Histological and biochemical distinctiveness of atypical aldosterone-producing adenomas responsive to upright posture and angiotensin

TSPAN12 (Tetraspanin 12) Is a Novel Negative Regulator of Aldosterone Production in Adrenal Physiology and Aldosterone-Producing Adenomas

BACKGROUND

Aldosterone-producing adenomas (APAs) are a major cause of primary aldosteronism, a condition of low-renin hypertension, in which aldosterone overproduction is usually driven by a somatic activating mutation in an ion pump or channel. TSPAN12 is differentially expressed in different subgroups of APAs suggesting a role in APA pathophysiology. Our objective was to determine the function of TSPAN12 (tetraspanin 12) in adrenal physiology and pathophysiology.

METHODS

APA specimens, pig adrenals under dietary sodium modulation, and a human adrenocortical cell line HAC15 were used for functional characterization of TSPAN12 in vivo and in vitro.

RESULTS

Gene ontology analysis of 21 APA transcriptomes dichotomized according to high versus low TSPAN12 transcript levels highlighted a function for TSPAN12 related to the renin-angiotensin system. TSPAN12 expression levels in a cohort of 30 APAs were inversely correlated with baseline plasma aldosterone concentrations (R=-0.47; P=0.009). In a pig model of renin-angiotensin system activation by dietary salt restriction, TSPAN12 mRNA levels and TSPAN12 immunostaining were markedly increased in the zona glomerulosa layer of the adrenal cortex. In vitro stimulation of human adrenocortical human adrenocortical cells with 10 nM angiotensin II for 6 hours caused a 1.6-fold±0.13 increase in TSPAN12 expression, which was ablated by 10 μM nifedipine (P=0.0097) or 30 μM W-7 (P=0.0022). Gene silencing of TSPAN12 in human adrenocortical cells demonstrated its inverse effect on aldosterone secretion under basal and angiotensin II stimulated conditions.

CONCLUSIONS

Our findings show that TSPAN12 is a negative regulator of aldosterone production and could contribute to aldosterone overproduction in primary aldosteronism.

Intrinsic Adrenal TWIK-Related Acid-Sensitive TASK Channel Dysfunction Produces Spontaneous Calcium Oscillations Sufficient to Drive AngII (Angiotensin II)-Unresponsive Hyperaldosteronism

Background:

Ion channel mutations in calcium regulating genes strongly associate with AngII (angiotensin II)-independent aldosterone production. Here, we used an established mouse model of in vivo aldosterone autonomy, Cyp11b2 -driven deletion of TWIK-related acid-sensitive potassium channels (TASK-1 and TASK-3, termed zona glomerulosa [zG]-TASK-loss-of-function), and selective pharmacological TASK channel inhibition to determine whether channel dysfunction in native, electrically excitable zG cell rosette-assemblies: (1) produces spontaneous calcium oscillatory activity and (2) is sufficient to drive substantial aldosterone autonomy.

Methods:

We imaged calcium activity in adrenal slices expressing a zG-specific calcium reporter (GCaMP3), an in vitro experimental approach that preserves the native rosette assembly and removes potentially confounding extra-adrenal contributions. In parallel experiments, we measured acute aldosterone production from adrenal slice cultures.

Results:

Absent from untreated WT slices, we find that either adrenal-specific genetic deletion or acute pharmacological TASK channel inhibition produces spontaneous oscillatory bursting behavior and steroidogenic activity (2.4-fold) that are robust, sustained, and equivalent to activities evoked by 3 nM AngII in WT slices. Moreover, spontaneous activity in zG-TASK-loss-of-function slices and inhibitor-evoked activity in WT slices are unresponsive to AngII regulation over a wide range of concentrations (50 pM to 3 µM).

Conclusions:

We provide proof of principle that spontaneous activity of zG cells within classic rosette assemblies evoked solely by a change in an intrinsic, dominant resting-state conductance can be a significant source of AngII-independent aldosterone production from native tissue.

Pathophysiology and histopathology of primary aldosteronism

Primary aldosteronism (PA) can be sporadic or familial and classified into unilateral and bilateral forms. Sporadic PA predominates with excessive aldosterone production usually arising from a unilateral aldosterone-producing adenoma (APA) or bilateral adrenocortical hyperplasia. Familial PA is rare and caused by germline variants, that partly correspond to somatic alterations in APAs. Classification into unilateral and bilateral PA determines the treatment approach but does not accurately mirror disease pathology. Some evidence indicates a disease continuum ranging from balanced aldosterone production from each adrenal to extreme asymmetrical bilateral aldosterone production. Nonetheless, surgical removal of the overactive adrenal in unilateral PA achieves highly successful outcomes and almost all patients are biochemically cured of their aldosteronism.

Cushing Syndrome in a Pediatric Patient With a KCNJ5 Variant and Successful Treatment With Low-dose Ketoconazole

CONTEXT

Pathogenic variants in KCNJ5, encoding the GIRK4 (Kir3.4) potassium channel, have been implicated in the pathogenesis of familial hyperaldosteronism type-III (FH-III) and sporadic primary aldosteronism (PA). In addition to aldosterone, glucocorticoids are often found elevated in PA in association with KCNJ5 pathogenic variants, albeit at subclinical levels. However, to date no GIRK4 defects have been linked to Cushing syndrome (CS).

PATIENT

We present the case of a 10-year-old child who presented with CS at an early age due to bilateral adrenocortical hyperplasia (BAH). The patient was placed on low-dose ketoconazole (KZL), which controlled hypercortisolemia and CS-related signs. Discontinuation of KZL for even 6 weeks led to recurrent CS.

RESULTS

Screening for known genes causing cortisol-producing BAHs (PRKAR1A, PRKACA, PRKACB, PDE11A, PDE8B, ARMC5) failed to identify any gene defects. Whole-exome sequencing showed a novel KCNJ5 pathogenic variant (c.506T>C, p.L169S) inherited from her father. In vitro studies showed that the p.L169S variant affects conductance of the Kir3.4 channel without affecting its expression or membrane localization. Although there were no effects on steroidogenesis in vitro, there were modest changes in protein kinase A activity. In silico analysis of the mutant channel proposed mechanisms for the altered conductance.

CONCLUSION

We present a pediatric patient with CS due to BAH and a germline defect in KCNJ5. Molecular investigations of this KCNJ5 variant failed to show a definite cause of her CS. However, this KCNJ5 variant differed in its function from KCNJ5 defects leading to PA. We speculate that GIRK4 (Kir3.4) may play a role in early human adrenocortical development and zonation and participate in the pathogenesis of pediatric BAH.

Biochemical, Histopathological, and Genetic Characterization of Posture-Responsive and Unresponsive APAs

CONTEXT AND OBJECTIVE

Posture-responsive and posture-unresponsive aldosterone-producing adenomas (APAs) account for approximately 40% and 60% of APAs, respectively. Somatic gene mutations have been recently reported to exist in approximately 90% of APAs. This study was designed to characterize the biochemical, histopathologic, and genetic properties of these 2 types of APA.

METHODS

Plasma levels of aldosterone and hybrid steroids (18-oxocortisol and 18-hydroxycortisol) were measured by liquid chromatography-tandem mass spectrometry. Immunohistochemistry for CYP11B2 (aldosterone synthase) and CYP17A1 (17α-hydroxylase) and deoxyribonucleic acid sequencing (Sanger and next-generation sequencing) were performed on APA tissue collected from 23 posture-unresponsive and 17 posture-responsive APA patients.

RESULTS

Patients with posture-unresponsive APA displayed higher (P < 0.01) levels of hybrid steroids, recumbent aldosterone and cortisol, larger (P < 0.01) zona fasciculata (ZF)-like tumors with higher (P < 0.01) expression of CYP17A1 (but not of CYP11B2) than patients with posture-responsive APA (most of which were not ZF-like). Of 40 studied APAs, 37 (92.5%) were found to harbor aldosterone-driving somatic mutations (KCNJ5 = 14 [35.0%], CACNA1D = 13 [32.5%], ATP1A1 = 8 [20.0%], and ATP2B3 = 2 [5.0%]), including 5 previously unreported mutations (3 in CACNA1D and 2 in ATP1A1). Notably, 64.7% (11/17) of posture-responsive APAs carried CACNA1D mutations, whereas 56.5% (13/23) of posture-unresponsive APAs harbored KCNJ5 mutations.

CONCLUSIONS

The elevated production of hybrid steroids by posture-unresponsive APAs may relate to their ZF-like tumor cell composition, resulting in expression of CYP17A1 (in addition to somatic gene mutation-driven CYP11B2 expression), thereby allowing production of cortisol, which acts as the substrate for CYP11B2-generated hybrid steroids.

Jamal AR, Sukor N, Solar M, Striessnig J, Brown MJ, Azizan EA. Aldosterone-Producing Adenomas

Mutations in KCNJ5 , ATP1A1 , ATP2B3 , CACNA1D , and CTNNB1 are thought to cause the excessive autonomous aldosterone secretion of aldosterone-producing adenomas (APAs). The histopathology of KCNJ5 mutant APAs, the most common and largest, has been thoroughly investigated and shown to have a zona fasciculata–like composition. This study aims to characterize the histopathologic spectrum of the other genotypes and document the proliferation rate of the different sized APAs. Adrenals from 39 primary aldosteronism patients were immunohistochemically stained for CYP11B2 to confirm diagnosis of an APA. Twenty-eight adenomas had sufficient material for further analysis and were target sequenced at hot spots in the 5 causal genes. Ten adenomas had a KCNJ5 mutation (35.7%), 7 adenomas had an ATP1A1 mutation (25%), and 4 adenomas had a CACNA1D mutation (14.3%). One novel mutation in exon 28 of CACNA1D (V1153G) was identified. The mutation caused a hyperpolarizing shift of the voltage-dependent activation and inactivation and slowed the channel’s inactivation kinetics. Immunohistochemical stainings of CYP17A1 as a zona fasciculata cell marker and Ki67 as a proliferation marker were used. KCNJ5 mutant adenomas showed a strong expression of CYP17A1, whereas ATP1A1 / CACNA1D mutant adenomas had a predominantly negative expression ( P value =1.20×10 −4 ). ATP1A1 / CACNA1D mutant adenomas had twice the nuclei with intense staining of Ki67 than KCNJ5 mutant adenomas (0.7% [0.5%–1.9%] versus 0.4% [0.3%–0.7%]; P value =0.04). Further, 3 adenomas with either an ATP1A1 mutation or a CACNA1D mutation had >30% nuclei with moderate Ki67 staining. In summary, similar to KCNJ5 mutant APAs, ATP1A1 and CACNA1D mutant adenomas have a seemingly specific histopathologic phenotype.

Primary Aldosteronism: Changing Definitions and New Concepts of Physiology and Pathophysiology Both Inside and Outside the Kidney

In the 60 years that have passed since the discovery of the mineralocorticoid hormone aldosterone, much has been learned about its synthesis (both adrenal and extra-adrenal), regulation (by renin-angiotensin II, potassium, adrenocorticotrophin, and other factors), and effects (on both epithelial and nonepithelial tissues). Once thought to be rare, primary aldosteronism (PA, in which aldosterone secretion by the adrenal is excessive and autonomous of its principal regulator, angiotensin II) is now known to be the most common specifically treatable and potentially curable form of hypertension, with most patients lacking the clinical feature of hypokalemia, the presence of which was previously considered to be necessary to warrant further efforts towards confirming a diagnosis of PA. This, and the appreciation that aldosterone excess leads to adverse cardiovascular, renal, central nervous, and psychological effects, that are at least partly independent of its effects on blood pressure, have had a profound influence on raising clinical and research interest in PA. Such research on patients with PA has, in turn, furthered knowledge regarding aldosterone synthesis, regulation, and effects. This review summarizes current progress in our understanding of the physiology of aldosterone, and towards defining the causes (including genetic bases), epidemiology, outcomes, and clinical approaches to diagnostic workup (including screening, diagnostic confirmation, and subtype differentiation) and treatment of PA.

Immunohistochemical, genetic and clinical characterization of sporadic aldosterone-producing adenomas

Adrenal glands removed for unilateral primary aldosteronism (PA) display marked histological heterogeneity. Recently reported somatic mutations in KCNJ5, ATP1A1, ATP2B3 and CACNA1D can partially account for these differences. In this study we aimed at combining phenotypic and genotypic characteristics, integrating genetic and immunohistochemistry correlates in sporadic PA. Seventy-one adrenal glands have been included in the study and analyzed for mutations in KCNJ5, ATP1A1, ATP2B3 and CACNA1D. Histological examination and immunohistochemical staining for CYP11B1 (11β-hydroxylase) and CYP11B2 (aldosterone synthase) were performed on aldosterone-producing adenomas (APAs) and adjacent adrenal cortex. In our cohort, the final histopathological diagnosis was multinodular hyperplasia in 22.5% of the patients and single nodule in 77.5%. Forty-five percent of the removed adrenals displayed extra-APA CYP11B2-positive cell nests (B2-CN). Among adrenal vein sampling parameters the suppression of contralateral adrenal was more frequent and the lateralization index was higher in the subgroup of patients without extra-APA B2-CN compared to the subgroup with extra-APA B2-CN. KCNJ5-mutated APAs were composed mainly of zona fasciculata-like cells with high expression of CYP11B1, while ATP1A1, ATP2B3 and CACNA1D-mutated APAs presented more frequently a zona-glomerulosa-like phenotype with high expression of CYP11B2. We observed a significant inverse correlation between CYP11B2 expression and the size of the nodules and, if CYP11B2 expression was corrected for tumor volume, a significant correlation with plasma aldosterone and aldosterone to renin ratio. Our findings indicate that combination of genotyping and immunohistochemistry improves the final histopathological diagnosis between single nodule and multinodular hyperplasia of the assessed adrenals.

Autoimmune mechanisms activating the angiotensin AT1 receptor in 'primary' aldosteronism

CONTEXT

The mechanisms causing excessive aldosterone production and hypertension in primary aldosteronism (PA) are complex and often incompletely recognized. Autoantibodies to the angiotensin AT1 receptor (AT1R) have been reported in some PA patients with an aldosterone-producing adenoma but not with idiopathic adrenal hyperplasia.

OBJECTIVE

We investigated whether these autoantibodies will activate AT1R and thereby potentially contribute to the pathophysiology of PA.

DESIGN

AT1R autoantibody activity in sera and/or IgG purified from 13 biochemically confirmed PA patients was measured using AT1R-transfected cells, and their contractile effects were assayed using perfused rat cremaster arterioles. Aldosterone stimulation was measured in vitro using isolated human adrenal carcinoma (HAC15) adrenal cells. These data were compared with sera obtained from a group of normotensive control subjects who were expected to have negligible AT1R autoantibodies.

RESULTS

Sera from each of the 13 PA patients significantly increased AT1R activation in AT1R-transfected cells compared with 20 control subjects, and this activity was inhibited by the selective AT1R blocker losartan. Sera and IgG purified from AT1R autoantibody-positive sera demonstrated significant vasoconstrictive effects in isolated rat cremaster arterioles and were blocked by losartan. Moreover, the AT1R autoantibody-positive IgG directly stimulated aldosterone production in the cultured adrenal cells and enhanced angiotensin-induced aldosterone production in these cells, and these effects were blocked by candesartan.

CONCLUSIONS

These data support a probable pathophysiological role for AT1R autoantibodies in PA and thereby raise important etiological and therapeutic implications.

Primary aldosteronism and potassium channel mutations

PURPOSE OF REVIEW

To summarize and discuss data from recent studies implicating mutations in potassium channel genes in the pathogenesis of primary aldosteronism.

RECENT FINDINGS

Potassium channel gene variants are associated with the primary aldosteronism phenotype in animals (Kcnma1, TASK-1, and TASK-3) and humans (HERG and KCNJ5). Germline KCNJ5 mutations cause bilateral, familial primary aldosteronism with variable severity and genotype:phenotype correlations. Somatic KCNJ5 mutations occur in approximately 40% of aldosterone-producing adenomas, and are associated with younger age, female sex, more severe primary aldosteronism, lack of responsiveness of plasma aldosterone to upright posture, and zona fasciculata histology. Of five so far described, G151R and L168R are by far the most common. KCNJ5 mutations lead to reduced K⁺/Na⁺ channel selectivity and Na⁺ influx, predisposing to cell membrane depolarization, increased calcium influx, increased expression of genes promoting aldosterone synthesis, and increased aldosterone production by adrenocortical cells. How they lead to adrenal cell proliferation and tumor development is less well understood.

SUMMARY

These findings shed considerable light on the pathophysiology of primary aldosteronism with the potential to lead to new diagnostic approaches and treatments.

Platt versus Pickering: what molecular insight to primary hyperaldosteronism tells us about hypertension

Recent genome-wide analyses have found 50 loci associated with variation in blood pressure but failed to advance understanding of the molecular basis of hypertension. Whether hypertension is not after all due to multiple common variants or is simply an order of magnitude more complex than previously suspected remains unsettled - in part because only a minority of subjects in the analyses had true hypertension. A better starting point than normotensive subjects for explaining hypertension may be the most common distinct cause of hypertension, primary hyperaldosteronism (PHA). The findings that 40% of patients with an aldosterone-producing adenoma (APA) of the adrenal have somatic gain-of-function mutations in a single gene, KCNJ5, and that this gene is, less frequently, mutated in inherited cases of PHA, potentially transform the understanding and management of hypertension. Firstly, they illustrate how hypertension could be due to a multiplicity of uncommon variants. Mutations that present with abnormal electrolytes and anatomy are the easiest to detect but are likely the tip of the iceberg. Secondly, we found a genotype:phenotype pattern, with KCNJ5 mutations inducing larger APAs in the cortisol-secreting zona fasciculata in young women. Smaller APAs without KCNJ5 mutations usually present in older men with resistant hypertension, having been overlooked earlier because of their size. This reflects their compact zona glomerulosa cells. Routine measurement of plasma renin in hypertension and a new positron emission tomography/computerized tomography allow prompt diagnosis and management of PHA before resistant hypertension ensues. Wider recognition of distinct phenotypes should permit earlier, specific treatment and reduce life-time risk of complications.

Primary aldosteronism in 2011: Towards a better understanding of causation and consequences

With primary aldosteronism now widely acknowledged as common and associated with both hypertension-related and non-hypertension-related pathology, research interest into its causes and consequences continues to grow. In 2011, major breakthroughs occurred in understanding the role and nature of underlying genetic disturbances and elucidating the pathophysiology of its cardiovascular sequelae.

Progress in primary aldosteronism: present challenges and perspectives

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

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.

Diagnosis and management of primary aldosteronism

Identifying primary aldosteronism within the hypertensive population is an important clinical challenge, as most patients with a unilateral source of excess aldosterone secretion are amenable to surgical cure. At least 20% of patients with primary aldosteronism have normal serum potassium levels. Therefore, screening tests should not be based on recognition of hypokalemia alone. Rather, the diagnosis should depend on identifying renin suppression and measuring the ratio of plasma aldosterone concentration to plasma renin activity. The diagnosis may be confirmed by performing an aldosterone suppression test after oral salt loading. Once primary aldosteronism has been established, it is necessary to exclude glucocorticoid-remediable aldosteronism and then proceed to localization studies. Detecting a unilateral source of aldosterone, usually due to an adenoma (Conn syndrome), is achieved by postural hormonal testing and confirmed by selective venous sampling (SVS) with measurement of aldosterone concentrations (expressed as the aldosterone/cortisol ratio) in each adrenal vein. SVS is enjoying a revival in many institutions as it is more sensitive and specific than either cross-sectional imaging or scintigraphy and has the potential to influence significantly both the diagnosis and clinical decision-making. Patients with unilateral disease are ideally treated by laparoscopic adrenalectomy. Patients in whom localization is not achieved usually have bilateral adrenal hyperplasia and are treated medically.

Familial hyperaldosteronism

Primary aldosteronism (PAL) may be as much as ten times more common than has been traditionally thought, with most patients normokalemic. The study of familial varieties has facilitated a fuller appreciation of the nature and diversity of its clinical, biochemical, morphological and molecular aspects. In familial hyperaldosteronism type I (FH-I), glucocorticoid-remediable PAL is caused by inheritance of an ACTH-regulated, hybrid CYP11B1/CYP11B2 gene. Genetic testing has greatly facilitated diagnosis. Hypertension severity varies widely, demonstrating relationships with gender, affected parent's gender, urinary kallikrein level, degree of biochemical disturbance and hybrid gene crossover point position. Analyses of aldosterone/PRA/cortisol 'day-curves' have revealed that (1) the hybrid gene dominates over wild type CYP11B2 in terms of aldosterone regulation and (2) correction of hypertension in FH-I requires only partial suppression of ACTH, and much smaller glucocorticoid doses than those previously recommended. Familial hyperaldosteronism type II is not glucocorticoid-remediable, and is clinically, biochemically and morphologically indistinguishable from apparently sporadic PAL. In one informative family available for linkage analysis, FH-II does not segregate with either the CYP11B2, AT1 or MEN1 genes, but a genome-wide search has revealed linkage with a locus in chromosome 7. As has already occurred in FH-I, elucidation of causative mutations is likely to facilitate earlier detection of PAL and other curable or specifically treatable forms of hypertension.

Concurrent secretion of aldosterone and cortisol from an adrenal adenoma - value of MRI in diagnosis

A 43-year-old female with a 24-years history of hypertension presented for further investigation and management of primary hyperaldosternoism. Postural studies were not conclusive and magnetic resonance (MR) imaging demonstrated a 27 x 18 mm lesion of the right adrenal gland which showed no signal loss during in and out of phase imaging. Although these appearances were considered to be atypical of those seen on MR in patients with aldosterone producing adrenal adenomas the patient underwent an adrenalectomy with removal of a 3 x 3 x 2 cm right adrenal mass. Post-operatively she became hypotensive and a 0900 hours serum cortisol was undetectable (< 50 nmol/l), consistent with adrenal insufficiency. Following the administration of hydrocortisone there was normalization of the blood pressure and subsequent adrenal stimulation tests confirmed the presence of functioning adrenal tissue albeit with an inadequate response. Cortisol measurement from preoperative samples revealed loss of normal diurnal rhythm whereas DHEAS levels both pre and postoperatively were undetectable, consistent with ACTH supression resulting from autonomous cortisol secretion in addition to aldosterone. Concurrent secretion of cortisol should always be considered in Conn's adenomas particularly when atypical radiological features are present.

Primary aldosteronism: learning from the study of familial varieties

Primary aldosteronism (PAL) has been traditionally regarded as a rare cause of hypertension and not worth looking for in the absence of hypokalemia. However, the availability of the aldosterone/renin ratio as a screening test and its application to a wider population of hypertensives has resulted in a marked increase in detection rate, suggesting that PAL is common, with most patients being normokalemic. The spectrum of PAL has been expanded further by the study of familial varieties, in which family screening efforts have permitted the recognition of earlier, sometimes even pre-clinical, stages of disease. Familial hyperaldosteronism type I(FH-I) In FH-I, inheritance of a 'hybrid' 11beta-hydroxylase/aldosterone synthase gene causes adrenocorticotrophic hormone (ACTH)-regulated aldosterone and 'hybrid steroid' (18hydroxy-cortisol and 18-oxo-cortisol) overproduction. Genetic testing, by Southern blot or polymerase chain reaction-based techniques, has greatly facilitated detection, being more convenient and more reliable than dexamethasone suppression testing, and has led to a fuller appreciation of the marked phenotypic variability in this disorder. The demonstration of excessive, abnormally regulated aldosterone production in normotensive subjects with FH-I suggests that absence of hypertension in such individuals cannot merely be attributed to lack of expression of the hybrid gene. Determinants of hypertension severity may include patient gender, gender of affected parent, degree of hybrid gene expression, and interactions with other genetic and environmental factors. Detailed biochemical studies, including analyses of aldosterone/PRA/cortisol 'day-curve' levels, have led to a fuller understanding of aldosterone regulation both before and in response to glucocorticoid treatment in this condition, and prompted a re-examination of current approaches to treatment Unless ACTH is completely suppressed by glucocorticoid treatment, the hybrid gene dominates over the wild-type aldosterone synthase genes in terms of aldosterone production, both in untreated and treated FH-I. This may in part be due to an abnormality affecting the functional expression of the 'wild-type' genes. Demonstration of persisting hybrid gene expression in patients rendered normotensive by very low doses of glucocorticoids suggests that currently recommended doses, aimed at normalizing aldosterone regulation (rather than blood pressure), may be too high, and may therefore place patients at unnecessary risk of developing Cushingoid side effects. Familial hyperaldosteronism type II (FH-II) Like FH-I, FH-II is associated with hyperaldosteronism and probable autosomal dominant inheritance. Unlike FH-I, hyperaldosteronism in FH-II is not dexamethasone suppressible, and is not associated with the hybrid gene mutation. Detection of adrenal mass lesions, which are frequently (17 of 57 patients in the Greenslopes Hospital series) responsible for PAL in FH-II, does not help to differentiate FH-II from FH-I, since mass lesions may also be common in that condition (detected in seven of 21 patients). Biochemically and morphologically, FH-II is indistinguishable from apparently non-familial PAL, and demonstrates similar variability even among individuals of the same family. In one informative family available for linkage analysis, FH-II does not segregate with either the AT1 gene or the CYP11B2 gene, or any other genetic defect in the chromosome 8q21-8qtel region. A genome-wide search is in progress. As has already occurred in FH-I, the elucidation of underlying genetic mutations in FH-II is likely to facilitate early detection, thereby helping to broaden its spectrum and to permit close follow-up and appropriately timed institution of specific therapy, and wider detection among patients with hypertension of potentially curable or specifically treatable forms.

Pathophysiology and diagnosis of primary aldosteronism

The pathophysiology of primary aldosteronism still remains unknown. In mRNA and protein levels, overexpression of aldosterone synthase (P-450aldo) is recognized, although abnormalities and defects of DNA and its upper stream have not been detected. Several candidate genes responsible for pathogenesis of primary aldosteronism, such as renin, angiotensin receptor type II, etc., have been proposed, but no decisive genes have been found. A relatively reliable screening for hyperaldosteronism is a determination of the ratio of the plasma aldosterone level to the plasma renin activity. For differentiating several types of aldosteronisms, the simplest test is the response of plasma aldosterone to two hours in an upright posture: plasma aldosterone rises in most patients with idiopathic hyperaldosteronism. In contrast, in cases of autonomous aldosterone-producing tumor, most patients show no response or even a decrease in plasma aldosterone concentration. The size and location of the aldosterone-producing adenoma are determined by using computed tomography.

Differential expression of type 1 angiotensin II receptor mRNA and aldosterone responsiveness to angiotensin in aldosterone-producing adenoma

Aldosterone secretion in most patients with aldosterone-producing adenomas (APAs) is typically unresponsive to angiotensin II stimulation (AII-unresponsive, AII-U). In some patients, however, plasma aldosterone increases in response to AII stimulation (AII-responsive, AII-R). This differential aldosterone responsiveness could be related to the levels of type 1 AII receptors (AT1R) in the APA. To test this hypothesis, plasma aldosterone levels in response to upright posture and/or sequential high- and low-salt diets were measured by radioimmunoassay in nine patients with APAs. AT1R mRNA levels in the adenomas were quantified by competitive reverse transcription-polymerase chain reaction and correlated to the cellular composition of the adenoma. Two patients were categorised as AII-R by an increase of plasma aldosterone greater than 50% over the baseline. The remaining seven patients who had blunted plasma aldosterone responses were classified as AII-U. Histologically, the AII-R APAs consisted predominantly of zona glomerulosa (ZG)-like cells (> 90%), while the AII-U APAs contained zona fasciculata (ZF)-like cells ranging from 28 to 72%. There was an inverse relationship between the levels of AT1R mRNA in the APA and the percentage of ZF-like cells in the adenoma (n = 9, r = 0.73, P < 0.05). In situ hybridisation findings demonstrated that AT1R mRNA was more uniform and intensive in ZG-like cells than in ZF-like cells. These results suggest that heterogenous aldosterone responsiveness to angiotensin in APAs is histologically dependent and related to the differential expression of AT1R mRNA in the adenoma.

Familial forms broaden the horizons for primary aldosteronism

The identification of familial forms of primary aldosteronism (PAL) has led to its detection in relatives of affected patients not suspected previously of having PAL. Many are normokalemic and some are even normotensive. This broadens the spectrum of PAL, permitting the study of its evolution and of intervention with specific therapy when hypertension develops. The genetic basis of one form involves steroid biosynthetic enzymes and the other form predisposes to hyperplasia and benign neoplasia.

Pheochromocytoma and primary aldosteronism: diagnostic approaches

Although adrenal-dependent hypertension is an uncommon form of hypertension, its diagnosis provides clinicians with a unique treatment opportunity, that is, to render a surgical cure or to achieve a dramatic response to pharmacologic therapy. The diagnosis of catecholamine-secreting tumors has evolved during the last 70 years to a straightforward stepwise algorithmic approach. Primary aldosteronism is now recognized as the most common form of secondary hypertension, and the screening methods for it are simple and reliable.

Primary aldosteronism: a new understanding

Primary aldosteronism (PAL) may always have a genetic basis. This leads to either abnormally regulated, increased biosynthesis (Familial Hyperaldosteronism Type I, FHI) or to unrestrained hyperplasia and neoplasia, usually benign. The distinction between diffuse hyperplasia, nodular hyperplasia and adenoma may be relatively unimportant in functional and etiological terms. The genetic basis must be understood before diagnosis of disease (FHI) or of predisposition (all other PAL) can be made at birth and appropriate surveillance commenced. The natural history of PAL other than FHI is for progressive increase in severity, with both adrenals eventually involved. Long-term follow-up of PAL is therefore mandatory, and postoperative assessment of residual non-suppressible aldosterone production by fludrocortisone suppression testing useful in defining biochemical cure or improvement, and the need for specific medical treatment.

Primary hyperaldosteronism: a missed diagnosis in 'essential hypertensives'?

BACKGROUND

It has been recognised recently that primary hyperaldosteronism may be more common than previously thought, the frequency of diagnosis being improved by screening using a plasma aldosterone concentration to renin activity ratio.

AIMS

To determine the frequency of primary hyperaldosteronism, screening with both plasma aldosterone to renin concentration (PRC) and activity (PRA) ratios, in normokalaemic subjects previously diagnosed as having essential hypertension.

METHODS

Plasma potassium, aldosterone and PRCs and PRA and blood pressure (BP) were measured in 74 hypertensive subjects previously diagnosed by one physician as having essential hypertension. A normal range for plasma aldosterone/renin ratios was determined in 147 control subjects. Hypertensive subjects with elevated aldosterone/renin ratios were further assessed for primary hyperaldosteronism using saline loading and fludrocortisone suppression. Those in whom plasma aldosterone concentration exceeded 140 pmol/L after suppression tests underwent adrenal vein sampling for measurement of aldosterone and cortisol concentrations as well as adrenal CT scanning to diagnose the cause of primary hyperaldosteronism. The main outcome measures were a diagnosis of aldosterone producing adenoma or bilateral adrenal hyperplasia based upon adrenal vein sampling.

RESULTS

Four subjects (5%) had an elevated plasma aldosterone to renin ratio using PRC and six (8%) using PRA. Two subjects (2.7%) in this selected population had primary hyperaldosteronism, both of whom had BP > 160/110 mmHg at the time of testing.

CONCLUSIONS

The frequency of normokalaemic primary hyperaldosteronism appears to be greater than previously thought, though the true incidence in the general population of hypertensive subjects remains unknown. The sensitivity of diagnosis (but not specificity) may be improved by measurement of the plasma aldosterone/renin ratio and PRC is at least as adequate as PRA for this process.

Production of 18-oxo-cortisol in subtypes of primary aldosteronism

1. In familial hyperaldosteronism type I (FH-I), expression of an adrenocorticotropic hormone (ACTH)-dependent hybrid 11 beta-hydroxylase/aldosterone synthase gene causes excessive 'hybrid steroid' (18-hydroxy- and 18-oxo-cortisol) production. In order to study the mechanism of elevated 'hybrid steroid' levels in angiotensin-unresponsive (AII-U) aldosterone-producing adenoma (APA), we compared responses of 24 h urinary 18-oxo-cortisol, aldosterone and cortisol to dexamethasone (0.5 mg q6h for 4 days) in 11 FH-I patients, 11 patients with AII-U APA, 11 patients with AII-responsive (AII-R) APA and 10 patients with bilateral adrenal hyperplasia (BAH). 2. Consistent, marked suppression (by at least 60%) of 18-oxo-cortisol levels by dexamethasone was seen in all groups except AII-U APA. Aldosterone levels were consistently suppressed to undetectable levels only in FH-I. Cortisol levels were suppressed to undetectable levels in all patients except two with AII-U APA. 3. Production of both 18-oxo-cortisol and aldosterone (and occasionally cortisol) in AII-U APA appears relatively ACTH-independent, consistent with a common mechanism involved in the formation of these two steroids from their respective precursors, which differs from that in FH-I. 4. In AII-R APA and BAH, 18-oxo-cortisol production appears markedly ACTH-dependent, but aldosterone production is not.

PCR-SSCP analysis of the promoter region of the renin gene in patients with aldosterone-producing adenomas

1. Aldosterone-producing adenomas (APA) of the adrenal gland may be responsive or un-responsive to the renin-angiotensin system. 2. We have described increased expression of renin mRNA in angiotensin-responsive aldosterone-producing adenomas (AII-R-APA) compared with angiotensin-un-responsive aldosterone-producing adenomas (AII-U-APA) and significantly different allelic frequencies of the BglI, TaqI and HinfI restriction fragment length polymorphisms of the renin gene between the two groups. 3. An area including the 5' flanking region -500 bp from exon 1, exon 1 and intron A contained no gross insertions or deletions when studied by a long polymerase chain reaction technique. 4. In the present study, polymerase chain reaction-single strand conformation polymorphism analysis (PCR-SSCP) revealed no single base pair alteration in the proximal promoter region (-600 bp to transcription start) of the renin gene in patients with APA (either AII-U-APA or AII-R-APA) when compared with normal subjects. 5. Therefore, mutations in this regulatory region do not appear to explain the different levels of renin gene expression observed in these two subtypes of APA.

Primary aldosteronism

The basic clinical pathophysiology of primary aldosteronism (PAL) was described by Conn in terms of autonomous production of aldosterone, secondary suppression of renin and development of hypertension with hypokalaemic alkalosis. Conn recognised a normokalaemic form of the syndrome and suggested that it might masquerade as essential hypertension and be not uncommon. This was hotly disputed at the time, and normokalaemic PAL considered rare until recently, and, as a consequence, overlooked. The advent of a simple screening test, the aldosterone-renin ratio, led to recognition that normokalaemic forms are not uncommon. In fact, PAL may be the commonest specifically treatable and potentially curable form of hypertension so far identified. In all patients with PAL confirmed by lack of suppressibility ("autonomy") of aldosterone production, Familial Hyperaldosteronism Type I (FH-I, glucocorticoid-remediable hyperaldosteronism, reviewed elsewhere in this issue) should first be excluded by dexamethasone suppression or genetic testing. Capable of causing fatal stroke in young people affected by this dominantly inherited disorder, it can be reversed by doses of glucocorticoids such as dexamethasone which partially suppress endogenous ACTH without producing "steroid" side-effects. The remaining varieties of PAL may eventually also be shown to have a genetic basis, but are currently treated either by excision of a solitary aldosterone-secreting tumour or by antagonism of aldosterone's action in the renal tubule. It is possible that both adrenal cortices are genetically predisposed to overproduction of aldosterone in all varieties of PAL, whether because of anomalous regulation of aldosterone secretion or because of a tendency towards hyperplasia and neoplasia. Aldosterone-producing adenomas (APA's) can be divided into two main subtypes based on morphology and biochemical behaviour. The first subtype to be morphologically and biochemically characterised is composed predominantly of fasciculata-like cells and is unresponsive to angiotensin II (ALL-U-APA). The more recently characterised subtype is composed predominantly of glomerulosa-like cells, is responsive to angiotensin II (AII-R-APA) and could previously have been misdiagnosed as bilateral hyperplasia. The renin gene is often overexpressed in the second variety of adenoma, and in surrounding non-tumorous cortex, and the two subgroups show different allelic frequencies for RFLP's of the constitutive renin gene and the constitutive ANP gene locus. Unilateral, solitary, benign adrenal cortical adenomas producing aldosterone (APA's) represent a potentially surgically curable form of hypertension. Adrenal venous sampling (AVS) should always be performed because APA's are biochemically recognisable by adrenal venous steroid measurement before they are identifiable by computerised tomography or scintigraphy, and adrenal masses seen on CT may not be responsible for PAL. The secretory activity of adrenal masses must therefore be established by AVS before surgical removal. Discovery of an adrenal mass on CT requires formulation of a plan, whether or not it is found to be secreting hormones in excess. Independently of the treatment of the patient's hypertension, an apparently nonfunctioning adrenal mass ("incidentaloma") should be removed if 2.5 cm or more in diameter, because of the risk of cancer. Smaller masses require long-term follow-up. Primary aldosteronism not lateralising on AVS should be treated with low dose spironolactone, or with amiloride. For any such patients intolerant of medical treatment, laparoscopic removal of the adrenal showing higher production of aldosterone on AVS is an option worthy of consideration.The resultant reduction in mass of tissue autonomously secreting aldosterone should improve hypertension, as aldosterone productions falls below a critical level, and may even be curative in the short, medium or long term, depending on the rate of growth and activity of au

Quantitative analysis of messenger ribonucleic acid encoding natriuretic peptide receptors in aldosterone-producing adenoma

There exist conflicting data regarding the inhibitory effect of atrial natriuretic peptide on aldosterone production from aldosterone-producing adenoma (APA). Natriuretic peptides mediate their actions through natriuretic peptide receptors (NPRs). Whether or not NPRs are present in the tumors remains controversial. To elucidate this paradox, gene expression of NPRs was examined by Northern blot analysis and competitive polymerase chain reaction in tumorous and non-tumorous portions of APA, and in normal adrenal gland from patients with renal cell carcinoma. The results of Northern blot analysis showed the presence of messenger ribonucleic acid (mRNA) of three NPRs in all adrenal tissues, including APA. The proportional expression of NPR gene transcripts in APA was type A (0.6%), type B (18.7%), and type C (80.7%). The levels, but not the proportions, of type C and possibly type B NPR mRNAs were lower in tumorous and non-tumorous portions of APA compared to those in normal adrenal gland (type C 190.2 +/- 24.5 [means +/- SEM, normal adrenal gland] > 168.1 +/- 20.8 [non-tumorous portion] > 112.2 +/- 15.5 [tumorous portion] pg/10 micrograms total RNA, F = 3.82, P < 0.05; type B 45.2 +/- 8.5 [normal adrenal gland] > 30.0 +/- 5.2 [non-tumorous portion] > 25.1 +/- 4.1 [tumorous portion] pg/10 micrograms total RNA, F = 3.03, P = 0.065). The mRNA levels of type C, rather than type A or type B, NPR were correlated with the percentage of zona fasciculata-like cells in APA (r = 0.90, P < 0.05). In conclusion we have demonstrated the presence of mRNA encoding the three NPRs in APA.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic outcome of primary aldosteronism: adrenalectomy versus enucleation of aldosterone-producing adenoma

Our followup study of 48 patients with primary aldosteronism concerns the results of 2 different operative methods. After preoperative localization of the unilateral solitary tumor 22 patients underwent unilateral adrenalectomy and 26 underwent enucleation of aldosterone-producing adenoma. Both operative methods improved hypertension, hypokalemia, the low urinary sodium-to-potassium ratio, suppressed plasma renin activity, high plasma aldosterone concentration, high urinary aldosterone excretion and high urinary kallikrein excretion in similar orders of magnitude for 5 years. Levels of plasma cortisol and plasma adrenocorticotropic hormone following respective operations were also identical. Five years postoperatively, ambulation and furosemide administration under low sodium diet stimuli remarkably enhanced plasma renin activity and plasma aldosterone concentration in the aldosterone-producing adenoma enucleation group (p < 0.001), almost similar to that of normal subjects but increment magnitudes were slight (p < 0.05 to < 0.01) in the adrenalectomy group. Preoperatively, angiotensin II infusion failed to increase plasma aldosterone concentration in patients with primary aldosteronism. After respective operations, responses of plasma aldosterone concentration to angiotensin II infusion and of plasma cortisol to adrenocorticotropic hormone administration in the aldosterone-producing adenoma enucleation group were more sensitive than those in the adrenalectomy group. There was no remission of recurrent hyperaldosteronism in either group throughout the study. These results suggest that angiotensin II induces aldosterone release by an activation of tumor uninvolved cortical cells and that the enucleation of aldosterone-producing adenoma is more preferable than unilateral adrenalectomy.

Primary aldosteronism--some genetic, morphological, and biochemical aspects of subtypes

Primary aldosteronism is the commonest cause of potentially curable hypertension when diagnosed in both florid and less florid forms. Genetic screening, so far available only for glucocorticoid-suppressible hyperaldosteronism, permits diagnosis from birth, before any biochemical or clinical abnormalities appear. Biochemical screening using the aldosterone-to-renin ratio permits diagnosis in the absence of raised aldosterone or of hypokalemia. Primary aldosteronism occurs in several familial forms. As well as the variety described in 1966 which is ACTH-dependent and glucocorticoid-suppressible, and not so far associated with tumors, another variety described in 1991 is not glucocorticoid-suppressible and is frequently associated with aldosterone-producing adenomas (APAs). Primary aldosteronism due to adrenocortical hyperplasia, adenoma, or carcinoma can also occur as part of the multiple endocrine neoplasia syndromes, where normoplasia, hyperplasia, benign neoplasia, and malignant neoplasia can exist in the same patient in the same endocrine gland(s) at the same time. The morphology of adrenocortical hyperplasia causing primary aldosteronism ranges from glomerulosa-like (idiopathic hyperplasia of the adrenals) to fasciculata-like (glucocorticoid-suppressible hyperaldosteronism). The morphology of adrenocortical neoplasia causing primary aldosteronism can also be either predominantly glomerulosa-like or fasciculata-like, in our experience equally often. Varying morphology of APAs is associated with varying responses of aldosterone to angiotensin II. Tumors predominantly fasciculata-like are unresponsive to angiotensin II, whereas those predominantly glomerulosa-like are responsive to angiotensin II. Both subtypes can be seen in a single family. Primary aldosteronism represents a spectrum of genetic disorders resulting in hyperplasia or neoplasia, but all are associated with some degree of autonomy of aldosterone production, independent of the renin-angiotensin system.

The renin gene and aldosterone-producing adenomas

Approximately one half of the aldosterone-producing adenomas (APA) removed from patients with primary aldosteronism in the Hypertension Unit at Greenslopes Hospital belong to a subgroup in which aldosterone levels are responsive to the renin-angiotensin system (angiotensin-responsive APA; AII-R-APA), unlike classical APAs in which aldosterone is unresponsive (AII-U-APA). Renin mRNA levels in AII-R-APA were elevated when compared with those in AII-U-APA or normal adrenal cortices. Renin mRNA levels in some adrenal cortices surrounding AII-R-APA (but never in AII-U-APA) were raised, suggesting that a genetic defect is not confined to the tumor. Renin gene RFLP analysis in peripheral blood DNA revealed a significant difference in allelic frequencies between patients with AII-R-APA and AII-U-APA, suggesting an association between an alteration in the renin gene and aldosterone responsiveness to the renin-angiotensin system in patients with APAs.

Genetics of primary aldosteronism

1. In 1991 we described a familial variety of primary hyperaldosteronism which was not glucocorticoid-suppressible and was associated with adenoma formation, and called it familial hyperaldosteronism type II (FH-II) in order to distinguish it from the glucocorticoid-suppressible variety described in 1966, familial hyperaldosteronism type I (FH-I). 2. In 1992 the genetic basis of FH-I was clarified by description of a hybrid gene. 3. Primary aldosteronism due to bilateral adrenocortical hyperplasia or to aldosterone-producing tumour can be part of the multiple endocrine neoplasia type I syndrome (MEN I), in which loss of heterozygosity has been described on chromosome 11q13. Loss of heterozygosity at the MEN I locus was found in five of 26 aldosterone-producing tumours from our series (by Japanese collaborators). These included two with adrenal cancer and two with FH-II. 4. We recently described an association of aldosterone responsiveness of aldosterone-producing adenomas with renin gene restriction fragment length polymorphisms, suggesting a possible role for renin genotype and intra-adrenal renin gene expression in the development and biochemical expression of some aldosterone-producing tumours. 5. We found abnormal karyotypes in 13 of 32 benign aldosterone-producing adenomas.

Renin-Independent hypermineralocorticoidism

Although renin-independent hypermineralocorticoidism is an uncommon form of hypertension, its diagnosis provides the clinician with a unique opportunity in the field of hypertension, that is, to render a surgical cure or to achieve a dramatic pharmacologic response in the treatment of hypertension. Primary aldosteronism is the most common form of renin-independent hypermineralocorticoidism. The plasma aldosterone concentration to plasma renin ratio is an excellent screening test for primary aldosteronism, the diagnosis of which should be confirmed by demonstrating unsuppressible urine or plasma levels of aldosterone. The subtype of primary aldosteronism dictates the most appropriate therapy. Computerized imaging of the adrenal glands and adrenal venous sampling assist in distinguishing unilateral (requiring surgical treatment) from bilateral (requiring pharmacologic treatment) adrenal disease. The forms of mineralocorticoid excess considered in the hypokalemic hypertensive patient with low aldosterone values include congenital adrenal hyperplasia (11 beta-hydroxylase and 17alpha-hydroxylase deficiencies), deoxycorticosterone-producing tumor, Cushing's syndrome, primary cortisol resistance, and 11 beta-hydroxysteroid dehydrogenase deficiency (apparent mineralocorticoid excess syndrome). The I1 beta-hydroxysteroid dehydrogenase deficiency may be congenital or acquired (for example, ingestion of licorice or carbenoxolone).

Renin gene polymorphism associated with aldosterone responsiveness to the renin-angiotensin system in patients with aldosterone-producing adenomas

1. Aldosterone levels in patients with unilateral aldosterone-producing adenomas may be responsive or unresponsive to the renin-angiotensin system, with the former often previously misdiagnosed as bilateral adrenal hyperplasia. 2. In tumours from patients in the responsive subgroup, renin mRNA is expressed in greater amounts than in tumours from patients in the unresponsive subgroup, or in normal adrenals. 3. We compared the frequency of four renin gene polymorphisms in peripheral blood DNA from the two subgroups and found significant associations between BglI, TaqI and HinfI restriction fragment length polymorphisms (RFLP) and aldosterone responsiveness. 4. Allelic variation in the constitutive renin gene was associated with a specific cause of hypertension.

Angiotensin-responsive aldosterone-producing adenomas: postoperative disappearance of aldosterone response to angiotensin

1. Nineteen out of 47 patients (40%) with confirmed unilateral aldosterone-producing adenoma (APA) were responsive to low-dose angiotensin II infusion (AII-R), as defined by an increase in plasma aldosterone concentration of > 50% over basal at 2 ng/kg per min for 60 min. 2. Seven to ten days after unilateral adrenalectomy, aldosterone was no longer responsive to angiotensin infusion in AII-R APA (100%, n = 17). Therefore, angiotensin responsiveness resides within the adenoma in AII-R APA. 3. The upright posture test for the differentiation of adenoma from hyperplasia was unreliable for the AII-R APA (26%), but generally reliable in the angiotensin-unresponsive subtype, (AII-U APA, 96%). 4. The reported predominance of females in APA was seen in AII-U APA (68%), but was reversed in AII-R APA (37%).

Cortisol production by aldosterone-producing adenomas in vitro

1. In vitro short-term production of cortisol by dispersed tumour and non-tumourous adrenal cortical cells was measured with and without added angiotensin II (AII) or adrenocorticotrophin (ACTH) in adrenals removed from five patients with primary aldosteronism. 2. Aldosterone-producing adenomas (APA) were classified as angiotensin responsive (AII-R) or angiotensin unresponsive (AII-U) based on pre-operative behaviour in vivo. 3. Cortisol was produced by both tumour and cortex in vitro without stimulation, and significantly more cortisol was generated by the cortex. 4. Addition of AII significantly increased cortisol production by both tumour and cortex to an equal extent. 5. Addition of ACTH also significantly increased cortisol production by both tumour and cortex, but tumours were more responsive than cortex. The response to ACTH exceeded the response to angiotensin in both tumour and cortex. 6. There was no obvious difference between AII-R and AII-U APA in terms of cortisol production.

Primary aldosteronism: hypertension with a genetic basis

Exciting developments in knowledge of primary aldosteronism include description of new subtypes and elucidation of the genetic basis of one variety. Furthermore, relatively simple biochemical screening (aldosterone/renin ratio) has disclosed that primary aldosteronism is more common than previously thought, by diagnosing patients at an earlier, normokalaemic stage. The mutant gene discovered in the glucocorticoid-suppressible variety (FHI) codes for an aldosterone biosynythetic enzyme normally controlled by angiotensin II, and now controlled by corticotropin. The zona fasciculata is hyperplastic and makes aldosterone and "hybrid steroids" 18-oxocortisol and 18-hydroxycortisol in excess, in response to ACTH but not to angiotensin II. Adrenal tumours have not yet been described in this condition. Aldosterone-producing adenomas (Conn's syndrome) are also commonly composed of zona fasciculata-like cells, make "hybrid steroids" in excess and are very sensitive to ACTH but not to angiotensin II. We have described a new variety of aldosterone-producing adenoma which is responsive to angiotensin II (AII-responsive APA), consists of at least 20% zona glomerulosa-like cells, and does not make "hybrid steroids" in excess. We have also described a new familial variety of primary aldosteronism that includes tumours and is not glucocorticoid-suppressible (FHII). We propose that primary aldosteronism is a spectrum of genetic diseases expressed as either hyperplasia or neoplasia, and that morphological and genetic diversity explains biochemical and clinical behaviour.

Clinical and pathological diversity of primary aldosteronism, including a new familial variety

1. Of 93 patients with primary aldosteronism seen during a 20 year period, 52 had an aldosterone-producing adenoma (APA) removed (five more await surgery), 14 had bilateral adrenal hyperplasia (BAH), three had glucocorticoid-suppressible hyperaldosteronism (GSH), one had adrenal carcinoma and 18 are yet to be categorized. 2. Seventy-three presented with hypertension and hypokalaemia. Others had markedly suppressed renal venous plasma renin activity (PRA) or elevated plasma aldosterone (PA)/PRA ratio, in new or resistant hypertensives. 3. The PA/PRA ratio was the most reliable screening test. 4. Diagnosis depended on the failure of suppression of aldosterone by salt loading and fludrocortisone. 5. Differentiation of BAH from APA depended on adrenal venous sampling comparing adrenal and peripheral venous PA/cortisol ratios. 6. A new familial variety of primary aldosteronism is described, with two affected members in each of three families. 7. Primary aldosteronism should be looked for in resistant and low-renin hypertension as well as in hypertension with hypokalaemia, and other family members should have PA/PRA measured if they are hypertensive.