Primary hyperaldosteronism in essential hypertensives: prevalence, biochemical profile, and molecular biology

Serum Alpha-1-Acid Glycoprotein-1 and Urinary Extracellular Vesicle miR-21-5p as Potential Biomarkers of Primary Aldosteronism

Primary aldosteronism (PA) is the most common cause of secondary hypertension and reaches a prevalence of 6-10%. PA is an endocrine disorder, currently identified as a broad-spectrum phenotype, spanning from normotension to hypertension. In this regard, several studies have made advances in the identification of mediators and novel biomarkers of PA as specific proteins, miRNAs, and lately, extracellular vesicles (EVs) and their cargo.

Aim

To evaluate lipocalins LCN2 and AGP1, and specific urinary EV miR-21-5p and Let-7i-5p as novel biomarkers for PA.

Subjects and Methods

A cross-sectional study was performed in 41 adult subjects classified as normotensive controls (CTL), essential hypertensives (EH), and primary aldosteronism (PA) subjects, who were similar in gender, age, and BMI. Systolic (SBP) and diastolic (DBP) blood pressure, aldosterone, plasma renin activity (PRA), and aldosterone to renin ratio (ARR) were determined. Inflammatory parameters were defined as hs-C-reactive protein (hs-CRP), PAI-1, MMP9, IL6, LCN2, LCN2-MMP9, and AGP1. We isolated urinary EVs (uEVs) and measured two miRNA cargo miR-21-5p and Let-7i-5p by Taqman-qPCR. Statistical analyses as group comparisons were performed by Kruskall-Wallis, and discriminatory analyses by ROC curves were performed with SPSS v21 and Graphpad-Prism v9.

Results

PA and EH subjects have significantly higher SBP and DBP (p <0.05) than the control group. PA subjects have similar hs-CRP, PAI-1, IL-6, MMP9, LCN2, and LCN2-MMP9 but have higher levels of AGP1 (p <0.05) than the CTL&EH group. The concentration and size of uEVs and miRNA Let-7i-5p did not show any difference between groups. In PA, we found significantly lower levels of miR-21-5p than controls (p <0.05). AGP1 was associated with aldosterone, PRA, and ARR. ROC curves detected AUC for AGP1 of 0.90 (IC 95 [0.79 - 1.00], p <0.001), and combination of AGP1 and EV-miR-21-5p showed an AUC of 0.94 (IC 95 [0.85 - 1.00], p<0.001) to discriminate the PA condition from EH and controls.

Conclusion

Serum AGP1 protein was found to be increased, and miR-21-5p in uEVs was decreased in subjects classified as PA. Association of AGP1 with aldosterone, renin activity, and ARR, besides the high discriminatory capacity of AGP1 and uEV-miR-21-5p to identify the PA condition, place both as potential biomarkers of PA.

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

In recent years, a substantial prevalence of primary aldosteronism (PA) has been demonstrated in both normotensive and mildly hypertensive cohorts. Consequently, a classic presentation of the syndrome, i. e. moderate-to-severe and resistant hypertension with concomitant hypokalemia, should be considered a tip-of-the-iceberg phenotype of a wide PA spectrum. Its entire range encompasses the non-classic clinical forms of mild hypertension and prehypertension but also several biochemical presentations, including patients who meet PA screening and confirmation test criteria, as well as those with either of them and those with other parameters indicating mineralocorticoid excess. In the current review, research insights on the pathogenetic background and clinical significance of autonomous aldosterone secretion (AAS) are presented, which is defined as a constellation of either: 1) normotension, normokalemia, a positive PA screening (high aldosterone-to-renin ratio) and/or confirmation test, or 2) hypertension, normokalemia and a positive PA screening but negative confirmation test. For this purpose, a literature search of the PubMed database was conducted. Advances in immunohistochemistry and genetic sequencing of isolated adrenal cells are provided as probable morphologic basis of the wide range of aldosterone secretion autonomy. Also, the role of corticotropin as an aldosterone secretagogue is discussed. To date, clinical studies depict consequences of subclinical PA phenotypes, such as increased mortality and risk of developing hypertension, impaired arterial and kidney function, association with metabolic syndrome and age, as well as osteoporosis.

Minor Change of Plasma Renin Activity during the Saline Infusion Test Provide an Auxiliary Diagnostic Value for Primary Aldosteronism

OBJECTIVE

To clarify whether it has some hidden diagnostic values for PA, especially in the case of an inconclusive SIT result, we investigated the difference in changes of plasma renin activity (PRA) during SIT between patients with PA and non-PA.

METHODS

We measured and compared the SIT parameters of 159 PA patients, 368 non-PA patients, and 43 inconclusive patients who were included in this study.

RESULTS

The PA group showed a minor change of PRA during the SIT (ΔPRA, defined as (pre-SIT PRA-post-SIT PRA)) compared with the non-PA group (0.17 ng/ml/h vs. 1.07 ng/ml/h, P < 0.001). According to ROC analysis, ΔPRA showed a greater AUC than post-SIT PRA (0.897 vs. 0.855, P < 0.001). The cutoff value was 0.5 ng/ml/h, with 90.3% sensitivity and 78.6% specificity. When combined with ARR post-SIT, it showed 81.6% sensitivity and 97.0% specificity for PA diagnosis. Further analysis of 43 patients with an inconclusive SIT result who completed AVS found that ΔPRA was smaller in the confirmed PA group compared with the unconfirmed PA group (0.19 ng/ml/h vs. 0.29 ng/ml/h, P < 0.05); there was no significant difference in PAC post-SIT between two groups. ΔPRA ≤ 0.21 ng/ml/h provides 71.4% sensitivity, 80.0% specificity, and 87.0% PPV for their PA diagnosis.

CONCLUSIONS

PA patients show minor PRA change during SIT; the change of PRA during SIT provides an auxiliary diagnostic value for PA, especially in patients with an inconclusive SIT result.

Effect of spironolactone on cardiovascular morbidity and mortality in patients with hypertension and glucose metabolism disorders (ESCAM): a study protocol for a pragmatic randomised controlled trial

INTRODUCTION

Hypertension combined with diabetes and hypokalemia is more likely to develop hyperaldosteronism and is at higher risk of cardiovascular events. There is evidence that activation of aldosterone and mineralocorticoid receptors may play a significant role in the occurrence of cardiovascular events in patients with hypertension and diabetes. Clinical studies have demonstrated that spironolactone can reduce the incidence of cardiovascular events in patients with chronic kidney diseases or severe heart failure. However, the effect of spironolactone on cardiovascular risk in patients with hypertension and glucose metabolism disorders (GMD) and low potassium has been scarcely studied. Therefore, this study aims to evaluate whether add-on spironolactone (conventional antihypertensive drugs alone vs conventional antihypertensive drugs+spironolactone) can reduce the morbidity and mortality of cardiovascular events in this population.

METHODS AND ANALYSIS

In this multicentre, randomised, parallel-controlled study, a total of 7140 hypertensive patients aged 45-75 years with GMD and low potassium will be randomised in a 1:1 manner to the control or the spironolactone group (20 mg/day or with a maximum dose of 40 mg). The primary objective is to estimate the difference in the HR of composite cardiovascular events between the two groups. We will also assess the effects of spironolactone on individual cardiovascular events and the progression of diabetes and renal dysfunction.

ETHICS AND DISSEMINATION

This protocol was approved by the Independent Ethics Committee of People's Hospital of Xinjiang Uygur Autonomous Region (no. 2020020618). The results will be disseminated in peer-reviewed journals and at scientific conferences.

TRIAL REGISTRATION NUMBER

ChiCTR2000028909.

COX-2-independent activation of renal (pro)renin receptor contributes to DOCA-salt hypertension in rats

It has been shown that cyclooxygenase (COX)-2-dependent activation of renal (pro)renin receptor (PRR) contributes to angiotensin II (ANG II)-induced hypertension. However, less is known about the involvement of this mechanism in ANG II-independent hypertension. The goal of the present study was to test whether or not COX-2-dependent upregulation of PRR serves as a universal mechanism contributing to ANG II-dependent and -independent hypertension. Here, we examined the association between renal COX-2 and PRR during deoxycorticosterone acetate (DOCA)-salt hypertension in rats. By immunoblot analysis and immunofluorescence, renal protein expression of PRR was remarkably upregulated by DOCA-salt treatment. Surprisingly, this upregulation of renal PRR expression was unaffected by a COX-2 inhibitor, celecoxib. To address the role of renal PRR to the pathogenesis of DOCA-salt hypertension, a decoy PRR inhibitor, PRO20, was infused to the renal medulla of uninephrectomized Sprague-Dawley rats for 14 days. Radiotelemetry demonstrated effective attenuation of DOCA-salt hypertension by intramedullary infusion of a PRR inhibitor, PRO20. In parallel, DOCA-salt-induced hypertrophy in the heart and kidney as well as proteinuria were improved, accompanied with blunted polydipsia and polyuria. In contrast, intravenous infusion of PRO20 was less effective in attenuating DOCA-salt hypertension and cardiorenal injury. Together, these results suggest that COX-2-independent activation of renal PRR contributes to DOCA-salt hypertension.

Chemogenetic activation of adrenocortical Gq signaling causes hyperaldosteronism and disrupts functional zonation

The mineralocorticoid aldosterone is produced in the adrenal zona glomerulosa (ZG) under the control of the renin-angiotensin II (AngII) system. Primary aldosteronism (PA) results from renin-independent production of aldosterone and is a common cause of hypertension. PA is caused by dysregulated localization of the enzyme aldosterone synthase (Cyp11b2), which is normally restricted to the ZG. Cyp11b2 transcription and aldosterone production are predominantly regulated by AngII activation of the Gq signaling pathway. Here, we report the generation of transgenic mice with Gq-coupled designer receptors exclusively activated by designer drugs (DREADDs) specifically in the adrenal cortex. We show that adrenal-wide ligand activation of Gq DREADD receptors triggered disorganization of adrenal functional zonation, with induction of Cyp11b2 in glucocorticoid-producing zona fasciculata cells. This result was consistent with increased renin-independent aldosterone production and hypertension. All parameters were reversible following termination of DREADD-mediated Gq signaling. These findings demonstrate that Gq signaling is sufficient for adrenocortical aldosterone production and implicate this pathway in the determination of zone-specific steroid production within the adrenal cortex. This transgenic mouse also provides an inducible and reversible model of hyperaldosteronism to investigate PA therapeutics and the mechanisms leading to the damaging effects of aldosterone on the cardiovascular system.

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.

Endocrine causes of hypertension in pregnancy

Hypertension is a common and morbid complication of pregnancy. While endocrine causes of secondary hypertension are not rare, women with these conditions do not often conceive, and even less commonly are these disorders diagnosed during pregnancy. This review will consider conditions of adrenal hormone excess that cause secondary hypertension: primary aldosteronism (PA), Cushing syndrome (CS), and pheochromocytoma/paraganglioma. We emphasize that pregnancy itself elicits changes in the regulation of aldosterone and cortisol production and standard endocrine testing algorithms. Furthermore, conventional imaging modalities and pharmacotherapies are often contraindicated in pregnancy, which complicates diagnosis and management. Nevertheless, surgical management in the second trimester is the preferred treatment strategy for most of these rare cases when feasible. This article will discuss the approach to patients with endocrine causes of hypertension during pregnancy with emphasis on those aspects that deviate from the assessment and treatment of non-pregnant patients.

Application of CT texture analysis to assess the localization of primary aldosteronism

We performed present study to investigate whether the localization of primary aldosteronism (PA) can be predicted using quantitative texture analysis on unenhanced computed tomography (CT). Plain CT data of 82 PA patients (54 unilateral (right-sided:left-sided = 24:30), 28 bilateral) were analyzed retrospectively. After semi-automatically setting the region of interest to include the whole adrenal gland, texture analyses were performed with or without a Laplacian of Gaussian filter with various spatial scaling factors (SSFs). Logistic regression analysis was performed using the extracted histogram-based texture features to identify parameters capable of predicting excessive aldosterone production. The result of adrenal venous sampling served as gold standard in present study. As a result, logistic regression analysis indicated that the mean gray level intensity (p = 0.026), the mean value of the positive pixels (p = 0.003) in the unfiltered image, and entropy (p = 0.027) in the filtered image (SSF: 2 mm) were significant parameters. Using the model constructed by logistic regression analysis and the optimum cutoff value, the localization of PA (three multiple choices of left, right or bilateral) was determined with an accuracy of 67.1% (55/82). CT texture analysis may provide a potential avenue for less invasive prediction of the localization of PA.

A short review of primary aldosteronism in a question and answer fashion

OBJECTIVES

The aim of this study was to present up to date information concerning the diagnosis and treatment of primary aldosteronism (PA). PA is the most common cause of endocrine hypertension. It has been reported up to 24% of selective referred hypertensive patients.

METHODS

We did a search in Pub-Med and Google Scholar using the terms: PA, hyperaldosteronism, idiopathic adrenal hyperplasia, diagnosis of PA, mineralocorticoid receptor antagonists, adrenalectomy, and surgery. We also did cross-referencing search with the above terms. We had divided our study into five sections: Introduction, Diagnosis, Genetics, Treatment, and Conclusions. We present our results in a question and answer fashion in order to make reading more interesting.

RESULTS

PA should be searched in all high-risk populations. The gold standard for diagnosis PA is the plasma aldosterone/plasma renin ratio (ARR). If this test is positive, then we proceed with one of the four confirmatory tests. If positive, then we proceed with a localizing technique like adrenal vein sampling (AVS) and CT scan. If the lesion is unilateral, after proper preoperative preparation, we proceed, in adrenalectomy. If the lesion is bilateral or the patient refuses or is not fit for surgery, we treat them with mineralocorticoid receptor antagonists, usually spironolactone.

CONCLUSIONS

Primary aldosteronism is the most common and a treatable case of secondary hypertension. Only patients with unilateral adrenal diseases are eligible for surgery, while patients with bilateral and non-surgically correctable PA are usually treated by mineralocorticoid receptor antagonist (MRA). Thus, the distinction between unilateral and bilateral aldosterone hypersecretion is crucial.

Prevalence and Histopathological Characteristics of KCNJ5 Mutant Aldosterone-Producing Adenomas in a Multi-Ethnic Malaysian Cohort

Studies on excised adrenals from primary aldosteronism patients have found that somatic mutations in KCNJ5 frequently cause excess aldosterone production in the culprit aldosterone-producing adenoma (APA). KCNJ5 mutant APAs were reported to be peculiarly overrepresented among young females and in Oriental cohorts, compared to their older male, or Caucasian counterparts. These larger APAs were also reported to have similarities with the zona fasciculata (ZF) in the adrenal both from the steroid production profile and the morphology of the cell. We therefore aimed to corroborate these findings by characterizing the APAs from a multi-ethnic Malaysian cohort. The prevalence of KCNJ5 mutations was estimated through targeted DNA sequencing of KCNJ5 in 54 APAs. Confirmation of APA sample acquisition was performed by CYP11B2 immunohistochemistry (IHC) staining. The ZF steroid production profile was based on the ZF enzyme CYP17A1 IHC staining, and ZF cell morphology was based on a high cytoplasm to nucleus ratio. Seventeen (31.5%) APAs studied, harbored a KCNJ5 mutation. No female over-representation was seen in this cohort though females were found to have a higher expression of CYP11B2 than males (p = 0.009; Mann-Whitney U test). Age at adrenalectomy correlated negatively with the percentage of ZF-like cells in the APA (p = 0.01; Spearman's rho) but not with the KCNJ5 genotype. KCNJ5 mutant APAs had a high percentage of ZF-like cells (and high CYP17A1 expression) but so did the wild-type APAs. In summary, prevalence of KCNJ5 mutant APAs in this cohort was similar to other Caucasian cohorts, however, over-representation of females did not occur, which is similar to some studies in Oriental cohorts.

Partnership trajectories and cardiovascular health in late life of older adults in England and Germany

Objectives

Previous studies have shown marital status differences in incidence and prevalence of cardiovascular disease and cardiovascular mortality. This study examines the consequences of partnership on biomarkers related to cardiovascular health of older men and women in Germany and England (C-reactive protein, HbA1c, systolic and diastolic blood pressure; and total cholesterol).

Methods

Data used is from older adults (60 +) from the German Survey of Health and Retirement Europe SHARE (n=955) and the English Longitudinal Study of Ageing ELSA (n=9707). Life course partnership is measured using the timing (age at first partnership), quantum (number of partnerships) and partnership trajectory. OLS for C-reactive protein, logistic regressions for systolic and diastolic blood pressure, and multinomial logistic regressions for cholesterol are used to investigate the associations between life course partnership characteristics and biomarkers, accounting for early age socioeconomic and health conditions.

Results

Timing of first partnership is associated with poor cardiovascular health in England, number of partnership transitions with poor health in Germany, and partnership trajectories are associated with cardiovascular health both in Germany and England. Men in trajectories with multiple marriages have higher CRP, and are more likely to have elevated systolic and diastolic BP. Trajectories containing single marital disruption for men and women are no longer associated with poor health after accounting for selection effects of childhood conditions. Respondents in widowed partnership trajectories have poorer cardiovascular health compared to those in intact committed relationships, whereas cohabitation trajectories do not differ in the associations with biomarkers from those in intact marriage.

Conclusion

The results offer better understanding of the pathways through which family events and processes are linked to health and support the hypothesis that adversity related to partnerships over the life course accumulates and contributes to worse cardiovascular health in later life measured by objective health measures.

•

This study investigates the longitudinal accumulated effects of partnership on cardiovascular health using haemostatic and inflammatory biomarkers in later-life, C-reactive protein, HbA1c, systolic and diastolic blood pressure; and total cholesterol.

•

Based on life course theory of cumulative disadvantage, the study finds support that the benefits and risks of marital status accumulate over the life-course. The effects are visible on biomarkers of older adults in both Germany and England in models that account for conditions in early life, health behaviors in adult life and sociodemographic factors.

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Data used is from older adults (60 +) form the German Survey of Health and Retirement Europe SHARE (n=955) and the English Longitudinal Study of Ageing ELSA (n=9707). Life course partnership is measured using the timing (age at first partnership), quantum (number of partnerships) and partnership sequence type.

Subtype prediction of primary aldosteronism by combining aldosterone concentrations in the left adrenal vein and inferior vena cava: a multicenter collaborative study on adrenal venous sampling

Subtype diagnosis of primary aldosteronism (PA) by adrenal vein sampling (AVS) is recommended as a mandatory step for indicating adrenal surgery. It is a technically demanding procedure, especially in the right adrenal vein. The aim of the study was to predict the subtype diagnosis in the absence of values from the right AVS. From the databases of nine centers (WAVES-J), 308 patients with PA who underwent successful AVS were studied. Based on the ipsilateral ratio (IR) (aldosterone/cortisol ratio of the left adrenal vein [A/C_{left AV}] / aldosterone/cortisol ratio of the inferior vena cava [A/C_IVC]), the patients were divided into two groups: the patients with IR ≥ 1.0 (n = 262) and those with IR < 1.0 (n = 46). In patients with IR > 1.0, the A/C_{left AV} was significantly higher in patients with the left unilateral subtype than in patients with the bilateral subtype. Receiver operating characteristic (ROC) curve analysis revealed that an A/C_{left AV} cutoff >68 showed 70.8% sensitivity and 93.5% specificity for the left unilateral subtype. On the other hand, in patients with IR < 1.0, the A/C_{left AV} was significantly lower in patients with the right unilateral subtype. ROC analysis revealed that an A/C_{left AV} cutoff <9 showed 86.7% sensitivity and 75.0% specificity for the right unilateral subtype. Hence, the combination of the IR and A/C ratio in the left adrenal vein is useful for predicting the subtype. The present results provide important information for patients with PA in whom AVS was unsuccessful in the right adrenal vein.

Screening for primary aldosteronism using the newly developed IDS-iSYS® automated assay system

BACKGROUND

The recommended approach to screening for primary aldosteronism (PA) in at-risk populations is to determine the ratio of aldosterone concentration (serum (SAC)/plasma (PAC)) to renin measured in plasma as activity (PRA) or concentration (DRC). However, lack of assay standardisation mandates the need for method-specific decision thresholds and clinical validation in the local population.

AIM

The study objective was to establish method-specific aldosterone: renin ratio (ARR) cut-offs for PA in men and women using the IDS-iSYS® assay system (IDS plc).

METHODS

A prospective cohort study design was used. PAC and DRC were measured immunochemically in ethylenediamine-tetraacetic acid (EDTA) plasma on the IDS-iSYS® instrument.

RESULTS

A total of 437 subjects (218 men, 219 women) were recruited including: healthy normotensive volunteers (n=266) and women taking the oral contraceptive pill (OCP; n=15); patients with essential hypertension (EH; n=128); confirmed PA (n=16); adrenal cortical carcinoma (ACC; n=3); Addison's disease (AD; n=4) and phaeochromocytoma/paraganglioma (PPGL; n=5). In this population, an ARR cut-off at >37.4 pmol/mIU provided 100% diagnostic sensitivity, 96% specificity and positive likelihood ratio for PA of 23:1. When the ARR decision threshold was stratified according to gender, a cut-off of >26.1 pmol/mIU in men and >113.6 pmol/mIU in women resulted in diagnostic sensitivity and specificity of 100%.

CONCLUSION

This study demonstrates that decision thresholds for PA should not only be method-specific but also gender-specific. However, given the small number of PA patients (n=16), particularly women (n=4), further validation through a prospective study with a larger PA cohort is required before the thresholds presented here could be recommended for routine clinical use.

Renin angiotensin aldosterone system altered in resistant hypertension in Sub-Saharan African diabetes patients without evidence of primary hyperaldosteronism

BACKGROUND

The renin-angiotensin-aldosterone system may be altered in patients with resistant hypertension. This study aimed to evaluate the relation between renin-angiotensin-aldosterone system activity and resistant hypertension in Cameroonian diabetes patients with resistant hypertension.

METHODS

We carried out a case-control study including 19 diabetes patients with resistant hypertension and 19 diabetes patients with controlled hypertension matched to cases according to age, sex and duration of hypertension since diagnosis. After collection of data, fasting blood was collected for measurement of sodium, potassium, chloride, active renin and plasma aldosterone of which the aldosterone-renin ratio was derived to assess the activity of renin-angiotensin-aldosterone system. Then, each participant received 2000 ml infusion of saline solution after which plasma aldosterone was re-assayed.

RESULTS

Potassium levels were lower among cases compared to controls (mean: (4.10 ± 0.63 mmol/l vs. 4.47 ± 0.58 mmol/l), though nonsignificant (p = 0.065). Active renin, plasma aldosterone both before and after the dynamic test and aldosterone-renin ratio were comparable between cases and controls (all p values > 0.05). Plasma aldosterone significantly decreased after the dynamic test in both groups (p < 0.001), but no participant exhibited a post-test value>280 pmol/l. We found a significant negative correlation between potassium ion and plasma aldosterone (ρ = -0.324; p = 0.047), the other correlations being weak and unsignificant.

CONCLUSION

Although this study failed to show an association between RH and primary hyperaldosteronism in our context, there was a hyperactivity of renin-angiotensin-aldosterone system. Moreover, this study confirms the importance of potassium dosage when screening the renin-angiotensin-aldosterone system.

New Advances in the Diagnostic Workup of Primary Aldosteronism

Primary aldosteronism is an important and common cause of hypertension that carries a high burden of morbidity. Outcomes, however, are excellent if diagnosed and treated appropriately. The diagnostic workup for primary aldosteronism is complex and comprises three steps: (1) screening, (2) confirmatory testing, and (3) subtype differentiation. In this review, we discuss recent advances in the diagnostic workup for primary aldosteronism. The development of accurate mass spectroscopy-based assays for measuring aldosterone will lead to improved confidence in all diagnostic aspects involving measurement of aldosterone, and accurate measurement of angiotensin II may soon advance us beyond the measurement of renin. We now have a greater understanding of hormonal influences on the aldosterone/renin ratio, which are particularly important when screening premenopausal women or those taking estrogen-containing preparations. Confirmatory testing is important, but there are limitations to the commonly used methods that have recently become more apparent, with new approaches offering a way forward. Adrenal venous sampling (AVS) is a challenging procedure but is important for deciding on treatment options. Success rates may be improved by the use of Synacthen stimulation and of rapid intraprocedural measurement of cortisol. Better understanding of AVS interpretation criteria allows improved prognostication and aids treatment decisions. The use of labeled metomidate positron emission tomography computed tomography scanning may also offer an alternative to AVS in some units. Although the diagnostic approach to patients with primary aldosteronism remains a complex multistep process in which attention to detail is important, recent advances will improve patient care and outcomes.

Role of the Renin-Angiotensin-Aldosterone System beyond Blood Pressure Regulation: Molecular and Cellular Mechanisms Involved in End-Organ Damage during Arterial Hypertension

Arterial hypertension is a common condition worldwide and an important predictor of several complicated diseases. Arterial hypertension can be triggered by many factors, including physiological, genetic, and lifestyle causes. Specifically, molecules of the renin-angiotensin-aldosterone system not only play important roles in the control of blood pressure, but they are also associated with the genesis of arterial hypertension, thus constituting a need for pharmacological interventions. Chronic high pressure generates mechanical damage along the vascular system, heart, and kidneys, which are the principal organs affected in this condition. In addition to mechanical stress, hypertension-induced oxidative stress, chronic inflammation, and the activation of reparative mechanisms lead to end-organ damage, mainly due to fibrosis. Clinical trials have demonstrated that renin-angiotensin-aldosterone system intervention in hypertensive patients lowers morbidity/mortality and inflammatory marker levels as compared to placebo patients, evidencing that this system controls more than blood pressure. This review emphasizes the detrimental effects that a renin-angiotensin-aldosterone system (RAAS) imbalance has on health considerations above and beyond high blood pressure, such as fibrotic end-organ damage.

The Aldosterone/Renin Ratio as a Diagnostic Tool for the Diagnosis of Primary Hypoaldosteronism in Newborns and Infants

BACKGROUND/AIMS

Primary hypoaldosteronism is a rare inborn disorder with life-threatening symptoms in newborns and infants due to an aldosterone synthase defect. Diagnosis is often difficult as the plasma aldosterone concentration (PAC) can remain within the normal range and thus lead to misinterpretation and delayed initiation of life-saving therapy. We aimed to test the eligibility of the PAC/plasma renin concentration (PRC) ratio as a tool for the diagnosis of primary hypoaldosteronism in newborns and infants. Meth ods: Data of 9 patients aged 15 days to 12 months at the time of diagnosis were collected. The diagnosis of primary hypoaldosteronism was based on clinical and laboratory findings over a period of 12 years in 3 different centers in Switzerland. To enable a valid comparison, the values of PAC and PRC were correlated to reference methods.

RESULTS

In 6 patients, the PAC/PRC ratio could be determined and showed constantly decreased values <1 (pmol/l)/(mU/l). In 2 patients, renin was noted as plasma renin activity (PRA). PAC/PRA ratios were also clearly decreased. The diagnosis was subsequently genetically confirmed in 8 patients.

CONCLUSION

A PAC/PRC ratio <1 pmol/mU and a PAC/PRA ratio <28 (pmol/l)/(ng/ml × h) are reliable tools to identify primary hypoaldosteronism in newborns and infants and help to diagnose this life-threatening disease faster.

Modulation of Immunity and Inflammation by the Mineralocorticoid Receptor and Aldosterone

The mineralocorticoid receptor (MR) is a ligand dependent transcription factor. MR has been traditionally associated with the control of water and electrolyte homeostasis in order to keep blood pressure through aldosterone activation. However, there is growing evidence indicating that MR expression is not restricted to vascular and renal tissues, as it can be also expressed by cells of the immune system, where it responds to stimulation or antagonism, controlling immune cell function. On the other hand, aldosterone also has been associated with proinflammatory immune effects, such as the release of proinflammatory cytokines, generating oxidative stress and inducing fibrosis. The inflammatory participation of MR and aldosterone in the cardiovascular disease suggests an association with alterations in the immune system. Hypertensive patients show higher levels of proinflammatory mediators that can be modulated by MR antagonism. Although these proinflammatory properties have been observed in other autoimmune and chronic inflammatory diseases, the cellular and molecular mechanisms that mediate these effects remain unknown. Here we review and discuss the scientific work aimed at determining the immunological role of MR and aldosterone in humans, as well as animal models.

Somatic mutations of the ATP1A1 gene and aldosterone-producing adenomas

Primary aldosteronism is the most common form of secondary hypertension. It affects approximately 10% of patients with hypertension and causes greater cardiovascular morbidity and mortality compared to essential hypertension of similar severity and duration. The cause of primary aldosteronism in about half of these patients is an aldosterone-producing adenoma; over half of these adenomas have mutations in one of several ion channels and pumps, including the potassium channel KCNJ5, calcium channel Cav1.3, α1 subunit of the sodium potassium ATPase, and membrane calcium ATPase 3. This review concentrates on the molecular and physiological mechanisms by which mutations of the ATP1A1 gene increase aldosterone production.

Cost-Effectiveness of Therapeutic Drug Monitoring in Diagnosing Primary Aldosteronism in Patients With Resistant Hypertension

Primary aldosteronism (PA) is present in up to 20% of patients with treatment-resistant hypertension (TRH). Investigation for PA in patients with TRH is recommended by current guidelines after medication nonadherence is excluded. Studies using therapeutic drug monitoring (TDM) have shown that >50% of patients with TRH are nonadherent to their prescribed antihypertensive medications. However, the relationship between the prevalence of PA and medication adherence as confirmed by TDM has not been previously assessed. A retrospective analysis from a hypertension referral clinic showed that prevalence of PA in adherent patients with TRH by TDM was significantly higher than in nonadherent patients (28% vs 8%, P<.05). Furthermore, cost analysis showed that TDM-guided PA screening was $590.69 less expensive per patient, with minimal impact on the diagnostic accuracy. These data support a TDM-guided PA screening approach as a cost-saving strategy compared with routine PA screening for TRH.

The evaluation and treatment of endocrine forms of hypertension

Endocrine hypertension is an important secondary form of hypertension, identified in between 5% and 10% of general hypertensive population. Primary aldosteronism is the most common cause of endocrine hypertension, accounting for 1%-10% in uncomplicated hypertension and 7%-20% in resistant hypertension. Other less common causes of endocrine hypertension include Cushing syndrome, pheochromocytoma, thyroid disorders, and hyperparathyroidism. Diagnosis requires a high index of suspicion and the use of appropriate screening tests based on clinical presentation. Failure to make proper diagnosis may lead to catastrophic complications or irreversible hypertensive target organ damage. Accordingly, patients who are suspected to have endocrine hypertension should be referred to endocrinologists or hypertension specialists who are familiar with management of the specific endocrine disorders.

Converging indications of aldosterone antagonists (spironolactone and eplerenone): a narrative review of safety profiles

The converging clinical effectiveness of mineralocorticoid receptor antagonists (MRAs) Spironolactone and Eplerenone has made their safety profiles/cost-effectiveness key determinants of "agents of choice" across a broad range of clinical indications. The clinical biology of the aldosterone molecule and its range of effects in varied organ systems have been well elucidated from recent mechanistic and systematic studies. Clinical experience with Spironolactone is well established, as is its adverse effects profile. The range of adverse effects experienced with Spironolactone subsequently led to its modification and synthesis of Eplerenone. Recent published reports have confirmed lower prevalence rates of sex-related adverse effects attributable to Eplerenone compared to Spironolactone. There is, however, not much to choose between these agents in regards to other adverse effects including hyperkalemia and kidney failure. As was the experience with Spironolactone, as more robust observational data on Eplerenone accrues, it is possible that the real-life experience of its adverse profile may be discordant with that reported by randomized controlled clinical trials (RCTs). In addition, its metabolism by the vulnerable and highly polymorphic cytochrome dependent pathway also makes it susceptible to various drug interactions. The potential implication of the latter (including morbidity and mortality) may take years to evolve.

Interfering with mineralocorticoid receptor activation: the past, present, and future

Aldosterone is a potent mineralocorticoid produced by the adrenal gland. Aldosterone binds to and activates the mineralocorticoid receptor (MR) in a plethora of tissues, but the cardiovascular actions of aldosterone are of primary interest clinically. Although MR antagonists were developed as antihypertensive agents, they are now considered to be important therapeutic options for patients with heart failure. Specifically, blocking only the MR has proven to be a difficult task because of its similarity to other steroid receptors, including the androgen and progesterone receptors. This lack of specificity caused the use of the first-generation mineralocorticoid receptor antagonists to be fraught with difficulty because of the side effects produced by drug administration. However, in recent years, several advances have been made that could potentially increase the clinical use of agents that inhibit the actions of aldosterone. These will be discussed here along with some examples of the beneficial effects of these new therapeutic agents.

Different expression of 11β-hydroxylase and aldosterone synthase between aldosterone-producing microadenomas and macroadenomas

Aldosterone-producing adenoma is a major subtype of primary aldosteronism. The number of cases of these adenomas, which are below the detection limit of computed tomography but diagnosed by adrenal venous sampling, has recently been increasing. However, the pathophysiology of these adenomas, especially those manifesting clinically overt hyperaldosteronism despite their small size, remains unknown. Therefore, we examined the correlation between tumor size and the status of intratumoral steroidogenic enzymes involved in aldosterone biosynthesis using immunohistochemistry. Forty patients with surgically proven aldosterone-producing adenomas were retrospectively studied. Multidetector computed tomography, adrenal venous sampling, and laparoscopic adrenalectomy were performed in all of the patients studied. The tumor area at the maximum diameter of the sections was precisely measured by ImageJ software. The status of the steroidogenic enzymes was immunohistochemically analyzed, and the findings were evaluated according to the H-score system, based on both the number of immunopositive cells and relative immunointensity. Adrenal masses were not detected by computed tomography in 20 patients. Blood pressure, plasma aldosterone concentration, urinary aldosterone excretion, and the number of antihypertensive agents also decreased significantly after the surgery in these patients, as well as in the patients with adenomas detectable by computed tomography. Maximum tumor area obtained in the specimens was significantly correlated with preoperative plasma aldosterone concentration, urinary aldosterone excretion, and the H score of 11β-hydroxylase and was inversely correlated with the H score of aldosterone synthase. These results demonstrated that small adenomas could produce sufficient aldosterone to cause clinically overt primary aldosteronism because of the significantly higher aldosterone synthase expression per tumor area.

Predictors of successful outcome after adrenalectomy for primary aldosteronism

The underlying cause of resistant hypertension after adrenalectomy for primary hyperaldosteronism remains controversial. The objective of this study was to identify preoperative factors predictive of resistant hypertension in patients after undergoing retroperitoneoscopic adrenalectomy. Between 2003 and 2009, 124 patients with unilateral aldosterone-producing adenoma or unilateral adrenal hyperplasia underwent retroperitoneoscopic adrenalectomy at our institution. Clinical and biochemical data were reviewed retrospectively at baseline and after a median follow-up time of 59.2 ± 37.2 months. Adrenalectomy cured hypertension in 68 patients (54.8%) and 43 (34.8%) had persistent hypertension that was much easier to control after surgery, whereas 13 patients (10.4%) had continued hypertension and poor blood pressure control. Multivariate regression analysis revealed that the main determinants of postoperative cure were duration of hypertension less than 5 years [odds ratio (OR): 6.515, 95% confidence interval (CI) 2.278-10.293), number of antihypertensive medications ≤2 (OR: 2.939, 95% CI 1.254-5.235), preoperative response to spironolactone (OR: 3.405, 95% CI 1.681-6.985), the TT genotype of the CYP11B2 gene (344 C/T) (OR: 2.765, 95% CI 1.221-4.986), and the presence of adenoma rather than hyperplasia (OR: 5.274, 95% CI 2.150-8.141). The main determinants of surgical cure or control of hypertension in patients with primary hyperaldosteronism were duration of hypertension, number of antihypertensive medications, preoperative response to spironolactone, the presence of adenoma, and CYP11B2 (344 C/T) genotype. Consideration of these factors may help in the evaluation of patients for surgery and for the identification of patients with continued postoperative hypertension that may require more long-term monitoring and treatment.

A case of primary aldosteronism who experienced cardiopulmonary arrest, was resuscitated and cured

A 45-year-old female went into cardiopulmonary arrest. She was in ventricular fibrillation (VF) and was defibrillated using an automated external defibrillator. After arrival at our hospital, electrocardiography monitoring showed QT prolongation. Serum potassium was low at 2.2 mEq/L, and hypokalemia-induced long QT syndrome was considered to be the cause of this patient's VF. An intravenous infusion of potassium and magnesium sulphate was started, which normalized her serum potassium and QTc interval, with no recurrence of ventricular arrhythmias. Endocrinological investigations showed a plasma renin activity of <0.1 ng/(mL h) and a plasma aldosterone concentration 258 pg/mL. Computed tomography scanning revealed a low signal area 16 mm × 20 mm in size of the right adrenal gland. From the above findings, this patient was diagnosed with a right adrenal tumor and primary aldosteronism. We concluded that the right adrenal tumor was excreting excess amounts of aldosterone from adrenal vein sampling, and performed laparascopic right adrenalectomy. Serum potassium levels rose immediately to normal levels postoperatively. We were able to withdraw her antihypertensive medication 3 months after adrenalectomy. We report a case of primary aldosteronism who experienced cardiopulmonary arrest, was resuscitated, and cured. <Learning objective: When you come across ventricular fibrillation, please consider one of the reasons is caused by hypokalemia due to primary aldosteronism. After an appropriate resuscitation, both hypokalemia and hypertension are completely curable by removing the adrenal tumor.>.

NP-59 SPECT/CT imaging in stage 1 hypertensive and atypical primary aldosteronism: a 5-year retrospective analysis of clinicolaboratory and imaging features

OBJECTIVE

We retrospectively analyzed all primary aldosteronism (PA) patients undergoing NP-59 SPECT/CT imaging with regard to their clinicolaboratory and imaging features, investigation, and outcomes.

MATERIAL AND METHODS

11 PA patients who presented to our hospital for NP-59 SPECT/CT imaging between April 2007 and March 2012 and managed here were analyzed.

RESULTS

Among 11 PA patients, eight (73%) had stage 1 hypertension, three (27%) stage 2 hypertension, four (36%) normal plasma aldosterone concentration, nine (82%) nonsuppressed plasma renin activity (PRA), six (55%) normal aldosterone-renin-ratio (ARR), eight (73%) serum potassium ≧3 mEq/L, seven (64%) subclinical presentation, seven (64%) negative confirmatory testing, and four (36%) inconclusive results on CT scan and seven (64%) on planar NP-59 scan. All 11 (100%) patients had positive results on NP-59 SPECT/CT scan. Two (18%) met typical triad and nine (82%) atypical triad. Among nine atypical PA patients, three (33%) had clinical presentation, six (67%) subclinical presentation, six (67%) negative confirmatory testing, and four (44%) inconclusive results on CT scan and six (67%) on planar NP-59 scan. All patients had improved outcomes. Significant differences between typical and atypical PA existed in PRA and ARR.

CONCLUSIONS

NP-59 SPECT/CT may provide diagnostic potential in stage 1 hypertensive and atypical PA.

Predictors of malignancy in primary aldosteronism

INTRODUCTION

Primary aldosteronism (PA, also Conn syndrome) is a benign disease in majority of cases. However, malignant transformation has been described. Present study reports on three cases of aldosterone producing adrenocortical carcinoma (APAC) in comparison to patients with benign PA.

PATIENTS AND METHODS

Data of patients undergoing adrenalectomy for benign PA were compared to patients with APAC. Retrospective chart analysis was performed. All patients received spironolactone for 6-8 weeks preoperatively.

RESULTS

Seventy-four patients underwent adrenalectomy for PA between 1994 and 2011. Three of them revealed an APAC. Patients with APAC presented with a significantly lower serum potassium level (1.7 mmol/l vs. 3.4 mmol/l, p = 0.001) and significant larger tumors (5.2 vs. 1.8 cm, p = 0.002). In addition, aldosterone/renin (A/R) ratio 675 in patients with APAC as compared to 74 in patients with benign PA (p = 0.0001). Sixty-eight of 71 patients with benign PA underwent minimal invasive surgery, whereas all three patients with APAC were operated conventionally. All patients with APAC developed disease recurrence 6-18 months postoperatively.

CONCLUSION

Tumor size >4 cm and a very high A/R ratio seems to predictors of malignancy in patients with PA. If these criteria are present, open adrenalectomy should be performed instead of endoscopic procedure.

Efficacy of adrenal venous sampling is increased by point of care cortisol analysis

Primary aldosteronism (PA) is a common cause of secondary hypertension and is caused by unilateral or bilateral adrenal disease. Treatment options depend on whether the disease is lateralized or not, which is preferably evaluated with selective adrenal venous sampling (AVS). This procedure is technically challenging, and obtaining representative samples from the adrenal veins can prove difficult. Unsuccessful AVS procedures often require reexamination. Analysis of cortisol during the procedure may enhance the success rate. We invited 21 consecutive patients to participate in a study with intra-procedural point of care cortisol analysis. When this assay showed nonrepresentative sampling, new samples were drawn after redirection of the catheter. The study patients were compared using the 21 previous procedures. The intra-procedural cortisol assay increased the success rate from 10/21 patients in the historical cohort to 17/21 patients in the study group. In four of the 17 successful procedures, repeated samples needed to be drawn. Successful sampling at first attempt improved from the first seven to the last seven study patients. Point of care cortisol analysis during AVS improves success rate and reduces the need for reexaminations, in accordance with previous studies. Successful AVS is crucial when deciding which patients with PA will benefit from surgical treatment.

Interaction between nitric oxide and superoxide in the macula densa in aldosterone-induced alterations of tubuloglomerular feedback

Tubuloglomerular feedback (TGF)-mediated constriction of the afferent arteriole is modulated by a balance between release of superoxide (O(2)(-)) and nitric oxide (NO) in macula densa (MD) cells. Aldosterone activates mineralocorticoid receptors that are expressed in the MD and induces both NO and O(2)(-) generation. We hypothesize that aldosterone enhances O(2)(-) production in the MD mediated by protein kinase C (PKC), which buffers the effect of NO in control of TGF response. Studies were performed in microdissected and perfused MD and in a MD cell line, MMDD1 cells. Aldosterone significantly enhanced O(2)(-) generation both in perfused MD and in MMDD1 cells. When aldosterone (10(-7) mol/l) was added in the tubular perfusate, TGF response was reduced from 2.4 ± 0.3 μm to 1.4 ± 0.2 μm in isolated perfused MD. In the presence of tempol, a O(2)(-) scavenger, TGF response was 1.5 ± 0.2 μm. In the presence of both tempol and aldosterone in the tubular perfusate, TGF response was further reduced to 0.4 ± 0.2 μm. To determine if PKC is involved in aldosterone-induced O(2)(-) production, we exposed the O(2)(-) cells to a nonselective PKC inhibitor chelerythrine chloride, a specific PKCα inhibitor Go6976, or a PKCα siRNA, and the aldosterone-induced increase in O(2)(-) production was blocked. These data indicate that aldosterone-stimulated O(2)(-) production in the MD buffers the effect of NO in control of TGF response, an effect that was mediated by PKCα.

Unilateral adrenal hyperplasia is a usual cause of primary hyperaldosteronism. Results from a Swedish screening study

BACKGROUND

The existence of unilateral adrenal hyperplasia (AH) has been considered a rare cause of primary hyperaldosteronism (PA).

METHODS

In a prospective study we screened for PA in a non-selected (NSP) and selected hypertensive population (SP), to define the cause of PA. We included 353 consecutive patients with hypertension; age 20 to 88 years, 165 women and 188 men, from a university-based Hypertension and Nephrology Outpatient clinics (123 SP) and two primary care centres, (230 NSP) from the same catch-up area. Serum aldosterone and plasma renin activity (PRA) were measured and the ARR calculated. Verifying diagnostic procedure was performed in patients with both elevated aldosterone and ARR. Patients diagnosed with PA were invited for adrenal venous sampling (AVS) and offered laparoscopic adrenalectomy when AVS found the disease to be unilateral.

RESULTS

After screening, 46 patients, 13% of the whole population (22.8% SP and 7.8% NSP) had aldosterone and ARR above the locally defined cut-off limits (0.43 nmol/l and 1.28 respectively). After diagnostic verification, 20 patients (6%) had PA, (14.5% SP and 1.4% NSP). Imaging diagnostic procedures with CT-scans and scintigraphy were inconclusive. AVS, performed in 15 patients verified bilateral disease in 4 and unilateral in 10 patients. One AVS failed. After laparoscopic adrenalectomy, 4 patients were found to have adenoma and 5 unilateral AH. One patient denied operation.

CONCLUSION

The prevalence of PA was in agreement with previous studies. The study finds unilateral PA common and unilateral AH as half of those cases. As may be suspected PA is found in much higher frequency in specialised hypertensive units compared to primary care centers. AVS was mandatory in diagnosis of unilateral PA.

A novel point mutation in the KCNJ5 gene causing primary hyperaldosteronism and early-onset autosomal dominant hypertension

CONTEXT

Aldosterone production in the adrenal zona glomerulosa is mainly regulated by angiotensin II, [K(+)], and ACTH. Genetic deletion of subunits of K(+)-selective leak (KCNK) channels TWIK-related acid sensitive K(+)-1 and/or TWIK-related acid sensitive K(+)-3 in mice results in primary hyperaldosteronism, whereas mutations in the KCNJ5 (potassium inwardly rectifying channel, subfamily J, member 5) gene are implicated in primary hyperaldosteronism and, in certain cases, in autonomous glomerulosa cell proliferation in humans.

OBJECTIVE

The objective of the study was to investigate the role of KCNK3, KCNK5, KCNK9, and KCNJ5 genes in a family with primary hyperaldosteronism and early-onset hypertension.

PATIENTS AND METHODS

Two patients, a mother and a daughter, presented with severe primary hyperaldosteronism, bilateral massive adrenal hyperplasia, and early-onset hypertension refractory to medical treatment. Genomic DNA was isolated and the exons of the entire coding regions of the above genes were amplified and sequenced. Electrophysiological studies were performed to determine the effect of identified mutation(s) on the membrane reversal potentials.

RESULTS

Sequencing of the KCNJ5 gene revealed a single, heterozygous guanine to thymine (G → T) substitution at nucleotide position 470 (n.G470T), resulting in isoleucine (I) to serine (S) substitution at amino acid 157 (p.I157S). This mutation results in loss of ion selectivity, cell membrane depolarization, increased Ca(2+) entry in adrenal glomerulosa cells, and increased aldosterone synthesis. Sequencing of the KCNK3, KCNK5, and KCNK9 genes revealed no mutations in our patients.

CONCLUSIONS

These findings explain the pathogenesis in a subset of patients with severe hypertension and implicate loss of K(+) channel selectivity in constitutive aldosterone production.

Active renin mass concentration to determine aldosterone-to-renin ratio in screening for primary aldosteronism

Background:

Active renin mass concentration (ARC) is independent of the endogenous level of angiotensinogen, and less variable and more reproducible than plasma renin activity. Reference values for the aldosterone-to-renin ratio (ARR) using ARC are still undefined. The objective of the present study was to determine the threshold of ARR using ARC measurement to screen for primary aldosteronism.

Methods:

A total of 211 subjects were included in the study, comprising 78 healthy normotensive controls, 95 patients with essential hypertension, and 38 patients with confirmed primary aldosteronism (20 with surgery-confirmed aldosterone-producing adenoma and 18 with idiopathic adrenal hyperplasia). Blood samples were drawn from ambulatory patients and volunteers in the mid-morning without specific dietary restriction for measuring plasma aldosterone concentration, ARC, and serum potassium.

Results:

Most normotensive controls and essential hypertension patients had ARR results below 100 pmol/ng, a value which corresponded to 3.3 times the median of these two groups.

Conclusion:

Patients with ARR values above this level should be considered for further investigation (confirmatory tests) or for repeat testing should ARR values be borderline. This study indicates that ARC can be used reliably in determining ARR for primary aldosteronism screening.

Changes in the perceived epidemiology of primary hyperaldosteronism

Primary aldosteronism has been considered a rare disease in the past years, affecting 1% of the hypertensive population. Subsequently, growing evidence of its higher prevalence is present in literature, although the estimates of disease range from 5 up to 20%, as in type 2 diabetes and resistant hypertension. The main reasons for these variations are associated with the selection of patients and diagnostic procedures. If we consider that hypertension is present in about 20% of the adult population, primary aldosteronism can no longer be considered a rare disease. Patients with primary aldosteronism have a high incidence of cardiovascular, cerebrovascular and kidney complications. The identification of these patients has therefore a practical value on therapy, and to control morbidities derived from vascular damage. The ability to identify the prevalence of a disease depends on the number of subjects studied and the methods of investigation. Epidemiological studies are affected by these two problems: there is not consensus on patients who need to be investigated, although testing is recommended in subjects with resistant hypertension and diabetes. The question of how to determine aldosterone and renin levels is open, particularly if pharmacological wash-out is difficult to perform because of inadequate blood pressure control.

Common secondary causes of resistant hypertension and rational for treatment

Resistant hypertension is defined as uncontrolled blood pressure despite the use of three antihypertensive drugs, including a diuretic, in optimal doses. Treatment resistance can be attributed to poor adherence to antihypertensive drugs, excessive salt intake, physician inertia, inappropriate or inadequate medication, and secondary hypertension. Drug-induced hypertension, obstructive sleep apnoea, primary aldosteronism, and chronic kidney disease represent the most common secondary causes of resistant hypertension. Several drugs can induce or exacerbate pre-existing hypertension, with non-steroidal anti-inflammatory drugs being the most common due to their wide use. Obstructive sleep apnoea and primary aldosteronism are frequently encountered in patients with resistant hypertension and require expert management. Hypertension is commonly found in patients with chronic kidney disease and is frequently resistant to treatment, while the management of renovascular hypertension remains controversial. A step-by-step approach of patients with resistant hypertension is proposed at the end of this review paper.

Primary aldosteronism: A Japanese perspective

Primary aldosteronism (PA) is the most common cause of secondary hypertension, accounting for 10% of all hypertension. Far from being benign, hypertension due to PA is associated with high cardiovascular morbidity and mortality. However, PA is still underdiagnosed in general practice. Recent reports strongly recommend that identifying patients with PA is cost-beneficial based on improved cardiovascular outcomes afforded by specific surgical and medical treatment. This review provides an update of PA including controversial aspects of diagnosis and treatment.

Diagnosis and treatment of primary aldosteronism

Primary aldosteronism involves more than 11% of hypertensive patients who are referred to specialized centers for the diagnosis and treatment of hypertension. If not diagnosed early it causes an excess damage to the heart, vessels and kidney, which translates into an cardiovascular events. Since these ominous consequences can be corrected with a timely diagnosis and an appropriate therapy, physicians should exercise a high degree of alert concerning the possibility that primary aldosteronism is present in hypertensive patients. The purpose of this review is to provide up-dated information on the strategy for case detection, the subtype differentiation and the management of primary aldosteronism.

Treatment of primary aldosteronism: Where are we now?

Primary aldosteronism (PA) is an important cause of secondary hypertension, is being increasingly diagnosed and may account for more than 10% of hypertensive patients, both in primary care and in referral centers. Aldosterone excess is associated with adverse cardiovascular, renal and metabolic effects that are in part hypertension-independent. Laparoscopic adrenalectomy remains the mainstay of treatment for unilateral forms of PA, whereas medical treatment is recommended for bilateral forms of PA. However, a favourable surgical outcome depends on several factors and many patients are not suitable for this treatment. On the other hand, surgery in patients considered to have bilateral PA may contribute to better blood pressure control. In this review, established and novel strategies for the management of different types of PA are discussed.

Resistant hypertension workup and approach to treatment

Resistant hypertension is defined as blood pressure above the patient's goal despite the use of 3 or more antihypertensive agents from different classes at optimal doses, one of which should ideally be a diuretic. Evaluation of patients with resistive hypertension should first confirm that they have true resistant hypertension by ruling out or correcting factors associated with pseudoresistance such as white coat hypertension, suboptimal blood pressure measurement technique, poor adherence to prescribed medication, suboptimal dosing of antihypertensive agents or inappropriate combinations, the white coat effect, and clinical inertia. Management includes lifestyle and dietary modification, elimination of medications contributing to resistance, and evaluation of potential secondary causes of hypertension. Pharmacological treatment should be tailored to the patient's profile and focus on the causative pathway of resistance. Patients with uncontrolled hypertension despite receiving an optimal therapy are candidates for newer interventional therapies such as carotid baroreceptor stimulation and renal denervation.

Genetic analyses of the chimeric CYP11B1/CYP11B2 gene in a Korean family with glucocorticoid-remediable aldosteronism

Glucocorticoid-remediable aldosteronism (GRA) is an autosomal-dominant inheritable form of hyperaldosteronism with early onset hypertension. GRA is caused by unequal crossing-over of the steroid 11 beta-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) genes. As a result of chimeric gene duplication, aldosterone is ectopically synthesized in the adrenal zona fasciculata under the control of adrenocorticotropin. Here, we describe three cases of GRA in a Korean family. The proband-a 21-yr-old female-was incidentally found to have high blood pressure (170/108 mmHg). Her 46-yr-old father had been treated twice for cerebral hemorrhage at the ages of 29 and 39 yr. Her 15-yr-old brother had a 2-yr history of hypertension; however, he was never treated. Their laboratory test results showed normokalemia, hyporeninemia, hyperaldosteronism, and a high plasma aldosterone concentration-to-plasma renin activity ratio. Normal saline loading failed to suppress aldosterone secretion. However, dexamethasone administration effectively suppressed their plasma aldosterone concentrations. Following genetic analyses with PCR and direct sequencing to document the chimeric gene and crossover site, respectively, we identified CYP11B1/CYP11B2 and determined the breakpoint of unequal crossover to be located between intron 2 of CYP11B1 and exon 3 of CYP11B2.

The role of TASK1 in aldosterone production and its expression in normal adrenal and aldosterone-producing adenomas

OBJECTIVES

Aldosterone production in the adrenal glomerulosa is mainly regulated by angiotensin II and K+. Adrenal glomerulosa cells are uniquely sensitive to extracellular K+. Genetic deletion of subunits of K+-selective leak-channels (KCNK), TASK1 and/or TASK3, in mice generates animals with hyperaldosteronism and histological changes in the adrenal cortex. Herein, we studied the expression of TASK1 in human adrenocortical cells, as well as its role in aldosterone production in H295R cells.

DESIGN

TASK1 expression was investigated by comparative microarray analysis of aldosterone-producing adenomas (APA) and normal adrenals (NAs). The effects of TASK1 knockdown by siRNA transfection were investigated in H295R cells. Fluo-4 fluorescent measurements of intracellular Ca2+ and pharmacological inhibition of Ca2+ -dependent calmodulin kinases (CaMK) were performed to better define the effects of TASK1 on Ca2+ signalling pathways.

RESULTS

Microarray analysis of APA and NA showed similar expression of TASK1 between these two groups. However, in APA, NA and H295R cells the expression of TASK1 was predominant when compared with other KCNK family members. Knockdown of TASK1 (with siRNA) induced the expression of steroidogenic acute regulatory (StAR) protein and aldosterone synthase (CYP11B2), and also stimulated pregnenolone and aldosterone production. Cells transfected with siTASK1 had increased intracellular Ca2+, leading to activation of CaMK and increased expression of CYP11B2.

CONCLUSIONS

Our study reveals the predominant expression of TASK1 over other KCNK family genes in the human adrenal cortex. Herein, we also described the role of TASK1 in the regulation of human aldosterone production through regulation of intracellular Ca2+ and CaMK signalling pathways.

Progress in primary aldosteronism: present challenges and perspectives

Primary Aldosteronism (PA) is a disorder of the adrenal zona glomerulosa (ZG) in which aldosterone secretion is increased and is relatively autonomous of normal regulatory mechanisms. A recent conference in Munich organized by Prof. Reincke addressed advances and challenges related to the screening, diagnosis, and identification of uni- and bilateral involvement of the diseased adrenal of PA. Some infrequently addressed issues are described herein. We postulate that most cases of PA are due to the activation by unknown mechanisms of subset of cells resulting in the formation of a multiple foci or nodules of hyperactive zona glomerulosa cells. This implies that one or several yet unidentified stimuli can drive aldosterone overproduction, as well as the proliferation of aldosterone-producing cells. Current diagnostic procedures allow to determine whether inappropriate aldosterone production is driven by one or both adrenal glands and thus to establish optimal treatment.

Rapid reversal of left ventricular hypertrophy and intracardiac volume overload in patients with resistant hypertension and hyperaldosteronism: a prospective clinical study

We have shown previously that patients with resistant hypertension and hyperaldosteronism have increased brain natriuretic peptide suggestive of increased intravascular volume. In the present study, we tested the hypothesis that hyperaldosteronism contributes to cardiac volume overload. Thirty-seven resistant hypertensive patients with hyperaldosteronism (urinary aldosterone > or = 12 microg/24 hours and plasma renin activity < or = 1.0 ng/mL per hour) and 71 patients with normal aldosterone status were studied. Both groups had similar blood pressure and left ventricular mass, whereas left and right ventricular end-diastolic volumes measured by cardiac MRI were greater in high versus normal aldosterone subjects (P<0.05). Spironolactone treatment (19 patients in the high aldosterone group and 15 patients from the normal aldosterone group participated in the follow-up) resulted in a significant decrease in clinic systolic blood pressure, right and left ventricular end diastolic volumes, left atrial volume, left ventricular mass, and brain natriuretic peptide at 3 and 6 months of follow-up in patients with high aldosterone, whereas in those with normal aldosterone status, spironolactone decreased blood pressure and left ventricular mass without changes in ventricular or atrial volumes or plasma brain natriuretic peptide. Hyperaldosteronism causes intracardiac volume overload in patients with resistant hypertension in spite of conventional thiazide diuretic use. Mineralocorticoid receptor blockade induces rapid regression of left ventricular hypertrophy irrespective of aldosterone status. In subjects with high aldosterone, mineralocorticoid receptor blockade induces a prominent diuretic effect compared with a greater vasodilatory effect in subjects with normal aldosterone status.

Hypertension of Kcnmb1-/- is linked to deficient K secretion and aldosteronism

Mice lacking the beta1-subunit (gene, Kcnmb1; protein, BK-beta1) of the large Ca-activated K channel (BK) are hypertensive. This phenotype is thought to result from diminished BK currents in vascular smooth muscle where BK-beta1 is an ancillary subunit. However, the beta1-subunit is also expressed in the renal connecting tubule (CNT), a segment of the aldosterone-sensitive distal nephron, where it associates with BK and facilitates K secretion. Because of the correlation between certain forms of hypertension and renal defects, particularly in the distal nephron, it was determined whether the hypertension of Kcnmb1(-/-) has a renal origin. We found that Kcnmb1(-/-) are hypertensive, volume expanded, and have reduced urinary K and Na clearances. These conditions are exacerbated when the animals are fed a high K diet (5% K; HK). Supplementing HK-fed Kcnmb1(-/-) with eplerenone (mineralocorticoid receptor antagonist) corrected the fluid imbalance and more than 70% of the hypertension. Finally, plasma [aldo] was elevated in Kcnmb1(-/-) under basal conditions (control diet, 0.6% K) and increased significantly more than wild type when fed the HK diet. We conclude that the majority of the hypertension of Kcnmb1(-/-) is due to aldosteronism, resulting from renal potassium retention and hyperkalemia.

The diagnosis and treatment of primary hyperaldosteronism in Germany: results on 555 patients from the German Conn Registry

BACKGROUND

Primary hyperaldosteronism (Conn's syndrome) is being diagnosed increasingly often. As many as 12% of patients with hypertension have the characteristic laboratory constellation of Conn's syndrome. Its diagnosis and treatment have not been standardized.

METHODS

The authors retrospectively analyzed data of 555 patients (327 men and 228 women, aged 55 +/- 13 years) who were treated for primary hyperaldosteronism in 5 different centers from 1990 to 2006. The objective was to determine center-specific features of diagnosis and treatment.

RESULTS

353 (63%) of the patients had the hypokalemic variant of primary hyperaldosteronism; 202 never had documented hypokalemia. The centers differed markedly with respect to the patients' clinical presentation, diagnostic testing of endocrine function, and diagnostic imaging techniques, including adrenal venous sampling. The adrenalectomy rate ranged from 15% to 46%.

CONCLUSIONS

The registry data reveal an unexpected heterogeneity in the diagnostic evaluation and treatment of primary hyperaldosteronism. National or international guidelines are needed so that these can be standardized.

TASK channel deletion in mice causes primary hyperaldosteronism

When inappropriate for salt status, the mineralocorticoid aldosterone induces cardiac and renal injury. Autonomous overproduction of aldosterone from the adrenal zona glomerulosa (ZG) is also the most frequent cause of secondary hypertension. Yet, the etiology of nontumorigenic primary hyperaldosteronism caused by bilateral idiopathic hyperaldosteronism remains unknown. Here, we show that genetic deletion of TWIK-related acid-sensitive K (TASK)-1 and TASK-3 channels removes an important background K current that results in a marked depolarization of ZG cell membrane potential. Although TASK channel deletion mice (TASK-/-) adjust urinary Na excretion and aldosterone production to match Na intake, they produce more aldosterone than control mice across the range of Na intake. Overproduction of aldosterone is not the result of enhanced activity of the renin-angiotensin system because circulating renin concentrations remain either unchanged or lower than those of control mice at each level of Na intake. In addition, TASK-/- mice fail to suppress aldosterone production in response to dietary Na loading. Autonomous aldosterone production is also demonstrated by the failure of an angiotensin type 1 receptor blocker, candesartan, to normalize aldosterone production to control levels in TASK-/- mice. Thus, TASK-/- channel knockout mice exhibit the hallmarks of primary hyperaldosteronism. Our studies establish an animal model of nontumorigenic primary hyperaldosteronism and identify TASK channels as a possible therapeutic target for primary hyperaldosteronism.

The aldosterone to renin ratio in the evaluation of patients with incidentally detected adrenal masses

Incidentally discovered adrenal masses are diagnosed with increasing frequency, especially among patients with hypertension. Thus, a reliable screening test for primary hyperaldosteronism (PA) is essential to avoid unnecessary diagnostic procedures to this population. The aim of the present study is the evaluation of aldosterone to renin ratio (ARR), using plasma renin concentration, in the diagnostic algorithm of patients with adrenal incidentaloma. A total of 123 individuals were studied: 17 patients with proven PA (age 55.5 +/- 1.4 years), 27 patients with nonfunctioning adrenal incidentaloma (age 60.3 +/- 1.8 years, 14 hypertensives and 13 normotensives) and 79 control subjects (age 58.7 +/- 1.4 years, 27 hypertensives and 52 normotensives). A receiver operating characteristic (ROC) analysis disclosed that an ARR > or =32 combines a sensitivity of 100% with a specificity of 96.2% for the diagnosis of PA. No difference in AlphaRR between hypertensive and normotensive individuals harbouring an adrenal incidentaloma and hypertensive and normotensive controls was found. Patients with adrenal incidentalomas with subtle glucocorticoid hypersecretion demonstrated similar ARR compared to patients with normal cortisol secretion. In conclusion, ARR is reliable for the exclusion of PA in patients with adrenal incidentalomas. Furthermore, subtle aldosterone hypersecretion, as indicated by increased ARR, in patients with adrenal incidentalomas is not associated with the presence of hypertension or subtle glucocorticoid hypersecretion.

[Molecular mechanism of cardiovascular damage induced by aldosterone]

Although the pro-inflammatory and pro-fibrotic actions of aldosterone on the vasculature have been reported, the effects and molecular mechanisms of aldosterone on endothelial function are yet to be determined. We investigated how aldosterone regulates endothelial nitric oxide synthase (eNOS) function in human umbilical vein endothelial cells (HUVECs). HUVECs were incubated for 16 hrs with 10(-7) mol/l of aldosterone. The concentration of reactive oxygen species (ROS) was estimated by measuring DCF chemiluminescence. Signal transduction was estimated by Western immunoblots. Realtime RT-PCR was performed to measure expression of transcripts of endogenous GTP cyclohydrolase-1 (GCH1) and components of NAD(P)H oxidase. In order to eliminate the possible effect of the glucocorticoid receptor (GR), and to emphasize the role of mineralocorticoid receptor (MR), we used GR siRNA and knocked down GR expression in several experiments. NO output was estimated by intracellular cGMP concentration. ROS production increased significantly in aldosterone-treated HUVEC, but was abolished by pre-treatment with eplerenone. Transcripts of p47(phox) were increased by aldosterone treatment. Vascular endothelial growth factor (VEGF)-induced eNOS Ser 1177 but not Akt Ser 473 phosphorylation levels were reduced significantly by pretreatment with aldosterone. Pretreatment with either eplerenone or okadaic acid restored phosphorylation levels of eNOS Ser 1177 in aldosterone-treated cells, suggesting that protein phosphatase (PP) 2A was upregulated by aldosterone via MR. The decrease in NO output caused by aldosterone pretreatment was reversed significantly by either 5,6,7,8-tetrahydrobiopterin (BH(4)), GCH1 overexpression, or p47(phox) knockdown. These results suggest that aldosterone inhibits eNOS function through bimodal mechanisms of BH(4) deficiency and PP2A activation.