Two-site automated chemiluminescent assay for measurement of immunoreactive renin

Measurement of renin is important for the clinical assessment of hypertensive patients and for the screening for primary aldosteronism. The aim of this study was to evaluate the performances of an automated immunoassay for measurement of immunoreactive renin. Functional sensitivity, in vitro stability, and reference values were determined. Method comparison with the plasma renin activity assay was also performed. Our results demonstrate that the Liaison^® direct renin assay may assist the clinician in the assessment of hypertensive patients and in the screening for primary aldosteronism.     

Prevelence of Primary Aldosteronism in an Urban Hypertensive Population

Objective: To determine the prevalence of primary aldosteronism (PA) in hypertensive patients presenting to the primary care clinic at The Mount Sinai Hospital, regardless of the degree of hypertension and to identify clinical criteria that should prompt screening for PA.Methods: An aldosterone:renin ratio (ARR, cutoff ≥20, with plasma aldosterone concentration [PAC] ≥10 and suppressed renin) was used to prospectively screen 296 hypertensive patients (blood pressure [BP] ≥140/90) over the age of 18 from August 2012 through May 2013. Subjects who screened positive then underwent confirmatory oral salt load testing (OSLT).Results: Of the 296 patients, 14 screened positive for PA, an overall prevalence of 4.7%. Six of the 14 cases underwent confirmatory OSLT, upon which 2 were confirmed positive, for a prevalence of 0.7%. Overall, patients with confirmed PA were more likely to have resistant hypertension (42.9% vs. 18.1% (P =.0334)) and require more antihypertensive agents (2.8 ± 1.2 agents vs. 2.1 ± 1.1 agents, P =.0213). There was a trend toward lower potassium values in the cases.Conclusion: The prevalence of PA in our clinic is much lower than in reports from certain “at-risk” populations. PA screening is indicated in patients with resistant hypertension, regardless of serum potassium levels.Abbreviations:ARR = aldosterone:renin ratioACTH = adrenocorticotropic hormoneAVS = adrenal venous samplingBP = blood pressureMRA = mineralocorticoid receptor antagonistOSLT = oral salt load confirmatory testPA = primary aldosteronismPAC = plasma aldosterone concentrationPCP = primary care providerPRA = plasma renin activity     

Mineralocorticoid Receptor Antagonists Decrease the Rates of Positive Screening for Primary Aldosteronism

Objective: Mineralocorticoid receptor antagonists (MRAs) are effective in patients with resistant hypertension and/or primary aldosteronism (PA). Screening for PA should ideally be conducted after stopping medications that might interfere with the renin-angiotensin-aldosterone system, but this is challenging in patients with recalcitrant hypertension or hypokalemia. Herein, we aimed to evaluate the impact of MRAs on PA screening in clinical practice.Methods: We conducted a retrospective cohort study of patients with hypertension who had plasma aldosterone and renin measurements before and after MRA use in a tertiary referral center, over 19 years.Results: A total of 146 patients, 91 with PA, were included and followed for up to 18 months. Overall, both plasma renin and aldosterone increased after MRA initiation (from median, interquartile range: 0.5 [0.1, 0.8] to 1.2 [0.6, 4.8] ng/mL/hour and from 19.1 [12.9, 27.7] to 26.4 [17.1, 42.3] ng/dL, respectively; P<.0001 for both), while the aldosterone/renin ratio (ARR) decreased from 40.3 (18.5, 102.7) to 23.1 (8.6, 58.7) ng/dL per ng/mL/hour (P<.0001). Similar changes occurred irrespective of the MRA treatment duration and other antihypertensives used. Positive PA screening abrogation after MRA initiation was found in 45/94 (48%) patients. Conversely, 17% of patients had positive PA screening only after MRA treatment, mostly due to correction of hypokalemia. An initially positive screening test was more likely altered by high MRA doses and more likely persistent in patients with confirmed PA or taking beta-blockers.Conclusion: MRAs commonly reduce ARR and the proportion of positive PA screening results. When PA is suspected, screening should be repeated off MRAs.Abbreviations: ACEI = angiotensin-converting enzyme inhibitor; ARB = angiotensin receptor blocker; ARR = aldosterone/renin ratio; DRC = direct renin concentration; MRA = mineralocorticoid receptor antagonist; PA = primary aldosteronism; PAC = plasma aldosterone concentration; PRA = plasma renin activity; RAAS = renin-angiotensin-aldosterone system     

Prolonged pseudoaldosteronism induced by glycyrrhizin.

We describe the natural recovery from the aggravated hypertension, hypokalemia and suppression of the renin-aldosterone axis after the glycyrrhizin discontinuation in two mild hypertensive women aged 71 and 68 years, who had been administered 273 to 546 mg glycyrrhizin daily for 1.5 and 6 months, respectively, for the treatment of liver disease. About one month after the glycyrrhizin discontinuation, acceleration of hypertension, hypokalemia and suppression of the renin-aldosterone system still continued in both patients. At this stage, sodium restriction resulted in the normalization of blood pressure with weight loss and the subsequent sodium repletion produced a rapid increase in blood pressure to hypertensive levels observed before sodium restriction, with weight gain. Plasma renin activity and plasma aldosterone were low and did not respond to sodium restriction. Inappropriately excessive amounts of potassium were also excreted in the presence of hypokalemia. About one and a half months later, the improvements of aggravated hypertension, hypokalemia and suppressed renin-aldosterone system gradually occurred in both patients. Sodium restriction performed about three months later in case 2 no longer produced the changes in blood pressure and body weight. Plasma renin activity and plasma aldosterone responded subnormally to sodium restriction. These results demonstrate that both patients had a prolongation of the syndrome resembling primary aldosteronism except the low plasma aldosterone level about one month after the glycyrrhizin discontinuation. The possible mechanisms by which this prolongation was caused are discussed.     

Development and evaluation of an immuno-MALDI (iMALDI) assay for angiotensin I and the diagnosis of secondary hypertension

Plasma renin activity (PRA) is an essential analytical tool for screening and diagnosis of secondary forms of hypertension. Typically, PRA is measured by competitive radioimmunoassay, but there are significant drawbacks to this technique including non-specificity, long analysis times, narrow calibration range, and the requirement for radionucleotides. In this paper, we report a method for plasma renin activity determination by immuno-MALDI mass spectrometry detection. This method overcomes the issues of non-specificity and long analytical times present with RIA, and does not require the use of radionucleotides. As an initial methodological evaluation, plasma renin activity results obtained by radioimmunoassay, LC/ESI-MS/MS, and immuno-MALDI on 64 samples from an outpatient primary aldosteronism screening program have been compared. A strong correlation was found between immuno-MALDI and radioimmunoassay (R² = 0.9412, 62/64 within the 95% CI of the Bland-Altman plot), and iMALDI and LC/ESI-MS/MS (R² = 0.9471, 62/64 within the 95% CI of the Bland-Altman plot). Technical replicates showed a 4.8% CV, while inter- and intra-day replicates showed CVs of 17.3% and 17.2% respectively. We have developed an assay capable of measuring PRA without the use of radionucleotides. This immuno-MALDI approach affords the specificity of MS while avoiding the long analytical run times and technical problems associated with HPLC. With the use of robotic sample preparation to optimize precision, this assay should be adaptable to clinical environments.     

Alpha-h-ANP injection in normals, low renin hypertension and primary aldosteronism

Atrial natriuretic peptide, a hormone secreted by the heart, is involved in salt and fluid homeostasis and also exerts an inhibitory effect on aldosterone production in vitro. In order to elucidate if this effect is also present in man, 6 normal volunteers, 5 low renin hypertensive patients (LRH) and 7 patients with primary aldosteronism (PA) have received 100 micrograms of alpha-h-Anp as bolus i.v. (The decrease in blood pressure was mild and transient in all groups, whereas a marked diuretic effect was observed in all hypertensives even in PA where high levels of endogenous ANP have been found. In normals we observed a significant decrease of plasma aldosterone values while in PA and LRH this effect was not evident. This phenomenon associated with a greater natriuretic effect in LRH and PA, as compared with normals, demonstrates the lack of the correlation between ANP-induced diuresis and aldosterone inhibiting properties.     

Primary aldosteronism caused by unilateral adrenal hyperplasia

In the hypertensive population, primary aldosteronism has been reported to have a prevalence of 0.1% to 2%, with the main causes being aldosterone-producing adenomas and bilateral hyperplasia. However, there is a third rare entity, called unilateral adrenal hyperplasia, that contributes to primary aldosteronism. Unilateral hyperplasia and primary aldosteronism are the subjects of this case review.     

A case of primary aldosteronism with chronic renal failure undergoing hemodialysis treatment

A 56-year-old man with primary aldosteronism and chronic renal failure undergoing hemodialysis is described. He complained of numbness of the extremities and showed persistent hypopotassemia in spite of anuria. In the endocrinological examination, a very high plasma aldosterone concentration was observed, while plasma renin activity was within the normal range. From the abdominal Computed Tomography (CT), adrenal scintigraphy, and segmental venous sampling data, he was diagnosed as primary aldosteronism due to left adrenocortical adenoma. In this case, hypopotassemia could not be explained by potassium loss through the kidneys, which suggests potassium excretion in the gastrointestinal tract as the mechanism of hypopotassemia. This was clearly shown from a potassium-balance study and the results of spironolactone administration. Our report is on the first case showing hypopotassemia due to primary aldosteronism in spite of anuria. If a patient treated with maintenance dialysis should have persistent hypopotassemia, as in the present report, it is necessary to consider an association with primary aldosteronism.     

Laboratory Investigation of Primary Aldosteronism

Availability and wider application of the plasma aldosterone/renin ratio (ARR) as a screening test for primary aldosteronism (PA) has led to the recognition that PA is the most common potentially curable and specifically treatable form of hypertension, possibly accounting for as many as 5–13% of patients. Aldosterone excess also has adverse cardiovascular consequences that go above and beyond hypertension development. These findings support the concept that PA plays an important role in cardiovascular disease states and should be systematically sought and specifically treated, and have led to the development of a US Endocrine Society clinical guideline for the detection, diagnosis and management of this condition. Reliable detection requires that interfering factors (including medications known to alter the ratio) are controlled before ARR measurement (or their effects taken into account), and reliable methods such as fludrocortisone suppression testing are used to confirm PA. Because computed tomography frequently misses aldosterone-producing adenomas yet demonstrates non-functioning nodules, adrenal venous sampling is the only dependable way to differentiate unilateral (surgically correctable) from bilateral (usually treated with aldosterone antagonist medications) forms of PA. For the glucocorticoid-remediable form of PA (familial hyperaldosteronism type I), genetic testing for the causative ‘hybrid’ 11beta-hydroxylase/aldosterone synthase gene has greatly facilitated detection. Laboratory assessment (including suppression testing post-operatively, and renin measurement during treatment with aldosterone antagonist medications) can assist in assessing therapeutic responses and in guiding ongoing management. Development of new, highly reliable high-throughput mass spectrometric methods for measuring aldosterone and renin should further enhance detection and reliability of diagnostic workup for PA.     

The Influence of a Heparin-Like Compound on Hypertension,Electrolytes and Aldosterone in Man

The mechanisms of the aldosterone-inhibiting and antihypertensive actions of heparin and certain other sulfated mucopolysaccharides were investigated in 13 hypertensive patients. N-formyl chitosan polysulfuric acid (RO 1-8307) was used rather than heparin because of its low anticoagulant activity. RO 1-8307 lowered aldosterone secretion in one patient with proved and one with probable primary aldosteronism; this indicates that the mucopolysaccharide does not inhibit aldosterone secretion via the renin-angiotensin mechanism. In six hypertensive patients RO 1-8307 caused a fall in the secretion of aldosterone and its probable immediate precursor, 18-hydroxycorticosterone; therefore it does not act at the last step in the synthesis of aldosterone. RO 1-8307 produced a prolonged clinical and biochemical remission in the two patients considered to have primary aldosteronism but did not influence blood pressure in five of seven patients in whom excessive aldosterone was probably not a major factor in the hypertension. It is concluded that the antihypertensive action of RO 1-8307, and perhaps of heparin as well, is largely due to suppression of aldosterone secretion.     

Plasma vasopressin variation and renin activity in normal active humans.

Plasma concentrations of vasopressin and plasma renin activity were measured every 30 min for 24 h in 5 normal active humans, in 1 normal woman confined to bed (except for brief periods up to the bathroom), in 2 active patients with primary aldosteronism and in 1 patient with low-renin hypertension. Plasma vasopressin varied markedly over the day and night in a pattern suggesting episodic secretion of the hormone in the normal subjects. Assumption of upright posture was accompanied by a rise in plasma levels from undetectable to 20--50 pg/ml. Episodic secretion, however, also occurred during bed rest and sleep. In contrast, patients with primary aldosteronism and low-renin hypertension had plasma vasopressin levels considerably lower than the normals, and their profiles of plasma concentration lacked the peaks seen in normals. In the normals, although vasopressin and renin secretion often coincided, only 2 of 6 studies showed a significant correlation between the plasma levels of the two hormones. This study, therefore, shows that vasopressin is secreted periodically in normal humans, that upright posture is an important modulator of secretory activity and that the renin-angiotensin system may or may not influence the pattern of secretion. In addition, it underlines the necessity of recumbency in establishing the existence of a circadian rhythm of plasma vasopressin levels.     

Frequency in hypertensives of alleles for a RFLP associated with the renin gene

The genetic basis of primary hypertension is not known. Renin is important in blood pressure and volume control and a HindIII restriction fragment length polymorphism (RFLP) is present within the human renin gene locus. To examine whether there is a relationship between this RFLP and primary hypertension, DNA and renin analyses were performed on leukocytes and plasma from hypertensive and normotensive individuals. In hypertensives the frequencies of alleles for the HindIII RFLP were found to be 0.55 and 0.45, compared with 0.60 and 0.40 in the total population of 231 subjects examined, a difference that was not statistically significant. There also appeared to be no significant difference in renin activity in plasma for hypertensive patients of each genotype, nor in their pre- or post-treatment blood pressures. We thus conclude that, within the limits of the present study, the suspected genetic abnormalities associated with primary hypertension in man do not appear to be related to a HindIII RFLP in the renin gene.     

Regulation of aldosterone secretion in primary aldosteronism.

Plasma aldosterone, plasma renin activity and plasma cortisol were determined in patients with primary aldosteronism in response to posture and at short-time intervals overnight while the patient were supine. In the 5 patients with an aldosterone-producing adenoma postural changes in plasma aldosterone were paralleled by those in cortisol while plasma renin activity was generally undetectable indicating an ACTH-dependent secretion of aldosterone. This concept was supported by the observation that in 3 of these patients who were tested overnight 1. episodic secretion of plasma aldosterone was paralleled by those of cortisol and 2. episodic secretion of plasma aldosterone could be blunted by dexamethasone. In the patient with idiopathic adrenal hyperplasia concomittant changes in plasma aldosterone and plasma renin activity occurred. The assumption that in this patient the fluctuations in plasma aldosterone were mediated through changes in renal renin secretion was supported by the finding that episodic secretion of plasma aldosterone persisted under suppression of ACTH-secretion by dexamethasone. Our results indicate, that the described procedures may all serve as diagnostic criteria to differentiate between aldosterone-producing adenoma and idiopathic adrenal hyperplasia.     

Steroids and hypertension

Primary aldosteronism is the principal disorder of zona glomerulosa and a number of subsets have been identified: unilateral adenoma; bilateral micro- or macro-nodular hyperplasia (idiopathic aldosteronism); primary hyperplasia and aldosterone-producing carcinoma either adrenal or ectopic. The diagnostic criteria for a correct differential diagnosis of these subsets are now quite reliable and our experience is presented in detail. Unfortunately the pathogenesis of most of these forms is still poorly recognized and requires further investigation. An extreme sensitivity to angiotensin II is present in patients with idiopathic aldosteronism, and a role for adrenal renin is now being advocated. A peculiar form of hyperaldosteronism is the glucocorticoid-remediable subtype. An unusual sensitivity of aldosterone to ACTH is present in this form. A qualitative biochemical abnormality in this disorder consists of marked over-production of products of the cortisol C18-oxidation pathway, 18-hydroxycortisol and 18-oxocortisol, which are more abundant than aldosterone and 18-hydroxycorticosterone. A family with three affected sibs has been studied by our group. In other clinical situations, classical zona fasciculata mineralocorticoids [deoxycorticosterone (DOC), corticosterone and their 18-hydroxy compounds] are secreted in excess. The hypertensive diseases of this zone are rare DOC-secreting tumors and two forms of congenital adrenal hyperplasia (CAH), the 11 beta-hydroxylase (11-OHDS) and the 17 alpha-hydroxylase deficiency syndromes (17-OHDS), which are identified by the presence of hypokalemia and suppressed renin activity. DOC is the only mineralocorticoid hormone (MCH) oversecreted in the 11-OHDS, while all ACTH-dependent MCH are very high in the 17-OHDS. The molecular basis of gene abnormalities of this disorder are currently under investigation, and preliminary data obtained in some of our patients are presented. Finally a syndrome of apparent mineralocorticoid excess, which is not a primary disorder of the adrenal cortex, describes the association of an unexplained hypermineralocorticoid state with a decreased rate of peripheral 11 beta-hydroxy dehydrogenation of cortisol to cortisone. Studies on this syndrome have led to the hypothesis that peripheral cortisol inactivation is the normal mechanism permitting specific mineralocorticoid recognition. The syndrome exists in two forms both characterized by a decreased turnover of a normal level of plasma cortisol, but in the type I variant an elevated cortisol/cortisone metabolite ratio is found, whereas in the type II variant this ratio is normal. Three patients of the latter form have recently been described by us and are shortly illustrated.(ABSTRACT TRUNCATED AT 400 WORDS)     

分侧肾上腺静脉取血与肾上腺CT对原发性醛固酮增多症诊断的价值比较研究

摘要 目的：研究原发性醛固酮增多症（PA）患者行分侧肾上腺静脉取血（AVS）、肾上腺CT诊断的效果。方法：数据遴选本院2018年1月-2021年11月收治的70例原发性醛固酮增多症患者,所有患者均行肾上腺CT、AVS诊断,对最终诊断结果比较分析。结果：收缩压、舒张压、空腹血糖、总胆固醇在单双侧间无差异（P＞0.05）,双侧肾素活性、血清醛固酮肾素比值较单侧存在差异（P＜0.05）;肾上腺CT与AVS诊断的符合率情况：肾上腺CT显示为单侧异常、双侧异常及双侧正常患者,AVS符合率分别为65.00 %、31.25 %、50.00 %;单独肾上腺CT诊断：灵敏度为57.1 %,特异度为25.7 %,肾上腺静脉采血诊断：灵敏度为74.3 %,特异度为42.9 %;并联联合诊断灵敏度为100.0 %,特异度为26.3 %,串联诊断灵敏度为19.5 %,特异度为100.0 %。结论：PA是临床常见疾病,具有患病率高、预后差等特点,临床依靠临床表现、血液生化检查诊断PA疾病,但仅借助血液生化检验进行诊断治疗较困难,功能定位是治疗关键。实际工作中,可以临床通过CT检查及AVS检查功能定位诊断,但对于PA患者来说,仅借助肾上腺CT诊断结果制定治疗方案,可能导致手术侧选择错误,建议愿意接受肾上腺手术治疗者,推荐先行AVS,正确选择治疗方案,达到改善预后作用,效果较理想、值得临床借鉴推广。     

New aspects on primary aldosteronism

The adrenal cortex synthesizes and releases steroid hormones, mainly mineralocorticoids and glucocorticoids. There is a functional zonation of the adrenal cortex and steroid synthesis is thoroughly regulated. Overproduction of aldosterone, primary aldosteronism, may be much more common than previously known and may be responsible for 10% of essential hypertension. Primary aldosteronism is characterized by autonomous production of aldosterone, suppressed renin activity, hypokalemia, and hypertension. The two most common forms are unilateral adenoma and bilateral hyperplasia. In spite of thorough clinical workup and careful histopathology it is often difficult to differentiate between adenoma and hyperplasia. The gene CYP11B2 encodes the steroid synthesizing enzymes for aldosterone production, while the genes CYP17 and CYP11B1 are needed for cortisol production. Most normal controls show expression of CYP11B2 in zona glomerulosa. Expression of CYP11B1 and CYP17 is seen in zona fasciculata and reticularis, whereas the expression of CYP21 is present in all three cortical layers. Adenomas from patients with primary aldosteronism show considerable variation in the expression of CYP11B2. Adenomas from patients with Cushing's syndrome have a strong expression of CYP11B1 and CYP17. In a patient material of 29 cases of primary aldosteronism, 4 patients had small nodules detected with expression of CYP11B2 gene. These nodules were not visualized on CT, whereas adrenal masses seen on CT in these patients showed CYP11B1 and CYP17 gene expression. This suggests that these small nodules are responsible for the aldosterone production and this is characteristic of nodular hyperplasia in patients with primary aldosteronism. In conclusion, this method to visualize mRNA gene expression of steroidogenic enzymes, and especially expression of CYP11B2, has increased the knowledge of adrenal pathophysiology. The results emphasize the value to include functional studies (venous sampling and/or scintigraphy) in the preoperative work up of patients with primary aldosteronism.     

Sodium outflow rate through lymphocyte cell membranes, serum levels of sodium, potassium, aldosterone, total catecholamines, 6-keto- PGF2alpha and plasma renin activity in patients with primary arterial hypertension treated with captopril]

Sodium ions outflow rate through lymphocyte membranes, serum sodium, potassium, aldosterone, total catecholamines and 6-keto-PGE alpha levels, and plasma renin activity were studied in patients with mild hypertension associated with low and hugh plasma renin activity treated with captopril in a single dose of 12.3 mg and after the treatment with daily doses of 12.5 mg and 25 mg for 3 days. It was found, that captopril in hypertensive patients with high plasma renin activity decreases both systolic and diastolic blood pressure, decelerates heart rate, and decreases serum total catecholamines and plasma renin activity. Sodium ions outflow rate and serum sodium, potassium, aldosterone, and 6-keto-PGE alpha remain unchanged. Captopril in hypertensive patients with low plasma renin activity. The remaining parameters are unchanged. Moreover, it was noted that serum 6-keto-PGE alpha levels are lower in hypertensive patients with low plasma renin activity.     

Effect of nifedipine on effective renal plasma flow, plasma renin activity and serum aldosterone, noradrenaline and adrenaline levels in healthy persons and in patients with primary moderate arterial hypertension

Blood pressure, plasma renin activity, and serum aldosterone, adrenaline and noradrenaline were investigated in healthy individuals and patients with the primary moderate hypertension following a single oral dose of 10 mg nifedipine. It was found that the drug is hypotensive in both healthy individuals and hypertensive patients. It does not affect the effective plasma flow throughout the kidneys as well as serum aldosterone and adrenaline whereas serum noradrenaline and plasma renin activity are increased.     

Digoxin-like substance in blood and hypertension in dialysed patients with chronic renal failure]

Concentration of free serotonin, adrenaline, noradrenaline, aldosterone and plasma renin activity have been assayed in blood of 18 patients with the primary arterial hypertension (WHO stage I) and in 10 healthy volunteers. It was found that blood free serotonin and noradrenaline are increased in hypertensive patient. No difference in adrenaline and aldosterone levels and plasma renin activity was seen. No significant correlation between free serotonin and assayed hormones was noted.