A new form of the syndrome of apparent mineralocorticoid excess

Diagnosis and Treatment of Monogenic Hypertension in Children

Although the majority of individuals with hypertension (HTN) have primary and polygenic HTN, monogenic HTN is a secondary type that is widely thought to play a key role in pediatric HTN, which has the characteristics of early onset, refractory HTN with a positive family history, and electrolyte disorders. Monogenic HTN results from single genetic mutations that contribute to the dysregulation of blood pressure (BP) in the kidneys and adrenal glands. It is pathophysiologically associated with increased sodium reabsorption in the distal tubule, intravascular volume expansion, and HTN, as well as low renin and varying aldosterone levels. Simultaneously increased or decreased potassium levels also provide clues for the diagnosis of monogenic HTN. Discovering the genetic factors that cause an increase in BP has been shown to be related to the choice of and responses to antihypertensive medications. Therefore, early and precise diagnosis with genetic sequencing and effective treatment with accurate antihypertensive agents are critical in the management of monogenic HTN. In addition, understanding the genetic architecture of BP, causative molecular pathways perturbing BP regulation, and pharmacogenomics can help with the selection of precision and personalized medicine, as well as improve morbidity and mortality in adulthood.

Classic and Nonclassic Apparent Mineralocorticoid Excess Syndrome

CONTEXT

Arterial hypertension (AHT) is one of the most frequent pathologies in the general population. Subtypes of essential hypertension characterized by low renin levels allowed the identification of 2 different clinical entities: aldosterone-mediated mineralocorticoid receptor (MR) activation and cortisol-mediated MR activation.

EVIDENCE ACQUISITION

This review is based upon a search of Pubmed and Google Scholar databases, up to August 2019, for all publications relating to endocrine hypertension, apparent mineralocorticoid excess (AME) and cortisol (F) to cortisone (E) metabolism.

EVIDENCE SYNTHESIS

The spectrum of cortisol-mediated MR activation includes the classic AME syndrome to milder (nonclassic) forms of AME, the latter with a much higher prevalence (7.1%) than classic AME but different phenotype and genotype. Nonclassic AME (NC-AME) is mainly related to partial 11βHSD2 deficiency associated with genetic variations and epigenetic modifications (first hit) and potential additive actions of endogenous or exogenous inhibitors (ie, glycyrrhetinic acid-like factors [GALFS]) and other factors (ie, age, high sodium intake) (second hit). Subjects with NC-AME are characterized by a high F/E ratio, low E levels, normal to elevated blood pressure, low plasma renin and increased urinary potassium excretion. NC-AME condition should benefit from low-sodium and potassium diet recommendations and monotherapy with MR antagonists.

CONCLUSION

NC-AME has a higher prevalence and a milder phenotypical spectrum than AME. NC-AME etiology is associated to a first hit (gene and epigene level) and an additive second hit. NC-AME subjects are candidates to be treated with MR antagonists aimed to improve blood pressure, end-organ damage, and modulate the renin levels.

The Low-Renin Hypertension Phenotype: Genetics and the Role of the Mineralocorticoid Receptor

A substantial proportion of patients with hypertension have a low or suppressed renin. This phenotype of low-renin hypertension (LRH) may be the manifestation of inherited genetic syndromes, acquired somatic mutations, or environmental exposures. Activation of the mineralocorticoid receptor is a common final mechanism for the development of LRH. Classically, the individual causes of LRH have been considered to be rare diseases; however, recent advances suggest that there are milder and "non-classical" variants of many LRH-inducing conditions. In this regard, our understanding of the underlying genetics and mechanisms accounting for LRH, and therefore, potentially the pathogenesis of a large subset of essential hypertension, is evolving. This review will discuss the potential causes of LRH, with a focus on implicated genetic mechanisms, the expanding recognition of non-classical variants of conditions that induce LRH, and the role of the mineralocorticoid receptor in determining this phenotype.

Apparent mineralocorticoid excess syndrome: an overview

Apparent mineralocorticoid excess (AME) syndrome results from defective 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2). This enzyme is co-expressed with the mineralocorticoid receptor (MR) in the kidney and converts cortisol (F) to its inactive metabolite cortisone (E). Its deficiency allows the unmetabolized cortisol to bind to the MR inducing sodium retention, hypokalemia, suppression of PRA and hypertension. Mutations in the gene encoding 11beta-HSD2 account for the inherited form, but a similar clinical picture to AME occurs following the ingestion of bioflavonoids, licorice and carbenoxolone, which are competitive inhibitors of 11beta-HSD2. Reduced 11beta-HSD2 activity may explain the increased sodium retention in preeclampsia, renal disease and liver cirrhosis. Relative deficiency of 11beta-HSD2 activity can occur in Cushing's syndrome due to saturation of the enzyme and explains the mineralocorticoid excess state that characterizes ectopic ACTH syndrome. Reduced placental 11beta-HSD2 expression might explain the link between reduced birth weight and adult hypertension. Polymorphic variability in the HSD11B2 gene in part determines salt sensitivity, a forerunner for adult hypertension onset. AME represents a spectrum of mineralocorticoid hypertension with severity reflecting the underlying genetic defect in the 11beta-HSD2; although AME is a genetic disorder, several exogenous compounds can bring about the symptoms by inhibiting 11beta-HSD2 enzyme. Substrate excess as seen in Cushing's syndrome and ACTH ectopic production can overwhelm the capacity of 11beta-HSD2 to convert F to E, leading up to an acquired form of AME.

Hydrolysis of conjugated steroids by the combined use of beta-glucuronidase preparations from helix pomatia and ampullaria: determination of urinary cortisol and its metabolites

This study describes the enzymatic hydrolysis of urinary conjugates of cortisol, cortisone, tetrahydrocortisol, allotetrahydrocortisol, and tetrahydrocortisone with beta-glucuronidase preparations from Helix pomatia and Ampullaria. The objective of the present studies was to find optimal hydrolysis conditions for these conjugated steroids. Assay of the isolated steroids was carried out by GC-MS using deuterium-labeled compounds as internal standards. The allotetrahydrocortisol conjugate was clearly the hardest to hydrolyze with enzyme from Helix pomatia and required increased enzyme concentration and prolonged incubation. Hydrolysis of a urine sample for 2.0 h with the simultaneous use of 3400 units/ml Ampullaria and 5400 units/ml Helix pomatia enzymes in 0.5 M acetate buffer at 55 degrees C achieved more complete cleavage of the urinary conjugates of the five steroids examined. It is thus advantageous to use the Ampullaria and Helix pomatia enzymes in combination to obtain the highest yield in the urinary corticosteroid assay.

Congenital deficiency of 11beta-hydroxysteroid dehydrogenase (apparent mineralocorticoid excess syndrome): diagnostic value of urinary free cortisol and cortisone

The syndrome of apparent mineralocorticoid excess (AME) is an inherited form of hypertension. This disorder results from an inability of the enzyme 11beta-hydroxysteroid dehydrogenase (11beta-OHSD) to inactivate cortisol to cortisone. The diagnosis of AME is usually based on an elevated ratio of cortisol to cortisone reduced metabolites in the urine [tetrahydrocortisol plus allotetrahydrocortisol to tetrahydrocortisone (THF+alloTHF/THE)]. The principal site of "A" ring reduction is the liver, but AME arises from mutation in the gene encoding 11beta-OHSD2 in the kidney. We used a gas chromatographic/mass spectrometric method to measure the urinary free cortisol (UFF) and free cortisone (UFE) in 24 patients affected by the two variants of AME [19 with the classical form (type I) and 5 with the mild form called AME type II] in order to provide a more reproducible in vivo measure of the renal enzymatic activity. Type I patients were divided into two groups: children under 12 and adults. UFF levels (microg/24 h) did not differ between under-12 controls and AME type I children (mean+/-SD, 9+/-4 and 15+/-12, respectively), but was significantly higher in affected adults compared to controls: (62+/-32 vs 29+/-8, p<0.01). No differences were found between adult controls and AME type II patients (29+/-8 and 37.0+/-14, respectively). UFE was undetectable in 63% of AME type I and significantly lower in AME type II (p<0.05). As a consequence UFF/UFE ratio was significantly higher in AME type I patients both in children and adults compared to controls (AME children: 5.1+/-2.6; normal children: 0.43+/-0.2, p<0.01; AME type I adults: 17.7+/-19.6; normal adults: 0.54+/-0.3 p<0.01). For AME type II, where UFE was detectable in every case, the UFF/UFE ratio was significantly higher than adult controls (2.75+/-1.5 vs 0.54+/-0.3, p<0.01). In conclusion, our study indicates that UFE and UFF/UFE ratio are sensitive markers of 11beta-OHSD2, directly reflecting the activity of the renal isozyme and readily identifying patients with AME. The presence of an altered UFF/UFE ratio in both types of AME, although with different degree of severity, calls for re-evaluation and the classification of AME as a single disorder.

Does kidney transplantation normalise cortisol metabolism in apparent mineralocorticoid excess syndrome?

The syndrome of apparent mineralocorticoid syndrome (AME) results from defective 11beta-hydroxysteroid dehydrogenase 2 (11beta-HSD2). This enzyme is co-expressed with the mineralocorticoid receptor (MR) in the kidney and converts cortisol to its inactive metabolite cortisone. Its deficiency allows the unmetabolized cortisol to bind to the MR inducing sodium retention, suppression of PRA and hypertension. Thus, the syndrome is a disorder of the kidney. We present here the first patient affected by AME cured by kidney transplantation. Formerly, she was considered to have a mild form of the syndrome (Type II), but progressively she developed renal failure which required dialysis and subsequent kidney transplantation. To test the ability of the transplanted kidney to normalise the patient's cortisol metabolism, we gave, in two different experiments, 25 and 50 mg/day of cortisone acetate or 15 and 30 mg/day of cortisol after inhibition of the endogenous cortisol by synthetic glucocorticoid (methylprednisolone and dexamethasone). The AME diagnostic urinary steroid ratios tetrahydrocortisol+5alphatetrahydrocortisol/tetrahydrocortisone and cortisol/cortisone were measured by gas chromatography/mass spectrometry. Transplantation resulted in lowering blood pressure and in normalization of serum K and PRA. After administration of a physiological dose of cortisol (15 mg/day), the urinary free cortisol/cortisone ratio was corrected (in contrast to the A-ring reduced metabolites ratio), confirming that the new kidney had functional 11beta-HSD2. This ratio was abnormally high when the supra-physiological dose of cortisol 30 mg/day was given. After cortisone administration, the tetrahydrocortisol+5alphatetrahydrocortisol/tetrahydrocortisone ratio resulted normalised with both physiological and supra-physiological doses, confirming that the hepatic reductase activity is not affected. As expected, the urinary free cortisol/cortisone ratio was normal with physiological, but increased after supra-physiological doses of cortisone. The described case indicates a normalisation of cortisol metabolism after kidney transplantation in AME patient and confirms the supposed pathophysiology of the syndrome. Moreover, it suggests a new therapeutic strategy in particularly vulnerable cohorts of patients inadequately responsive to drug therapy or with kidney failure.

Genetic, biochemical, and clinical studies of patients with A328V or R213C mutations in 11betaHSD2 causing apparent mineralocorticoid excess

Apparent mineralocorticoid excess is a recessively inherited hypertensive syndrome caused by mutations in the 11beta-hydroxysteroid dehydrogenase type 2 gene, which encodes the enzyme normally responsible for converting cortisol to inactive cortisone. Failure to convert cortisol to cortisone in mineralocorticoid-sensitive tissues permits cortisol to bind to and activate mineralocorticoid receptors, causing hypervolemic hypertension. Typically, these patients have increased ratios of cortisol to cortisone and of 5alpha- to 5beta-cortisol metabolites in serum and urine. We have studied 3 patients in 2 families with severe, apparent mineralocorticoid excess and other family members in terms of their genetic, biochemical, and clinical parameters, as well as normal controls. Two brothers were homozygous for an A328V mutation and the third patient was homozygous for an R213C mutation in the 11beta-hydroxysteroid dehydrogenase type 2 gene; both mutations caused a marked reduction in the activity of the encoded enzymes in transfection assays. The steroid profiles of the 7 heterozygotes and 2 other family members studied were completely normal. The results of a novel assay used to distinguish 5alpha- and 5beta-tetrahydrometabolites suggest that 5beta-reductase activity is reduced or inhibited in apparent mineralocorticoid excess. In 1 patient undergoing renal dialysis for chronic renal insufficiency, direct control of salt and water balance completely corrected the hypertension, emphasizing the importance of mineralocorticoid action in this syndrome.

11 beta-Hydroxysteroid dehydrogenase and the syndrome of apparent mineralocorticoid excess

Whereas aldosterone is normally a much stronger mineralocorticoid than cortisol in vivo, mineralocorticoid receptors have identical in vitro affinities for these hormones. The in vivo specificity of the receptors is, at least in part, the result of activity of 11-HSD, an enzyme located in most mineralocorticoid target tissues that converts cortisol to cortisone. Cortisone is not a ligand for the receptor, whereas aldosterone is not a substrate of the enzyme. The syndrome of AME is a rare form of juvenile hypertension in which 11-HSD is defective. This deficiency allows mineralocorticoid receptors to be occupied by cortisol, leading to hypertension, because plasma concentrations of cortisol are much higher than those of aldosterone. Licorice, which contains 11-HSD inhibitors, causes a similar syndrome. There are two known isozymes of 11-HSD. The liver or type I isozyme is expressed at high levels in the liver, has a relatively low affinity for steroids (micromolar Km), catalyzes both dehydrogenation and the reverse reductase reaction, and utilizes NADP+ or NADPH as cofactors. The kidney or type 2 isozyme is expressed at high levels in the kidney and placenta, has a high affinity (nanomolar Km) for steroids, catalyzes only dehydrogenation, and utilizes NAD+ as a cofactor. Mutations in the HSD11B2 (HSD11K) gene encoding the kidney isozyme of 11-HSD have been detected in all kindreds with AME studied thus far. This gene represents a candidate locus for the common, "essential" form of hypertension.

Quantitation of cortisol and related 3-oxo-4-ene steroids in urine using gas chromatography/mass spectrometry with stable isotope-labeled internal standards

A method for the profiling of several important 3-oxo-4-ene urinary steroids is reported. The methodology is combined gas chromatography/mass spectrometry (GC/MS) utilizing stable isotope-labeled internal standards. The following standards were obtained or easily synthesized: [9, 11, 12, 12-2H4]cortisol, [1,2-2H2] and [9, 12, 12-2H2]cortisone, [1,2-2H2]6 beta-hydroxycortisol, and [1,2-2H2]18-hydroxycortisol. We found the following excretions of free steroids for normal adult males and females: cortisol (males mean +/- SD, 35 +/- 13; females mean +/- SD, 23 +/- 13), cortisone (males mean +/- SD, 58 +/- 23; females mean +/- SD, 50 +/- 22), 6 beta-hydroxycortisol (males mean +/- SD, 164 +/- 59; females mean +/- SD, 108 +/- 55), and 18-hydroxycortisol (males mean +/- SD, 148 +/- 55; females mean +/- SD, 71 +/- 30). For 18-hydroxycortisol in particular, the excretions were much higher for males than for females. We found that the larger part of urinary cortisol and cortisone is not free but is released from conjugation by enzymes present in snail digestive juice. Using a pooled urine sample from an equal number of male and female subjects, we found that for cortisol 29% was excreted free, 28% as glucuronide and 43% as other conjugates (probably sulfates). For cortisone 41% was free, 45% beta-glucuronide and 14% as other conjugates. Relatively little (3-8%) of the hydroxylated cortisols were excreted conjugated.

Diagnosis and treatment of a child with the syndrome of apparent mineralocorticoid excess type 1

We report the case of a 16-month-old boy who presented with chronic vomiting, failure to thrive, arterial hypertension and medullary nephrocalcinosis. Laboratory results revealed hypokalaemia, metabolic alkalosis, increased urinary potassium excretion and a hyporeninaemic hypoaldosteronism. Chromatographic determination of urinary steroid metabolites showed an abnormal elevation of tetrahydrocortisol and allo-tetrahydrocortisol compared to tetrahydrocortisone; this pattern of urinary steroid excretion is essential for the diagnosis of the syndrome of apparent mineralocorticoid excess type 1 and believed to be a result of the underlying metabolic defect, a decreased activity of the 11 beta-hydroxysteroid dehydrogenase. A second variant, called syndrome of apparent mineralocorticoid excess type 2, has similar clinical features but lacks the typical urinary steroid profile. Therapy with spironolactone resulted in growth, weight gain and blood pressure control.

Extra-adrenal effects of metyrapone include inhibition of the 11-oxoreductase activity of 11 beta-hydroxysteroid dehydrogenase: a model for 11-HSD I deficiency

BACKGROUND AND OBJECTIVE

Previous studies suggesting effects of metyrapone on extra-adrenal corticosteroid metabolism have involved significant alterations in plasma cortisol. We have therefore studied effects of metyrapone on urinary excretion of steroids in a group of patients treated concurrently with hydrocortisone so that changes in plasma cortisol were minimized.

DESIGN

Replacement doses of hydrocortisone (30 mg/day) were given concurrently with metyrapone (2-4 g/day) for 2 weeks. Blood samples were taken and 24-hour urinary steroid collections were made at baseline and after 1 and 2 weeks of treatment.

PATIENTS

Subjects were 6 female patients with major depression from a trial of metyrapone as an antidepressant.

MEASUREMENTS

Urinary steroid profiles were measured by gas chromatography; plasma cortisol and urinary free cortisol were measured by fluorescence immunoassay.

RESULTS

Plasma cortisol levels were not significantly decreased by treatment, while excretion of 11-deoxycortisol metabolites increased eightfold after 2 weeks indicating that concurrent hydrocortisone administration had not suppressed the adrenal. Ratios reflecting 11 beta-hydroxy/11-oxo metabolites of cortisol were significantly decreased, consistent with inhibition of the 11-oxoreductase activity of 11 beta-hydroxysteroid dehydrogenase (11-HSD). Other changes included significant decreases in the rates of 5 alpha vs 5 beta and of 20 alpha vs 20 beta reduction of corticosteroids.

CONCLUSIONS

Metyrapone has multiple effects on extra-adrenal corticosteroid metabolism and is the only agent we know of which selectively inhibits 11-oxoreductase. Metyrapone thus provides a model for 11-HSD I deficiency and a tool for in-vitro studies of cortisol-cortisone interconversion. The results also suggest mechanisms whereby corticosteroid effects can be regulated separately from corticosteroid synthesis.

Human hypertension caused by mutations in the kidney isozyme of 11 beta-hydroxysteroid dehydrogenase

The syndrome of apparent mineralocorticoid excess (AME) is an inherited form of human hypertension thought to result from a deficiency of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD). This enzyme normally converts cortisol to inactive cortisone and is postulated to thus confer specificity for aldosterone upon the mineralocorticoid receptor. We have analysed the gene encoding the kidney isozyme of 11 beta HSD and found mutations on both alleles in nine of 11 AME patients (eight of nine kindreds). These mutations markedly affect enzymatic activity. They thus permit cortisol to occupy the renal mineralocorticoid receptor and thereby cause sodium retention and hypertension.

Corticosteroid receptor antagonists: a current perspective

This review aims to highlight a selection of antagonists for the mineralocorticoid and glucocorticoid receptors. Concepts of these receptor systems are described, as is the mechanism of action of these steroids in the brain and periphery. Examples of commonly available and newly synthesized antimineralocorticoids and antiglucocorticoids are given, together with their pharmacological profiles and, when appropriate, clinical and therapeutic applications.

The activities of 5 beta-reductase and 11 beta-hydroxysteroid dehydrogenase in essential hypertension

The activities of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) and 5 beta-reductase were analyzed in 39 normotensive controls and 128 patients with essential hypertension. The activity of 11 beta-HSD was obtained by dividing the 24-hour urinary tetrahydrocortisone by the sum of tetrahydrocortisol (THF) and allotetrahydrocortisol (aTHF), whereas the activity of 5 beta-reductase was obtained by dividing the 24-hour urinary THF by aTHF. The activity of 5 beta-reductase was significantly lower in essential hypertensives compared with normotensive controls (P < 0.05). However, the activity of 11 beta-HSD did not differ between normotensive controls and essential hypertensives. A positive correlation between the activities of 11 beta-HSD and 5 beta-reductase was observed in essential hypertensives (r = 0.60, P < 0.01). Neither 11 beta-HSD nor 5 beta-reductase activity correlated with indices of renal mineralocorticoid receptor activation, which were assessed by determination of plasma potassium and urinary excretion of sodium as well as potassium. Taken together, these results suggest that disturbances of one of the inactivation pathways of cortisol may contribute to the pathogenesis of hypertension.

Apparent mineralocorticoid excess type II

The syndrome of apparent mineralocorticoid excess (AME) is currently understood to reflect impaired peripheral metabolism of cortisol, which is then able to activate the non-selective mineralocorticoid (MC) receptor. The failure of glucocorticoid inactivation at the MC target tissue level in AME involves abnormal activity of 11 beta-hydroxysteroid dehydrogenase, with impaired conversion of cortisol to cortisone, and also of 5 beta-reductase. We have discovered a new form of AME (Type II) in four patients with the same clinical picture of hypertension, hypokalemia, and suppressed renin-angiotensin-aldosterone system, but in whom this conversion seems either to be normal (since cortisol to cortisone metabolite ratio is normal) or to be impaired in both directions, leaving the ratio unchanged. Both types are characterized by a profound decrease in cortisol turnover quotient and Ring A reduction constant. Short-term dexamethasone treatment is effective in correcting the MC-derived abnormalities, while in the long term the addition of other antihypertensive drugs may be required to control the severity of hypertension.

Organ-specific actions of 11 beta-hydroxysteroid dehydrogenase in humans: implications for the pathophysiology of hypertension

Elucidation of a role for 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) in modulating ligand access to renal mineralocorticoid receptors, together with identification of expression of the enzyme in most mammalian tissues, has raised the possibility (i) that glucocorticoid metabolism might influence corticosteroid receptor activation in other sites which are relevant to blood pressure control (e.g., vascular smooth muscle), and (ii) that abnormal 11 beta-OHSD expression might play a pathogenic role in common forms of hypertension (e.g., essential hypertension and the syndrome of ectopic ACTH secretion). This article reviews data from human experiments which suggest that 11 beta-OHSD has tissue-specific actions which can increase or decrease sensitivity of both mineralocorticoid and glucocorticoid receptors to cortisol, and that assessment of cortisol sensitivity may prove equally important as assessment of cortisol secretion rates in hypertensive patients.

Congenital and acquired syndromes of apparent mineralocorticoid excess

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) interconverts cortisol and cortisone. Congenital deficiency of the renal isoform of the enzyme results in hypertension, hypokalemia and suppression of the renin-angiotensin-aldosterone system--the apparent mineralocorticoid excess syndrome (AME). In these patients cortisol acts as a potent mineralocorticoid. Suppression of plasma cortisol with dexamethasone results in natriuresis, potassium retention and reduction in blood pressure. Ingestion of excess liquorice or taking carbenoxolone produces an acquired form of AME. The active component of liquorice is glycyrrhetinic acid (GE) and carbenoxolone is the hemisuccinate derivative. Both GE and carbenoxolone are potent inhibitors of 11 beta-OHSD. In vitro studies have shown that 11 beta-OHSD is present in aldosterone-selective tissues and acts as an autocrine mechanism which prevents cortisol from gaining access to the non-specific mineralocorticoid receptor (MR). Congenital or acquired absence of this enzyme allows cortisol to bind to MR resulting in AME. 11 beta-OHSD also appears to be important in controlling cortisol access to glucocorticoid receptors. Variable placental 11 beta-OHSD may alter foetal exposure to maternal cortisol and affect growth as indicated by the correlation between foetal weight and placental 11 beta-OHSD. Thus the tissue-specific distribution, ontogeny and modulation of this enzyme allows it to dictate glucocorticoid effects in addition to its key role in ensuring the specificity of the MR.

When is cortisol a mineralocorticoid?

(1) Decreased 11 beta-OHSD activity permits binding of cortisol to the Type I (mineralocorticoid) receptor in humans, thereby producing spironolactone-inhibitable Na+ retention, hypokalemia and hypertension, the syndrome of apparent mineralocorticoid excess (AME). (2) Blockade of either the Type I receptor with spironolactone or the Type II (glucocorticoid) receptor with RU-486 does not consistently abolish the effects of stress level cortisol on Na+ retention and hypertension in acute studies in normal humans, suggesting the existence of an additional glucocorticoid receptor. (3) Enhanced glucocorticoid 6 beta-hydroxylation could play an etiologic role in certain hypertensive syndromes. (4) Both decreased 11 beta-OHSD and increased 6 beta-OHase are candidates as intermediate phenotypes for the remote phenotype essential hypertension.

Evidence for cortisol as the mineralocorticoid in the syndrome of apparent mineralocorticoid excess

The hypothesis that cortisol is the functioning mineralocorticoid in the syndrome of apparent mineralocorticoid excess was tested by suppressing its secretion with dexamethasone. The subjects were two siblings with the type 2 form of this syndrome in which the defect in the peripheral metabolism of cortisol lies predominantly in ring A reduction but not in 11 beta-hydroxy dehydrogenation of cortisol to cortisone. Low dosage dexamethasone improved the hypokalemia within several days and hypertension was corrected after 3 weeks of treatment. Mineralocorticoid manifestations remained in remission during 10 yr of therapy with the synthetic glucocorticoid during which normal growth and development were restored. The effectiveness of dexamethasone supports the hypothesis that cortisol is the functioning mineralocorticoid in the AME syndrome.

Synthesis of a deuterium-labeled cortisol for the study of its rate of 11 beta-hydroxy dehydrogenation in man

11 beta-Hydroxy dehydrogenation of cortisol to cortisone is specifically impaired in the syndrome of apparent mineralocorticoid excess. This defect bears on the pathogenesis of the disorder by unmasking the potential mineralocorticoid agonism of unmetabolized cortisol at or near mineralocorticoid target tissues. A specific index of this defect is provided by measurement of the formation of tritiated water following the administration of [3H]11 alpha-cortisol. We have explored the use of a non-radioactive tracer to follow this unidirectional dehydrogenation reaction but because of the relatively lower sensitivity of measurement of 2H2O compared to 3H2O in body fluids, use of the corresponding [2H]11 alpha-cortisol was not feasible. We have devised instead a method incorporating additional deuterium atoms into cortisol to measure unidirectional 11 beta-hydroxy dehydrogenation not by the formation of labeled water but by the determination of the dehydrogenated cortisol product from its residual deuterium content. Cortisol-d4 metabolized to cortisone-d3 is conveniently measured by the techniques of organic mass spectrometry. The synthesis of cortisol-9 alpha, 11 alpha, 12 alpha 12 beta-d4 and the validation of its isotopic distribution by mass spectrometry and nuclear magnetic resonance is described.