Primary aldosteronism, diagnosed by the aldosterone to renin ratio, is a common cause of hypertension

Managing resistant hypertension: focus on mineralocorticoid-receptor antagonists

Mineralocorticoid-receptor antagonists (MRAs) have proven to be effective in some types of hypertension, especially in resistant hypertension (RHTN). In this phenotype of hypertension, the renin-angiotensin-aldosterone pathway plays an important role, with MRAs being especially effective in reducing blood pressure. In this review, we show the relevance of aldosterone in RHTN, as well as some clinical characteristics of this condition and the main concepts involving its pathophysiology and cardiovascular damage. We analyzed the mechanisms of action and clinical effects of two current MRAs - spironolactone and eplerenone - both of which are useful in RHTN, with special attention to the former. RHTN represents a significant minority (10%-15%) of hypertension cases. However, primary-care physicians, cardiologists, nephrologists, neurologists, and geriatricians face this health problem on a daily basis. MRAs are likely one of the best pharmacological options in RHTN patients; however, they are still underused.

Commentary on the Endocrine Society Practice Guidelines: Consequences of adjustment of antihypertensive medication in screening of primary aldosteronism

The Endocrine Society guidelines suggest to screen patients with primary aldosteronism (PA) free of hypertensive medications or alternatively to switch to drugs known to have minimal influence on the aldosterone to renin ratio (ARR). We retrospectively investigated the impact of such strategy on clinical outcome. 25 patients with PA and 25 with essential hypertension (EH) were studied. Initially all subjects were evaluated biochemically and received if possible an adjustment of their medication following the guidlines. Mineralocorticoid antagonists were discontinued in all subjects. Only 26 of 50 patients could be studied under optimal conditions (drug free or on medication with minimal influence on ARR) whereas the remaining 24 subjects had to receive additional drugs (such as ACE inhibitor, angiotensin-2 receptor blocker, or betablockers) because of initial blood pressure or comorbidities. Every fifth patient with a switch of the medication experienced a significant increase in blood pressure. 13 of 25 of PA patients needed potassium supplementation (105+/-25 mEq per day; range 8-320 mEq). Nine of these patients remained hypokalemic despite substitution (serum K 2.82+/-0.07 mmol/l), with 7 classified severely hypokalemic (<.3.0). We observed 6 serious adverse events requiring hospitalization including hypertensive crisis (n = 3), atrial fibrillation (n = 1), heart failure (n = 1) and ICD triggered electric shock (n = 1). In conclusion, in our experience the adjustment of the antihypertensive treatment during screening for PA is only possible in approximately half of patients and can cause severe side effect. Such recommendation, therefore, must include a note of caution because of possibly deleterious side effects.

Diagnosis and management of primary aldosteronism

PURPOSE OF REVIEW

To illustrate the steps for clinical management of primary aldosteronism from screening evaluation to surgical and/or medical treatment.

RECENT FINDINGS

It is now widely accepted that primary aldosteronism represents the most common form of endocrine hypertension and its early diagnosis is crucial for hypertensive patients who can be cured by the surgical removal of an aldosterone-secreting adenoma or benefit from a specific medical treatment with mineralocorticoid receptor antagonists. Recent evidence indicates that hyperaldosteronism is indeed associated with detrimental consequences on cardiovascular system, renal function and glucose metabolism.

SUMMARY

The diagnostic protocol for primary aldosteronism requires multistep evaluation and should begin with a screening test, followed when appropriate, by confirmatory test and functional and anatomical evaluation. Finally, although it is technically difficult and the cut-off levels for acceptance of the success are not standardized, the subtype forms should be identified using a selective adrenal venous sampling.

Primary aldosteronism, a major form of low renin hypertension: from screening to diagnosis

There is general consensus on the use of (but not cut-off values for) the aldosterone/plasma renin activity ratio as a screening test for primary aldosteronism. There is also agreement on the need for subsequent confirmatory testing, but not on the protocols to be chosen. The four most common confirmatory tests in clinical practice are oral sodium loading, intravenous saline infusion, captopril challenge and fludrocortisone administration plus sodium loading. The choice of test reflects multiple variables: patient factors (including accessibility, compliance and safety), established practice and cost. Finally, subtype forms and lateralization of aldosterone production should be established by bilateral adrenal venous sampling, despite its technical difficulty and varying criteria for success.

Hyperaldosteronism: a commonly occurring underlying feature of essential hypertension and the metabolic syndrome?

Individuals with primary aldosteronism make up a substantial proportion of those with hypertension. Less well appreciated is what appears to be inappropriately elevated aldosterone secretion in hypertensive patients who do not meet the criteria for true primary aldosteronism. This finding is particularly true of African-Americans. An additional, recently described, aspect of aldosterone excess is its apparent contribution to insulin resistance as evidenced by the frequent association of primary aldosteronism with the metabolic syndrome. Thus in the management of, not only hypertension, but also certain metabolic conditions, greater consideration should be given to the participation of aldosterone.

Clinical and genetic correlates of aldosterone-to-renin ratio and relations to blood pressure in a community sample

Aldosterone:renin ratio (ARR) is used to screen for hyperaldosteronism. Data regarding correlates of ambulatory ARR in the community and its relation to hypertension incidence are limited. We defined clinical correlates of ARR, determined its heritability, tested for association and linkage, and related ARR to blood pressure (BP) progression in nonhypertensive individuals among 3326 individuals from the Framingham Heart Study (53% women; mean age: 59 years). Ambulatory morning ARR (serum aldosterone and plasma renin concentrations) were related to clinical covariates, genetic variation across the REN locus, a 10-cM linkage map, and among nonhypertensive participants (n=1773) to progression of >or=1 Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure BP category (optimal: <120/80 mm Hg, normal: 120 to 129/80 to 84 mm Hg, high normal: 130 to 139/85 to 89 mm Hg, hypertension: >or=140/90 mm Hg), or incident hypertension (systolic BP: >or=140 mm Hg, diastolic BP: >or=90 mm Hg, or use of antihypertensive treatment). ARR was positively associated with age, female sex, untreated hypertension, total/high-density lipoprotein cholesterol ratio, hormone replacement therapy, and beta-blocker use, but negatively associated with angiotensin-converting enzyme inhibitor and diuretic use. ARR was heritable (h(2)=0.40), had modest linkage to chromosome 11p (logarithm of the odds: 1.89), but was not associated with 17 common variants in REN (n=1729). On follow-up (mean: 3 years), 607 nonhypertensive individuals (34.2%) developed BP progression, and 283 (16.0%) developed hypertension. Higher baseline logARR was associated with increased risk of BP progression (odds ratio per SD increment: 1.23; 95% CI: 1.11 to 1.37) and hypertension incidence (odds ratio per SD increment: 1.16; 95% CI: 1.00 to 1.33). ARR is a heritable trait influenced by clinical and genetic factors. There is a continuous gradient of increasing risk of BP progression across ARR levels in nonhypertensive individuals.

Screening for primary aldosteronism

Normokalaemic manifestation of primary aldosteronism is a frequent cause of secondary hypertension. It occurs in approximately 5-12% of all patients with hypertension, primarily patients with severe and uncontrolled blood pressure. Main causes are bilateral adrenal hyperplasia (2/3 of cases) and aldosterone-producing adenoma (1/3 of cases). Screening is performed by measurement of the aldosterone/renin ratio, which is raised in affected patients. Suspicion of primary aldosteronism due to a pathological ratio requires confirmatory testing e.g. by saline infusion test or fludrocortisone suppression test. If the diagnosis is confirmed, the underlying cause of aldosterone excess needs to be identified because therapy differs. First, adrenal imaging (CT/MRI) is performed, which is followed by postural testing in cases with a unilateral lesion. Concordant results confirm the diagnosis of an aldosterone-producing adenoma and allow treatment to proceed to adrenalectomy. In cases of equivocal results or normal/bilaterally enlarged adrenal glands on imaging, adrenal venous sampling must be performed for subtype differentiation.

High frequency of primary hyperaldosteronism among hypertensive patients from a primary care area in Sweden

OBJECTIVE

To search for primary hyperaldosteronism (PHA) among previously known hypertensive patients in primary care, using the aldosterone/renin ratio (ARR), and to evaluate clinical and biochemical characteristics in patients with high or normal ratio.

DESIGN

Patient survey study.

SETTING AND SUBJECTS

The study population was recruited by written invitation among hypertensive patients in two primary care areas in Sweden. A total of 200 patients met the criteria and were included in the study.

MAIN OUTCOME MEASURES

The ARR was calculated from serum aldosterone and plasma renin concentrations. The cut-off level for ARR was set to 100, as confirmed in 28 healthy subjects. Patients with increased ARR were considered for a confirmatory test, using the fludrocortisone suppression test.

RESULTS

Of 200 patients, 50 patients had ARR > 100; 26 patients were further evaluated by fludrocortisone suppression test. Seventeen of these patients had an incomplete aldosterone inhibition.

CONCLUSION

In total 17 of 200 evaluated patients (8.5%) had an incomplete suppression with fludrocortisone. This confirms previous reports on a high frequency of PHA. No significant biochemical or clinical differences were found among hypertensive patients with PHA compared with the whole sample.

Optimal use and interpretation of the aldosterone renin ratio to detect aldosterone excess in hypertension

With the introduction of the aldosterone/renin ratio as a screening test, the detection rate of primary aldosteronism has increased considerably. Nevertheless, no consensus has so far been reached regarding the cutoff points, operating characteristics or indeed even the reference values for reporting the aldosterone/renin ratio using plasma active renin (ng/l or mU/l) measured by immunoradiometric assay. We review the characteristics of this ratio in normal individuals, essential hypertension and primary hyperaldosteronism in an attempt to reach an agreement regarding its optimum use and interpretation - both using the renin activity or concentration. It seems that the optimal cutoff for patients with primary aldosteronism is above 30 ng/dl per mug/l/h or 800 pmol/l per mug/l/h or 130 pmol/ng or 80 pmol/mU. We explore enhancing measures such as captopril loading or use with a plasma aldosterone cutoff as well as pitfalls with the test such as confounding medications or the need for confirmatory testing. For the latter, demonstration of autonomous aldosterone production via salt loading is widely used, but may not be most advantageous and may even be contraindicated in patients with severe hypertension. The renin stimulation test may be an alternative being safe, well tolerated, and cost effective.

The syndromes of low-renin hypertension: "separating the wheat from the chaff"

Primary aldosteronism (PA) is characterized by hypertension and suppressed renin activity with or without hypokalemia and comprises the aldosterone-producing adenoma (APA) and bilateral adrenal hyperplasia or idiopatic hyperaldosteronism (IHA). In recent series employing the aldosterone (aldo, ng/dL):renin (ng/mL·h) ratio (ARR) for screening, prevalence of PA among hypertensives soars to 8-20%; current predominance of IHA (>80%) over APA suggests the inclusion of former low-renin essential hypertensives (LREH), in whom plasma aldo can be reduced by suppressive maneuvers. We evaluated the test characteristics of the ARR obtained retrospectively from 127 patients with PA (81 APA; 46 IHA) and 55 with EH (30 LREH; 25 NREH) studied from 1975 to 1990. Using the combined ROC-defined cutoffs of 27 for the ARR and 12ng/dL for aldo, we obtained 89.8% sensitivity (Ss) and 98.2% specificity (Sp) in discriminating PA from EH: all APA and 72% of the IHA patients had values above these limits, but only one (3%) with LREH. Among the 46 IHA patients, 10 (21.7%) had ARR <27, four of whom with aldo <12ng/dL, virtually indistinguishable from LREH. Use of higher cutoff values (ARR >100; aldo >20) may attain 84%Ss and 82.6%Sp in separating APA from IHA. Because IHA and LREH ("the chaff") may be spectrum stages from the same disease, definite discrimination between these entities seems immaterial. However, precise identification of the APA ("the wheat") is critical, since it is the only surgically curable form of PA. Thus, while patients who may harbor an APA must be thoroughly investigated and surgically treated, non-tumoral disease (IHA and LREH) may be best treated with an aldo-receptor antagonist that will also prevent the aldo-mediated inflammatory effects involved in myocardial fibrosis and abnormal cardiac remodeling.

Rapid Screening Test for Primary Hyperaldosteronism: Ratio of Plasma Aldosterone to Renin Concentration Determined by Fully Automated Chemiluminescence Immunoassays

Background: The ratio of plasma aldosterone concentration to plasma renin activity (PAC/PRA) is the most common screening test for primary hyperaldosteronism (PHA), but it is not standardized among laboratories. We evaluated new automated assays for the simultaneous measurement of PAC and plasma renin concentration (PRC).

Methods: We studied 76 healthy normotensive volunteers and 28 patients with confirmed PHA. PAC and PRC were measured immunochemically in EDTA plasma on the Nichols Advantage® chemiluminescence analyzer, and PRA was determined by an activity assay.

Results: In volunteers, PAC varied from 33.3 to 1930 pmol/L, PRA from 1.13 to 19.7 ng · mL−1 · h−1 (0.215 ng · mL−1 · h−1 = 1 pmol · L−1 · s−1), and PRC from 5.70 to 116 mU/L. PAC/PRA ratios ranged from 4.35 to 494 (pmol/L)/(ng · mL−1 · h−1) and PAC/PRC ratios from 0.69 to 71.0 pmol/mU. In PHA patients, PAC ranged from 158 to 5012 pmol/L, PRA from 0.40 to 1.70 ng · mL−1 · h−1, and PRC from 0.80 to 11.7 mU/L. PAC/PRA ratios were between 298 and 6756 (pmol/L)/(ng · mL−1 · h−1) and PAC/PRC ratios between 105 and 2328 pmol/mU. Whereas PAC or PRC showed broad overlap between PHA patients and volunteers, the PAC/PRC ratio indicated distinct discrimination of these two groups at a cutoff of 71 pmol/mU.

Conclusion: The PAC/PRC ratio offers several practical advantages compared with the PAC/PRA screening method. The present study offers preliminary evidence that it may be a useful screening test for PHA. Further studies are required to validate these results, especially in hypertensive cohorts.