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Mast cells are immune cells present in adrenals from various species. Proliferation and activation of adrenal mast cells seem to be influenced by environment, since they increase during summer and in response to sodium restriction in frogs and mouse, respectively. Although the physiological factors regulating adrenal mast cell activity have not been identified, they might involve neurotransmitters and the renin-angiotensin system. Some data indicate that adrenal mast cells stimulate proliferation of steroidogenic cells in the zona glomerulosa and activate the mineralocorticoid production. In human, mast cell degranulation stimulates aldosterone synthesis through the release of serotonin (5-HT) and activation of 5-HT4 receptors. Increase in mast cell population and upregulation of the 5-HT signaling pathway occur in aldosterone-producing adenomas. In particular, aldosterone-producing adenoma cells overexpress 5-HT4 receptors and are hyper-responsive to 5-HT4 receptor agonists. These data suggest that the intra-adrenal serotonergic regulatory system represents a potential target for development of both adrenal imaging methods to evaluate the lateralization of aldosterone production, and pharmacological treatments of primary aldosteronism. [ABSTRACT FROM AUTHOR]

Over the past six years, the genetic basis of a significant fraction of primary aldosteronism (PA) cases has been solved. Breakthrough discoveries include the role of somatic variants in the KCNJ5, CACNA1D, ATP1A1, and ATP2B3 genes as causes of aldosterone-producing adenomas (APAs), and the recognition of three novel hyperaldosteronism syndromes with germline variants in the KCNJ5, CACNA1D, and CACNA1H genes. The description of somatic variants in CACNA1D and ATP1A1 in aldosterone-producing cell clusters (APCCs) suggests that these clusters are precursors of some aldosterone-producing adenomas. Yet, a number of questions remain unanswered. These include the genetic basis of about 40 % of APAs without somatic variants in known genes. Do technical issues explain this finding, or are the unexplained APAs due to somatic copy number variation or rare variants in thus-far undiscovered genes? Similarly, the role of CTNNB1 (beta catenin) variants in APA pathogenesis is still unclear. The major question to be solved is the genetic basis of bilateral adrenal hyperplasia (BAH). Is BAH due to the bilateral occurrence of APCCs, to germline variants, or perhaps due to unknown serum factors? Lastly, the etiology of unsolved cases of apparently familial hyperaldosteronism remains to be discovered. It is expected that genetic studies over the next few years will lead to answers to at least some of the questions raised. [ABSTRACT FROM AUTHOR]

The current pathological diagnosis of aldosterone-producing adenoma (APA) is challenging because no histological markers of aldosterone production are available in routine practice. A previous study demonstrated that Disabled-2 (DAB2) is a specific marker of the zona glomerulosa (ZG) in rodents. The aim of the present study was to investigate the significance of immunohistochemical staining to detect DAB2 in the adrenal tissue of patients with APA. We investigated the expression of DAB2 in 36 adrenal glands with APA, 23 adrenal glands with cortisol-producing adenoma (CPA), and 33 adrenal glands with non-functioning adenoma (NFA). Immunohistochemical staining was performed using anti-DAB2 antibodies on paraffinembedded sections. We analysed the expression of DAB2 semiquantitatively by scoring staining intensity, and assessed the correlation of this information with the clinical findings. DAB2 mRNA expression in adenoma tissues was evaluated by RT-PCR. DAB2 was highly expressed in the ZG in normal human adrenal glands. DAB2 expression was heterogeneous in APA, with spotted, strong staining noted in most samples (25 of 36 APA). CPA and NFA also exhibited extensive low or moderate DAB2 expression. DAB2 mRNA was significantly increased and positively correlated with CYP11B2 in APA (p < 0.05). In APA, the DAB2 score adjusted for tumour volume was positively correlated with plasma aldosterone (p < 0.05). Patients with low or moderate DAB2 staining more frequently exhibited high blood pressure and were diagnosed at a younger age compared with patients with high DAB2 staining. The present study clearly demonstrates that DAB2 is a specific marker of the ZG in normal human adrenal glands but that DAB2 immunostaining is not sufficiently powerful for histopathological diagnosis of APA. DAB2 might be involved in excessive aldosterone biosynthesis and correlate with specific clinical characteristics of APA patients. [ABSTRACT FROM AUTHOR]

Identification and management of patients with primary aldosteronism are of utmost importance because it is a frequent cause of endocrine hypertension, and affected patients display an increase of cardio- and cerebro-vascular events, compared to essential hypertensives. Distinction of primary aldosteronism subtypes is of particular relevance to allocate the patients to the appropriate treatment, represented by mineralocorticoid receptor antagonists for bilateral forms and unilateral adrenalectomy for patients with unilateral aldosterone secretion. Subtype differentiation of confirmed hyperaldosteronism comprises adrenal CT scanning and adrenal venous sampling. In this review, we will discuss different clinical scenarios where execution, interpretation of adrenal vein sampling and subsequent patient management might be challenging, providing the clinician with useful information to help the interpretation of controversial procedures. [ABSTRACT FROM AUTHOR]

Somatic mutations have been identified in the KCNJ5 gene (encoding the potassium channel GIRK4) in aldosterone-producing adenomas (APA). Most of these mutations are located in or near the selectivity filter of the GIRK4 channel pore and several have been shown to lead to the constitutive overproduction of aldosterone. KCNJ5 mutations in APA are more frequent in women; however, this gender dimorphism is a reported phenomenon of Western but not East Asian populations. In this review we discuss some of the issues that could potentially underlie this observation. [ABSTRACT FROM AUTHOR]

Primary aldosteronism (PA) has a prevalence in the general hypertensive population from 5 to 10%, and is widely recognized as the most frequent form of secondary hypertension. The 2 main PA subtypes are aldosterone producing adenoma (APA) and bilateral adrenal hyperplasia (BAH) that account for 95% of all PA cases. The diagnosis of PA is a 3-step process that comprises screening, confirmatory testing, and subtype differentiation. The different categories of patients at an increased risk of PA who should thus undergo a screening test were described in the first Endocrine Society (ES) Practice Guidelines for diagnosis and treatment of PA published in 2008. These categories include patients with Joint National Committee Stage 2, Stage 3, or drug-resistant hypertension; hypertension, and spontaneous or diuretic-induced hypokalemia; hypertension with adrenal incidentaloma; hypertension and a family history of early-onset hypertension or cerebrovascular accident at a young age and all hypertensive first degree relatives of patients with PA. Recently, a growing number of studies have linked PA with the metabolic syndrome, diabetes, and obstructive sleep apnea that may be partly responsible for the higher rate of cardio and cerobrovascular accidents in PA patients. The aim of this review is to discuss, which patients should be screened for PA, focusing not only on the well-established categories of the ES Guidelines, but also on additional other group of patients with a potentially high prevalence of PA that has emerged from recent research. [ABSTRACT FROM AUTHOR]