Genetics of mineralocorticoid excess: an update for clinicians

Report on three cases of familial primary aldosteronism type IV

Primary aldosteronism is the most common cause of secondary hypertension, which is caused by increased aldosterone secretion in the adrenal cortex and contains many subtypes, among which familial hyperaldosteronism is relatively rare. Familial hyperaldosteronism can be divided into four subtypes based on its clinical manifestations and mutated genes: FH-I, FH-II, FH-III, and FH-IV. This article reports on three patients with FH-IV: a mother and her two sons. They were diagnosed with hypertension in other hospitals, and hypokalemia was found during hospitalization in our department. Diltiazem and terazosin were used for elution for 1 month. Renin and aldosterone levels in standing or supine positions improved, and the aldosterone-to-renin ratio was positive. Primary aldosteronism was diagnosed based on improved saline and captopril inhibition tests. As the three patients were blood-related immediate family members, gene screening was performed, diagnosing them with FH-IV. This article reports the clinical characteristics of the three cases in combination with related literature to improve the understanding of FH-IV.

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.

Endocrine Hypertension: A Practical Approach

Elevated blood pressure resulting from few endocrine disorders (endocrine hypertension) accounts for a high proportion of cases of secondary hypertension. Although some features may be suggestive, many cases of endocrine hypertension remain silent until worked up for the disease. A majority of cases result from primary aldosteronism. Other conditions that can cause endocrine hypertension are: congenital adrenal hyperplasia, Liddle syndrome, pheochromocytomas, Cushing's syndrome, acromegaly, thyroid diseases, primary hyperparathyroidism and iatrogenic hormone manipulation. Early identification and treatment of the cause of endocrine hypertension may help to reduce morbidity and mortality related to these disorders. This article gives a comprehensive and practical approach to the diagnosis and management of endocrine hypertension.

Emerging Roles of the Mineralocorticoid Receptor in Pathology: Toward New Paradigms in Clinical Pharmacology

The mineralocorticoid receptor (MR) and its ligand aldosterone are the principal modulators of hormone-regulated renal sodium reabsorption. In addition to the kidney, there are several other cells and organs expressing MR, in which its activation mediates pathologic changes, indicating potential therapeutic applications of pharmacological MR antagonism. Steroidal MR antagonists have been used for decades to fight hypertension and more recently heart failure. New therapeutic indications are now arising, and nonsteroidal MR antagonists are currently under development. This review is focused on nonclassic MR targets in cardiac, vascular, renal, metabolic, ocular, and cutaneous diseases. The MR, associated with other risk factors, is involved in organ fibrosis, inflammation, oxidative stress, and aging; for example, in the kidney and heart MR mediates hormonal tissue-specific ion channel regulation. Genetic and epigenetic modifications of MR expression/activity that have been documented in hypertension may also present significant risk factors in other diseases and be susceptible to MR antagonism. Excess mineralocorticoid signaling, mediated by aldosterone or glucocorticoids binding, now appears deleterious in the progression of pathologies that may lead to end-stage organ failure and could therefore benefit from the repositioning of pharmacological MR antagonists.

SFE/SFHTA/AFCE consensus on primary aldosteronism, part 5: Genetic diagnosis of primary aldosteronism

While the majority of cases of primary aldosteronism (PA) are sporadic, four forms of autosomal-dominant inheritance have been described: familial hyperaldosteronism (FH) types I to IV. FH-I, also called glucocorticoid-remediable aldosteronism, is characterized by early and severe hypertension, usually before the age of 20 years. It is due to the formation of a chimeric gene between the adjacent CYP11B2 and CYP11B1 genes (coding for aldosterone synthase and 11β-hydroxylase, respectively). FH-I is often associated with family history of stroke before 40years of age. FH-II is clinically and biochemically indistinguishable from sporadic forms of PA and is only diagnosed on the basis of two or more affected family members. No causal genes have been identified so far and no genetic test is available. FH-III is characterized by severe and early-onset hypertension in children and young adults, resistant to treatment and associated with severe hypokalemia. Mild forms, resembling FH-II, have been described. FH-III is due to gain-of-function mutations in the KCNJ5 gene. Recently, a new autosomal-dominant form of familial PA, FH-IV, associated with mutations in the CACNA1H gene, was described in patients with hypertension and PA before the age of 10years. In rare cases, PA may be associated with complex neurologic disorder involving epileptic seizures and cerebral palsy (Primary Aldosteronism, Seizures, and Neurologic Abnormalities [PASNA]) due to de novo germline CACNA1D mutations.

SFE/SFHTA/AFCE consensus on primary aldosteronism, part 4: Subtype diagnosis

To establish the cause of primary aldosteronism (PA), it is essential to distinguish unilateral from bilateral adrenal aldosterone secretion, as adrenalectomy improves aldosterone secretion and controls hypertension and hypokalemia only in the former. Except in the rare cases of type 1 or 3 familial hyperaldosteronism, which can be diagnosed genetically and are not candidates for surgery, lateralized aldosterone secretion is diagnosed on adrenal CT or MRI and adrenal venous sampling. Postural stimulation tests and (131)I-norcholesterol scintigraphy have poor diagnostic value and (11)C-metomidate PET is not yet available. We recommend that adrenal CT or MRI be performed in all cases of PA. Imaging may exceptionally identify adrenocortical carcinoma, for which the surgical objectives are carcinologic, and otherwise shows either normal or hyperplastic adrenals or unilateral adenoma. Imaging alone carries a risk of false positives in patients over 35 years of age (non-aldosterone-secreting adenoma) and false negatives in all patients (unilateral hyperplasia). We suggest that all candidates for surgery over 35 years of age undergo adrenal venous sampling, simultaneously in both adrenal veins, without ACTH stimulation, to confirm the unilateral form of the hypersecretion. Sampling results should be confirmed on adrenal vein cortisol assay showing a concentration at least double that found in peripheral veins. Aldosterone secretion should be considered lateralized when aldosterone/cortisol ratio on the dominant side is at least 4-fold higher than contralaterally.

Clinicopathologic Correlates of Primary Aldosteronism

Primary aldosteronism is the most common cause of secondary hypertension, incurring significant cardiovascular morbidity and mortality. Our understanding of this disease has evolved substantially during the past decade. Recently, the molecular basis of primary aldosteronism has begun to be unraveled, with the discovery of mutations in potassium channel (KCNJ5), ATPases (ATP1A1, ATP2B3), and calcium channel (CACNA1D), and aberrant Wnt/β-catenin signaling. The most recent data suggest that 95% of cases are sporadic, whereas 5% of cases are hereditary. Pathologic correlates of primary aldosteronism include adrenal cortical hyperplasia, adenoma, and carcinoma. Although the most common clinical presentation is bilateral adrenal cortical hyperplasia, this entity is usually treated medically. Therefore, in the setting of primary aldosteronism, surgical pathologists are most commonly exposed to adrenocortical adenomas and the odd occasional carcinoma. This review provides an update on the current knowledge of primary aldosteronism and discusses the clinicopathologic correlations of this important disease.

Inherited forms of mineralocorticoid hypertension

Aldosterone plays an essential role in the maintenance of fluid and electrolyte homeostasis in the distal nephron. Monogenic forms of mineralocorticoid hypertension result from genetic defects leading to excessive production of aldosterone (or other mineralocorticoids) from the adrenal cortex or to illegitimate mineralocorticoid effects in the kidney. They are characterized in the majority of cases by early onset, severe or resistant hypertension and associated with suppressed renin levels. Depending on their causes, these diseases are distinguished at the clinical and biochemical level and differently affect aldosterone levels and kalemia. The diagnosis is confirmed by genetic testing, which allows in many cases targeted treatment to prevent severe cardiovascular consequences of high blood pressure or aldosterone excess. In this review we describe the different forms of inherited mineralocorticoid hypertension, providing an overview of their clinical and biochemical features, their underlying genetic defects and specific therapeutic options.

Hypertension: renin-angiotensin-aldosterone system alterations

Blockers of the renin-angiotensin-aldosterone system (RAAS), that is, renin inhibitors, angiotensin (Ang)-converting enzyme (ACE) inhibitors, Ang II type 1 receptor antagonists, and mineralocorticoid receptor antagonists, are a cornerstone in the treatment of hypertension. How exactly they exert their effect, in particular in patients with low circulating RAAS activity, also taking into consideration the so-called Ang II/aldosterone escape that often occurs after initial blockade, is still incompletely understood. Multiple studies have tried to find parameters that predict the response to RAAS blockade, allowing a personalized treatment approach. Consequently, the question should now be answered on what basis (eg, sex, ethnicity, age, salt intake, baseline renin, ACE or aldosterone, and genetic variance) a RAAS blocker can be chosen to treat an individual patient. Are all blockers equal? Does optimal blockade imply maximum RAAS blockade, for example, by combining ≥2 RAAS blockers or by simply increasing the dose of 1 blocker? Exciting recent investigations reveal a range of unanticipated extrarenal effects of aldosterone, as well as a detailed insight in the genetic causes of primary aldosteronism, and mineralocorticoid receptor blockers have now become an important treatment option for resistant hypertension. Finally, apart from the deleterious ACE-Ang II-Ang II type 1 receptor arm, animal studies support the existence of protective aminopeptidase A-Ang III-Ang II type 2 receptor and ACE2-Ang-(1 to 7)-Mas receptor arms, paving the way for multiple new treatment options. This review provides an update about all these aspects, critically discussing the many controversies and allowing the reader to obtain a full understanding of what we currently know about RAAS alterations in hypertension.

Genetic and molecular aspects of hypertension

Until recently, significant advances in our understanding of the mechanisms of blood pressure regulation arose from studies of monogenic forms of hypertension and hypotension, which identified rare variants that primarily alter renal salt handling. Genome-wide association and exome sequencing studies over the past 6 years have resulted in an unparalleled burst of discovery in the genetics of blood pressure regulation and hypertension. More importantly, genome-wide association studies, while expanding the list of common genetic variants associated with blood pressure and hypertension, are also uncovering novel pathways of blood pressure regulation that augur a new era of novel drug development, repurposing, and stratification in the management of hypertension. In this review, we describe the current state of the art of the genetic and molecular basis of blood pressure and hypertension.

Mineralocorticoid and apparent mineralocorticoid syndromes of secondary hypertension

The mineralocorticoid aldosterone is a key hormone in the regulation of plasma volume and blood pressure in man. Excessive levels of this mineralocorticoid have been shown to mediate metabolic disorders and end-organ damage more than what can be attributed to its effects on blood pressure alone. Inappropriate excess levels of aldosterone contribute significantly to the cardiorenal metabolic syndrome and target organ injury that include atherosclerosis, myocardial hypertrophy, fibrosis, heart failure, and kidney disease. The importance of understanding the role of excess mineralocorticoid hormones such as aldosterone in resistant hypertension and in those with secondary hypertension should be visited. Primary aldosteronism is one of the commonly identified causes of hypertension and is treatable and/or potentially curable. We intend to review the management of mineralocorticoid-induced hypertension in the adult population along with other disease entities that mimic primary aldosteronism.

Progress in aldosteronism: a review of the prevalence of primary aldosteronism in pre-hypertension and hypertension

Primary aldosteronism (PA) secondary to excessive and/or autonomous aldosterone secretion from the renin-angiotensin system accounts for ∼10% of cases of hypertension and is primarily caused by bilateral adrenal hyperplasia (BAH) or aldosterone-producing adenomas (APAs). Although the diagnosis has traditionally been supported by low serum potassium levels, normokalaemic and even normotensive forms of PA have been identified expanding further the clinical phenotype. Moreover, recent evidence has shown that serum aldosterone correlates with increased blood pressure (BP) in the general population and even moderately raised aldosterone levels are linked to increased cardiovascular morbidity and mortality. In addition, aldosterone antagonists are effective in BP control even in patients without evidence of dysregulated aldosterone secretion. These findings indicate a higher prevalence of aldosterone excess among hypertensive patients than previously considered that could be attributed to disease heterogeneity, aldosterone level fluctuations related to an ACTH effect or inadequate sensitivity of current diagnostic means to identify apparent aldosterone excess. In addition, functioning aberrant receptors expressed in the adrenal tissue have been found in a subset of PA cases that could also be related to its pathogenesis. Recently a number of specific genetic alterations, mainly involving ion homeostasis across the membrane of zona glomerulosa, have been detected in ∼50% of patients with APAs. Although specific genotype/phenotype correlations have not been clearly identified, differential expression of these genetic alterations could also account for the wide clinical phenotype, variations in disease prevalence and performance of diagnostic tests. In the present review, we critically analyse the current means used to diagnose PA along with the role that ACTH, aberrant receptor expression and genetic alterations may exert, and provide evidence for an increased prevalence of aldosterone dysregulation in patients with essential hypertension and pre-hypertension.

Genetics of primary aldosteronism

OBJECTIVE

The American Association of Clinical Endocrinologists Adrenal Scientific Committee has developed a series of articles to update members on the genetics of adrenal diseases.

METHODS

Case presentation, discussion of literature, table, and bullet point conclusions.

RESULTS

Primary aldosteronism (PA) is the most common form of secondary hypertension. Early detection, surveillance, and treatment of PA may mitigate future cardiovascular risk. The genetics of PA are rapidly evolving, and the consideration for genetic causes of PA are growing. Three inheritable forms of PA are now recognized: familial hyperaldosteronism type I (glucocorticoid-remediable aldosteronism), familial hyperaldosteronism type II, and familial hyperaldosteronism type III. The recent discovery of familial hyperaldosteornism type III spurred a flurry of international and collaborative research that is identifying more genetic and molecular causes of PA that relate to mutations in membrane electrolyte transport channels of zona glomerulosa cells.

CONCLUSION

This article reviews the various genetic forms of PA, including a focus on the molecular mechanisms involved, diagnosis, and treatment.

Regulation of aldosterone synthesis and secretion

Aldosterone is a steroid hormone synthesized in and secreted from the outer layer of the adrenal cortex, the zona glomerulosa. Aldosterone is responsible for regulating sodium homeostasis, thereby helping to control blood volume and blood pressure. Insufficient aldosterone secretion can lead to hypotension and circulatory shock, particularly in infancy. On the other hand, excessive aldosterone levels, or those too high for sodium status, can cause hypertension and exacerbate the effects of high blood pressure on multiple organs, contributing to renal disease, stroke, visual loss, and congestive heart failure. Aldosterone is also thought to directly induce end-organ damage, including in the kidneys and heart. Because of the significance of aldosterone to the physiology and pathophysiology of the cardiovascular system, it is important to understand the regulation of its biosynthesis and secretion from the adrenal cortex. Herein, the mechanisms regulating aldosterone production in zona glomerulosa cells are discussed, with a particular emphasis on signaling pathways involved in the secretory response to the main controllers of aldosterone production, the renin-angiotensin II system, serum potassium levels and adrenocorticotrophic hormone. The signaling pathways involved include phospholipase C-mediated phosphoinositide hydrolysis, inositol 1,4,5-trisphosphate, cytosolic calcium levels, calcium influx pathways, calcium/calmodulin-dependent protein kinases, diacylglycerol, protein kinases C and D, 12-hydroxyeicostetraenoic acid, phospholipase D, mitogen-activated protein kinase pathways, tyrosine kinases, adenylate cyclase, and cAMP-dependent protein kinase. A complete understanding of the signaling events regulating aldosterone biosynthesis may allow the identification of novel targets for therapeutic interventions in hypertension, primary aldosteronism, congestive heart failure, renal disease, and other cardiovascular disorders.

EJE prize 2014: current and evolving treatment options in adrenocortical carcinoma: where do we stand and where do we want to go?

Adrenocortical carcinoma (ACC) is not only a rare and heterogeneous disease but also one of the most aggressive endocrine tumors. Despite significant advances in the last decade, its pathogenesis is still only incompletely understood and overall therapeutic means are unsatisfactory. Herein, we provide our personal view of the currently available treatment options and suggest the following research efforts that we consider timely and necessary to improve therapy: i) for better outcome in localized ACCs, surgery should be restricted to experienced centers, which should then collaborate closely to address the key surgical questions (e.g. best approach and extent of surgery) in a multicenter manner. ii) For the development of better systemic therapies, it is crucial to elucidate the exact molecular mechanisms of action of mitotane. iii) A prospective trial is needed to address the role of cytotoxic drugs in the adjuvant setting in aggressive ACCs (e.g. mitotane vs mitotane+cisplatin). iv) For metastatic ACCs, new regimens should be investigated as first-line therapy. v) Several other issues (e.g. the role of radiotherapy and salvage therapies) might be answered - at least in a first step - by large retrospective multicenter studies. In conclusion, although it is unrealistic to expect that the majority of ACCs can be cured within the next decade, international collaborative efforts (including multiple translational and clinical studies) should allow significant improvement of clinical outcome of this disease. To this end, it might be reasonable to expand the European Network for the Study of Adrenal Tumors (ENSAT) to a truly worldwide international network - INSAT.

Overview of the genetic determinants of primary aldosteronism

Primary aldosteronism is the most common cause of secondary hypertension. The syndrome accounts for 10% of all cases of hypertension and is primarily caused by bilateral adrenal hyperplasia or aldosterone-producing adenoma. Over the last few years, the use of exome sequencing has significantly improved our understanding of this syndrome. Somatic mutations in the KCNJ5, ATP1A1, ATP2B3 or CACNA1D genes are present in more than half of all cases of aldosterone-producing adenoma (~40%, ~6%, ~1% and ~8%, respectively). Germline gain-of-function mutations in KCNJ5 are now known to cause familial hyperaldosteronism type III, and an additional form of genetic hyperaldosteronism has been reported in patients with germline mutations in CACNA1D. These genes code for channels that control ion homeostasis across the plasma membrane of zona glomerulosa cells. Moreover, all these mutations modulate the same pathway, in which elevated intracellular calcium levels lead to aldosterone hyperproduction and (in some cases) adrenal cell proliferation. From a clinical standpoint, the discovery of these mutations has potential implications for patient management. The mutated channels could be targeted by drugs, in order to control hormonal and overgrowth-related manifestations. Furthermore, some of these mutations are associated with high cell turnover and may be amenable to diagnosis via the sequencing of cell-free (circulating) DNA. However, genotype-phenotype correlations in patients harboring these mutations have yet to be characterized. Despite this recent progress, much remains to be done to elucidate the yet unknown mechanisms underlying sporadic bilateral adrenal hyperplasia.