Glucocorticoid-remediable aldosteronism and pregnancy

Familial hyperaldosteronism: an European Reference Network on Rare Endocrine Conditions clinical practice guideline

We describe herein the European Reference Network on Rare Endocrine Conditions clinical practice guideline on diagnosis and management of familial forms of hyperaldosteronism. The guideline panel consisted of 10 experts in primary aldosteronism, endocrine hypertension, paediatric endocrinology, and cardiology as well as a methodologist. A systematic literature search was conducted, and because of the rarity of the condition, most recommendations were based on expert opinion and small patient series. The guideline includes a brief description of the genetics and molecular pathophysiology associated with each condition, the patients to be screened, and how to screen. Diagnostic and treatment approaches for patients with genetically determined diagnosis are presented. The recommendations apply to patients with genetically proven familial hyperaldosteronism and not to families with more than one case of primary aldosteronism without demonstration of a responsible pathogenic variant.

Primary aldosteronism in pregnancy

Primary aldosteronism (PA) is the most common form of secondary hypertension. Although hypertensive disorders seem to affect around 5-10% of pregnancies worldwide, literature counts less than 80 cases of PA diagnosed during the peri-partum period. In this review we discuss about current knowledge on pathophysiology, natural history, diagnosis and treatment of PA in pregnancy. Because of the physiologic changes in the renin-angiotensin-aldosterone system (RAAS) and the contraindication to both confirmatory test and subtype differentiation, diagnosis of PA during pregnancy is challenging and relies mostly on detection of low/suppressed renin and high aldosterone levels. The course of pregnancy in patients with PA is highly variable, ranging from progesterone-induced amelioration of blood pressure (BP) control to severe and resistant hypertension with potential maternal and fetal complications. Mineralcorticoid receptor antagonists (MRA) are the recommended and most effective drugs for treatment of PA. As the anti-androgenic effect of spironolactone can potentially interfere with sexual development, their prescription is not recommended during pregnancy. On the other side, eplerenone, has proven to be safe and effective in 6 pregnant women and may be added to conventional first line drug regimen in presence of resistant hypertension or persistent hypokalemia. Ideally, patients with unilateral forms of PA should undergo adrenalectomy prior to conception, however, when PA is diagnosed during pregnancy and medical therapy fails to adequately control hypertension or its complications, adrenalectomy can be considered during the second trimester in case of unilateral adrenal mass at MRI-scan.

Management and Outcomes of Primary Aldosteronism in Pregnancy: A Systematic Review

Primary aldosteronism (PA) in pregnancy (PAP) can be a serious condition and is challenging to diagnose. This study was conceived to help in the diagnosis of PAP and provide suggestions on management of PAP based on evidence retrieved using a Population, Intervention, Comparison, and Outcome search strategy. Based on the changes of aldosterone and renin occurring in normal pregnancies, we developed a nomogram that will allow to identify PAP cases. Moreover, we found that published PAP cases fell into 4 main groups differing for management and outcomes: (1) unilateral medically treated, (2) unilateral surgically treated, (3) bilateral medically treated and (4) familial forms. Results showed that complications involved 62.2% of pregnant women with nonfamilial PA and 18.5% of those with familial hyperaldosteronism type I. Adrenalectomy during pregnancy in women with PAP did not improve maternal and fetal outcomes, over medical treatment alone. Moreover, cure of maternal hypertension and mother and baby outcome were better when unilateral PA was discovered and surgically treated before or after pregnancy. Therefore, fertile women with arterial hypertension should be screened for PA before pregnancy and, if necessary, subtyped to identify unilateral forms of PA. This will allow to furnish adequate counseling, a chance for surgical cure and, therefore, for a pregnancy not complicated by aldosterone excess.

Characteristics and Outcomes in Primary Aldosteronism Patients Harboring Glucocorticoid-Remediable Aldosteronism

The clinical characteristics and surgical prognosis of glucocorticoid-remediable aldosteronism (GRA, also known as familial hyperaldosteronism type 1, FH-I) have not been widely studied. Using data from the Taiwan Primary Aldosteronism Investigation (TAIPAI) registry retrospectively, we describe the associated clinical factors for GRA and clinical predictors of surgical outcomes among identified GRA patients. We found 79 GRA-positive (51.2 ± 13.8 years; women 39 (49.4%)) and 114 GRA-negative primary aldosteronism (PA) patients matched with age, gender, and body mass index. Lower plasma aldosterone concentrations (PACs) and aldosterone-renin ratios were found among GRA-positive individuals. Multivariable logistic regression demonstrated that a PAC ≤ 40 ng/dL could predict concealed GRA individuals (OR 0.523, p = 0.037). Low serum potassium (OR 0.285, p = 0.008), but not the presence of GRA, was associated with hypertension-remission. Of note, PRA (OR 11.645, p = 0.045) and hypokalemia (OR 0.133, p = 0.048) were associated with hypertension-remission in GRA patients. Unilateral primary aldosteronism patients harboring concomitant GRA were not associated with inferior hypertension-remission after an adrenalectomy. Low serum potassium and high PRA were positively associated with hypertension-remission in GRA patients.

A systematic review of pathophysiology and management of familial hyperaldosteronism type 1 in pregnancy

PURPOSE

Familial hyperaldosteronism type 1 (FH-1) is a rare autosomal dominant form of primary aldosteronism, which features a marked phenotypic heterogeneity, ranging from mild to severe forms of arterial hypertension that can be complicated by stroke and cardiovascular events at a young age. As affected patients usually reach the fertile age, transmission of the disease to offspring is common. Notwithstanding this, reports of FH-1 in pregnancy are limited and there is a lack of treatment guidelines.

METHODS AND RESULTS

We searched the PubMed and EuropePMC databases with a PICO strategy to retrieve available information on management of FH-1 patients during pregnancy. We could identify seven relevant articles, which are herein reviewed.

CONCLUSION

Based on available information on pathophysiology and treatment of FH-1 in pregnancy, recommendations for the rational management of FH-1 in pregnancy are provided.

Familial hyperaldosteronism type 1 and pregnancy: successful treatment with low dose dexamethasone

PURPOSE

Familial hyperaldosteronism type 1 (FH-1) is an autosomal dominant form of primary aldosteronism (PA), featuring a marked phenotypic heterogeneity, ranging from mild forms of PA and arterial hypertension (HT) to severe forms complicated by stroke at a young age. Affected patients usually reach the fertile age; hence, transmission of the disease to offspring is common. Notwithstanding this, only anecdotal reports of FH-1 in pregnancy exist and recommendations for treatment remain vague.

MATERIALS AND METHODS AND RESULTS

We herein report on a novel FH-1 pedigree featuring very severe HT, fatal aortic dissection, and high rate of early stroke, where a young FH-1 woman was successfully managed throughout pregnancy with low-dose dexamethasone.

CONCLUSIONS

Based on this experience and on available information on pathophysiology of FH-1 in pregnancy, the pros and cons of dexamethasone administration in the treatment of FH-1 in pregnancy are also discussed.

Familial Aggregation and Heritability of Aldosteronism with Cardiovascular Events

CONTEXT

To date, the effect of positive family history as a risk factor of primary aldosteronism (PA) is largely unknown. Studies have failed to distinguish the heritability of PA as well as the associations between positive family history of PA and clinical outcomes.

OBJECTIVES

We quantified the prevalence, the extent of familial aggregation, the heritability of PA among family members of patients with PA, and the association between positive PA family history and major cardiovascular events (MACE).

DESIGN AND SETTINGS

Using the Taiwan National Health Insurance Database, 30 245 077 National Health Insurance beneficiaries (both alive and those deceased between January 1, 1999, and December 31, 2015) were identified.

RESULTS

We identified 7902 PA patients. Forty-four had PA (0.3%) among 10 234 individuals with affected parents, 2298 with affected offspring, 1924 with affected siblings, and 22 with affected twins. A positive family history was associated with the adjusted relative risk (RR) (95% confidence interval [CI]) of 11.60 (7.63-17.63) for PA in people with an affected first-degree relative. In subgroup analysis, the risk for PA across all relationships (parent, siblings, offspring, and spouse) showed highly significant differences to PA without family history. The accountability for phenotypic variance of PA was 51.0% for genetic factors, 24.9% for shared environmental factors, and 24.1% for nonshared environmental factors. PA patients with an affected first-degree relative were associated with an increased risk for composite major cardiovascular events (RR 1.31; 95% CI 1.24-1.40, P < .001) compared with PA patients without family history.

CONCLUSION

Familial clustering of PA exists among a population-based study, supporting a genetic susceptibility leading to PA. There is increased coaggregation of MACE in first-degree relatives of PA patients. Our findings suggest a strong genetic component in the susceptibility of PA, involving different kinships.

Endocrine causes of hypertension in pregnancy

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

Management of adrenal tumors in pregnancy

Adrenal diseases, including Cushing syndrome (CS), primary aldosteronism (PA), pheochromocytoma, and adrenocortical carcinoma, are uncommon in pregnancy; a high degree of clinical suspicion must exist. Physiologic changes to the hypothalamus-pituitary-adrenal axis in a normal pregnancy result in increased cortisol, renin, and aldosterone levels, making the diagnosis of CS and PA in pregnancy challenging. However, catecholamines are not altered in pregnancy and allow a laboratory diagnosis of pheochromocytoma that is similar to that of the nonpregnant state. Although adrenal tumors in pregnancy result in significant maternal and fetal morbidity, and sometimes mortality, early diagnosis and appropriate treatment often improve outcomes.

Progress in primary aldosteronism: mineralocorticoid receptor antagonists and management of primary aldosteronism in pregnancy

Primary aldosteronism (PA) is the most common cause of secondary hypertension. In this review, we discuss the diagnosis and management of PA during pregnancy based on the literature. As aldosterone and renin are physiologically increased during pregnancy and confirmation tests are not recommended, the diagnosis of PA during pregnancy relies on a repeatedly suppressed plasma renin level. Mineralocorticoid receptor antagonists (MRAs) are the most effective drugs to treat hypertension and hypokalemia in patients with PA. However, spironolactone (FDA pregnancy category C) might lead to undervirilization of male infants due to the anti-androgenic effects. Although data in the literature are very limited, treatment with spironolactone is not recommended. Eplerenone (FDA pregnancy category B) is a selective MRA without anti-androgenic potential. If MRA treatment is required in pregnancy, eplerenone appears to be a safe and effective alternative, although symptomatic treatment with approved antihypertensive drugs and supplementation with potassium is the first choice. In case of aldosterone-producing adenoma, laparoscopic adrenalectomy is a therapeutic option in the second trimester of pregnancy.

In vivo and ex vivo analysis of tubule function

Analysis of tubule function with in vivo and ex vivo approaches has been instrumental in revealing renal physiology. This work allows assignment of functional significance to known gene products expressed along the nephron, primary of which are proteins involved in electrolyte transport and regulation of these transporters. Not only we have learned much about the key roles played by these transport proteins and their proper regulation in normal physiology but also the combination of contemporary molecular biology and molecular genetics with in vivo and ex vivo analysis opened a new era of discovery informative about the root causes of many renal diseases. The power of in vivo and ex vivo analysis of tubule function is that it preserves the native setting and control of the tubule and proteins within tubule cells enabling them to be investigated in a "real-life" environment with a high degree of precision. In vivo and ex vivo analysis of tubule function continues to provide a powerful experimental outlet for testing, evaluating, and understanding physiology in the context of the novel information provided by sequencing of the human genome and contemporary genetic screening. These tools will continue to be a mainstay in renal laboratories as this discovery process continues and as we continue to identify new gene products functionally compromised in renal disease.

Adrenal disorders in pregnancy

Pregnancy is marked by alterations in a number of endocrine systems, including activation of the renin-angiotensin-aldosterone system and the hypothalamic-pituitary-adrenal axis. The placenta, the fetal adrenal glands and the liver constitute an interactive endocrine entity, known as the fetoplacental unit. In the fetoplacental unit, the fetal adrenal glands are the primary source of dehydroepiandrosterone sulphate, which is further metabolized by the fetal liver and placenta to produce a variety of oestrogens. Several disorders can affect both the fetal and maternal adrenal glands during pregnancy. The most common fetal adrenal disorder, steroid 21-hydroxylase deficiency, leads to abnormalities in sexual development and can be life threatening for the neonate. Although rare, maternal adrenal disorders are associated with considerable maternal mortality and morbidity if not promptly recognized and treated. However, diagnosis is often difficult to establish because of the endocrine changes occurring during normal pregnancies and the lack of reference values for the majority of the adrenal steroids. This Review provides an overview of adrenal steroid metabolism during pregnancy and focuses on diagnosis and treatment of the most common fetal and maternal adrenal disorders.

Regulation of transport in the connecting tubule and cortical collecting duct

The central goal of this overview article is to summarize recent findings in renal epithelial transport,focusing chiefly on the connecting tubule (CNT) and the cortical collecting duct (CCD).Mammalian CCD and CNT are involved in fine-tuning of electrolyte and fluid balance through reabsorption and secretion. Specific transporters and channels mediate vectorial movements of water and solutes in these segments. Although only a small percent of the glomerular filtrate reaches the CNT and CCD, these segments are critical for water and electrolyte homeostasis since several hormones, for example, aldosterone and arginine vasopressin, exert their main effects in these nephron sites. Importantly, hormones regulate the function of the entire nephron and kidney by affecting channels and transporters in the CNT and CCD. Knowledge about the physiological and pathophysiological regulation of transport in the CNT and CCD and particular roles of specific channels/transporters has increased tremendously over the last two decades.Recent studies shed new light on several key questions concerning the regulation of renal transport.Precise distribution patterns of transport proteins in the CCD and CNT will be reviewed, and their physiological roles and mechanisms mediating ion transport in these segments will also be covered. Special emphasis will be given to pathophysiological conditions appearing as a result of abnormalities in renal transport in the CNT and CCD.

Adrenal disorders in pregnancy

Adrenal disorders may manifest during pregnancy de novo, or before pregnancy undiagnosed or diagnosed and treated. Adrenal disorders may present as hormonal hypofunction or hyperfunction, or with mass effects or other nonendocrine effects. Pregnancy presents special problems in the evaluation of the hypothalamic-pituitary-adrenal axis in addition to the usual considerations. The renin-angiotensin-aldosterone axis undergoes major changes during pregnancy. Nevertheless, the common adrenal disorders are associated with morbidity during pregnancy and their management is more complicated. A high index of suspicion must be maintained for these disorders lest they go unrecognized and untreated.

Hyperaldosteronism in pregnancy

Aldosterone is a key regulator of electrolyte and water homeostasis and plays a central role in blood pressure regulation. Hormonal changes during pregnancy, among them increased progesterone and aldosterone production, lead to the required plasma volume expansion of the maternal body as an accommodation mechanism for fetus growth. This review discusses the regulation of aldosterone production by aldosterone synthase (CYP11B2); the impact on aldosterone secretion due to the presence of a chimeric gene originating from a crossover between CYP11B1 and CYP11B2 in glucocorticoid remediable aldosteronism (GRA) — the inherited form of hypertension; enhanced aldosterone production in aldosterone-producing adenoma (APA); and idiopathic hyperaldosteronism (IHA). Features of hyperaldosteronism are also found in patients with apparent mineralocorticoid excess (AME), in which glucocorticoids exacerbate activation of the mineralocorticoid receptor (MR) because of a defect in the 11β-hydroxysteroid dehydrogenase type 2 enzyme. Regulation of aldosterone production and tissue-specific activation of the mineralocorticoid receptor are prerequisites for optimal control of body fluids and blood pressure during pregnancy and contribute largely to the wellbeing of the mother-to-be.

Diagnosis and treatment of low-renin hypertension

Plasma renin levels can be used to classify hypertension. A significant proportion of hypertensive individuals display a low-renin profile and thus low-renin hypertension (LRH) requires appropriate diagnosis and treatment. LRH includes essential, secondary and genetic forms, the most common of which are low-renin essential hypertension and primary aldosteronism. Several studies have investigated the relationship between PRA status and clinical response to different antihypertensive therapies. The present review will discuss the differential diagnosis of LRH subtypes and the most appropriate treatment options based on the pathophysiological background of this condition.

Genetics of arterial hypertension and hypotension

Human hypertension affects affects more than 20% of the adult population in industrialized countries, and it is implicated in millions of deaths worldwide each year from stroke, heart failure and ischemic heart disease. Available evidence suggests a major genetic impact on blood pressure regulation. Studies in monogenic hypertension revealed that renal salt and volume regulation systems are predominantly involved in the genesis of these disorders. Mutations here affect the synthesis of mineralocorticoids, the function of the mineralocorticoid receptor, epithelial sodium channels and their regulation by a new class of kinases, termed WNK kinases. It has been learned from monogenic hypotension that almost all ion transporters involved in the renal uptake of Na(+) have a major impact on blood pressure regulation. For essential hypertension as a complex disease, many candidate genes have been analysed. These include components of the renin-angiotensin-aldosterone system, adducin, beta-adrenoceptors, G protein subunits, regulators of G protein signalling (RGS) proteins, Rho kinases and G protein receptor kinases. At present, the individual impact of common polymorphisms in these genes on the observed blood pressure variation, on risk for stroke and as predictors of antihypertensive responses remains small and clinically irrelevant. Nevertheless, these studies have greatly augmented our knowledge on the regulation of renal functions, cellular signal transduction and the integration of both. Together, this provides the basis for the identification of novel drug targets and, hopefully, innovative antihypertensive drugs.

Resolution of hypertension during pregnancy in familial hyperkalemia and hypertension with the WNK4 Q565E mutation

OBJECTIVE

Secondary hypertension during pregnancy usually carries high maternal and fetal morbidity and mortality rates. A rare form of monogenic hypertension is familial hyperkalemia and hypertension, which is caused by mutations in the kinases WNK1 or WNK4 and other unknown molecular defects. The purpose of the study was to examine the course of pregnancy in hypertensive women with familial hyperkalemia and hypertension.

STUDY DESIGN

We prospectively studied 2 pregnancies of a woman with familial hyperkalemia and hypertension and the Q565E WNK4 mutation (pregnancies 1 and 2) and retrospectively studied the course of 2 pregnancies in another woman who was an affected member of this largest family described in the literature.

RESULTS

Both women had hypertension (170-190/105-110 mm Hg), hyperkalemia (5.3-6.0 mmol/L), and hypercalciuria, all of which were well controlled by thiazides. During pregnancies, thiazides were discontinued; throughout the pregnancy, the blood pressure remained normal at 120 to 130/75 to 85 mm Hg; however, hyperkalemia and hypercalciuria, which were documented in pregnancies 1 and 2, persisted. Renin and aldosterone levels (which were measured in pregnancies 1 and 2) rose towards their end. Four normal infants were born. A woman with familial hyperkalemia and hypertension of unknown molecular defect who had 2 pregnancies with hypertension exacerbation and premature deliveries was described previously.

CONCLUSION

In familial hyperkalemia and hypertension with the WNK4 mutation, pregnancy ameliorates hypertension; however, hyperkalemia and hypercalciuria persist. This dissociation may shed light on the pathogenesis of familial hyperkalemia and hypertension, on pregnancy-related hypertension, and on the mechanism of action of WNK4 kinase, a major regulator of cellular ion transport.

Glucocorticoid-remediable aldosteronism

Glucocorticoid-remediable aldosteronism (GRA) is a monogenic form of human hypertension that predisposes to cerebral hemorrhage. As a result of a chimeric gene duplication, aldosterone is ectopically synthesized in the cortisol-secreting zona fasciculata of the adrenal gland under the control of adrenocorticotropin (ACTH). Hypertension frequently has its onset during childhood and is usually refractory to standard anti-hypertensives such as ACE inhibitors and beta-blockers. Hypokalemia can develop in those treated with a potassium-wasting diuretic, but random potassium levels are usually normal. Diagnosis has been facilitated by the availability of a genetic test. Suppression of ACTH release with exogenous dexamethasone is a useful diagnostic and therapeutic strategy. Treatment with the mineralocorticoid receptor antagonists spironolactone and epleronone is also efficacious. The diagnosis of GRA facilitates directed therapies and screening of at-risk individuals and kindreds.

Genetics of primary aldosteronism

Over the last few years, much progress has been made in understanding the genetic basis of primary aldosteronism. This has led to the diagnosis of the familial forms and has aided the understanding of the basis of sporadic forms of the disease. Such information can be exploited to improve the therapeutic approaches used not only for patients with primary aldosteronism, but also with other forms of hypertension. Here, we review the genetic and the phenotypic features of the familial forms, the genetic variants that influence the sporadic forms and the structure and regulation of the CYP11B1 and CYP11B2 genes.

Glucocorticoid-Remediable Aldosteronism

Glucocorticoid remediable aldosteronism (GRA) appears to be the most common monogenic form of human hypertension. As a result of chimeric gene duplication, aldosterone is ectopically synthesized in the zona fasciculata of the adrenal gland under the control of adrenocorticotropin (ACTH). Affected individuals are typically hypertensive, often with onset in youth, and demonstrate refractoriness to standard antihypertensives such as angiotensin-converting enzyme inhibitors and beta-blockers. GRA subjects are normokalemic but often develop hypokalemia when treated with a potassium-wasting diuretic. Analysis of affected kindreds has demonstrated a high prevalence of early cerebral hemorrhage, largely as a result of aneurysms. Identification of affected individuals should allow direct neurovascular screening and targeted antihypertensive therapy.

Hereditary disorders of potassium homeostasis

There has been a dramatic recent increase in the understanding of the renal epithelial transport systems with the identification, cloning and characterization of a large number of membrane transport proteins. The aim of this chapter is to integrate this body of knowledge with the understanding of the clinical disorders that accompany gain, loss or dysregulation of function of these transport systems. The specific focus is on the best-defined human clinical syndromes in which there are derangements in potassium (K(+)) homeostasis. The focus is on inherited syndromes, rather than on acquired syndromes due to tubular transport defects, and the therapeutic approaches address chronic derangements of K(+) homeostasis rather than acute interventions directed at life-threatening hyperkalaemia.

Renal genetic disorders related to K+ and Mg2+

The recent knowledge of the renal epithelial transport systems has exploded with the identification, cloning, and characterization of a large number of membrane transport proteins. The fundamental aspects of these transporters are beginning to emerge at the molecular level and are summarized in the accompanying contributions in this volume of the Annual Review of Physiology. The aim of my review is to integrate this body of knowledge with the understanding of the clinical disorders of human mineral homeostasis that accompany gain, loss, or dysregulation of function of these transport systems. The specific focus is on the best defined human clinical syndromes in which there are derangements in K(+) and Mg(2+) homeostasis.

Japanese family with glucocorticoid-remediable aldosteronism diagnosed by long-polymerase chain reaction

We report a Japanese family with glucocorticoid-remediable aldosteronism (GRA) in whom gene abnormality was identified by the long-polymerase chain reaction (PCR) method. The proband was a 21-year-old female incidentally found to have high blood pressure (173/107 mmHg). Laboratory tests showed hypokalemia (3.7 mmol/l), and high plasma aldosterone concentration (PAC, 234 pg/ml) with suppressed plasma renin activity (PRA, <0.1 ng/ml/h). The circadian rhythm pattern and the results of a rapid adrenocorticotrophic hormone (ACTH) test indicated ACTH-dependent changes in PAC. Imaging studies showed no adrenal mass on either side. A dexamethasone (Dexa) suppression test (1.0 mg/day orally for 7 days) showed a marked decrease of PAC 2 days after administration, and this decreased level was maintained throughout Dexa administration. High blood pressure and hypokalemia also improved during Dexa treatment. The proband's younger sister was 19 years old and had hypertension, PAC of 231 pg/ml, and PRA <0.1 ng/ml/h. The mother was 53 years old and had hypertension, PAC of 98.5 pg/ml, and PRA <0.1 ng/ml/h. The proband's elder sister was a 22-year-old normotensive with PAC of 110 pg/ml and PRA of 0.1 ng/ml. Long-PCR was performed for detection of the chimeric gene associated with GRA, using DNA samples from all four cases and two normal control subjects. Although the aldosterone synthase gene was expressed among all DNA samples, the chimeric gene was detected only in the proband, her younger sister and her mother. Our clinical data and genetic investigation confirmed the presence of GRA in this Japanese family.

Genetic forms of human hypertension

Our basic understanding of sodium mechanisms provides unique insights into epithelial transport processes, and unusual clinical syndromes can arise from mutations of these ion transporters. These genetic disorders affect sodium balance, with both sodium-retaining and sodium-wasting conditions being the consequence. A major focus of such studies has been the epithelial sodium channel, which can be activated by mutations in the channel subunits or mineralocorticoid receptor, and changes in the response to or production of mineralocorticoids. As a result, there are now clearly defined Mendelian syndromes in which epithelial sodium channel activity is 'dysregulated', with the subsequent development of systemic hypertension with suppressed plasma renin activity that can be attributed to a primary renal mechanism. Applying these insights to the far more common disorder of low renin hypertension may shed new light on the underlying pathophysiology of this common form of human hypertension, and more clearly define the interactions of dietary constituents such as sodium and potassium in the regulation of blood pressure.