TWIK-Related Acid-Sensitive TASK Channel Dysfunction Produces Spontaneous Calcium Oscillations Sufficient to Drive AngII (Angiotensin II)-Unresponsive Hyperaldosteronism

Background:

Ion channel mutations in calcium regulating genes strongly associate with AngII (angiotensin II)-independent aldosterone production. Here, we used an established mouse model of in vivo aldosterone autonomy, Cyp11b2 -driven deletion of TWIK-related acid-sensitive potassium channels (TASK-1 and TASK-3, termed zona glomerulosa [zG]-TASK-loss-of-function), and selective pharmacological TASK channel inhibition to determine whether channel dysfunction in native, electrically excitable zG cell rosette-assemblies: (1) produces spontaneous calcium oscillatory activity and (2) is sufficient to drive substantial aldosterone autonomy.

Methods:

We imaged calcium activity in adrenal slices expressing a zG-specific calcium reporter (GCaMP3), an in vitro experimental approach that preserves the native rosette assembly and removes potentially confounding extra-adrenal contributions. In parallel experiments, we measured acute aldosterone production from adrenal slice cultures.

Results:

Absent from untreated WT slices, we find that either adrenal-specific genetic deletion or acute pharmacological TASK channel inhibition produces spontaneous oscillatory bursting behavior and steroidogenic activity (2.4-fold) that are robust, sustained, and equivalent to activities evoked by 3 nM AngII in WT slices. Moreover, spontaneous activity in zG-TASK-loss-of-function slices and inhibitor-evoked activity in WT slices are unresponsive to AngII regulation over a wide range of concentrations (50 pM to 3 µM).

Conclusions:

We provide proof of principle that spontaneous activity of zG cells within classic rosette assemblies evoked solely by a change in an intrinsic, dominant resting-state conductance can be a significant source of AngII-independent aldosterone production from native tissue.

Progress on Genetic Basis of Primary Aldosteronism

Primary aldosteronism (PA) is a heterogeneous group of disorders caused by the autonomous overproduction of aldosterone with simultaneous suppression of plasma renin activity (PRA). It is considered to be the most common endocrine cause of secondary arterial hypertension (HT) and is associated with a high rate of cardiovascular complications. PA is most often caused by a bilateral adrenal hyperplasia (BAH) or aldosterone-producing adenoma (APA); rarer causes of PA include genetic disorders of steroidogenesis (familial hyperaldosteronism (FA) type I, II, III and IV), aldosterone-producing adrenocortical carcinoma, and ectopic aldosterone-producing tumors. Over the last few years, significant progress has been made towards understanding the genetic basis of PA, classifying it as a channelopathy. Recently, a growing body of clinical evidence suggests that mutations in ion channels appear to be the major cause of aldosterone-producing adenomas, and several mutations within the ion channel encoding genes have been identified. Somatic mutations in four genes (KCNJ5, ATP1A1, ATP2B3 and CACNA1D) have been identified in nearly 60% of the sporadic APAs, while germline mutations in KCNJ5 and CACNA1H have been reported in different subtypes of familial hyperaldosteronism. These new insights into the molecular mechanisms underlying PA may be associated with potential implications for diagnosis and therapy.