Potentially high prevalence of primary aldosteronism in a primary-care population

Adrenal incidentalomas: presentation and clinical work-up

BACKGROUND

Through the widespread use of imaging techniques with great sensitivity, adrenal tumours are often diagnosed as an incidental finding. The majority of these adrenal lesions are benign and without evidence of endocrine activity or malignancy. However, in addition to the classic forms of overt adrenal hypersecretion, it has become evident in recent years that even modest adrenal hormonal autonomy, as exhibited in clinically silent phaeochromocytoma, normokalaemic primary aldosteronism and subclinical Cushing syndrome, is associated with significant morbidity. Thus, hormone hypersecretion and growth kinetics must be ruled out for each patient using specific tests to avoid associated morbidity.

CONCLUSIONS

Detection and differential diagnosis of subtle changes in adrenal hormone secretion can pose a diagnostic challenge to the clinician, and accurate diagnosis is dependent on use of tests with reliable sensitivity and specificity.

Phenotypic consequences of variation across the aldosterone synthase and 11-beta hydroxylase locus in a hypertensive cohort: data from the MRC BRIGHT Study

BACKGROUND

Aldosterone is an important cardiovascular hormone; 15% of hypertensive subjects have alteration in aldosterone regulation, defined by a raised ratio of aldosterone to renin (ARR). Studies of the aldosterone synthase gene (CYP11B2) have focused on a single nucleotide polymorphism in the 5'promoter region (-344 C/T). In normotensive subjects, the T allele associates with raised levels of the 11-deoxysteroids, deoxycorticosterone and 11-deoxycortisol which are substrates for 11beta-hydroxylase, encoded by the adjacent and homologous gene, CYP11B1. We have speculated that this altered 11beta-hydroxylase efficiency leads to increased ACTH drive to the adrenal gland to maintain cortisol production and reported herein the association between the -344 C/T single nucleotide polymorphism (SNP) and adrenal steroid production in subjects with essential hypertension.

METHODS

The CYP11B2-344 C/T polymorphism was genotyped and urinary excretion of adrenal steroid metabolites was measured (by GCMS) in 511 unrelated hypertensives from the Medical Research Council (MRC) British Genetics of Hypertension (BRIGHT) study.

RESULTS

Thirty-five per cent of subjects were homozygous for the -344T allele whilst 16% were CC homozygotes. There was no difference in cortisol excretion rate between the two genotype groups but the index of adrenal 11beta-hydroxylation (ratio of tetrahydrodeoxycortisol/total cortisol) was significantly higher in the TT group (P < 0.005) than in the CC group. Excretion rates of the major urinary metabolite of aldosterone (tetrahydroaldosterone) correlated strongly with the ACTH-regulated steroids, cortisol (r = 0.437, P < 0.0001) and total androgen metabolites (r = 0.4, P < 0.0001) in TT but not CC subjects.

CONCLUSIONS

Hypertensives homozygous for the -344 T allele of CYP11B2 demonstrate altered 11beta-hydroxylase efficiency (CYP11B1); this is consistent with the hypothesis of a genetically determined increase in adrenal ACTH drive in these subjects. The correlation between excretion of aldosterone and cortisol metabolites and suggests that, in TT subjects, ACTH exerts an important common regulatory influence on adrenal corticosteroid production in subjects with hypertension.

Outcomes of laparoscopic adrenalectomy for hyperaldosteronism

BACKGROUND

Primary hyperaldosteronism is a frequent cause of resistant hypertension and is amenable to surgical intervention when caused by a unilateral aldosterone-producing adenoma. The aim of this study was to investigate the long-term results of laparoscopic adrenalectomy in the control of hypertension caused by primary hyperaldosteronism.

METHODS

A prospective case series of patients undergoing laparoscopic adrenalectomy for hyperaldosteronism was studied. Blood pressure (BP), serum aldosterone levels, plasma renin activity, serum potassium and antihypertensive requirement were measured before and after adrenalectomy.

RESULTS

Sixty-two patients with hyperaldosteronism underwent laparoscopic adrenalectomy in the period from December 1995 to August 2005. The median follow up was 59 months. There was a significant decrease in both systolic blood pressure and diastolic blood pressure at final follow up compared with that before operation. Systolic blood pressure decreased from 149 mmHg to 129 mmHg at final follow up (P < 0.0001). Diastolic blood pressure decreased from 89 mmHg to 80 mmHg (P < 0.0001). Antihypertensive requirement was decreased from an average of 2.6 separate medications preoperatively to 1.4 medications at final follow up (P < 0.0001). Serum aldosterone levels were significantly lower (698 (confidence interval 534-862) pg/mL vs 181 (confidence interval 139-225) pg/mL, P < 0.0001). Overall, 34% of patients had cure of hypertension and did not require any antihypertensive agent. A further 51% had improvement in BP control, whereas 5% had no change or had worsening hypertension. Multivariate regression analysis showed that age and gland size were independent factors predicting sustained hypertension after surgery.

CONCLUSION

In appropriately selected patients with primary hyperaldosteronism, laparoscopic adrenalectomy is effective in improving long-term BP control. Larger adrenal gland size and older age at time of surgery are predictors of persisting hypertension.

The Association of Aldosterone With Obesity-Related Hypertension and the Metabolic Syndrome

Overweight and obesity are associated with arterial hypertension. Given the large increase in the obesity prevalence worldwide, the number of obese patients with hypertension is likely to increase substantially in the near future. Overweight and obese patients are exposed to an important metabolic and cardiovascular risk. The understanding of the mechanisms linking obesity to hypertension is important for specific prevention and therapy in this population. There is some evidence that obesity is associated with an increased aldosterone level. To date, 2 mechanisms may explain the interaction of fat tissue with the renin-angiotensin-aldosterone system, and therefore explain, in part, obesity-related hypertension. First, human adipose tissue produces several components of the renin-angiotensin-aldosterone system, mainly adipose tissue-derived angiotensinogen. Second, increased fatty acid production in the obese patient, especially nonesterified fatty acids, might stimulate aldosterone production, independent of renin. A better understanding of these mechanisms might have implications for the management of hypertension in overweight and obese patients. Because aldosterone also is associated with blood glucose and blood lipids, selective aldosterone blockade may represent a particularly attractive therapeutic strategy in obese patients with a clustering of cardiovascular risk factors.

Role of radiology in the management of primary aldosteronism

The diagnosis of primary aldosteronism, the most common form of secondary hypertension, is based on clinical and biochemical features. Although radiology plays no role in the initial diagnosis, it has an important role in differentiating between the two main causes of primary aldosteronism: aldosterone-producing adenoma (APA) and bilateral adrenal hyperplasia (BAH). This distinction is important because APAs are generally managed surgically and BAH medically. Adrenal venous sampling is considered the standard of reference for determining the cause of primary aldosteronism but is technically demanding, operator dependent, costly, and time consuming, with a low but significant complication rate. Other imaging modalities, including computed tomography, magnetic resonance imaging, and adrenal scintigraphy, have also been used to determine the cause of primary aldosteronism. Cross-sectional imaging has traditionally focused on establishing the diagnosis of an APA, with that of BAH being one of exclusion. A high specificity for detecting an APA is desirable, since it will avert unnecessary surgery in patients with BAH. However, an overreliance on cross-sectional imaging can lead to the incorrect treatment of affected patients, mainly due to the wide variation in the reported diagnostic performance of these modalities. A combination of modalities is usually required to confidently determine the cause of primary aldosteronism. The quest for optimal radiologic management of primary aldosteronism continues just over a half century since this disease entity was first described.

The influence of serum aldosterone and the aldosterone-renin ratio on pulse wave velocity in hypertensive patients

OBJECTIVE

The aldosterone-renin ratio (ARR) is widely used to screen for primary aldosteronism, and may reflect a relative excess of aldosterone secretion compared with renin secretion. Excess aldosterone may have a detrimental effect on vascular stiffness. We therefore hypothesized that ARR and aldosterone are independently correlated with pulse wave velocity (PWV) in hypertensive patients.

METHODS

The study consisted of 438 hypertensive patients. Serum aldosterone and plasma renin activity were measured in a sitting position using standard techniques. The PWV was determined by measuring the heart to femoral PWV (hfPWV) and brachial to ankle PWV with a VP-2000 pulse wave unit.

RESULTS

Group 1 was defined as patients with ARR of at least 20 (n = 53) with serum aldosterone >or= 12 ng/dl, while the remainder comprised group 2. Comparisons between the two groups reveal group 1 tended to have higher age, significantly higher proportion of women and higher systolic/diastolic blood pressure. Patients in group 1 also had a significantly higher index of central arterial stiffness (hfPWV 1048 +/- 202 vs 978 +/- 182, P = 0.010) compared with group 2. Multiple linear regression revealed that aldosterone, but not the ARR, is significantly associated with hfPWV but not brachial to ankle PWV, after controlling for age, systolic blood pressure and heart rate at the time of PWV measurement, body mass index, gender, low-density lipoprotein-cholesterol, triglyceride, high-density lipoprotein-cholesterol, blood pressure medication and statins.

CONCLUSIONS

Serum aldosterone is significantly associated with central aortic PWV in hypertensive patients. The results demonstrate a possible role for aldosterone in developing central aortic stiffness and increased PWV in hypertensive patients.

Prevalence of primary aldosteronism: should we screen for primary aldosteronism before treating hypertensive patients with medication?

The present review examines various reports describing prevalence of primary aldosteronism (PA) among hypertensives and the screening method of PA to better understand the current concepts used for diagnosing and managing PA among clinicians as well as specialists. Here, we describe and compare the prevalence of PA in Japan, which is well known to induce various vascular complications due to hyperaldosteronemia, resulting in cerebral infarction, myocardial infarction and renal failure, with that in another Asian area, US, European countries, Australia and Africa. The incidence rates for PA among hypertensives were recently reported to be widely raged between 3.2% and 20%. Those discrepancies are due in part to the completely different characteristics of the starting subjects used for studying the prevalence. Moreover, the criteria for screening PA among hypertensives, including aldosterone-renin ratio (ARR), and confirmatory tests for definitely diagnosing PA, such as saline infusion test are varied. We had already reported that a diagnosis of PA was made in 61 (6%) of the 1,020 hypertensive patients during the past five years, from 1995 until 1999. In our study, only 18% of the patients showed a serum K level of 3.3 mEq/l or less. Thus, many clinicians seem to misdiagnose PA as essential hypertension, because of absence of hypokalemia. Finally, we describe highlight key evidence for optimal methods for screening and definitely diagnosing PA among hypertensive patients in order to avoid misjudgment before or after treating hypertensive patients.

Aldosterone as a cardiovascular risk hormone

The pathophysiological role of aldosterone in the development of cardiovascular disease has long been considered to be due its potent volume expansion/hypertensive effect mainly via mineralocorticoid receptor (MR) expressed in renal tubular epithelial cells. However, recent accumulating lines of evidence from clinical and experimental studies have suggested that direct cardiovascular effect of aldosterone contributes to the development of cardiovascular injury via MRs in non-epithelial tissue. A series of recent clinical studies have revealed that patients with primary aldosteronism have higher incidence of cardiovascular and renal complications than those with essential hypertension, and that aldosterone antagonism has cardiovascular protective effect in patients with heart failure independent from blood pressure. Numerous experimental studies have shown that both inflammation and oxidative stress play an initial and key role in the development of aldosterone-induced cardiovascular injury via non-epithelial MR activation. In this review, we discuss recent research progress in aldosterone and MR effects, with special emphasis on the pathophysiological role of aldosterone in cardiovascular diseases and the possible molecular mechanism(s) of cardiovascular injury by non-epithelial MR activation.

Does the aldosterone:renin ratio predict the efficacy of spironolactone over bendroflumethiazide in hypertension? A clinical trial protocol for RENALDO (RENin-ALDOsterone) study

Background

High blood pressure is an important determinant of cardiovascular disease risk. Treated hypertensives do not attain a risk level equivalent to normotensives. This may be a consequence of suboptimal blood pressure control to which indiscriminate use of antihypertensive drugs may contribute. Indeed the recent ALLHAT[1]study suggests that thiazides should be given first to virtually all hypertensives. Whether this is correct or whether different antihypertensive therapies should be targeted towards different patients is a major unresolved issue, which we address in this study.

The measurement of the ratio of aldosterone: renin is used to identify hypertensive subjects who may respond well to treatment with the aldosterone antagonist spironolactone. It is not known if subjects with a high ratio have aldosteronism or aldosterone-sensitive hypertension is debated but it is important to know whether spironolactone is superior to other diuretics such as bendroflumethiazide in this setting.

Methods/design

The study is a double-blind, randomised, crossover, controlled trial that will randomise 120 hypertensive subjects to 12 weeks treatment with spironolactone 50 mg once daily and 12 weeks treatment with bendroflumethiazide 2.5 mg once daily. The 2 treatment periods are separated by a 2-week washout period. Randomisation is stratified by aldosterone: renin ratio to include equal numbers of subjects with high and low aldosterone: renin ratios.

Primary Objective – To test the hypothesis that the aldosterone: renin ratio predicts the antihypertensive response to spironolactone, specifically that the effect of spironolactone 50 mg is greater than that of bendroflumethiazide 2.5 mg in hypertensive subjects with high aldosterone: renin ratios.

Secondary Objectives – To determine whether bendroflumethiazide induces adverse metabolic abnormalities, especially in subjects with high aldosterone: renin ratios and if baseline renin measurement predicts the antihypertensive response to spironolactone and/or bendrofluazide

Discussion

The numerous deleterious effects of hypertension dictate the need for a systematic approach for its treatment. In spite of various therapies, resistant hypertension is widely prevalent. Among various factors, primary aldosteronism is an important cause of resistant hypertension and is now more commonly recognised. More significantly, hypertensives with primary aldosteronism are also exposed to various other deleterious effects of excess aldosterone. Hence treating hypertension with specific aldosterone antagonists may be a better approach in this group of patients. It may lead on to better blood pressures with fewer medications.

Mineralocorticoid hypertension and hypokalemia

Mineralocorticoid hypertension is hypertension associated with the presence of hypokalemia, metabolic alkalosis, and suppression of plasma renin. Mineralocorticoid hypertension represents only 10% of patients with essential hypertension. However, its recognition is important because it is a potentially reversible cause of hypertension. Primary hyperaldosteronism is the most common form of mineralocorticoid hypertension. It is current clinical practice to use the plasma aldosterone-renin ratio and the absolute plasma aldosterone level as screening tests. Confirmatory suppression tests and adrenal imaging are performed in appropriate patients. Three monogenic forms of mineralocorticoid hypertension have been identified including Liddle's syndrome, glucocorticoid-remediable hypertension, and apparent mineralocorticoid excess. In a number of patients with mineralocorticoid hypertension, hypokalemia can be a variable finding. This review highlights mineralocorticoid biology and important features of primary hyperaldosteronism and monogenic hypertension.

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

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

Noninvasive adrenal imaging in hyperaldosteronism: is it accurate for correctly identifying patients who should be selected for surgery?

BACKGROUND AND AIMS

The most common causes of hyperaldosteronism (HA) are bilateral idiopathic hyperaldosteronism (IHA), aldosterone-producing adenoma (APA), and unilateral primary adrenal hyperplasia (PAH). We evaluated if non-invasive preoperative imaging studies are able to reliably differentiate these causes of hyperaldosteronism.

METHODS

The medical records of 50 consecutive patients with HA were reviewed. Follow up was obtained by outpatient consultation or phone contact.

RESULTS

Thirty-five patients (70%) underwent successful adrenalectomy for APA, basing on the computed tomography (CT) scan results only. All these patients were biochemically cured. The remaining 15 patients underwent dexamethasone suppression adrenal cortical scintiscan (ACS) because of equivocal or inconclusive CT scan. In 11 of these patients, ACS showed a bilateral uptake, suggesting IHA. They were followed-up. In the remaining four patients, ACS showed a unilateral uptake. These patients underwent adrenalectomy. Final histology showed APA in three patients and PAH in one. They were biochemically cured. Sensitivity of combined non-invasive imaging procedures (CT and ACS) in detecting histologically proven and biochemically cured APA and PAH was 100%.

CONCLUSION

Non-invasive adrenal imaging studies are accurate in distinguishing between IHA and APA/PAH. Invasive diagnostic tests (adrenal venous sampling) should be indicated only when they do not conclusively localize hypersecretion.

Functional effects of genetic variants in the 11beta-hydroxylase (CYP11B1) gene

OBJECTIVE

We previously described an association between the -344C/T 5'-untranslated region (UTR) polymorphism in the CYP11B2 (aldosterone synthase) gene and hypertension with a raised aldosterone to renin ratio (ARR); the same genetic variant is also associated with impaired adrenal 11beta-hydroxylase efficiency. The -344 polymorphism does not seem to be functional, so is likely to be in linkage with variants in CYP11B1 that determine the associated variation in 11beta-hydroxylase efficiency. We therefore aimed to determine whether there is an association between CYP11B1 variants and hypertension and/or an altered ARR.

DESIGN AND MEASUREMENTS

We screened 160 subjects divided into four groups, normotensive controls, unselected hypertensive subjects, and hypertensive subjects with either a high (> or = 750) or low ARR (< or = 200), for variants in the coding region of CYP11B1 by single-stranded conformation polymorphism (SSCP) and direct sequencing. The effects of these variants on enzyme function were assessed by conversion of 11-deoxycortisol to cortisol and 11-deoxycorticosterone (DOC) to corticosterone.

RESULTS

Eight novel missense mutations were identified in the CYP11B1 gene that alter the encoded amino acids: R43Q, L83S, H125R, P135S, F139L, L158P, L186V and T196A. In each case they were heterozygous changes. However, no mutations were identified that could account for hypertension and/or a raised ARR. The variants L158P and L83S severely impaired enzyme function while R43Q, F139L, P135S and T196A enzymes resulted in product levels that were approximately 30-50% that of wild-type levels. The variant enzymes H125R and L186V resulted in substrate-specific alterations in enzyme function. H125R decreased conversion of 11-deoxycortisol to cortisol and L186V increased 11-deoxycortisol conversion. Neither had an effect on the conversion of DOC to corticosterone.

CONCLUSION

No variants were identified in the coding region of CYP11B1 that could account for hypertension and/or a raised ARR. However, this in vitro study identifies the importance of these affected residues to enzyme function and will inform subsequent studies of structure-function relationships.

Association between aldosterone production and variation in the 11beta-hydroxylase (CYP11B1) gene

CONTEXT

Variation in the region of chromosome 8 including the genes steroid 11beta-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) influences mineralocorticoid and glucocorticoid metabolism. However, the relative importance of polymorphisms in CYP11B1 and CYP11B2 in determining these phenotypes is unknown.

OBJECTIVE

Our objective was to investigate genetic influences of the CYP11B1 and CYP11B2 genes on mineralocorticoid metabolism.

DESIGN

We measured 24-h urinary excretion of the key metabolites of the principal mineralocorticoids, glucocorticoids and androgens secreted by the adrenal cortex. We genotyped polymorphisms spanning the CYP11B1 and CYP11B2 genes, which together capture all common variations at the locus.

PARTICIPANTS

Participants included 573 members of 105 British Caucasian families ascertained on a hypertensive proband.

MAIN OUTCOME MEASURES

We assessed heritability of urinary tetrahydroaldosterone (THAldo) excretion and association of THAldo excretion with genotype.

RESULTS

The heritability of THAldo excretion was 52% (P < 10(-6)). There was significant association between THAldo and genotype at several of the CYP11B1/B2 polymorphisms. The strongest association was observed at the rs6387 (2803A/G) polymorphism in intron 3 of CYP11B1 (P = 0.0004). Association followed a codominant model with a 21% higher THAldo excretion per G allele. Genotype at rs6387 accounted for 2.1% of the total population variability of THAldo. We found significant association between THAldo excretion and urinary total androgen excretion, urinary tetrahydrodeoxycortisol level, and urinary cortisol metabolites (all P < 0.001).

CONCLUSIONS

Aldosterone synthesis is highly heritable and is affected by genotype at CYP11B1. Our findings support the hypothesis that genetically determined differences in 11-hydroxylation efficiency can have downstream effects on mineralocorticoid synthesis. Such effects may be of relevance to the development of low-renin essential hypertension.

Adrenocortical Tumorigenesis

Through the widespread use of imaging techniques with great sensitivity adrenal tumors are often diagnosed as an incidental finding. Although the majority of these adrenal lesions are benign and without evidence of endocrine activity or malignancy, hormone hypersecretion needs to be ruled out by specific tests. In addition to the classical forms of overt adrenocortical hypersecretion, it has become evident over the recent years that modest adrenocortical steroid autonomy as present in normokalemic primary aldosteronism and subclinical Cushing's syndrome is also associated with a significant morbidity. However, detection and differential diagnosis of these subtle changes in adrenal steroidogenesis can pose a diagnostic challenge to the clinician and is dependent on tests with reliable sensitivity and specificity. Regulation of adrenocortical development and growth, which results in clinical symptoms if disrupted, is dependent upon the distinct spatiotemporal expression of a variety of transcription factors as well as stimulation by extra-adrenal peptide hormones. Contributions to the elucidation of growth regulation of the adrenal cortex come from rare familiar syndromes associated with adrenocortical tumors, expression studies of adrenal tumor samples, in vitro studies on adrenocortical tumor cell lines, and mouse models displaying adrenal growth defects. In this review, we will summarize the important molecular aspects of adrenal tumorigenesis and highlight some prospects for clinical applications.

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.

Monogenic mineralocorticoid hypertension

Monogenic mutations leading to excessive activation of the mineralocorticoid pathway result, almost always, in suppressed renin and hypertension in adult life and sometimes in hypokalaemia and alkalosis, which can be severe. In most of these syndromes, precise molecular changes in specific steroidogenic or effector genes have been identified, permitting appreciation of (1) pathophysiology, (2) great diversity of phenotype and (3) possibility of genetic methods of diagnosis. Yet to be achieved elucidation of the genetic basis of familial hyperaldosteronism type II, the most common and clinically significant of them, will enhance detection of primary aldosteronism, currently the commonest specifically treatable and potentially curable form of hypertension. While classic, complete-phenotype presentations of monogenic forms of mineralocorticoid hypertension are rarely recognised, more subtle genetic expression causing less florid manifestations could represent a significant proportion of so-called 'essential hypertension.'

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.

[Modern pharmacological aspects of hyperaldosteronism therapy]

The prevalence of primary hyperaldosteronism is 5-10% of all hypertensive patients, and clearly above the estimated prevalence in the past. In nearly 30% of patients with therapy resistant hypertension, primary hyperaldosteronism is detected if they are investigated thoroughly. This will result in 1.5 to 2.5 million people in Germany suffering from primary hyperaldosteronism. Besides efficient diagnostic procedures, an effective treatment is of increasing importance. The aldosterone-producing adenoma (Conn's syndrome) is primarily cured by operation, in most cases performed endoscopically. Bilateral hyperplasia, which is found in two-thirds of primary hyperaldosteronism, is treated primarily by mineralocorticoid receptor antagonist: 12.5-50 mg/day spironolactone (in case of anti-androgenic side-effects alternatively by 50-100 mg/day eplerenone). If the blood pressure can not be lowered by this first-line treatment, an additional treatment with potassium-sparing diuretics, calcium-antagonists, ACE-inhibitors or angiotensin-2-antagonists is necessary. The start of medication should be closely monitored by serum electrolyte and creatinine controls.

Hypertension and the expanding role of aldosterone

Aldosterone is the principal human mineralocorticoid and plays a significant role in hypertension and cardiovascular morbidity. Classically, aldosterone is synthesized in the adrenal zona glomerulosa and binds to mineralocorticoid receptors in the cytosol of target epithelial cells. Nonepithelial and rapid nongenomic actions of aldosterone have now also been described, as well as a number of extra-adrenal sites of synthesis, including the central nervous system. Recent studies also suggest that elevated aldosterone biosynthesis, as defined by an increased aldosterone-to-renin ratio, is present in up to 15% of essential hypertensives and that aldosterone levels predict the development of hypertension in normotensive individuals. Furthermore, mineralocorticoid-receptor antagonists demonstrate that aldosterone is a significant contributor to cardiovascular pathology. In this article, we present the evidence behind these findings and explore the expanding role of aldosterone as a key cardiovascular hormone.

Analysis of screening and confirmatory tests in the diagnosis of primary aldosteronism: need for a standardized protocol

BACKGROUND

The upright serum aldosterone/upright plasma renin activity ratio (ARR) has been recommended as a screening tool for the diagnosis of primary aldosteronism.

OBJECTIVE

We reviewed the data collected from hypertensive patients in order to define retrospectively the cut-off values and evaluate the reliability of the ARR and of the saline infusion test in the diagnosis of primary aldosteronism.

PATIENTS

In 157 patients referred to our unit with a suspicion of primary aldosteronism, 61 of whom had confirmed primary aldosteronism [26 aldosterone-producing adenoma (APA); 35 idiopathic hyperaldosteronism], the supine and upright ARR, and the ARR after the administration of captopril and losartan were calculated, and the results of the saline infusion test were analysed.

RESULTS

Choosing 40 as the cut-off value, the upright ARR had 100% sensitivity and 84.4% specificity. The post-captopril and post-losartan ARR were slightly more specific, but at the cost of a lower sensitivity. A cut-off value of 7 ng/dl for serum aldosterone at the end of the saline infusion in patients with an upright ARR of 40, gave 100% specificity and a positive predictive value. Furthermore, APA patients showed increased mean levels of aldosterone/cortisol ratio after the saline infusion test.

CONCLUSION

Our data reinforce the superiority of a standardized upright ARR as a screening test in the diagnosis of primary aldosteronism, identifying 40 as an ideal cut-off value. Saline infusion represents a useful test to confirm such a diagnosis, with a serum aldosterone level of 7 ng/dl as a satisfactory cut-off value. Some more information is obtained when the aldosterone/cortisol ratio is considered.

The pharmacological treatment of primary aldosteronism

Aldosterone is increasingly considered to have a fundamental role in the pathophysiology of cardiovascular disease. Primary aldosteronism is a much more common cause of secondary hypertension than once suspected, accounting for approximately 10% of cases. Screening for primary aldosteronism should be considered even in the presence of normokalaemia. The non-classical effects of aldosterone, some of which are transcription-independent, may be of similar or greater importance than its traditional effects on the kidney. Treatment of primary aldosteronism should be specific and aim to ameliorate all hormone-related effects of aldosterone, not just the most obvious manifestation of hypertension. Mineralocorticoid antagonism, shown to lead to significant additional survival advantage in heart failure, offers the best prospect for achieving therapeutic goals. For the increasing proportion of patients with primary aldosteronism suitable for long-term medical treatment, mineralocorticoid receptor blockade (better tolerated with eplerenone) should be considered the most appropriate choice of treatment, pending the development of better alternatives.

Clinical outcomes of laparoscopic adrenalectomy for lateralizing nodular hyperplasia

BACKGROUND

Nodular adrenal hyperplasia (NAH) may mimic the biochemical characteristics of an aldosterone-producing adenoma. The authors evaluated the outcomes of unilateral laparoscopic adrenalectomy in the setting of lateralizing aldosterone hypersecretion by NAH.

METHODS

Retrospective review of consecutive patients who underwent a laparoscopic adrenalectomy for primary hyperaldosteronism owing to NAH was performed. Patient demographics, perioperative symptoms, medications, radiographic findings, and serum chemistries were analyzed. Response to operation was classified according to postoperative control of hypertension and hypokalemia as resolved, improved, or refractory.

RESULTS

From January 1999 to October 2004, 15 patients underwent a laparoscopic unilateral adrenalectomy for hyperaldosteronism owing to lateralizing NAH. Nine (60%) patients presented with > or =5 years of hypertension, including 8 (53%) patients with labile or malignant hypertension. Ten (67%) patients had hypokalemia. Abdominal imaging results were normal in 9 (60%) patients. All patients underwent adrenal venous sampling (94% successfully), which revealed an average adjusted aldosterone ratio of 17.6 (range, 1.2 to 75.9). At a mean follow-up of 26 (range, 4 to 58) months, hypertension had resolved in 4 (27%), improved in 8 (53%), and was refractory in 3 (20%) patients. Hypokalemia resolved in all patients. There were no complications, conversions, or mortalities.

CONCLUSION

This series shows that unilateral adrenalectomy for lateralizing NAH results in eradication of hypokalemia and resolution or significant improvement in hypertension in 80% of patients at long-term follow-up. When lateralization of aldosterone production is noted, laparoscopic adrenalectomy provides significant clinical improvement even in patients with a pathologic diagnosis of NAH.

Primary aldosteronism: Diagnostic and therapeutic considerations

Recent evaluations indicate that primary aldosteronism (PA) is common in patients with hypertension. In patients with mild to moderate hypertension the prevalence of PA is 5% to 10%, whereas in subjects with resistant hypertension the prevalence is approximately 20%. As such, PA has become the most common secondary cause of hypertension. Such high prevalence rates are distinctly different from earlier assessments in which PA was found to be rare, with a prevalence of generally less than 1% of hypertensive patients. Why PA is seemingly so much more common now than when first described remains unknown. Accurate identification of PA allows for specific therapy with aldosterone antagonists or with surgical resection of aldosterone-producing adenomas. Determination of the plasma aldosterone to plasma renin activity ratio is an effective screen for PA in that it has a high negative predictive value even in the setting of ongoing antihypertensive therapy. Its specificity, however, is low such that a high ratio is suggestive of PA but must be confirmed by demonstration of high and autonomous secretion of aldosterone.

Comparison of adrenal vein sampling value between aldosterone producing adrenal adenoma and non-functioning adrenal adenoma: evaluation using receiver operating characteristic analysis

PURPOSE

To evaluate adequate criteria for adrenal vein sampling values in patients with aldosterone producing adrenal adenoma (APA), retrospectively.

MATERIAL AND METHODS

Between 1988 and 2002, 59 hypertensive patients (15 M and 44 F, aged 47.58 +/- 9.45 years) were referred to our hospital and diagnosed with APA based on established criteria. During the same period, 23 patients with non-functioning adrenal adenoma (11 M and 12 F aged 53.56 +/- 11.76 years) were diagnosed based on computed tomography and laboratory data.

RESULTS

All 82 patients were enrolled in the present study. Bilateral adrenal vein sampling (AVS) for measurement of plasma aldosterone (A) and cortisol (C) was performed, and a receiver operating characteristics (ROC) analysis was conducted to establish the best criteria from the AVS-derived index in patients with APA. A (APA side)/A (contralateral side) was confirmed to provide the best diagnostic accuracy {(>2.5: right APA, sensitivity 83.3%, specificity 79.5%), (> 3: left APA, sensitivity 84.2%, specificity 76.9)}. The Az values for A (APA side)/A (contralateral side) were 0.8948 and 0.9260 for right and left APA, respectively.

CONCLUSION

The A (APA side)/A (contralateral side) value was the best compromise for sensitivity and false-positive rate for lateralization of APA.

Hiperaldosteronismo primario: análisis de una serie de 54 pacientes

BACKGROUND AND OBJECTIVE

The prevalence of primary aldosteronism (PA) has experienced an important increase, and many authors consider this condition as the main cause of secondary hypertension (HT).

PATIENTS AND METHOD

Retrospective study of a series of 54 patients having PA who were studied in our Unit between 1999 and 2003.

RESULTS

The prevalence of PA was 5.1%. Out of 54 PA cases, 13 corresponded to aldosterone-producing adenomas (APA), 30 to bilateral adrenal hyperplasia (BAH), one was one case of nodular bilateral hyperplasia and another case was a nodular unilateral hyperplasia. In 9 cases, an etiologic diagnosis could not be done. APA were more frequent in women and BAH in men; with regard to sex, no significant differences were found. The blood pressure (BP) was significantly higher in patients with APA compared with BAH patients. In patients with APA, kalemia was significantly lower than in BAH patients. Adrenal CT scan identified 90% of APA, while scintigraphy detected 100% of BAH. Spironolactone therapy significantly decreased the BP in APA and BAH patients, although this fall was higher in patients with APA.

CONCLUSIONS

The prevalence of PA was 5.1%. Although the tests used for the screening and diagnosis of PA are controversial, a PA ought to be investigated in all patients with refractory HT, independently of the existence of hypokalemia. Spironolactone is an effective therapy for BAH and it is an adequate option for APA treatment when an adrenalectomy is not viable.

Low renin hypertensive states: perspectives, unsolved problems, future research

Some causes of low renin hypertension are familial with known genetic bases. One of them, primary aldosteronism, is specifically treatable by mineralocorticoid receptor blockers or by surgery, and has at least two different familial varieties. These have provided insights into its natural history, with long normotensive and normokalemic phases, and variable expression within the same family. Primary aldosteronism was considered rare, but recent work beginning in 1992 suggests that it might be the most common curable cause of hypertension, worth screening for in every hypertensive. Evidence is now compelling that inappropriate aldosterone for salt status can cause not only hypertension, but vascular inflammation and end-organ damage, preventable by mineralocorticoid receptor blockade.

Primary hyperaldosteronism, a mediator of progressive renal disease in cats

In recent years, there has been renewed interest in primary hyperaldosteronism, particularly because of its possible role in the progression of kidney disease. While most studies have concerned humans and experimental animal models, we here report on the occurrence of a spontaneous form of (non-tumorous) primary hyperaldosteronism in cats. At presentation, the main physical features of 11 elderly cats were hypokalemic paroxysmal flaccid paresis and loss of vision due to retinal detachment with hemorrhages. Primary hyperaldosteronism was diagnosed on the basis of plasma concentrations of aldosterone (PAC) and plasma renin activity (PRA), and the calculation of the PAC:PRA ratio. In all animals, PACs were at the upper end or higher than the reference range. The PRAs were at the lower end of the reference range, and the PAC:PRA ratios exceeded the reference range. Diagnostic imaging by ultrasonography and computed tomography revealed no or only very minor changes in the adrenals compatible with nodular hyperplasia. Adrenal gland histopathology revealed extensive micronodular hyperplasia extending from zona glomerulosa into the zona fasciculata and reticularis. In three cats, plasma urea and creatinine concentrations were normal when hyperaldosteronism was diagnosed but thereafter increased to above the upper limit of the respective reference range. In the other eight cats, urea and creatinine concentrations were raised at first examination and gradually further increased. Even in end-stage renal insufficiency, there was a tendency to hypophosphatemia rather than to hyperphosphatemia. The histopathological changes in the kidneys mimicked those of humans with hyperaldosteronism: hyaline arteriolar sclerosis, glomerular sclerosis, tubular atrophy and interstitial fibrosis. The non-tumorous form of primary hyperaldosteronism in cats has many similarities with "idiopathic" primary hyperaldosteronism in humans. The condition is associated with progressive renal disease, which may in part be due to the often incompletely suppressed plasma renin activity.

Primary aldosteronism: actual epidemics or false alarm?

The prevalence of "primary aldosteronism" (PAL) cannot be precisely determined at this time, given 1) lack of a universally accepted definition, and 2) normotensive as well as normokalemic phases in the evolutionary development of a disease eventually characterized by hypertension and hypokalemia. The exception is fully genetically characterised forms such as glucocorticoid-suppressible hyperaldosteronism, the true prevalence of which could be proven today by universal screening using a single blood sample, but this is neither practical nor appropriate. Controversy has arisen regarding the rareness, or otherwise, of PAL because of 1) rediscovery in the last 12 years of the normokalemic phase described by Conn, 2) application of widely available methods for measurement of aldosterone and renin to "screening", 3) variable quality of these methods, and of their application, and 4) lack of the necessary "diagnostic", in addition to "screening", tests in some studies. PAL is significantly more common than previously thought, and a very important potentially curable form of hypertension. Early diagnosis and specific treatment avoids morbidity. The current focus on increased detection is essential, and will help to resolve the question of prevalence.

Mechanisms of hypertension: the expanding role of aldosterone

Hypertension is a common disorder that affects a large heterogeneous patient population. Subgroups can be identified on the basis of their responses to hormonal and biologic stimuli. These subgroups include low-renin hypertensives and nonmodulators. Aldosterone, the principal human mineralocorticoid, is increasingly recognized as playing a significant role in cardiovascular morbidity, and its role in hypertension has recently been reevaluated with studies that suggest that increased aldosterone biosynthesis (as defined by an elevated aldosterone to renin ratio) is a key phenotype in up to 15% of individuals with hypertension. It was reported previously that a polymorphism of the gene (C to T conversion at position -344) encoding aldosterone synthase is associated with hypertension, particularly in individuals with a high ratio. However, the most consistent association with this variant is a relative impairment of adrenal 11beta-hydroxylation. This review explores the evidence for this and provides a hypothesis linking impaired 11beta-hydroxylation and hypertension with a raised aldosterone to renin ratio. It is also speculated that there is substantial overlap between this group of patients and previously identified low-renin hypertensives and nonmodulators. Thus, these groups may form a neurohormonal spectrum reflecting different stages of hypertension or indeed form sequential steps in the natural history of hypertension in genetically susceptible individuals.

Clinical manifestation of aldosteronoma

Formerly, fewer than 1% of patients with hypertension were believed to have primary hyperaldosteronism; however, recent studies have suggested a higher prevalence, in 5% to 10% of patients with hypertension. Hypokalemia is not necessary for the diagnosis and is probably a sign of more advanced disease. The best diagnostic test is the plasma aldosterone concentration to plasma renin activity (PAC/PRA) ratio. Excess aldosterone level has a deleterious effect on the cardiovascular system. Aldosteronomas should be differentiated from idiopathic hyperaldosteronism (IHA),because they are curable by laparoscopic adrenalectomy.

The current epidemic of primary aldosteronism

Until recently, primary aldosteronism was considered to be a rare cause of identifiable or secondary hypertension. Over the past 10 years, a steadily growing number of reports have claimed that this condition is much more common, present in 5-40% of all hypertensive patients, which translates into many millions of patients. The primary basis for this current epidemic is the application of a relatively simple screening test, the plasma aldosterone to renin ratio (ARR). Despite growing recognition that the ARR is neither sensitive nor specific, its advocates recommend that it should be a routine procedure in evaluation of all hypertensives. Evidence is provided that this recommendation will lead to massive increases in costs, both in money and in morbidity, while providing benefit to only a very small number of patients who would not be aided by continuation of previous diagnostic protocols.

Towards selectively modulating mineralocorticoid receptor function: lessons from other systems

Although there is clinical utility in blocking mineralocorticoid receptor (MR) action, the usefulness of available MR antagonists is limited because of cross-reactivity with the androgen and progesterone receptors (spironolactone) or possibly by low affinity for MR (eplerenone). MR binds aldosterone and physiologic glucocorticoids, such as cortisol, which both can act as MR agonists in epithelial tissues. However, in preliminary studies aldosterone and cortisol appear to induce different conformations in non-epithelial tissues; in the cardiomyocyte, cortisol usually acts as an MR antagonist, whereas in vascular smooth muscle cortisol mimics aldosterone actions if it can access MR, just as it does in the kidney. Thus, there are needs for improved MR antagonists with higher selectivity and potency and, if possible, for compounds that lock MR into specific desirable conformations. Efforts are underway to modulate selectively the action of many nuclear receptors, and insights from one nuclear receptor may be applicable to others given the similarities in structure and function. We have used traditional approaches aided by X-ray crystallography to obtain several classes of selective ligands that modulate thyroid receptor (TR) action. We describe the properties of these selective TR modulators here, and discuss the possibility that similar approaches to ligand design may yield MR interacting compounds with improved specificity and, possibly, tissue specificity.

Increased diagnosis of primary aldosteronism, including surgically correctable forms, in centers from five continents

Primary aldosteronism (PA) is a common form of endocrine hypertension previously believed to account for less than 1% of hypertensive patients. Hypokalemia was considered a prerequisite for pursuing diagnostic tests for PA. Recent studies applying the plasma aldosterone/plasma renin activity ratio (ARR) as a screening test have reported a higher prevalence. This study is a retrospective evaluation of the diagnosis of PA from clinical centers in five continents before and after the widespread use of the ARR as a screening test. The application of this strategy to a greater number of hypertensives led to a 5- to 15-fold increase in the identification of patients affected by PA. Only a small proportion of patients (between 9 and 37%) were hypokalemic. The annual detection rate of aldosterone-producing adenoma (APA) increased in all centers (by 1.3-6.3 times) after the wide application of ARR. Aldosterone-producing adenomas constituted a much higher proportion of patients with PA in the four centers that employed adrenal venous sampling (28-50%) than in the center that did not (9%). In conclusion, the wide use of the ARR as a screening test in hypertensive patients led to a marked increase in the detection rate of PA.

Active renin versus plasma renin activity to define aldosterone-to-renin ratio for primary aldosteronism

BACKGROUND

In recent years, the assessment of the plasma aldosterone-to-renin ratio (ARR) has become an established screening method for the diagnosis of primary aldosteronism. Plasma renin activity (PRA) is usually measured to define ARR although, increasingly, renin concentration alone is often measured in clinical routine.

OBJECTIVE

To determine the threshold of ARR using active renin concentration to screen for primary aldosteronism.

DESIGN AND PARTICIPANTS

To determine the ARR threshold based on plasma immunoreactive renin concentration (irR), we measured plasma aldosterone concentration (PAC), irR and PRA in 36 hypertensive patients, nine thereof with adrenal adenoma, and compared ARRs calculated from irR and PRA, respectively.

SETTING

Single-centre, hypertension clinic in a tertiary care hospital.

RESULTS

PRA ranged from 0.41-14.9 ng/ml per h and irR from 1.1-72 ng/l. There was an excellent correlation between PRA and irR (r = 0.98, P < 0.0001) and between ARRPRA and ARRirR (r = 0.96, P < 0.0001). An ARRPRA > 750 pmol/l per ng/ml per h was previously found to be highly predictive of primary aldosteronism because 90% of the corresponding patients failed to suppress PAC upon saline infusion or fludrocortisone. The corresponding threshold value for ARRirR was 150 pmol/ng in our patients. Using these cut-offs, nine subjects had both increased ARRPRA and ARRirR while, in three patients, either ARRPRA or ARRirR were increased. The nine patients with increased ARRPRA and ARRirR also had PAC > 650 pmol/l. Only these patients had adrenal adenomas.

CONCLUSIONS

The ARR threshold to screen for primary aldosteronism may be based on measurement of irR. An ARRirR > 150 pmol/ng may indicate primary aldosteronism.

Aldosterone Excretion Among Subjects With Resistant Hypertension and Symptoms of Sleep Apnea

OBJECTIVE

The severity of obstructive sleep apnea (OSA) correlates with the difficulty of controlling BP. The mechanism, however, by which sleep apnea contributes to the development of resistant hypertension remains obscure. Having observed a high prevalence of OSA among hypertensive subjects with primary hyperaldosteronism, we hypothesized a possible association between sleep apnea and aldosterone excretion.

DESIGN

In consecutive subjects referred to a university clinic for resistant hypertension, we prospectively determined plasma renin activity (PRA), plasma aldosterone concentration (PAC), and 24-h urinary aldosterone excretion during high dietary salt ingestion. In addition, all subjects completed the Berlin Questionnaire, a survey designed to identify subjects at risk of having sleep apnea. Primary hyperaldosteronism (PA) was defined as a PRA < 1.0 ng/mL/h and 24-h urinary aldosterone excretion > 12 micro g during high urinary sodium excretion (> 200 mEq/24 h).

RESULTS

Of the 114 subjects evaluated, 72 subjects had a high probability and 42 subjects had a low probability of having sleep apnea based on their responses to the Berlin Questionnaire. Subjects at high risk for sleep apnea were almost two times more likely to have PA diagnosed (36 vs 19%, p < 0.05), tended to have lower PRA (1.2 +/- 1.8 ng/mL/h vs 1.9 +/- 4.1 ng/mL/h), and had significantly greater 24-h urinary aldosterone excretion (13.6 +/- 9.6 micro g vs 9.8 +/- 7.6 micro g, p < 0.05) compared to subjects at low risk of sleep apnea.

CONCLUSION

These data provide evidence of increased aldosterone excretion in subjects with resistant hypertension and symptoms of sleep apnea. While the causality of this association is unknown, it is hypothesized that sleep apnea contributes to the development of resistant hypertension by stimulating aldosterone excretion.

Hyperaldosteronism and pheochromocytoma: new tricks and tests

Hyperaldosteronism, previously thought to represent only 1% to 2% of cases of hypertension, may cause as much as 25% of hypertension in a primary care setting. The renin/aldosterone ratio is the best test for initial screening, followed by localization if possible. Aldosterone antagonists, such as spironolactone, and surgery are the mainstays of treatment. Pheochromocytomas are rare, but because they are a curable cause of hypertension and potentially fatal if not found, important to diagnose. Clinical presentation is variable; however, if symptoms are present, they usually include hypertension, hyperhydrosis, headaches, or palpitations sometimes occurring in dramatic fashion. Once a diagnosis is entertained, appropriate laboratory confirmation is essential. Positive laboratory confirmation then leads to localization of the tumor for eventual surgical removal. New biochemical tests and imaging procedures are making the difficult job of diagnosing and finding these tumors.

Primary aldosteronism

Approaching the fiftieth year since its original description, primary aldosteronism is now thought to be the commonest potentially curable and specifically treatable form of hypertension. Correct identification of patients with primary aldosteronism requires that the effects of time of day, posture, dietary sodium intake, potassium levels and medications on levels of aldosterone and renin be carefully considered. Accurate elucidation of the subtype is essential for optimal treatment, and adrenal venous sampling is the only reliable means of differentiating aldosterone-producing adenoma from bilateral adrenal hyperplasia. With genetic testing already available for one inherited form, making more cumbersome biochemical testing for that subtype virtually obsolete and bringing about improvements in treatment approach, an intense search is underway for genetic mutations causing other, more common familial varieties of primary aldosteronism.

Clinical and molecular aspects of adrenocortical tumourigenesis

Adrenal masses are a common problem affecting 3-7% of the population. The majority turn out to be benign adrenocortical adenomas, which may be functional or non-functional. Much more rarely, these masses represent a primary adrenal carcinoma. It is becoming increasingly recognized that of the benign functioning adenomas or hyperplasias, the majority will hypersecrete aldosterone and this will be more frequently detected when hypertensive populations are screened for this disease. In contrast, the incidence of primary adrenocortical carcinoma has remained steady and for this disease, surgery represents the mainstay of treatment. The advent of laparoscopic adrenal surgery has lowered the threshold size for recommending surgery for asymptomatic adrenal masses and as such, an increased proportion of adrenocortical cancers are being resected and detected at an earlier stage. Recent progress has been made in our understanding of the key genetic changes which underpin the biology of this disease. Progression from adrenal adenoma to carcinoma involves a monoclonal proliferation of cells which, among other defects, have undergone chromosomal duplication at the 11p15.5 locus leading to overexpression of the IGF2 gene and abrogation of expression of the CDKN1C and H19 genes. TP53 is involved in progression to carcinoma in a subset of patients and the frequency of ACTH receptor deletion needs to be more fully explored. Other key oncogenes and tumour suppressor genes remain to be identified although the chromosomal loci in which they lie can be identified at 17p, 1p, 2p16 and 11q13 for tumour suppressor genes and chromosomes 4, 5 and 12 for oncogenes.

Forms of mineralocorticoid hypertension

Hypertension with hypokalemia, metabolic alkalosis, and suppressed plasma renin activity defines mineralocorticoid hypertension. Mineralocorticoid hypertension is the consequence of an overactivity of the epithelial sodium channel expressed at the apical membrane of renal cells in the distal nephron. This is usually the case when the mineralocorticoid receptor is activated by its physiologic substrate aldosterone. The best known form of mineralocorticoid hypertension is an aldosterone-producing adrenal tumor leading to primary aldosteronism. Primary aldosteronism can also be caused by unilateral or bilateral adrenal hyperplasia and rarely adrenal carcinoma. Interestingly, most of the inherited monogenic disorders associated with hypertension involve an excessive activation of the mineralocorticoid axis. In some of these disorders, mineralocorticoid hypertension results from activation of the mineralocorticoid receptor by other steroids (cortisol, deoxycorticosterone), by primary activation of the receptor itself, or by constitutive overactivity of the renal epithelial sodium channel. The present review addresses the physiology and significance of the key players of the mineralocorticoid axis, placing emphasis on the conditions leading to mineralocorticoid hypertension.

Minireview: primary aldosteronism--changing concepts in diagnosis and treatment

Primary aldosteronism affects 5-13% of patients with hypertension. Patients with hypertension and hypokalemia and most patients with treatment-resistant hypertension should undergo screening for primary aldosteronism with a plasma aldosterone concentration to plasma renin activity ratio. A high plasma aldosterone concentration to plasma renin activity ratio is a positive screening test result, a finding that warrants confirmatory testing. For those patients that want to pursue a surgical cure, the accurate distinction between the subtypes (unilateral vs. bilateral adrenal disease) of primary aldosteronism is a critical step. The subtype evaluation may require one or more tests, the first of which is imaging the adrenal glands with computed tomography, followed by selective use of adrenal venous sampling. Because of the deleterious cardiovascular effects of aldosterone, normalization of circulating aldosterone or aldosterone receptor blockade should be part of the management plan for all patients with primary aldosteronism. Unilateral laparoscopic adrenalectomy is an excellent treatment option for patients with unilateral aldosterone-producing adenoma. Bilateral idiopathic hyperaldosteronism should be treated medically. In addition, aldosterone-producing adenoma patients may be treated medically if the medical treatment includes mineralocorticoid receptor blockade.

Aldo is back: recent advances and unresolved controversies in hyperaldosteronism

PURPOSE OF REVIEW

Hyperaldosteronism in its various forms is a recognized secondary cause of hypertension, yet the frequency of these disorders and the appropriate evaluation of suspected patients remain controversial. This review will summarize recent literature concerning the frequency of hyperaldosteronism in the hypertensive population, insight from uncommon forms of hyperaldosteronism, and new developments in the diagnosis and treatment of this condition.

RECENT FINDINGS

Several series report that around 10% of hypertensive patients have some form of hyperaldosteronism, but aldosterone-producing adenomas are rare. Diagnostic criteria for idiopathic hyperaldosteronism remain controversial, as is the wisdom of widespread screening. Patients with even mild hyperaldosteronism, however, which could be a continuum with low-renin hypertension, may respond exceptionally well to mineralocorticoid antagonism. Eplerenone, a new mineralocorticoid receptor antagonist without antiandrogen side effects, has been an effective antihypertensive in clinical trials and appears to be particularly suitable for low-renin hypertensives. Accumulating evidence suggests that aldosterone excess is cardiotoxic and nephrotoxic, suggesting that mineralocorticoid blockade has specific benefits beyond blood pressure reduction. For patients with severe, confirmed hyperaldosteronism, selective adrenal vein sampling is the only reliable method for determining the source of the aldosterone.

SUMMARY

Hyperaldosteronism, when defined with liberal criteria, could account for a substantial portion of hypertension. Few of these patients will harbor adrenal adenomas, but those with severe hypertension and hypokalemia often require adrenal vein sampling to direct surgery. With more precise diagnostic strategies, better treatments, and evolving evidence of pathological consequences of aldosterone excess, subtle disorders of aldosterone excess demand precise definition and specific treatment.

Better blood pressure control: how to combine drugs

Prospective comparisons of different drug classes have shown that differences in blood pressure control, rather than differences between drug classes, have the over-riding influence on overall outcome. The same studies have also reinforced the need, in the majority of patients, to use combinations of drugs in order to achieve the target of <140/85 mmHg. By contrast, most patients in routine practice receive single agents and consequently fail to achieve target blood pressure. This failure reflects in part the emphasis in individual studies and subsequent guidelines on comparison of individual drugs. In this article we show how the consistency of both theory and a broad range of evidence permits a didactic approach to combination therapy. Our advice is based on the growing recognition that essential hypertension and its treatment fall into two main categories. Younger Caucasians usually have renin-dependent hypertension that responds well to angiotensin-converting-enzyme inhibition or angiotensin receptor blockade (A) or ss blockade (B). Most other patients have low-renin hypertension that responds better to calcium channel blockade (C) or diuretics (D). These latter drugs activate the renin system rendering patients responsive to the addition of renin suppressive therapy. Coincidence of the initials of these main drug classes with the first four letters of the alphabet permits an AB/CD rule, according to which recommended combinations are one drug from each of the "AB" and "CD" categories of drugs. However, the diabetogenic potential of the older "B" and "D" classes leads us to advise against combining "B" and "D" in older patients, and to recommend "A" + "C" + "D" as standard triple therapy for resistant hypertension.