Genetics of primary aldosteronism

Who needs to be screened for primary aldosteronism?

The prevalence of patients with primary aldosteronism (PA) is about 5%-15% in hypertensive patients, and it is common cause of secondary hypertension in clinical practice. Two major causes of PA are noted, namely bilateral adrenal hyperplasia and aldosterone-producing adenoma, and the general diagnosis is based on three steps: (1) screening, (2) confirmatory testing, and (3) subtype differentiation (Figure 1). The recommendation for screening patients is at an increased risk of PA, here we focus on which patients should be screened for PA, not only according to well-established guidelines but for potential patients with PA. We recommend screening for 1) patients with resistant or persistent hypertension, 2) hypertensive patients with hypokalemia (spontaneous or drug-induced), 3) young hypertensive patients (age <40 years), and 4) all hypertensive patients with a history of PA in first-degree relatives. Moreover, we suggest screening for 1) hypertensive patients themselves or first-degree relatives with early target organ damage, such as stroke and other diseases, 2) all hypertensive patients with a concurrent adrenal incidentaloma, 3) hypertensive patients with obstructive sleep apnea, 4) hypertensive patients with atrial fibrillation unexplained by structural heart defects and/or other conditions resulting in the arrhythmia, 5) hypertensive patients with anxiety and other psychosomatic symptoms, and 6) hypertensive patients without other comorbidities to maintain cost-effectiveness.

Who should be screened for primary aldosteronism? A comprehensive review of current evidence

Arterial hypertension is a major risk factor for cardiovascular disease. The prevalence of primary aldosteronism (PA) ranges from 5% to 10% in the general hypertensive population and is regarded as one of the most common causes of secondary hypertension. There are two major causes of PA: bilateral adrenal hyperplasia and aldosterone-producing adenoma. The diagnosis of PA comprises screening, confirmatory testing, and subtype differentiation. The Endocrine Society Practice Guidelines for the diagnosis and treatment of PA recommends screening of patients at an increased risk of PA. These categories include patients with stage 2 and 3 hypertension, drug-resistant hypertension, hypertensive with spontaneous or diuretic-induced hypokalemia, hypertension with adrenal incidentaloma, hypertensive with a family history of early onset hypertension or cerebrovascular accident at a young age, and all hypertensive first-degree relatives of patients with PA. Recently, several studies have linked PA with obstructive sleep apnea and atrial fibrillation unexplained by structural heart defects and/or other conditions known to cause the arrhythmia, which may be partly responsible for the higher rates of cardiovascular and cerebrovascular accidents in patients with PA. The aim of this review is to discuss which patients should be screened for PA, focusing not only on well-established guidelines but also on additional groups of patients with a potentially higher prevalence of PA, as has been reported in recent research.

Understanding primary aldosteronism: impact of next generation sequencing and expression profiling

Primary aldosteronism (PA) encompasses a broad, heterogeneous group of disorders including both sporadic and familial forms (familial hyperaldosteronism type I, II and III). PA is the most common form of secondary hypertension and associated with a higher rate of cardiovascular complications, compared with essential hypertension. Despite significant progress in the diagnosis and management of PA, until recently the molecular mechanisms leading to inappropriate aldosterone production were largely unknown. The introduction of next-generation sequencing has had a profound impact on the field of human genetics and has given new insight in the molecular determinants that lead to both sporadic and familial forms of PA. Here we review the recent progress toward understanding of the genetic and molecular mechanisms leading to autonomous aldosterone production in PA.

Association of CYP11B2 polymorphisms with susceptibility to primary aldosteronism: a meta-analysis

The association of CYP11B2 gene polymorphisms with the risk of primary aldosteronism (PA) was controversial in previous studies. Here we selected two commonly studied CYP11B2 alleles: T-344C, A2718G to explore their associations with PA risk by meta-analyses of published case-control studies. Six electronic databases were searched for relevant studies up to November 2012. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using random or fixed effects model. Seven studies (621 cases and 1027 controls) on T-344C polymorphism, three studies (327 cases and 336 controls) on A2718G polymorphism were finally included. Then significant association was observed between T-344C polymorphism and idiopathic hyperaldosteronism (IHA) under three genetic models (CC vs. TT, OR=0.544, 95% CI=0.324~0.914; CT vs. TT, OR=0.554, 95% CI=0.406~0.757; CC+CT vs. TT, OR=0.542, 95% CI=0.402~0.731). But patients with aldosterone-producing adenoma had no significant association with T-344C polymorphism under all genetic models except CT vs. TT model. Concerning A2718G polymorphism, a decreased PA risk was observed only under GG+GA vs AA model. But this association disappeared after removing the studies not in Hardy-Weinberg equilibrium. The evidence accumulated suggested that -344C allele may be associated with decreased risk of IHA and there was still no enough evidence to indicate the association of A2718G polymorphism with PA risk.

Primary idiopathic hyperaldosteronism in clinical practice

Primary hyperaldosteronism (PHA) is a clinical syndrome that develops as a result of excess production of aldosterone by adrenal glomerular zone, where aldosterone secretion is completely or partially autonomous in relation to the renin-angiotensin system. This factor leads to the development low renin arterial hypertension (AH). Primary idiopathic hyperaldosteronism is one of the forms of PHA. The prevalence of this form is variously estimated from 20 to 55% of patients with PHA. Morphological substrate primary idiopathic hyperaldosteronism is a bilateral micro- or macronodular adrenal hyperplasia. This article summarizes the contemporary view of the pathogenesis, clinical presentation, diagnosis and treatment of idiopathic hyperaldosteronism.

Diagnosis and treatment of primary aldosteronism

Primary aldosteronism is the most common form of secondary hypertension. The detection of primary aldosteronism is of particular importance, not only because it provides an opportunity for a targeted treatment (surgical for APA and medical with mineralocorticoid receptor antagonists for BAH), but also because it has been extensively demonstrated that patients affected by PA are more prone to cardiovascular events and target organ damage than essential hypertensives. According to the Endocrine Society Guidelines diagnosis of PA is made following a rigorous flow-chart comprising screening, confirmation/exclusion testing and subtype diagnosis. In the present review we describe briefly the published diagnostic strategies of the Guidelines, highlighting new evidence that has become recently available and discuss issues that still need to be addressed by future research.

Evaluation of primary aldosteronism

PURPOSE OF REVIEW

The purpose of this review is to briefly summarize current knowledge on diagnosis and treatment of primary aldosteronism, the most frequent cause of endocrine hypertension.

RECENT FINDINGS

The prevalence of primary aldosteronism increases with the severity of hypertension, from 2% in patients with grade 1 hypertension to 20% among resistant hypertensives. The detection of primary aldosteronism is of particular importance, not only because it provides an opportunity for a targeted treatment but also because it has been extensively demonstrated that patients affected by primary aldosteronism are more prone to cardiovascular events and target organ damage than patients with essential hypertension. The diagnosis of primary aldosteronism is a three-step process; screening, confirmation and subtype diagnosis.

SUMMARY

We review, the strategies to correctly identify primary aldosteronism, highlighting the central role of the new guidelines and the diagnostic aspects still under debate.

Roles of clinical criteria, computed tomography scan, and adrenal vein sampling in differential diagnosis of primary aldosteronism subtypes

CONTEXT

In patients with primary aldosteronism (PA), it is fundamental to distinguish between subtypes that benefit from different therapies. Computed tomography (CT) scans lack sensitivity and specificity and must be followed by adrenal venous sampling (AVS). Because AVS is not widely available, a list of clinical criteria that indicate the presence of an aldosterone-producing adenoma (APA) has been suggested.

OBJECTIVE AND DESIGN

The objective of the study was to test the sensitivity and specificity of the last generation CT scans, test prospectively the usefulness of clinical criteria in the diagnosis of APA, and develop a flow chart to be used when AVS is not easily available.

SETTING

Hypertensive patients referred to our hypertension unit were included in our study.

PATIENTS

Seventy-one patients with confirmed PA participated in our study.

INTERVENTION

All patients had a CT scan and underwent AVS.

MAIN OUTCOME MEASURE

Final diagnosis of APA was the main measure.

RESULTS

A total of 44 and 56% of patients were diagnosed as having an APA and a bilateral adrenal hyperplasia (BAH), respectively. Twenty percent of patients with PA displayed hypokalemia. CT scans displayed a sensitivity of 0.87 and a specificity of 0.71. The posture test displayed a lower sensitivity and specificity (0.64 and 0.70, respectively). The distribution grades of hypertension were not significantly different between APA and BAH. Biochemical criteria of high probability of APA displayed a sensitivity of 0.32 and a specificity of 0.95.

CONCLUSIONS

This study underlines the central role of AVS in the subtype diagnosis of PA. The use of the clinical criteria to distinguish between APA and BAH did not display a satisfactory diagnostic power.

Diagnosis and treatment of low-renin hypertension

Plasma renin levels can be used to classify hypertension. A significant proportion of hypertensive individuals display a low-renin profile and thus low-renin hypertension (LRH) requires appropriate diagnosis and treatment. LRH includes essential, secondary and genetic forms, the most common of which are low-renin essential hypertension and primary aldosteronism. Several studies have investigated the relationship between PRA status and clinical response to different antihypertensive therapies. The present review will discuss the differential diagnosis of LRH subtypes and the most appropriate treatment options based on the pathophysiological background of this condition.

Primary aldosteronism: current knowledge and controversies in Conn's syndrome

Primary aldosteronism has been recognized as a common cause of secondary hypertension, accounting for approximately 10% of the hypertensive population. Screening should be applied in hypertensive patients presenting with one of the following: hypokalemia, refractory hypertension, suggestive family history, or an incidentally detected adrenal mass. The most advocated screening test at present is the aldosterone-to-renin ratio, which has a high sensitivity but low specificity. The specificity increases if patients with low aldosterone concentrations are excluded. Published cut-off values vary depending on the hormone assay and the investigated population. Before screening, antihypertensive treatment, especially aldosterone antagonists and beta-blockers, should be discontinued. A pathologic result requires additional work up to prove mineralocorticoid excess. Subtype differentiation is performed by adrenal venous sampling combined with imaging (CT or MRI). One-third of cases are due to aldosterone-producing adenomas, for which the preferred treatment is laparoscopic adrenalectomy. Bilateral adrenal hyperplasia (idiopathic aldosteronism) underlies two-thirds of cases and requires treatment with aldosterone antagonists. Treatment is started with low doses of spironolactone (25-50 mg once daily), which often results in substantial improvements in hypertension.

Prevalence of Primary Aldosteronism among Unselected Hypertensive Patients: A Prospective Study Based on the Use of an Aldosterone/Renin Ratio above 25 as a Screening Test

Primary aldosteronism (PA) has been considered a rare cause of hypertension. The introduction of the aldosterone/renin ratio (ARR) as a screening test has led to an increase in the detection rate. The aim of this study was to evaluate the prevalence of PA among unselected hypertensive patients by using an ARR >25 as a screening test. We studied 3,000 consecutive unselected hypertensive patients. Blood samples for the determination of plasma renin activity (PRA), aldosterone (ALD) and electrolytes were drawn in the morning, and patients with an ARR >25 underwent intravenous saline infusion as a confirmatory test. Adrenal CT and a dexamethasone suppression test were performed in patients with confirmed PA. Patients with a positive dexamethasone test underwent genetic testing for glucocorticoid-remediable aldosteronism (GRA). Out of 3,000 hypertensives, 684 (22.8%) showed an ARR >25 and 177 of them (5.9% of the whole population) had a positive saline loading test. Only 44 of them (24.8%) were hypokalemic. CT was performed in all the patients with confirmed PA and 53 of them (29.9%) had a solitary adrenal macroadenoma, 112 (63.3%) had bilateral adrenal enlargement and 12 (6.8%) had normal appearing adrenal glands. Of 177 patients given dexamethasone to identify GRA, 8 (4.5%) showed aldosterone suppression but only one (0.1%) tested positive for the chimeric gene. In conclusion, our findings indicate that standardized application of an ARR >25 to unselected hypertensive patients, followed by i.v. saline loading as a confirmatory test, can result in the detection of a large number of patients with PA (5.9% of the studied population), most of whom are normokalemic. Bilateral adrenal hypertrophy represents the more common form of PA.

Genetic information in the diagnosis and treatment of hypertension

Advancement in cardiovascular science should be measured by a number of new diagnostic and therapeutic options applied in clinical practice as a result of translational research. Hypertension genetics is a good example of such a successful transfer of knowledge from bench to bedside. There are genetic methods currently used as diagnostic tools in patients presenting with secondary forms of hypertension, including primary hyperaldosteronism, Cushing's syndrome, pheochromocytoma, and chronic kidney disease. Directed treatment that corrects pathophysiologic abnormalities is available for several monogenic forms of hypertension as a result of uncovering their underlying genetic mechanisms. Progress in hypertension pharmacogenetics and pharmacogenomics brings closer a perspective of personalized antihypertensive treatment and gene transfer strategies, which, although still considered as innovative approaches, may soon become options to treat, control, and, possibly, cure hypertension.

Primary aldosteronism: diagnostic and treatment strategies

Primary aldosteronism is caused by bilateral idiopathic hyperplasia in approximately two-thirds of cases and aldosterone-producing adenoma in one-third. Most patients with primary aldosteronism are normokalemic. In the clinical setting of normokalemic hypertension, patients who have resistant hypertension and hypertensive patients with a family history atypical for polygenic hypertension should be tested for primary aldosteronism. The ratio of plasma aldosterone concentration to plasma renin activity has been generally accepted as a first-line case-finding test. If a patient has an increased ratio, autonomous aldosterone production must be confirmed with an aldosterone suppression test. Once primary aldosteronism is confirmed, the subtype needs to be determined to guide treatment. The initial test in subtype evaluation is CT imaging of the adrenal glands. If surgical treatment is considered, adrenal vein sampling is the most accurate method for distinguishing between unilateral and bilateral adrenal aldosterone production. Optimal treatment for aldosterone-producing adenoma or unilateral hyperplasia is unilateral laparoscopic adrenalectomy. The idiopathic bilateral hyperplasia and glucocorticoid-remediable aldosteronism subtypes should be treated pharmacologically. All patients treated pharmacologically should receive a mineralocorticoid receptor antagonist, a drug type that has been shown to block the toxic effects of aldosterone on nonepithelial tissues.

Diagnosis of primary aldosteronism: from screening to subtype differentiation

Numerous studies conducted in recent years have reported an increase in the prevalence of primary aldosteronism (PA). This increase has arisen because of changes in our screening methods used to detect PA, notably the widespread use of the ratio of plasma aldosterone concentration to plasma renin activity. A positive screening result, however, is not diagnostic and requires a confirmatory test. Strategies for screening and confirmation of PA and the techniques to identify the two main subtypes of PA--aldosterone-producing adenoma (APA) and bilateral adrenal hyperplasia (BAH)--are particularly important because hypertension in APA can be cured by adrenalectomy, whereas individuals affected with BAH can receive targeted medical treatment with mineralocorticoid receptor antagonists.