Comprehensive re-sequencing of adrenal aldosterone producing lesions reveal three somatic mutations near the KCNJ5 potassium channel selectivity filter

Shifting paradigms in primary aldosteronism: reconsideration of screening strategy via integrating pathophysiological insights

Several decades have passed since the description of the first patient with primary aldosteronism (PA). PA was initially classified in two main forms: aldosterone-producing adenoma (APA) and idiopathic hyperaldosteronism (IHA). However, the pathogenesis of PA has now been shown to be far more complex. For this reason, the traditional classification needs to be updated. Given the recent advancements in our understanding of PA pathogenesis, we should reevaluate how frequent PA cases are, beginning with the reconstruction of the screening strategy. Recent studies consistently indicated that PA has been identified in 22% of patients with resistant hypertension and 11% even in normotensives. The frequency is influenced by the screening strategy and should be based on understanding the pathogenesis of PA. Progress has been made to promote our understanding of the pathogenesis of PA by the findings of aldosterone driver mutations, which have been found in normotensives and hypertensives. In addition, much clinical evidence has been accumulated to indicate that there is a spectrum in PA pathogenesis. In this review, we will summarize the recent progress in aldosterone measurement methods based on LC-MS/MS and the current screening strategy. Then, we will discuss the progress of our understanding of PA, focusing on aldosterone driver mutations and the natural history of PA. Finally, we will discuss the optimal strategy to improve screening rate and case detection.

Molecular and Genetics Perspectives on Primary Adrenocortical Hyperfunction Disorders

Adrenocortical disorders encompass a broad spectrum of conditions ranging from benign hyperplasia to malignant tumors, significantly disrupting hormone balance and causing a variety of clinical manifestations. By leveraging next-generation sequencing and in silico analyses, recent studies have uncovered the genetic and molecular pathways implicated in these transitions. In this review, we explored the molecular and genetic alterations in adrenocortical disorders, with a particular focus on the transitions from normal adrenal function to hyperfunction. The insights gained are intended to enhance diagnostic and therapeutic strategies, offering up-to-date knowledge for managing these complex conditions effectively.

NT-proBNP levels in patients with primary hyperaldosteronism and autonomous cortisol cosecretion

CONTEXT

Patients with primary aldosteronism (PA) have higher cardiac comorbidities including more pronounced left ventricular hypertrophy than patients with essential hypertension.

OBJECTIVE

Autonomous cortisol cosecretion (ACS) is a common subtype in PA associated with a worse metabolic profile.

HYPOTHESIS

Autonomous cortisol cosecretion may affect myocardial parameters and result in a worse cardiac outcome compared to patients with PA and without ACS.

METHODS

Three hundred and sixty-seven patients with PA undergoing 1 mg dexamethasone suppression test (DST) and echocardiography at baseline from 2 centers of the German Conn's Registry were included. Follow-up for up to 3.8 years was available in 192 patients.

RESULTS

Patients with PA and ACS had higher NT-proBNP levels at baseline compared to patients with PA without ACS (114 vs 75.6 pg/mL, P = .02), but showed no difference in echocardiography values. NT-proBNP levels showed a significant positive correlation (r = 0.141, P = .011) with cortisol levels after DST at baseline. In response to therapy of PA, NT-proBNP levels decreased, but remained significantly higher in patients with ACS compared to patients without ACS. At follow-up, left ventricle end-diastolic dimension (LVEDD) decreased significantly only in patients without ACS. Left atrial diameter (LAD) decreased significantly in patients without ACS and in female patients with ACS but not in male patients. Left ventricular mass index (LVMI) significantly improved in female patients without ACS but remained unchanged in female patients with ACS as well as in male patients at follow-up.

CONCLUSIONS

In patients with PA, concomitant ACS is associated with a worse cardiac profile and only partial recovery even years after initiation of targeted PA therapy.

Cardiovascular Outcomes of KCNJ5 Mutated Aldosterone-Producing Adenoma: A Systematic Review

BACKGROUND

While clinical features of KCNJ5-mutated aldosterone-producing adenoma (APA) have been reported, evidence of its clinical outcomes is lacking. We aimed to synthesize available literature about the associations between KCNJ5 mutation with cardiovascular and metabolic outcomes among patients with APA.

METHODS

In this systematic review of observational studies, MEDLINE and Embase were searched through August 2022. Two independent authors screened the search results and extracted data from eligible observational studies investigating cardiovascular or metabolic outcomes between KCNJ5-mutated APAs and KCNJ5-non-mutated APAs. Risk of Bias In Non-randomized Studies of Interventions was used to assess the quality of the included studies.

RESULTS

A total of 573 titles/abstracts were screened and after the expert opinion of the literature, full text was read in 20 titles/abstracts, of which 12 studies were included. Across 3 studies comparing the baseline or change in the cardiac function between KCNJ5-mutated APAs and KCNJ5-non-mutated APAs, all studies reported the association between impaired cardiac functions and KCNJ5 mutation status. Among 6 studies evaluating the cure of hypertension after surgery, all studies showed that KCNJ5 mutation was significantly associated with the cure of hypertension. In quality assessment, 7 studies were at serious risk of bias, while the remaining studies were at moderate risk of bias.

CONCLUSIONS

This systematic review provided evidence of the significant association between KCNJ5 mutation and unfavorable cardiovascular outcomes in patients with primary aldosteronism. Further research is needed to improve the quality of evidence on this topic and elucidate the underlying mechanisms of the potential burden of KCNJ5 mutation.

Screening and diagnosis of primary aldosteronism. Consensus document of all the Spanish Societies involved in the management of primary aldosteronism

Primary aldosteronism (PA) is the most frequent cause of secondary hypertension (HT), and is associated with a higher cardiometabolic risk than essential HT. However, PA remains underdiagnosed, probably due to several difficulties clinicians usually find in performing its diagnosis and subtype classification. The aim of this consensus is to provide practical recommendations focused on the prevalence and the diagnosis of PA and the clinical implications of aldosterone excess, from a multidisciplinary perspective, in a nominal group consensus approach by experts from the Spanish Society of Endocrinology and Nutrition (SEEN), Spanish Society of Cardiology (SEC), Spanish Society of Nephrology (SEN), Spanish Society of Internal Medicine (SEMI), Spanish Radiology Society (SERAM), Spanish Society of Vascular and Interventional Radiology (SERVEI), Spanish Society of Laboratory Medicine (SEQC(ML)), Spanish Society of Anatomic-Pathology, Spanish Association of Surgeons (AEC).

Relevance of KCNJ5 in Pathologies of Heart Disease

Abnormalities in G-protein-gated inwardly rectifying potassium (GIRK) channels have been implicated in diseased states of the cardiovascular system; however, the role of GIRK4 (Kir3.4) in cardiac physiology and pathophysiology has yet to be completely understood. Within the heart, the KACh channel, consisting of two GIRK1 and two GIRK4 subunits, plays a major role in modulating the parasympathetic nervous system's influence on cardiac physiology. Being that GIRK4 is necessary for the functional KACh channel, KCNJ5, which encodes GIRK4, it presents as a therapeutic target for cardiovascular pathology. Human variants in KCNJ5 have been identified in familial hyperaldosteronism type III, long QT syndrome, atrial fibrillation, and sinus node dysfunction. Here, we explore the relevance of KCNJ5 in each of these diseases. Further, we address the limitations and complexities of discerning the role of KCNJ5 in cardiovascular pathophysiology, as identical human variants of KCNJ5 have been identified in several diseases with overlapping pathophysiology.

New advances in endocrine hypertension: from genes to biomarkers

Hypertension (HT) is a major cardiovascular risk factor that affects 10% to 40% of the general population in an age-dependent manner. Detection of secondary forms of HT is particularly important because it allows the targeted management of the underlying disease. Among hypertensive patients, the prevalence of endocrine HT reaches up to 10%. Adrenal diseases are the most frequent cause of endocrine HT and are associated with excess production of mineralocorticoids (mainly primary aldosteronism), glucocorticoids (Cushing syndrome), and catecholamines (pheochromocytoma). In addition, a few rare diseases directly affecting the action of mineralocorticoids and glucocorticoids in the kidney also lead to endocrine HT. Over the past years, genomic and genetic studies have allowed improving our knowledge on the molecular mechanisms of endocrine HT. Those discoveries have opened new opportunities to transfer knowledge to clinical practice for better diagnosis and specific treatment of affected subjects. In this review, we describe the physiology of adrenal hormone biosynthesis and action, the clinical and biochemical characteristics of different forms of endocrine HT, and their underlying genetic defects. We discuss the impact of these discoveries on diagnosis and management of patients, as well as new perspectives related to the use of new biomarkers for improved patient care.

Cardiovascular and metabolic characters of KCNJ5 somatic mutations in primary aldosteronism

BACKGROUND

Primary aldosteronism (PA) is the leading cause of curable endocrine hypertension, which is associated with a higher risk of cardiovascular and metabolic insults compared to essential hypertension. Aldosterone-producing adenoma (APA) is a major cause of PA, which can be treated with adrenalectomy. Somatic mutations are the main pathogenesis of aldosterone overproduction in APA, of which KCNJ5 somatic mutations are most common, especially in Asian countries. This article aimed to review the literature on the impacts of KCNJ5 somatic mutations on systemic organ damage.

EVIDENCE ACQUISITION

PubMed literature research using keywords combination, including "aldosterone-producing adenoma," "somatic mutations," "KCNJ5," "organ damage," "cardiovascular," "diastolic function," "metabolic syndrome," "autonomous cortisol secretion," etc.

RESULTS

APA patients with KCNJ5 somatic mutations are generally younger, female, have higher aldosterone levels, lower potassium levels, larger tumor size, and higher hypertension cure rate after adrenalectomy. This review focuses on the cardiovascular and metabolic aspects of KCNJ5 somatic mutations in APA patients, including left ventricular remodeling and diastolic function, abdominal aortic thickness and calcification, arterial stiffness, metabolic syndrome, abdominal adipose tissue, and correlation with autonomous cortisol secretion. Furthermore, we discuss modalities to differentiate the types of mutations before surgery.

CONCLUSION

KCNJ5 somatic mutations in patients with APA had higher left ventricular mass (LVM), more impaired diastolic function, thicker aortic wall, lower incidence of metabolic syndrome, and possibly a lower incidence of concurrent autonomous cortisol secretion, but better improvement in LVM, diastolic function, arterial stiffness, and aortic wall thickness after adrenalectomy compared to patients without KCNJ5 mutations.

Genetic Dissection of Primary Aldosteronism in a Patient With MEN1 and Ipsilateral Adrenocortical Carcinoma and Adenoma

BACKGROUND

Adrenal tumors are found in up to 40% of patients with multiple endocrine neoplasia type 1 (MEN1). However, adrenocortical carcinomas (ACC) and primary aldosteronism (PA) are rare in MEN1.

CASE

A 48-year-old woman known to have primary hyperparathyroidism and hypertension with hypokalemia was referred for a right complex 8-cm adrenal mass with a 38.1 SUVmax uptake on 18F-FDG PET/CT. PA was confirmed by saline suppression test (aldosterone 1948 pmol/L-1675 pmol/L; normal range [N]: <165 post saline infusion) and suppressed renin levels (<5 ng/L; N: 5-20). Catecholamines, androgens, 24-hour urinary cortisol, and pituitary panel were normal. A right open adrenalectomy revealed a concomitant 4-cm oncocytic ACC and a 2.3-cm adrenocortical adenoma. Immunohistochemistry showed high expression of aldosterone synthase protein in the adenoma but not in the ACC, supporting excess aldosterone production by the adenoma.

GENETIC ANALYSIS

After genetic counseling, the patient underwent genetic analysis of leucocyte and tumoral DNA. Sequencing of MEN1 revealed a heterozygous germline pathogenic variant in MEN1 (c.1556delC, p.Pro519Leufs*40). The wild-type MEN1 allele was lost in the tumoral DNA of both the resected adenoma and carcinoma. Sequencing analysis of driver genes in PA revealed a somatic pathogenic variant in exon 2 of the KCNJ5 gene (c.451G>A, p.Gly151Arg) only in the aldosteronoma.

CONCLUSION

To our knowledge, we describe the first case of adrenal collision tumors in a patient carrying a germline pathogenic variant of the MEN1 gene associated with MEN1 loss of heterozygosity in both oncocytic ACC and adenoma and a somatic KCNJ5 pathogenic variant leading to aldosterone-producing adenoma. This case gives new insights on adrenal tumorigenesis in MEN1 patients.

Primary aldosteronism - a multidimensional syndrome

Primary aldosteronism is a common cause of hypertension and is a risk factor for cardiovascular and renal morbidity and mortality, via mechanisms mediated by both hypertension and direct insults to target organs. Despite its high prevalence and associated complications, primary aldosteronism remains largely under-recognized, with less than 2% of people in at-risk populations ever tested. Fundamental progress made over the past decade has transformed our understanding of the pathogenesis of primary aldosteronism and of its clinical phenotypes. The dichotomous paradigm of primary aldosteronism diagnosis and subtyping is being redefined into a multidimensional spectrum of disease, which spans subclinical stages to florid primary aldosteronism, and from single-focal or multifocal to diffuse aldosterone-producing areas, which can affect one or both adrenal glands. This Review discusses how redefining the primary aldosteronism syndrome as a multidimensional spectrum will affect the approach to the diagnosis and subtyping of primary aldosteronism.

Update on the Genetics of Primary Aldosteronism and Aldosterone-Producing Adenomas

PURPOSE OF THE REVIEW

Primary aldosteronism (PA) is the leading cause of secondary hypertension, accounting for over 10% of patients with high blood pressure. It is characterized by autonomous production of aldosterone from the adrenal glands leading to low-renin levels. The two most common forms arise from bilateral adrenocortical hyperplasia (BAH) and aldosterone-producing adenoma (APA). We discuss recent discoveries in the genetics of PA.

RECENT FINDINGS

Most APAs harbor variants in the KCNJ5, CACNA1D, ATP1A1, ATP2B3, and CTNNB1 genes. With the exception of β-catenin (CTNNB1), all other causative genes encode ion channels; pathogenic variants found in PA lead to altered ion transportation, cell membrane depolarization, and consequently aldosterone overproduction. Some of these genes are found mutated in the germline state (CYP11B2, CLCN2, KCNJ5, CACNA1H, and CACNA1D), leading then to familial hyperaldosteronism, and often BAH rather than single APAs. Several genetic defects in the germline or somatic state have been identified in PA. Understanding how these molecular abnormalities lead to excess aldosterone contributes significantly to the elucidation of the pathophysiology of low-renin hypertension. It may also lead to new and more effective therapies for this disease acting at the molecular level.

Histopathology and Genetic Causes of Primary Aldosteronism in Young Adults

CONTEXT

Due to its rare incidence, molecular features of primary aldosteronism (PA) in young adults are largely unknown. Recently developed targeted mutational analysis identified aldosterone-driver somatic mutations in aldosterone-producing lesions, including aldosterone-producing adenomas (APAs), aldosterone-producing nodules (APNs), and aldosterone-producing micronodules, formerly known as aldosterone-producing cell clusters.

OBJECTIVE

To investigate histologic and genetic characteristics of lateralized PA in young adults.

METHODS

Formalin-fixed, paraffin-embedded adrenal tissue sections from 74 young patients with lateralized PA (<35 years old) were used for this study. Immunohistochemistry (IHC) for aldosterone synthase (CYP11B2) was performed to define the histopathologic diagnosis. Somatic mutations in aldosterone-producing lesions were further determined by CYP11B2 IHC-guided DNA sequencing.

RESULTS

Based on the CYP11B2 IHC results, histopathologic classification was made as follows: 48 APAs, 20 APNs, 2 multiple aldosterone-producing nodules (MAPN), 1 double APN, 1 APA with MAPN, and 2 nonfunctioning adenomas (NFAs). Of 45 APAs with successful sequencing, 43 (96%) had somatic mutations, with KCNJ5 mutations being the most common genetic cause of young-onset APA (35/45, 78%). Of 18 APNs with successful sequencing, all of them harbored somatic mutations, with CACNA1D mutations being the most frequent genetic alteration in young-onset APN (8/18, 44%). Multiple CYP11B2-expressing lesions in patients with MAPN showed several aldosterone-driver mutations. No somatic mutations were identified in NFAs.

CONCLUSION

APA is the most common histologic feature of lateralized PA in young adults. Somatic KCNJ5 mutations are common in APAs, whereas CACNA1D mutations are often seen in APNs in this young PA population.

Clinical Translationality of KCNJ5 Mutation in Aldosterone Producing Adenoma

Hypertension due to primary aldosteronism poses a risk of severe cardiovascular complications compared to essential hypertension. The discovery of the KCNJ5 somatic mutation in aldosteroene producing adenoma (APA) in 2011 and the development of specific CYP11B2 antibodies in 2012 have greatly advanced our understanding of the pathophysiology of primary aldosteronism. In particular, the presence of CYP11B2-positive aldosterone-producing micronodules (APMs) in the adrenal glands of normotensive individuals and the presence of renin-independent aldosterone excess in normotensive subjects demonstrated the continuum of the pathogenesis of PA. Furthermore, among the aldosterone driver mutations which incur excessive aldosterone secretion, KCNJ5 was a major somatic mutation in APA, while CACNA1D is a leading somatic mutation in APMs and idiopathic hyperaldosteronism (IHA), suggesting a distinctive pathogenesis between APA and IHA. Although the functional detail of APMs has not been still uncovered, its impact on the pathogenesis of PA is gradually being revealed. In this review, we summarize the integrated findings regarding APA, APM or diffuse hyperplasia defined by novel CYP11B2, and aldosterone driver mutations. Following this, we discuss the clinical implications of KCNJ5 mutations to support better cardiovascular outcomes of primary aldosteronism.

Pathogenesis of Primary Aldosteronism: Impact on Clinical Outcome

Primary aldosteronism (PA) is the most common form of secondary arterial hypertension, with a prevalence of approximately 20% in patients with resistant hypertension. In the last decade, somatic pathogenic variants in KCNJ5, CACNA1D, ATP1A1 and ATP2B3 genes, which are involved in maintaining intracellular ionic homeostasis and cell membrane potential, were described in aldosterone-producing adenomas (aldosteronomas). All variants in these genes lead to the activation of calcium signaling, the major trigger for aldosterone production. Genetic causes of familial hyperaldosteronism have been expanded through the report of germline pathogenic variants in KCNJ5, CACNA1H and CLCN2 genes. Moreover, PDE2A and PDE3B variants were associated with bilateral PA and increased the spectrum of genetic etiologies of PA. Of great importance, the genetic investigation of adrenal lesions guided by the CYP11B2 staining strongly changed the landscape of somatic genetic findings of PA. Furthermore, CYP11B2 staining allowed the better characterization of the aldosterone-producing adrenal lesions in unilateral PA. Aldosterone production may occur from multiple sources, such as solitary aldosteronoma or aldosterone-producing nodule (classical histopathology) or clusters of autonomous aldosterone-producing cells without apparent neoplasia denominated aldosterone-producing micronodules (non-classical histopathology). Interestingly, KCNJ5 mutational status and classical histopathology of unilateral PA (aldosteronoma) have emerged as relevant predictors of clinical and biochemical outcome, respectively. In this review, we summarize the most recent advances in the pathogenesis of PA and discuss their impact on clinical outcome.

Genetic Alterations in Benign Adrenal Tumors

The genetic basis of most types of adrenal adenomas has been elucidated over the past decade, leading to the association of adrenal gland pathologies with specific molecular defects. Various genetic studies have established links between variants affecting the protein kinase A (PKA) signaling pathway and benign cortisol-producing adrenal lesions. Specifically, genetic alterations in GNAS, PRKAR1A, PRKACA, PRKACB, PDE11A, and PDE8B have been identified. The PKA signaling pathway was initially implicated in the pathogenesis of Cushing syndrome in studies aiming to understand the underlying genetic defects of the rare tumor predisposition syndromes, Carney complex, and McCune-Albright syndrome, both affected by the same pathway. In addition, germline variants in ARMC5 have been identified as a cause of primary bilateral macronodular adrenal hyperplasia. On the other hand, primary aldosteronism can be subclassified into aldosterone-producing adenomas and bilateral idiopathic hyperaldosteronism. Various genes have been reported as causative for benign aldosterone-producing adrenal lesions, including KCNJ5, CACNA1D, CACNA1H, CLCN2, ATP1A1, and ATP2B3. The majority of them encode ion channels or pumps, and genetic alterations lead to ion transport impairment and cell membrane depolarization which further increase aldosterone synthase transcription and aldosterone overproduction though activation of voltage-gated calcium channels and intracellular calcium signaling. In this work, we provide an overview of the genetic causes of benign adrenal tumors.

Primary Aldosteronism: Where Are We Now? Where to From Here?

Primary aldosteronism, the most common secondary form of hypertension, is thought to be present in ≈5% to 10% of hypertensive adults. However, recent studies indicate that its prevalence may be at least 3-fold higher based on the identification of renin-independent (autonomous) aldosterone production that is not suppressible with dietary sodium loading in a large fraction of adults with primary hypertension. Currently, the screening rate for primary aldosteronism in adults with primary hypertension is <1%. This review summarizes current thinking about primary aldosteronism from the standpoint of 3 key questions: Where are we now? Where to from here? So how do we get there?

Disorders of the adrenal cortex: Genetic and molecular aspects

Adrenal cortex produces glucocorticoids, mineralocorticoids and adrenal androgens which are essential for life, supporting balance, immune response and sexual maturation. Adrenocortical tumors and hyperplasias are a heterogenous group of adrenal disorders and they can be either sporadic or familial. Adrenocortical cancer is a rare and aggressive malignancy, and it is associated with poor prognosis. With the advance of next-generation sequencing technologies and improvement of genomic data analysis over the past decade, various genetic defects, either from germline or somatic origin, have been unraveled, improving diagnosis and treatment of numerous genetic disorders, including adrenocortical diseases. This review gives an overview of disorders associated with the adrenal cortex, the genetic factors of these disorders and their molecular implications.

Somatic mutations of GNA11 and GNAQ in CTNNB1-mutant aldosterone-producing adenomas presenting in puberty, pregnancy or menopause

Most aldosterone-producing adenomas (APAs) have gain-of-function somatic mutations of ion channels or transporters. However, their frequency in aldosterone-producing cell clusters of normal adrenal gland suggests a requirement for codriver mutations in APAs. Here we identified gain-of-function mutations in both CTNNB1 and GNA11 by whole-exome sequencing of 3/41 APAs. Further sequencing of known CTNNB1-mutant APAs led to a total of 16 of 27 (59%) with a somatic p.Gln209His, p.Gln209Pro or p.Gln209Leu mutation of GNA11 or GNAQ. Solitary GNA11 mutations were found in hyperplastic zona glomerulosa adjacent to double-mutant APAs. Nine of ten patients in our UK/Irish cohort presented in puberty, pregnancy or menopause. Among multiple transcripts upregulated more than tenfold in double-mutant APAs was LHCGR, the receptor for luteinizing or pregnancy hormone (human chorionic gonadotropin). Transfections of adrenocortical cells demonstrated additive effects of GNA11 and CTNNB1 mutations on aldosterone secretion and expression of genes upregulated in double-mutant APAs. In adrenal cortex, GNA11/Q mutations appear clinically silent without a codriver mutation of CTNNB1.

Aldosterone-producing adenoma-harbouring KCNJ5 mutations is associated with lower prevalence of metabolic disorders and abdominal obesity

OBJECTIVE

Aldosterone overproduction and lipid metabolic disturbances between idiopathic hyperaldosteronism (IHA) and unilateral aldosterone-producing adenoma (APA) have been inconsistently linked in patients with primary aldosteronism. Moreover, KCNJ5 mutations are prevalent among APAs and enhance aldosterone synthesis in adrenal cortex. We aimed to investigate the prevalence of metabolic syndrome (MetS) in each primary aldosteronism subtype and observe the role of KCNJ5 mutations among APAs on the distribution of abdominal adipose tissues quantified using computed tomography (CT), including their changes postadrenalectomy.

DESIGN AND METHODS

We retrospectively collected 244 and 177 patients with IHA and APA at baseline. Patients with APA had undergone adrenalectomy, and gene sequencing revealed the absence (n = 75) and presence (n = 102) of KCNJ5 mutations. We also recruited 31 patients with APA who had undergone CT-scan 1-year postadrenalectomy.

RESULTS

The patients with APA harbouring KCNJ5 mutations had significantly lower prevalence of MetS and smaller distribution in waist circumference, subcutaneous adipose tissue (SAT), and visceral adipose tissue (VAT) than the other groups. Logistic regression analysis indicated that the VAT area correlated significantly with KCNJ5 mutations among the APAs. Only participants with KCNJ5 mutations had significant increases in triglycerides, cholesterol, SAT, and VAT after 1-year postadrenalectomy.

CONCLUSION

This study is the first to demonstrate that MetS and abdominal obesity were less prevalent in the patients with APA harbouring KCNJ5 mutations compared with the IHA group and the non-KCNJ5-mutated APA group. Increasing prevalence of dyslipidaemia and abdominal obesity was observed in patients with KCNJ5 mutations 1-year postadrenalectomy.

GENETICS IN ENDOCRINOLOGY: Impact of race and sex on genetic causes of aldosterone-producing adenomas

Primary aldosteronism (PA) is a common cause of secondary hypertension. Recent technological advances in genetic analysis have provided a better understanding of the molecular pathogenesis of this disease. The application of next-generation sequencing has resulted in the identification of somatic mutations in aldosterone-producing adenoma (APA), a major subtype of PA. Based on the recent findings using a sequencing method that selectively targets the tumor region where aldosterone synthase (CYP11B2) is expressed, the vast majority of APAs appear to harbor a somatic mutation in one of the aldosterone-driver genes, including KCNJ5, ATP1A1, ATP2B3, CACNA1D, CACNA1H, and CLCN2. Mutations in these genes alter intracellular ion homeostasis and enhance aldosterone production. In a small subset of APAs, somatic activating mutations in the CTNNB1 gene, which encodes β-catenin, have also been detected. Accumulating evidence suggests that race and sex impact the somatic mutation spectrum of APA. Specifically, somatic mutations in the KCNJ5 gene, encoding an inwardly rectifying K+ channel, are common in APAs from Asian populations as well as women regardless of race. Associations between APA histology, genotype, and patient clinical characteristics have also been proposed, suggesting a potential need to consider race and sex for the management of PA patients. Herein, we review recent findings regarding somatic mutations in APA and discuss potential roles of race and sex on the pathophysiology of APA as well as possible clinical implications.

Trends in cause-related comorbidities in hospitalized patients with secondary hypertension in China from 2013 to 2016: a retrospective analysis of hospital quality monitoring system data

BACKGROUND

Secondary hypertension has emerged as a major public health problem in China. Early diagnosis and treatment can significantly improve the clinical outcomes. However, data on the current cause composition in China are seldom reported.

OBJECTIVE

To describe the trends in cause-related comorbidities in hospitalized patients with secondary hypertension in China from 2013 to 2016.

METHODS

This was a retrospective analysis based on the national Hospital Quality Monitoring System (HQMS) database, which collects information from the front pages of in-hospital medical records. Hospitalized patients with secondary hypertension from 746 tertiary hospitals that consistently uploaded data to the HQMS from 2013 to 2016 were enrolled. All diagnoses were identified using International Classification of Diseases version 10 (ICD-10) diagnostic codes. Descriptive analyses were used to determine the proportions of secondary hypertension causes and changing trends over 4 years.

RESULT

The study collected data on 402 371 hospitalized patients with secondary hypertension from the HQMS during 2013-2016. Secondary hypertension caused by renal parenchymal disease ranked first and accounted for more than 50%. Obstructive sleep apnea syndrome (OSAS) followed closely with a rate of approximately 25%. Primary aldosteronism presented the highest proportion among all causes of endocrine hypertension. Regarding longitudinal changes over time, the rates of renal hypertension showed a significant downward trend from 2013 to 2016 (P < 0.001). In contrast, OSAS, endocrine hypertension, renal vascular disease, and aorta diseases maintained a significant upward trend from 2013 to 2016 (P < 0.001). The rates of these diseases in women with common secondary hypertension was higher than that of men, except in patients with OSAS (P < 0.001). In addition, renal parenchymal diseases and renal vascular diseases gradually decreased with age, whereas OSAS and aortic diseases gradually increased with age. The proportion of endocrine hypertension in the middle-aged group was higher than the other two age groups.

CONCLUSION

The study provides important information on the changing trends of cause rate of secondary hypertension modified by age and sex in China during 2013-2016. Renal parenchymal disease is still the most common cause of secondary hypertension with a decreasing trend, followed by OSAS with an increasing trend.

Update on Genetics of Primary Aldosteronism

Primary aldosteronism (PA) is the most common form of secondary hypertension, with a prevalence of 5–10% among patients with hypertension. PA is mainly classified into two subtypes: aldosterone-producing adenoma (APA) and bilateral idiopathic hyperaldosteronism. Recent developments in genetic analysis have facilitated the discovery of mutations in KCNJ5, ATP1A1, ATP2B3, CACNA1D, CACNA1H, CLCN2, and CTNNB1 in sporadic or familial forms of PA in the last decade. These findings have greatly advanced our understanding of the mechanism of excess aldosterone synthesis, particularly in APA. Most of the causative genes encode ion channels or pumps, and their mutations lead to depolarization of the cell membrane due to impairment of ion transport. Depolarization activates voltage-gated Ca²⁺ channels and intracellular calcium signaling and promotes the transcription of aldosterone synthase, resulting in overproduction of aldosterone. In this article, we review recent findings on the genetic and molecular mechanisms of PA.

Primary aldosteronism

In 1955 Dr Jerome Conn first documented primary aldosteronism (PA). Since then, screening, diagnosis and treatment have developed, in the process both refining and complicating management. Currently, screening requires 4-6 weeks of lead-up, including major changes in antihypertensive therapy, followed by a blood draw for plasma aldosterone concentration (PAC) and plasma renin activity (PRA) or concentration (PRC). Screening is considered indicative of PA on the basis of the PAC and the aldosterone to renin ratio (ARR). This is then followed by one or more of 6 confirmatory/exclusion tests. Three things have changed. First is now incontrovertible evidence that a single spot PAC is a deeply flawed index of true aldosterone status, so that many referred patients with PA fall at the first hurdle. A valid index of aldosterone status is an integrated value, measured as urinary aldosterone excretion (UEA) over 24 h. On the basis of the UEA, the prevalence of PA appears to be 3-5 times higher than the currently accepted figure of 5-10% of hypertensives. The second is the recognition that inadequately treated PA has a cardiovascular risk profile ~threefold that of matched essential hypertensives. Third is the realization that <1% of hypertensives are ever screened for PA, who are thus in double jeopardy for the risks of untreated PA on top of those for hypertension per se. Taken together, this a major if occult public health issue; if it is to be addressed, radical changes in management are needed. Some are in screening, which needs to be simply done on all newly-presenting hypertensives; others are major simplifications of screening in established hypertension. The front-line actors need to be Internists/Primary Care Providers; the costs will be significant, but much less than those of increased morbidity/premature mortality in unrecognized PA. Possible suggestions as to how best to address this constitute the final chapter of this article.

Molecular Genetic and Genomic Alterations in Cushing's Syndrome and Primary Aldosteronism

The genetic alterations that cause the development of glucocorticoid and/or mineralocorticoid producing benign adrenocortical tumors and hyperplasias have largely been elucidated over the past two decades through advances in genomics. In benign aldosterone-producing adrenocortical tumors and hyperplasias, alteration of intracellular calcium signaling has been found to be significant in aldosterone hypersecretion, with causative defects including those in KCNJ5, ATP1A1, ATP2B3, CACNA1D, CACNA1H, and CLCN2. In benign cortisol-producing adrenocortical tumors and hyperplasias abnormal cyclic adenosine monophosphate-protein kinase A signaling has been found to play a central role in tumorigenesis, with pathogenic variants in GNAS, PRKAR1A, PRKACA, PRKACB, PDE11A, and PDE8B being implicated. The role of this signaling pathway in the development of Cushing's syndrome and adrenocortical tumors was initially discovered through the study of the underlying genetic defects causing the rare multiple endocrine neoplasia syndromes McCune-Albright syndrome and Carney complex with subsequent identification of defects in genes affecting the cyclic adenosine monophosphate-protein kinase A pathway in sporadic tumors. Additionally, germline pathogenic variants in ARMC5, a putative tumor suppressor, were found to be a cause of cortisol-producing primary bilateral macronodular adrenal hyperplasia. This review describes the genetic causes of benign cortisol- and aldosterone-producing adrenocortical tumors.

Unravelling the Genetic Basis of Primary Aldosteronism

Primary aldosteronism (PA), a condition characterized by autonomous aldosterone hypersecretion, constitutes the most common cause of secondary hypertension. Over the last decade, major breakthroughs have been made in the field of genetics underpinning PA. The advent and wide application of Next Generation Sequencing (NGS) technology led to the identification of several somatic and germline mutations associated with sporadic and familial forms of PA. Somatic mutations in ion-channel genes that participate in aldosterone biosynthesis, including KCNJ5, CACNA1D, ATP1A1, and ATP2B3, have been implicated in the development of aldosterone-producing adenomas (APAs). On the other hand, germline variants in CLCN2, KCNJ5, CACNA1H, and CACNA1D genes have been implicated in the pathogenesis of the familial forms of PA, FH-II, FH-III, and F-IV, as well as PA associated with seizures and neurological abnormalities. However, recent studies have shown that the prevalence of PA is higher than previously thought, indicating the need for an improvement of our diagnostic tools. Further research is required to recognize mild forms of PA and to investigate the underlying molecular mechanisms.

What Did We Learn from the Molecular Biology of Adrenal Cortical Neoplasia? From Histopathology to Translational Genomics

Approximately one-tenth of the general population exhibit adrenal cortical nodules, and the incidence has increased. Afflicted patients display a multifaceted symptomatology-sometimes with rather spectacular features. Given the general infrequency as well as the specific clinical, histological, and molecular considerations characterizing these lesions, adrenal cortical tumors should be investigated by endocrine pathologists in high-volume tertiary centers. Even so, to distinguish specific forms of benign adrenal cortical lesions as well as to pinpoint malignant cases with the highest risk of poor outcome is often challenging using conventional histology alone, and molecular genetics and translational biomarkers are therefore gaining increased attention as a possible discriminator in this context. In general, our understanding of adrenal cortical tumorigenesis has increased tremendously the last decade, not least due to the development of next-generation sequencing techniques. Comprehensive analyses have helped establish the link between benign aldosterone-producing adrenal cortical proliferations and ion channel mutations, as well as mutations in the protein kinase A (PKA) signaling pathway coupled to cortisol-producing adrenal cortical lesions. Moreover, molecular classifications of adrenal cortical tumors have facilitated the distinction of benign from malignant forms, as well as the prognostication of the individual patients with verified adrenal cortical carcinoma, enabling high-resolution diagnostics that is not entirely possible by histology alone. Therefore, combinations of histology, immunohistochemistry, and next-generation multi-omic analyses are all needed in an integrated fashion to properly distinguish malignancy in some cases. Despite significant progress made in the field, current clinical and pathological challenges include the preoperative distinction of non-metastatic low-grade adrenal cortical carcinoma confined to the adrenal gland, adoption of individualized therapeutic algorithms aligned with molecular and histopathologic risk stratification tools, and histological confirmation of functional adrenal cortical disease in the context of multifocal adrenal cortical proliferations. We herein review the histological, genetic, and epigenetic landscapes of benign and malignant adrenal cortical neoplasia from a modern surgical endocrine pathology perspective and highlight key mechanisms of value for diagnostic and prognostic purposes.

Approaches to Gene Mutation Analysis Using Formalin-Fixed Paraffin-Embedded Adrenal Tumor Tissue From Patients With Primary Aldosteronism

Aldosterone production is physiologically under the control of circulating potassium and angiotensin II as well as adrenocorticotropic hormone and other secretagogues such as serotonin. The adrenal's capacity to produce aldosterone relies heavily on the expression of a single enzyme, aldosterone synthase (CYP11B2). This enzyme carries out the final reactions in the synthesis of aldosterone and is expressed almost solely in the adrenal zona glomerulosa. From a disease standpoint, primary aldosteronism (PA) is the most common of all adrenal disorders. PA results from renin-independent adrenal expression of CYP11B2 and production of aldosterone. The major causes of PA are adrenal aldosterone-producing adenomas (APA) and adrenal idiopathic hyperaldosteronism. Our understanding of the genetic causes of APA has significantly improved through comprehensive genetic profiling with next-generation sequencing. Whole-exome sequencing has led to the discovery of mutations in six genes that cause renin-independent aldosterone production and thus PA. To facilitate broad-based prospective and retrospective studies of APA, recent technologic advancements have allowed the determination of tumor mutation status using formalin-fixed paraffin-embedded (FFPE) tissue sections. This approach has the advantages of providing ready access to archival samples and allowing CYP11B2 immunohistochemistry-guided capture of the exact tissue responsible for inappropriate aldosterone synthesis. Herein we review the methods and approaches that facilitate the use of adrenal FFPE material for DNA capture, sequencing, and mutation determination.

Adrenal Incidentaloma

An adrenal incidentaloma is now established as a common endocrine diagnosis that requires a multidisciplinary approach for effective management. The majority of patients can be reassured and discharged, but a personalized approach based upon image analysis, endocrine workup, and clinical symptoms and signs are required in every case. Adrenocortical carcinoma remains a real concern but is restricted to <2% of all cases. Functional adrenal incidentaloma lesions are commoner (but still probably <10% of total) and the greatest challenge remains the diagnosis and optimum management of autonomous cortisol secretion. Modern-day surgery has improved outcomes and novel radiological and urinary biomarkers will improve early detection and patient stratification in future years to come.

Ion Channel Function and Electrical Excitability in the Zona Glomerulosa: A Network Perspective on Aldosterone Regulation

Aldosterone excess is a pathogenic factor in many hypertensive disorders. The discovery of numerous somatic and germline mutations in ion channels in primary hyperaldosteronism underscores the importance of plasma membrane conductances in determining the activation state of zona glomerulosa (zG) cells. Electrophysiological recordings describe an electrically quiescent behavior for dispersed zG cells. Yet, emerging data indicate that in native rosette structures in situ, zG cells are electrically excitable, generating slow periodic voltage spikes and coordinated bursts of Ca²⁺ oscillations. We revisit data to understand how a multitude of conductances may underlie voltage/Ca²⁺ oscillations, recognizing that zG layer self-renewal and cell heterogeneity may complicate this task. We review recent data to understand rosette architecture and apply maxims derived from computational network modeling to understand rosette function. The challenge going forward is to uncover how the rosette orchestrates the behavior of a functional network of conditional oscillators to control zG layer performance and aldosterone secretion.

Prevalence of Somatic Mutations in Aldosterone-Producing Adenomas in Japanese Patients

CONTEXT

Results of previous studies demonstrated clear racial differences in the prevalence of somatic mutations among patients with aldosterone-producing adenoma (APA). For instance, those in East Asian countries have a high prevalence of somatic mutations in KCNJ5, whereas somatic mutations in other aldosterone-driving genes are rare.

OBJECTIVES

To determine somatic mutation prevalence in Japanese APA patients using an aldosterone synthase (CYP11B2) immunohistochemistry (IHC)-guided sequencing approach.

METHOD

Patients with a unilateral form of primary aldosteronism who underwent adrenalectomy at the Tohoku University Hospital were studied. Based on CYP11B2 immunolocalization of resected adrenals, genomic DNA was isolated from the relevant positive area of 10% formalin-fixed, paraffin-embedded tissue of the APAs. Somatic mutations in aldosterone-driving genes were studied in APAs by direct Sanger sequencing and targeted next-generation sequencing.

RESULTS

CYP11B2 IHC-guided sequencing determined APA-related somatic mutations in 102 out of 106 APAs (96%). Somatic KCNJ5 mutation was the most frequent genetic alteration (73%) in this cohort of Japanese patients. Somatic mutations in other aldosterone-driving genes were also identified: CACNA1D (14%), ATP1A1 (5%), ATP2B3 (4%), and CACNA1H (1%), including 2 previously unreported mutations. KCNJ5 mutations were more often detected in APAs from female patients compared with those from male patients [95% (36/38) vs 60% (41/68); P < 0.0001].

CONCLUSION

IHC-guided sequencing defined somatic mutations in over 95% of Japanese APAs. While the dominance of KCNJ5 mutations in this particular cohort was confirmed, a significantly higher KCNJ5 prevalence was detected in female patients. This study provides a better understanding of genetic spectrum of Japanese APA patients.

Minimally invasive partial versus total adrenalectomy for unilateral primary hyperaldosteronism-a retrospective, multicenter matched-pair analysis using the new international consensus on outcome measures

BACKGROUND

Primary hyperaldosteronism is a recognized risk factor for myocardial infarction, stroke, and atrial fibrillation. Minimally invasive adrenalectomy is the first-line treatment for localized primary hyperaldosteronism. Whether minimally invasive adrenalectomy should be performed using a cortex-sparing technique (partial minimally invasive adrenalectomy) or not (total minimally invasive adrenalectomy) remains a subject of debate. The aim of our study was to evaluate the clinical and biochemical efficacy of both procedures and to examine the morbidity associated with partial minimally invasive adrenalectomy versus total minimally invasive adrenalectomy in a multicenter study.

METHODS

Using a retrospective study design, we determined the efficacy, morbidity, and mortality of partial minimally invasive adrenalectomy and total minimally invasive adrenalectomy. The Primary Aldosteronism Surgical Outcome Study classification was used to explore clinical and biochemical success. Matched-pair analysis was used in order to address possible bias.

RESULTS

We evaluated 234 matched patients with unilateral primary hyperaldosteronism: 78 (33.3%) underwent partial minimally invasive adrenalectomy, and 156 (66.7%) were treated with total minimally invasive adrenalectomy. Complete clinical success was achieved in 40.6%, and partial clinical success in an additional 52.6% of patients in the entire cohort. Complete biochemical success was seen in 94.0% of patients. Success rates and the incidence of perioperative complications were comparable between groups. Both postoperative hypocortisolism (11.5% vs 25.0% after partial minimally invasive adrenalectomy and total minimally invasive adrenalectomy, respectively; P < .001) and postoperative hypoglycemia (2.6% vs 7.1% after partial minimally invasive adrenalectomy and total minimally invasive adrenalectomy; P = .039) occurred more frequently after total minimally invasive adrenalectomy.

CONCLUSION

Our study provides evidence that patients with unilateral primary hyperaldosteronism are good surgical candidates for partial minimally invasive adrenalectomy. Not only is the surgical outcome comparable to that of total minimally invasive adrenalectomy, but also postsurgical morbidity, particularly in terms of hypocortisolism and hypoglycemia, may be reduced.

Biochemical, Histopathological, and Genetic Characterization of Posture-Responsive and Unresponsive APAs

CONTEXT AND OBJECTIVE

Posture-responsive and posture-unresponsive aldosterone-producing adenomas (APAs) account for approximately 40% and 60% of APAs, respectively. Somatic gene mutations have been recently reported to exist in approximately 90% of APAs. This study was designed to characterize the biochemical, histopathologic, and genetic properties of these 2 types of APA.

METHODS

Plasma levels of aldosterone and hybrid steroids (18-oxocortisol and 18-hydroxycortisol) were measured by liquid chromatography-tandem mass spectrometry. Immunohistochemistry for CYP11B2 (aldosterone synthase) and CYP17A1 (17α-hydroxylase) and deoxyribonucleic acid sequencing (Sanger and next-generation sequencing) were performed on APA tissue collected from 23 posture-unresponsive and 17 posture-responsive APA patients.

RESULTS

Patients with posture-unresponsive APA displayed higher (P < 0.01) levels of hybrid steroids, recumbent aldosterone and cortisol, larger (P < 0.01) zona fasciculata (ZF)-like tumors with higher (P < 0.01) expression of CYP17A1 (but not of CYP11B2) than patients with posture-responsive APA (most of which were not ZF-like). Of 40 studied APAs, 37 (92.5%) were found to harbor aldosterone-driving somatic mutations (KCNJ5 = 14 [35.0%], CACNA1D = 13 [32.5%], ATP1A1 = 8 [20.0%], and ATP2B3 = 2 [5.0%]), including 5 previously unreported mutations (3 in CACNA1D and 2 in ATP1A1). Notably, 64.7% (11/17) of posture-responsive APAs carried CACNA1D mutations, whereas 56.5% (13/23) of posture-unresponsive APAs harbored KCNJ5 mutations.

CONCLUSIONS

The elevated production of hybrid steroids by posture-unresponsive APAs may relate to their ZF-like tumor cell composition, resulting in expression of CYP17A1 (in addition to somatic gene mutation-driven CYP11B2 expression), thereby allowing production of cortisol, which acts as the substrate for CYP11B2-generated hybrid steroids.

Aldosterone-Mediated Sodium Retention Is Reflected by the Serum Sodium to Urinary Sodium to (Serum Potassium)2 to Urinary Potassium (SUSPPUP) Index

The serum sodium to urinary sodium ratio divided by the (serum potassium)² to urinary potassium ratio (SUSPPUP formula) reflects aldosterone action. We here prospectively investigated into the usefulness of the SUSPPUP ratio as a diagnostic tool in primary hyperaldosteronism. Parallel measurements of serum and urinary sodium and potassium concentrations (given in mmol/L) in the fasting state were done in 225 patients. Of them, 69 were diagnosed with primary aldosteronism (PA), 102 with essential hypertension (EH), 26 with adrenal insufficiency (AI) and 28 did not suffer from the above-mentioned disorders and were assigned to the reference group (REF). The result of the SUSPPUP formula was highest in the PA group (7.4, 4.2–12.3 L/mmol), followed by EH (3.2, 2.3–4.3 L/mmol), PA after surgery (3.9, 3.0–6.0 L/mmol), REF (3.4 ± 1.4 L/mmol) and AI (2.9 +/− 1.2 L/mmol). The best sensitivity in distinguishing PA from EH was reached by multiplication of the aldosterone to renin-ratio (ARR) with the SUSPPUP formula (92.7% at a cut off > 110 L/mmol), highest specificity was reached by the SUSPPUP determinations (87.2%). The integration of the SUSPPUP ratio into the ARR helps to improve the diagnosis of hyperaldosteronism substantially.

Developments in Primary Aldosteronism Subtyping Using Steroid Profiling

Adrenal venous sampling is the standard of care for identifying patients with unilateral primary aldosteronism, which is often caused by an aldosterone producing adenoma and can be cured with surgery. The numerous limitations of adrenal venous sampling, including its high cost, scarce availability, technical challenges, and lack of standardized protocols, have driven efforts to develop alternative, non-invasive tools for the diagnosis of aldosterone producing adenomas. Seminal discoveries regarding the pathogenesis of aldosterone producing adenomas made over the past decade have leveraged hypotheses-driven research of steroid phenotypes characteristic of various aldosterone producing adenomas. In parallel, the expanding availability of mass spectrometry has enabled the simultaneous quantitation of many steroids in single assays from small volume biosamples. Steroid profiling has contributed to our evolving understanding about the pathophysiology of primary aldosteronism and its subtypes. Herein, we review the current state of knowledge regarding the application of multi-steroid panels in assisting with primary aldosteronism subtyping.

Primary Aldosteronism: Where Are We Now? Where to from Here?

The past nine years have seen major advances in establishing the etiology of unilateral primary aldosteronism, and very possibly that of bilateral hyperaldosteronism, in response to somatic mutations in aldosterone synthase expressing cells. Though there have been important advances in the management of primary aldosteronism, in small but convincing studies, they represent minor changes to current guidelines. What has been totally absent is consideration of the public health issue that primary aldosterone represents, and the public policy issues that would be involved in addressing the disorder. In his introduction to PiPA 6, Martin Reincke calculated that only one in a thousand patients in Germany with primary aldosteronism were treated appropriately, an astounding figure for any disease in the 21st century. Towards remedying this totally unacceptable public health issue, the author proposes a radical simplification and streamlining of screening for primary aldosteronism, and the management of most patients by general practitioners. The second bottle-neck in current management is that of mandatory adrenal venous sampling for all but 1-2% of patients, a costly procedure requiring rare expertise. Ideally, it should be reserved - on the basis of likelihood, enhanced imaging, or peripheral steroid profiles - for a small minority of patients with clear evidence for unilateral disease. Only when costs are minimized and roadblocks removed will primary aldosteronism be properly treated as the public health issue that it is.

Adrenocortical tumorigenesis: Lessons from genetics

Advances in genomics over the past two decades have allowed for elucidation of the genetic alterations leading to the development of adrenocortical tumors and/or hyperplasias. These molecular changes were initially discovered through the study of rare familial tumor syndromes such as McCune-Albright Syndrome, Carney complex, Li-Fraumeni syndrome, and Beckwith-Wiedemann syndrome, with the identification of alterations in genes and molecular pathways that subsequently led to the discovery of aberrations in these or related genes and pathways in sporadic tumors. Genetic alterations in GNAS, PRKAR1A, PRKACA, PRKACB, PDE11A, and PDE8B, that lead to aberrant cyclic adenosine monophosphate-protein (cAMP) kinase A signaling, were found to play a major role in the development of benign cortisol-producing adrenocortical tumors and/or hyperplasias, whereas genetic defects in KCNJ5, ATP1A1, ATP2B3, CACNA1D, CACNA1H, and CLCN2 were implicated in the development of benign aldosterone-producing tumors and/or hyperplasias through modification of intracellular calcium signaling. Germline ARMC5 defects were found to cause the development of primary bilateral macronodular adrenocortical hyperplasia with glucocorticoid and/or mineralocorticoid oversecretion. Adrenocortical carcinoma was linked primarily to aberrant p53 signaling and/or Wnt-β-catenin signaling, as well as IGF2 overexpression, with frequent genetic alterations in TP53, ZNRF3, CTNNB1, and 11p15. This review focuses on the genetic underpinnings of benign cortisol- and aldosterone-producing adrenocortical tumors/hyperplasias and adrenocortical carcinoma.

Primary aldosteronism diagnostics: KCNJ5 mutations and hybrid steroid synthesis in aldosterone-producing adenomas

Primary aldosteronism (PA) is characterized by autonomous aldosterone production by renin-independent mechanisms and is most commonly sporadic. While 60-70% of sporadic PA can be attributed to bilateral hyperaldosteronism, the remaining 30-40% is caused by a unilateral aldosterone-producing adenoma (APA). Somatic mutations in or near the selectivity filter the KCNJ5 gene (encoding the potassium channel GIRK4) have been implicated in the pathogenesis of both sporadic and familial PA. Several studies using tumor tissue, peripheral and adrenal vein samples from PA patients have demonstrated that along with aldosterone, the hybrid steroids 18-hydroxycortisol (18OHF) and 18-oxocortisol (18oxoF) are a hallmark of APA harboring KCNJ5 mutations. Herein, we review the recent advances with respect to the molecular mechanisms underlying the pathogenesis of PA and the steroidogenic fingerprints of KCNJ5 mutations. In addition, we present an outlook toward the future of PA subtyping and diagnostic work-up utilizing steroid profiling.

Genetic, Cellular, and Molecular Heterogeneity in Adrenals With Aldosterone-Producing Adenoma

Supplemental Digital Content is available in the text.

Aldosterone-producing adenoma (APA) cause primary aldosteronism—the most frequent form of secondary hypertension. Somatic mutations in genes coding for ion channels and ATPases are found in APA and in aldosterone-producing cell clusters. We investigated the genetic, cellular, and molecular heterogeneity of different aldosterone-producing structures in adrenals with APA, to get insight into the mechanisms driving their development and to investigate their clinical and biochemical correlates. Genetic analysis of APA, aldosterone-producing cell clusters, and secondary nodules was performed in adrenal tissues from 49 patients by next-generation sequencing following CYP11B2 immunohistochemistry. Results were correlated with clinical and biochemical characteristics of patients, steroid profiles, and histological features of the tumor and adjacent adrenal cortex. Somatic mutations were identified in 93.75% of APAs. Adenoma carrying KCNJ5 mutations had more clear cells and cells expressing CYP11B1, and fewer cells expressing CYP11B2 or activated β-catenin, compared with other mutational groups. 18-hydroxycortisol and 18-oxocortisol were higher in patients carrying KCNJ5 mutations and correlated with histological features of adenoma; however, mutational status could not be predicted using steroid profiling. Heterogeneous CYP11B2 expression in KCNJ5-mutated adenoma was not associated with genetic heterogeneity. Different mutations were identified in secondary nodules expressing aldosterone synthase and in independent aldosterone-producing cell clusters from adrenals with adenoma; known KCNJ5 mutations were identified in 5 aldosterone-producing cell clusters. Genetic heterogeneity in different aldosterone-producing structures in the same adrenal suggests complex mechanisms underlying APA development.

Old and new genes in primary aldosteronism

Primary aldosteronism (PA) is the most common form of secondary hypertension affecting 5%-10% of patients with arterial hypertension. In PA, high blood pressure is associated with high aldosterone and low renin levels, and often hypokalemia. In a majority of cases, autonomous aldosterone production by the adrenal gland is caused by an aldosterone producing adenoma (APA) or bilateral adrenal hyperplasia (BAH). During the last ten years, a better knowledge of the pathophysiology of PA came from the discovery of somatic and germline mutations in different genes in both sporadic and familial forms of the disease. Those genes code for ion channels and pumps, as well as proteins involved in adrenal cortex development and function. Targeted next generation sequencing following immunohistochemistry guided detection of aldosterone synthase expression allows detection of somatic mutations in up to 90% of APA, while whole exome sequencing has discovered the genetic causes of four different familial forms of PA. The identification, in BAH, of somatic mutations in aldosterone producing cell clusters open new perspectives in our understanding of the bilateral form of the disease and the development of new therapeutic approaches.

Molecular and Electrophysiological Analyses of ATP2B4 Gene Variants in Bilateral Adrenal Hyperaldosteronism

Primary aldosteronism (PA) is the most common cause of secondary hypertension with a high prevalence among patients with resistant hypertension. Despite the recent discovery of somatic variants in aldosterone-producing adenoma (APA)-associated PA, causes for PA due to bilateral aldosterone production (bilateral hyperaldosteronism; BHA) remain unknown. Herein, we identified rare gene variants in ATP2B4, in a cohort of patients with BHA. ATP2B4 belongs to the same family of Ca-ATPases as ATP2B3, which is involved in the pathogenesis of APA. Endogenous ATP2B4 expression was characterized in adrenal tissue, and the gene variants were functionally analyzed for effects on aldosterone synthase (CYP11B2) expression, steroid production in basal and agonist-stimulated conditions, and for changes in biophysical properties of channel properties. Knockdown of ATP2B4 in HAC15 exhibited reduced angiotensin II stimulation in one of four shRNA clones. Stable HAC15 cell lines with doxycycline (dox) - inducible wild-type and variant forms of ATP2B4 - were generated, and dox-induced upregulation of ATP2B4 mRNA and protein was confirmed. However, ATP2B4 variants did not alter basal or agonist-stimulated CYP11B2 expression. Whole-cell recordings in HAC15 cells indicated robust endogenous ATP2B4 conductance in native cells but reduced conductance with overexpressed WT and variant ATP2B4. The previously defined PA-causing ATP2B3 variant served as a positive control and exhibited elevated CYP11B2 mRNA. In conclusion, while this study did not confirm a pathogenic role for ATP2B4 variants in BHA, we describe the sequencing analysis for familial and sporadic BHA and outline a template for the thorough in vitro characterization of gene variants.

The Effects of Different Calcium Channel Blockers on Aldosterone-Producing Adenoma Cells

Purpose: The aim of this study is to examine the effects of different kinds of calcium channel blockers (CCBs) on primary aldosterone-producing adenoma (APA) mainly with KCNJ5 mutations. Primary cultured APA cells were treated with different calcium channel blockers (L/T type CCB benidipine, T-type CCB mibefradil and L-type CCB nifedipine), and aldosterone secretagogues with or without nifedipine. Aldosterone level, aldosterone synthase (CYP11B2) mRNA expression and cell proliferation were detected. The results showed that all three CCBs significantly inhibit aldosterone secretion and CYP11B2 mRNA expression. Benidipine was relatively more effective than mibefradil or nifedipine. In addition, only mibefradil marginally inhibited cell proliferation. Adrenocorticotropin (ACTH) had a much stronger effect in stimulating aldosterone secretion and promoting cell proliferation from APA's than angiotensin II (ATII). Different from ACTH and ATII, potassium had no effect. Nifedipine inhibited the basal and ACTH-, ATII-elicited aldosterone secretion. Twenty three of 24 APAs had somatic KCNJ5 mutation. In conclusion, benidipine, mibefradil and nifedipine significantly inhibit aldosterone secretion in primary cultured APA cells.

[Primary aldosteronism : Genetics and pathology]

BACKGROUND

Primary aldosteronism, the excessive production of the steroid hormone aldosterone, is the most common cause of secondary hypertension. Common subforms include bilateral adrenal hyperplasia and aldosterone-producing adenoma.

OBJECTIVES

The goal of this review is to summarize important publications on the genetic basis of primary aldosteronism.

RESULTS

Somatic mutations in the KCNJ5, CACNA1D, ATP1A1, and ATP2B3 genes have been described as causes of aldosterone-producing adenomas. They eventually all lead to increased cellular calcium influx and aldosterone production. The mechanisms of rare CTNNB1 mutations are less defined. Correlations between mutations and different histologic characteristics as well as gender and ethnicity remain unexplained. Recent publications suggest that bilateral hyperplasia is at least partially due to so-called aldosterone-producing cell clusters, often with mutations in CACNA1D. Rare familial forms show mutations in the CYP11B2, CLCN2, KCNJ5, CACNA1H, or CACNA1D genes.

CONCLUSIONS

These results suggest that a significant fraction of primary aldosteronism is due to somatic mutations in single genes.

Genetic causes of primary aldosteronism

Primary aldosteronism is characterized by at least partially autonomous production of the adrenal steroid hormone aldosterone and is the most common cause of secondary hypertension. The most frequent subforms are idiopathic hyperaldosteronism and aldosterone-producing adenoma. Rare causes include unilateral hyperplasia, adrenocortical carcinoma and Mendelian forms (familial hyperaldosteronism). Studies conducted in the last eight years have identified somatic driver mutations in a substantial portion of aldosterone-producing adenomas, including the genes KCNJ5 (encoding inwardly rectifying potassium channel GIRK4), CACNA1D (encoding a subunit of L-type voltage-gated calcium channel Ca_V1.3), ATP1A1 (encoding a subunit of Na⁺/K⁺-ATPase), ATP2B3 (encoding a Ca²⁺-ATPase), and CTNNB1 (encoding ß-catenin). In addition, aldosterone-producing cells were recently reported to form small clusters (aldosterone-producing cell clusters) beneath the adrenal capsule. Such clusters accumulate with age and appear to be more frequent in individuals with idiopathic hyperaldosteronism. The fact that they are associated with somatic mutations implicated in aldosterone-producing adenomas also suggests a precursor function for adenomas. Rare germline variants of CYP11B2 (encoding aldosterone synthase), CLCN2 (encoding voltage-gated chloride channel ClC-2), KCNJ5, CACNA1H (encoding a subunit of T-type voltage-gated calcium channel Ca_V3.2), and CACNA1D have been reported in different subtypes of familial hyperaldosteronism. Collectively, these studies suggest that primary aldosteronism is largely due to genetic mutations in single genes, with potential implications for diagnosis and therapy.

Adrenalectomy Completely Cured Hypertension in Patients With Familial Hyperaldosteronism Type I Who Had Somatic KCNJ5 Mutation

CONTEXT

Familial hyperaldosteronism type I (FH-I) or glucocorticoid-remediable aldosteronism (GRA) is caused by unequal crossing over of the steroid 11β-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) genes. Somatic KCNJ5 mutations have not been reported in patients with GRA; therefore, the appropriate treatment and prognosis of such concurrent cases remain unknown.

CASE DESCRIPTION

Two siblings of a Taiwanese family with GRA were found to have adrenal adenomas and somatic KCNJ5 mutations. Complete clinical cure was achieved after unilateral adrenalectomy. Furthermore, the conversion site of the chimeric gene was identified by direct sequencing.

CONCLUSIONS

We report the coexistence of a somatic KCNJ5 mutation and GRA. Patients with GRA whose blood pressure management develops resistance to glucocorticoid treatment could therefore benefit from a lateralization test. The promising outcomes after unilateral adrenalectomy presented in this report offer new perspectives for further research into various PA subtypes.

A Diagnostic Approach to Adrenocortical Tumors

Adrenocortical tumors range from primary bilateral micronodular or macronodular forms of adrenocortical disease to conventional adrenocortical adenomas and carcinomas. Accurate classification of these neoplasms is critical given the varied pathogenesis, clinical behavior, and outcome of these different lesions. Confirmation of adrenocortical origin, diagnosing malignancy, providing relevant prognostic information in adrenocortical carcinoma, and correlation of laboratory results with clinicopathologic findings are among the important responsibilities of pathologists who evaluate these lesions. This article focuses on a practical approach to the evaluation of adrenocortical tumors with an emphasis on clinical and imaging findings, morphologic characteristics, and multifactorial diagnostic schemes and algorithms.

Primary Aldosteronism: KCNJ5 Mutations and Adrenocortical Cell Growth

Aldosterone-producing adenomas with somatic mutations in the KCNJ5 G-protein-coupled inwardly rectifying potassium channel are a cause of primary aldosteronism. These mutations drive aldosterone excess, but their role in cell growth is undefined. Our objective was to determine the role of KCNJ5 mutations in adrenal cell proliferation and apoptosis. The Ki67 proliferative index was positively correlated with adenoma diameter in aldosterone-producing adenomas with a KCNJ5 mutation (r=0.435, P=0.007), a negative correlation was noted in adenomas with no mutation detected (r=-0.548, P=0.023). Human adrenocortical cell lines were established with stable expression of cumate-inducible wild-type or mutated KCNJ5. Increased cell proliferation was induced by low-level induction of KCNJ5-T158A expression compared with control cells (P=0.009), but increased induction ablated this difference. KCNJ5-G151R displayed no apparent proliferative effect, but KCNJ5-G151E and L168R mutations each resulted in decreased cell proliferation (difference P<0.0001 from control cells, both comparisons). Under conditions tested, T158A had no effect on apoptosis, but apoptosis increased with expression of G151R (P<0.0001), G151E (P=0.008), and L168R (P<0.0001). We generated a specific KCNJ5 monoclonal antibody which was used in immunohistochemistry to demonstrate strong KCNJ5 expression in adenomas without a KCNJ5 mutation and in the zona glomerulosa adjacent to adenomas irrespective of genotype as well as in aldosterone-producing cell clusters. Double immunofluorescence staining for KCNJ5 and CYP11B2 (aldosterone synthase) showed markedly decreased KCNJ5 immunostaining in CYP11B2-positive cells compared with CYP11B2-negative cells in aldosterone-producing adenomas with a KCNJ5 mutation. Together, these findings support the concept that cell growth effects of KCNJ5 mutations are determined by the expression level of the mutated channel.

RNA Sequencing Provides Novel Insights into the Transcriptome of Aldosterone Producing Adenomas

Aldosterone producing adenomas (APAs) occur in the adrenal glands of around 30% of patients with primary aldosteronism, the most common form of secondary hypertension. Somatic mutations in KCNJ5, ATP1A1, ATP2B3, CACNA1D and CTNNB1 have been described in ~60% of these tumours. We subjected 15 aldosterone producing adenomas (13 with known mutations and two without) to RNA Sequencing and Whole Genome Sequencing (n = 2). All known mutations were detected in the RNA-Seq reads, and mutations in ATP2B3 (G123R) and CACNA1D (S410L) were discovered in the tumours without known mutations. Adenomas with CTNNB1 mutations showed a large number of differentially expressed genes (1360 compared to 106 and 75 for KCNJ5 and ATP1A1/ATP2B3 respectively) and clustered together in a hierarchical clustering analysis. RT-PCR in an extended cohort of 49 APAs confirmed higher expression of AFF3 and ISM1 in APAs with CTNNB1 mutations. Investigation of the expression of genes involved in proliferation and apoptosis revealed subtle differences between tumours with and without CTNNB1 mutations. Together our results consolidate the notion that CTNNB1 mutations characterize a distinct subgroup of APAs.

Immunohistopathology and Steroid Profiles Associated With Biochemical Outcomes After Adrenalectomy for Unilateral Primary Aldosteronism

Unilateral primary aldosteronism (PA) is the most common surgically curable form of hypertension that must be accurately differentiated from bilateral PA for therapeutic management (surgical versus medical). Adrenalectomy results in biochemical cure (complete biochemical success) in almost all patients diagnosed with unilateral PA; the remaining patients with partial or absent biochemical success comprise those with persisting aldosteronism who were misdiagnosed as unilateral PA preoperatively. To identify determinants of postsurgical biochemical outcomes, we compared the adrenal histopathology and the peripheral venous steroid profiles of patients with partial and absent or complete biochemical success after adrenalectomy for unilateral PA. A large multicenter cohort of adrenals from patients with absent and partial biochemical success (n=43) displayed a higher prevalence of hyperplasia (49% versus 21%; P=0.004) and a lower prevalence of solitary functional adenoma (44% versus 79%; P<0.001) compared with adrenals from age- and sex-matched patients with PA with complete biochemical success (n=52). We measured the peripheral plasma steroid concentrations in a subgroup of these patients (n=43) and in a group of patients with bilateral PA (n=27). Steroid profiling was associated with histopathologic phenotypes (solitary functional adenoma, hyperplasia, and aldosterone-producing cell clusters) and classified patients according to biochemical outcome or diagnosis of bilateral PA. If validated, peripheral venous steroid profiling may be a useful tool to guide the decision to perform surgery based on expectations of biochemical outcome after the procedure.