Glucocorticoid-Remediable Aldosteronism

CME Review Article #18

CHIEF EDITOR’S NOTE: This article is the 18th of 36 that will be published in 2001 for which a total of up to 36 Category 1 CME credits can be earned. Instructions for how credits can be earned appear following the Table of Contents. Glucocorticoid-Remediable Aldosteronism

Robert G. Dluhy, M.D.*

Glucocorticoid-remediable aldosteronism (GRA) eralocorticoid-excess state. GRA is caused by a represents a rare, heriditary form of primary aldos- chimeric gene duplication that results from unequal teronism which is inherited in an autosomal domi- crossing over between the highly homologous 11- nant fashion. GRA is characterized by early onset hydroxylase (CYP11B1) and aldosterone synthase of moderate-to-severe hypertension and suppressed (CYP11B2) genes. The chimeric gene represents a plasma renin activity. The family history is often fusion of the 5'adrenocorticotropin-responsive reg- positive for a history of early hemorrhagic stroke. ulatory region of the 11-hydroxylase gene and the However, the clinical and biochemical features that 3' coding sequence of the aldosterone synthase deﬁne mineralcorticoid excess states, such as hy- gene. This results in ectopic expression of aldos- pokalemia, are not consistently present in GRA. terone synthase activity in the zona fasciculata, the Accordingly, recognition of this syndrome can be zone of the adrenal gland that normally secretes difﬁcult. In GRA, aldosterone secretion is solely cortisol. This mutation explains the physiology and regulated by adrenocorticotropin. As a result, the genetics of GRA and provides the basis for a simple administration of exogenous glucocorticoids will direct genetic test for this disorder. ■ suppress the hypothalamic-pituitary axis and suppress aldosterone levels, thereby relieving the min- The Endocrinologist 2001; 11: 263–268

Learning Objectives: suppressible hyperaldosteronism (more recently renamed • Identify the demographic, pathophysiologic, and glucocorticoid-remediable aldosteronism (GRA), or familial genetic features of glucocorticoid-remediable al- hyperaldosteronism type I). GRA was found to have an au- dosteronism (GRA), emphasizing those that dis- tosomal dominant pattern of inheritance, and earlier physi- tinguish it from other forms of aldosteronism. ologic studies revealed that plasma renin activity (PRA) was • Recall the phenotypic expression of GRA and the suppressed and aldosterone secretion was solely regulated by best way to diagnose it. adrenocorticotrophic hormone (ACTH). • Describe and contrast options for treating GRA.

Historical Background Prevalence n 1966, Sutherland and Laidlaw described a syn- GRA is considered a rare cause of primary aldostero- drome of hypertension, hyperaldosteronism, nism with an estimated incidence of 1% to 3% of cases. I and hypokalemia that was found in a family and However, the diagnosis of a new case of GRA can yield a ❦ was reversed by exogenous glucocorticoid ther- large number of affected individuals in a family if the pedi- apy [1]. The disorder was called dexamethasone- gree is expanded and at-risk individuals are tested. Cases of GRA have been reported worldwide. Many Professor of Medicine, Harvard Medical School, Associate Director, Endocrine Hypertension Division, Brigham and Women’s Hospital, Boston, Massachusetts. affected families in North America are of Celtic ancestry; Address correspondence to: Robert G. Dluhy, M.D., Brigham and Women’s no known cases are reported among blacks. Unlike other Hospital, 221 Longwood Avenue, Boston, MA 02115. etiologies of primary aldosteronism, which are usually diag- *The author has disclosed that he has no significant relationships with or financial nosed in the third to fifth decades of life, GRA is present interest in any commercial companies that pertain to this educational activity. from birth onward, occurring equally among males and fe-

263 Glucocorticoid-Remediable Aldosteronism males. Co-investigators at Harvard Medical School in Boston, Massachusetts and Yale University School of Med- icine in New Haven, Connecticut who published the ini- tial discovery of the mutation causing GRA (see below) have established an International Registry for GRA. Free genetic screening is provided (telephone number: 800–722-5520 ext. 28481 or www.partners.org/bwh/gra) and the clinical characteristics of affected pedigrees have been recorded in an effort to characterize the GRA phenotype (see below).

Pathophysiology Figure 1. Steroidogenesis in the normal adrenal cortex and in the glucocorticoid-remediable aldosteronism (GRA) adrenal. A. The biosyn- Aldosterone production in normal subjects is regu- thetic pathway of aldosterone in the normal zona glomerulosa. B. In the lated by the renin-angiotensin system and potassium. Thus, normal zona fasciculata cortisol is the normal end product; in the GRA adrenal cortisol is the further 18-oxygenated to the compounds, 18- aldosterone secretion is normally positively regulated by hydroxycortisol (18-OH-F) and 18-oxocortisol (18-OXO-F). These angiotensin II (Ang II) and by potassium balance, with compounds are a unique biochemical phenotype to diagnose GRA. (Re- high levels stimulating and low levels reducing aldosterone printed with permission: Rich GM, Ulick S, Cook S, et al.: Glucocorti- coid-remediable aldosteronism in a large kindred: clinical spectrum and secretion. In normal subjects, ACTH transiently stimulates diagnosis using a characteristic biochemical phenotype. Ann Intern Med aldosterone secretion but a continuous, prolonged ACTH 1992; 116: 813–20.) infusion (over 24–48 hours) leads to a return of aldosterone levels to baseline. In contrast, in GRA aldosterone secre- Clinical Phenotype tion is solely regulated by ACTH with GRA subjects show- Blood Pressure ing an exaggerated response to infused ACTH and a failure to exhibit the expected normal decline after continuous New index cases of GRA continue to be discovered, ACTH administration [2]. In GRA, the renin-angiotensin most commonly in hypertensive children. As a result, a pos- system is suppressed and there is an absence of the normal sible diagnosis of GRA should be considered in all hyper- potassium-induced increase in aldosterone secretion [3]. It tensive children, especially those with suppressed PRA. A is likely that this dysregulation of aldosterone secretion recent study of 20 children with GRA underscores the im- solely by a hormone (ACTH) that is not sensitive to portance of considering the diagnosis of GRA in the setting sodium balance results in this mineralocorticoid excess of severe hypertension [5]. Fifty percent (8 of 16) of the state. As a corollary of the sole regulation of aldosterone by GRA children in this study were classified as having severe ACTH in GRA, the administration of exogenous gluco- hypertension (99th centile for age and sex) (Fig. 2); the corticoids will suppress the hypothalamic-pituitary axis, presence of severe diastolic and systolic hypertension to- suppress aldosterone levels, reactivate suppressed PRA lev- gether particularly called for an evaluation for GRA. The els and reverse this mineralocorticoid excess state [1]. diagnosis of hypertension in childhood or adolescence is of- The adrenal cortex in GRA also produces large quan- ten delayed, which may reflect the failure of clinicians to ap- tities of novel 18-oxygenated cortisol compounds (18- preciate the normative blood pressure levels in these patient oxocortisol [18-OXO-F]; 18-hydroxycortisol [18-OH-F]) groups (blood pressure classification in children and adoles- [4] (Fig. 1). These so-called “hybrid” steroids share struc- cents requires reference to sex- and age-specific blood pres- tural features of both the cortisol-producing zona fascicu- sure centile nomograms) [6]. Thus the blood pressure levels lata and the aldosterone-producing zona glomerulosa (that in GRA-affected children are typically lower than values is, these compounds are both 17 and 18 oxidized). GRA is used to define hypertension in adults, but are usually higher easily distinguished from aldosterone-producing adenoma than age- or sex-matched controls. (APA), the only other condition in which there is over- Hypertension associated with GRA across all age production of 18-OXO-F and 18-OH-F, because the levels groups is often refractory to conventional antihyperten- of these compounds are 20 to 30 times higher than normal sive agents. In addition, the blood pressure in GRA- in GRA compared with only modest elevations in APA. It affected subjects within and between pedigrees is often is not clear whether 18-OXO-F and 18-OH-F possess highly variable; some affected individuals are normoten- sodium-retaining properties and contribute to the pheno- sive, whereas others have only mild hypertension. This typic variability of this mineralocorticoid excess state. variability in blood pressure levels in GRA may relate to

264 Volume 11, Number 4 Glucocorticoid-Remediable Aldosteronism

Hemorrhagic Stroke A retrospective review of 27 pedigrees with geneti- cally proven GRA has documented an increased prevalence of early cerebrovascular complications, primarily cerebral hemorrhage, which is associated with high mortality (61%) [8]. In this study, cerebrovascular complications were present in 48% of all GRA pedigrees and 18% of all GRA patients, and the mean age at the time of stroke was 32 years. As a result, a prominent history of early hemorrhagic stroke in a family is also a clue to the diagnosis of GRA. The underlying mechanism of these cerebral he- morrhages in many patients was documented to be secon- dary to intracranial aneurysm. This report recommended screening of asymptomatic GRA patients with magnetic resonance angiography, beginning at puberty and every 5 years thereafter (as in adult polycystic kidney disease where there is a similar frequency of aneurysm) [8].

Genotype GRA is inherited as an autosomal dominant trait that follows classic Mendelian genetics. Lifton et al. discovered the genetic basis of GRA in 1992 [9]. In a large pedigree, Figure 2. Blood pressure centiles for females (0–13 years) and blood pressure levels in GRA-positive hypertensive females (n 9). Centile GRA-affected subjects were shown to possess a chim- percentile for age, sex, and height; SBP systolic blood pressure; DBP eric gene duplication that resulted from unequal crossing diastolic blood pressure; yrs. years. over between the highly homologous 11-hydroxylase either other hereditary factors that regulate blood pressure (CYP11B1) and aldosterone synthase (CYP11B2) genes or variation in dietary sodium intake. Thus the family his- (Fig. 3). These genes are located in close proximity to each tory in GRA does not invariably reveal a history of severe other on chromosome 8 and share more than 90% base- hypertension in ﬁrst-degree relatives of affected subjects. pair homology. The chimeric gene represents a fusion of the 5’ adrenocorticotropin-responsive regulatory region of Potassium Levels 11 -hydroxylase gene (expressed normally in the cortisol- Although GRA is a mineralocorticoid excess state associated with hyperaldosteronism and suppressed PRA, normokalemia is the rule in affected individuals unless potassium-wasting diuretics, such as hydrochlorothiazide, are administered [7]. The mechanism(s) for the absence of hypokalemia in GRA is unknown, but there does not appear to be impairment in renal responsiveness to potassium loading or mineralocorticoid treatment [3]. Alternatively, the hyperaldosteronism in GRA is mild, with random aldosterone levels usually in the normal or high-normal range, albeit inappropriate for the suppressed levels of Figure 3. The chimeric gene duplication in GRA resulting from unequal PRA. There is also a distinct plasma aldosterone (PA) crossing over between the homologous aldosterone synthase and 11 -hydroxylase genes that are located in close proximity on chromosome 8. This diurnal variation in GRA, with low levels during the chimeric gene fuses the 5’ regulatory sequences of the 11-hydroxylase evening hours because of the sole regulation of aldosterone gene and the 3’ coding sequences of the aldosterone synthase gene (de- by ACTH. Both factors may contribute to a mild miner- picted as occurring in the intron between exons 3 and 4). (Reprinted with permission: Lifton RP, Dluhy RG, Powers M, et al.: A chimeric 11-hy- alocorticoid excess state in GRA with minimal/modest droxylase/aldosterone synthase gene causes glucocorticoid-remediable al- potassium-wasting compared with that seen in APA. dosteronism and human hypertension. Nature 1992; 355: 262–5.)

The Endocrinologist 265 Glucocorticoid-Remediable Aldosteronism producing zona fasciculata) and the 3’ coding sequences of gene expected to cause GRA (involving exons 4,5, and 6 the aldosterone synthase gene. The result of this gene du- from CYP11B2) have been found in a sample of low renin plication is ectopic expression of aldosterone synthase ac- hypertensive patients, patients with aldosteronism, and 90 tivity in the cortisol-producing zona fasciculata (Fig. 4). normotensive individuals [13]. As a result, aldosterone and the novel steroids 18-OH-F and 18-OXO-F are all produced ectopically in the zona fas- Diagnosing GRA ciculata under the regulation of ACTH from cortisol and steroid precursors. Importance of the Medical and Family Histories In 11 additional GRA pedigrees, all affected subjects Screening is obviously indicated for all at-risk indi- proved to have chimeric gene duplications [10]. In these viduals in diagnosed GRA pedigrees. Diagnosis of GRA subjects, a minimum of eight independent mutations with without knowledge of the presence of the syndrome in a five different sites of crossing over were identified, indicat- family member can be difficult, due to the variable GRA ing that these mutations arose independently and not from phenotype (see above). For example, affected subjects are a single ancestral mutation. Confirmation of the presence usually normokalemic and their blood pressures can range of such chimeric gene mutations has also been reported in from normotension to severe hypertension. Nevertheless, another study of four additional patients from unrelated the medical history is often the cornerstone for making the GRA pedigrees [11]. diagnosis of GRA. The diagnosis of GRA should strongly DNA sequence analyses of the duplicated genes from be considered in a patient with hypertension of early on- these unrelated pedigrees indicate that the sites of fusion are set, especially in children or an individual with a family variable, but in all cases are upstream of exon 5, suggesting history of juvenile hypertension in first-degree relatives. that encoded amino acids in exon 5 are essential for aldos- Many patients are refractory to conventional antihyper- terone synthase enzymatic function [10, 11]. Similarly, by tensive agents or have a tendency to become hypokalemic expression of various chimeric genes constructed in vitro, if potassium-wasting diuretics are administered. There of- Pascoe et al. have demonstrated that when these genes are ten is a prominent family history of early mortality or mor- fused after exon 5, aldosterone synthase enzymatic activity is bidity from hemorrhagic stroke [8]. undetectable [11]. Transfection studies with cDNA encod- ing hybrids between the highly homologous CYP11B1 (11- Biochemical Assessment hydroxylase) and CYP11B2 (aldosterone synthase) enzymes have also shown that two amino acid changes, Ser288Gly PRA will be suppressed in GRA patients unless aldos- and Val320Ala, are sufficient to convert CYP11B1 into an terone antagonists have been used as therapeutic agents. efficient aldosterone-producing enzyme [12]. These results Therefore, nonsuppressed PRA levels in the absence of suggest that a gene conversion involving exons 5 and 6, in such therapy strongly argues against a diagnosis of GRA. which these residues are encoded, could cause a novel form However, the presence of a suppressed PRA level is non- of GRA. However, to date no conversions of the CYP11B1 specific, with up to 20% of adult essential hypertensives having a PRA level 2 ng/mL/hour. GRA patients also have abnormal PA/PRA ratios (30). Aldosterone blood levels and urinary aldosterone excretion rates are usually normal or mildly elevated but this is abnormal in the setting of suppressed levels of PRA. Serum potassium is usually normal and accordingly hypokalemia lacks sensitivity as a screening test for GRA [7]. The diagnosis of GRA is supported by dexamethasone suppression testing (DST) (0.5 mg every 6 hours during 2 Figure 4. Left, normal adrenal gland. Aldosterone is produced in the zona glomerulosa under the regulation of angiotensin II and potassium; days). A fall in aldosterone to nearly undetectable levels af- the production of cortisol in the zona fasciculata is regulated by adreno- ter DST in GRA is expected and reflects the sole control of corticotropic hormone (ACTH). Aldosterone synthase activity is ex- aldosterone by ACTH in this disorder [1]. As a result, a pressed only in the zona glomerulosa. Right, GRA adrenal. Ectopic expression of aldosterone synthase activity in the zona fasciculata results post-DST PA below 4ng/dL will correctly diagnose GRA in production of aldosterone and the novel steroids 18-OH-F and 18- patients with high sensitivity and specificity [14]. Signifi- OXO-F under the regulation of ACTH. (Reprinted with permission: cant suppression of aldosterone levels after DST also occurs Lifton RP, Dluhy RG, Powers M, et al.: Hereditary hypertension caused by chimaeric gene duplications and ectopic expression of aldosterone in APA patients reflecting the well-recognized regulation synthase. Nat Genet 1993; 2: 66–74.) of aldosterone by ACTH in this disorder. However, au-

266 Volume 11, Number 4 Glucocorticoid-Remediable Aldosteronism tonomous production of aldosterone in APA accounts for equivalent dosing with a cortisol analogue). Target blood the failure of aldosterone levels to fall to very low or nearly pressure in children should be guided by age-specific blood undetectable levels. pressure percentiles (Fig. 2) [6]. Children should be followed by pediatricians with careful attention paid to linear growth A Unique Biochemical Phenotype to detect any diminution as a result of overtreatment. Urinary excretion of the 18-oxygenated cortisol com- Rarely glucocorticoid-treated patients have exhibited pounds 18-OH-F and 18-OXO-F are markedly elevated symptoms of hypoaldosteronism with salt wasting, hy- (up to 30 times normal levels) and provide a specific potension, and hyperkalemia soon after such treatment is means to diagnose GRA (see above) [4]. However, mea- instituted. Hypoaldosteronism occurs because ectopic al- surement of urinary 18-OH-F and 18-OXO-F is difficult dosterone production in the zona fasciculata falls to nearly and not usually available. undetectable levels while the zona glomerulosa is hypo- functional as a result of the prior suppression of the renin- Genetic Testing angiotensin system. Biochemical testing, such as DST and 24-hour urine Mineralocorticoid Antagonists collections, are often inconvenient and especially difficult Spironolactone, a competitive antagonist of the miner- to perform in pediatric patients. As a result genetic testing alocorticoid receptor that is usually the agent of first choice is preferred and is 100% sensitive and specific to diagnose in the medical treatment of the multiple etiologies of pri- GRA, requiring only a single blood collection for leuko- mary aldosteronism, is also effective in treating GRA pa- cyte DNA assessment. After DNA extraction, the hybrid tients. Adult GRA patients should be started at 50 mg twice or chimeric gene can be detected by the Southern blot ap- daily with meals, with subsequent upward titration as toler- proach (developed by Lifton et al. [9]) or more recently by ated until blood pressure is controlled. Potassium-wasting di- the long-polymerase-chain-reaction-based approach [15]. uretics (hydrochlorothiazide 12.5 to 25 mg or furosemide 40 The advantage of the “long-polymerase chain reaction” to 80 mg/day) may be added in an attempt to further achieve method is that it is considerably faster and cheaper than sodium depletion; close monitoring of serum potassium is Southern blotting. important if these diuretics are used. Because spironolactone binds to androgen receptors and also blocks testosterone Treatment biosynthesis, erectile dysfunction, decreased libido, and gy- necomastia are side effects in men. Menstrual irregularities The hypertension in GRA is often refractory to con- are seen in women because spironolactone also binds to pro- ventional antihypertensive therapy with most patients in- gesterone receptors. A promising new agent, epleronone, a adequately controlled by maximal doses of two or three selective inhibitor of the mineralocorticoid receptor that antihypertensive agents. Moreover, the gratifying reduc- does not bind to androgen or progesterone receptors, may ul- tion in blood pressure in response to directed monotherapy timately be the agent of choice to treat GRA patients. underscores the importance of diagnosing GRA [5]. Amiloride blocks the aldosterone-regulated epithelial sodium channel in the distal nephron and is an alternative Glucocorticoid Suppression to spironolactone treatment in GRA. Divided dosing Traditionally, suppression of adrenocorticotropin with should be used starting at 5 mg twice daily with a maximum dexamethasone has been used to treat the hypertension dose of 15 mg twice daily. Triamterene also inhibits sodium- associated with GRA [1]. First, suppression of the hypothal- potassium exchange in the distal nephron by blocking amic-pituitary-adrenal axis does not always result in nor- sodium conductance channels. Like amiloride, its effects are malization of blood pressure in GRA; this may relate to independent of aldosterone receptor blockade. A divided end-organ injury (e.g., renal nephrosclerosis), concomitant dosing regiment should be used with maximum doses of 300 essential hypertension or, rarely, autonomous production of mg/day. Adverse effects of this drug are uncommon but in- aldosterone in patients with longstanding GRA. A more clude rash, weakness, fatigue, and abnormalities of liver en- important issue is potential toxicity (Cushing syndrome) as- zymes. sociated with excessive glucocorticoid dosing, especially in children. When a decision to use glucocorticoids is made, Dihydropyridine Calcium Channel Blockers the smallest effective dose should be used; suppressive The dihydropyridine calcium channel blockers, such as steroid dosing should also be determined relative to body the extended-release formulation of nifedipine and amlodip- surface area (8 to 10 mg of hydrocortisone/ m2/day, or bio- ine, have been advocated in the medical management of pri-

The Endocrinologist 267 Glucocorticoid-Remediable Aldosteronism mary aldosteronism because this class of medication has been corticoid-remediable aldosteronism (GRA) is associated with se- shown to inhibit aldosterone biosynthesis in vitro. However, vere hypertension in early childhood. J Pediatr 2001; 138: 715–20. 6. Lieberman E: Pediatric hypertension: clinical perspective. Mayo the aldosterone reduction in response to these agents in vivo Clin Proc 1994; 69: 1098–107. in various etiologies of primary aldosteronism has generally 7. Rich GM, Ulick S, Cook S, Wang JZ, Lifton RP, Dluhy RG: Glu- been disappointing. The antihypertensive response to di- cocorticoid-remediable aldosteronism in a large kindred: clinical spectrum and diagnosis using a characteristic biochemical pheno- hydropyridine calcium channel blockers, however, can be type. Ann Intern Med 1992; 116: 813–20. gratifying in many patients with primary aldosteronism, in- 8. Litchfield WR, Anderson BF, Weiss RJ, Lifton RP, Dluhy RG: In- cluding GRA (R.G.D., unpublished data). However, these tracranial aneurysm and hemorrhagic stroke in glucocorticoid-remediable aldosteronism. Hypertension 1998; 31: 445–50. medications should be viewed as second-line agents. 9. Lifton RP, Dluhy RG, Powers M, et al.: A chimeric 11 beta-hy- A sodium-restricted diet (2g/day) is also recom- droxylase/aldosterone synthase gene causes glucocorticoid-remedi- mended in conjunction with pharmacologic treatment be- able aldosteronism and human hypertension. Nature 1992; 355: cause it will minimize potassium wasting and may lower 262–5. 10. Lifton RP, Dluhy RG, Powers M, et al.: Hereditary hypertension blood pressure. To date, no randomized studies have been caused by chimeric gene duplications and ectopic expression of al- performed that compare various treatment regimens in dosterone synthase. Nat Genet 1993; 2: 66–74. GRA. 11. Pascoe L, Curnow KM, Slutsker L, et al.: Glucocorticoid-suppressible hyperaldosteronism results from hybrid genes created by unequal crossovers between CYP11B1 and CYP11B2. Proc Natl Acad References Sci U S A 1992; 89: 8327–31. 12. Curnow KM, Mulatero P, Emeric-Blanchouin N, Aupetit-Faisant 1. Sutherland DJ, Ruse JL, Laidlaw JC: Hypertension, increase aldos- B, Corvol P, Pascoe L: The amino acid substitutions Ser288Gly and terone secretion and low plasma renin activity relieved by dexam- Val320Ala convert the cortisol producing enzyme, CYP11B1, into ethasone. Can Med Assoc J 1996; 95: 1109–19. an aldosterone producing enzyme. Nat Struct Biol 1997; 4: 32–5. 2. Ganguly A, Weinberger MH, Guthrie GP, Fineberg NS: Adrenal 13. Mulatero P, Curnow KM, Aupetit-Faisant B, et al.: Recombinant steroid responses to ACTH in glucocorticoid-suppressible aldostero- CYP11B genes encode enzymes that can catalyze conversion of 11- nism. Hypertension 1984; 6: 563–7. deoxycortisol to cortisol, 18-Hydroxycortisol, and 18-Oxocortisol. 3. Litchfield WR, Coolidge C, Silva P, et al.: Impaired potassium- J Clin Endocrinol Metab 1998; 83: 3996–4001. stimulated aldosterone production: a possible explanation for nor- 14. Litchfield WR, New MI, Coolidge C, Lifton RP, Dluhy RG: Evalu- mokalemic glucocorticoid-remediable aldosteronism. J Clin Endo- ation of the dexamethasone suppression test for the diagnosis of glu- crinol Metab 1997; 82: 1507–10. cocorticoid-remediable aldosteronism. J Clin Endocrinol Metab 4. Gomez-Sanchez CE, Montgomery M, Ganguly A, et al.: Elevated 1997; 82: 3570–3. urinary excretion of 18-oxo-cortisol in gluccocorticoid-remediable 15. Stowasser M, Gartside MG, Gordon RD: A PCR-based method of aldosteronism. J Clin Endocrinol Metab 1984; 59: 1022–4. screening individuals of all ages, from neonates to the elderly, for fa- 5. Dluhy RG, Anderson BF, Harlin B, Ingelfinger J, Lifton RP: Gluco- milial hyperaldosteronism type I. Aust N Z J Med 1997; 27: 685–90.

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