- Author: Gabriel I Uwaifo, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP more...
Although initially considered a rarity, primary aldosteronism now is considered one of the more common causes of secondary hypertension (HTN). Litynski reported the first cases, but Conn was the first to well characterize the disorder, in 1956. Conn syndrome, as originally described, refers specifically to primary aldosteronism due to the presence of an adrenal aldosteronoma (aldosterone-secreting benign adrenal neoplasm). (See Etiology.)
Based on older data, it was originally estimated that primary aldosteronism accounted for less than 1% of all patients with HTN. Subsequent data, however, indicated that it may actually occur in as many as 5-15% of patients with HTN. Primary aldosteronism may occur in an even greater percentage of patients with treatment-resistant HTN and may be considerably underdiagnosed; this is especially true if patients with treatment-refractory HTN are not specifically referred for evaluation to an endocrinologist. (See Epidemiology.)
Although primary aldosteronism is still a considerable diagnostic challenge, recognizing the condition is critical because primary aldosteronism–associated HTN can often be cured (or at least optimally controlled) with the proper surgical or medical intervention. The diagnosis is generally 3-tiered, involving an initial screening, a confirmation of the diagnosis, and a determination of the specific subtype of primary aldosteronism. (See Presentation, Workup, Treatment, and Medication.)
Although prior studies suggested that aldosteronomas were the most common cause of primary aldosteronism (70-80% of cases), later epidemiologic work indicated that the prevalence of aldosteronism due to bilateral idiopathic adrenal hyperplasia (IAH; sometimes also abbreviated as BAH) is higher than had previously been believed. These reports suggested that IAH may be responsible for as many as 75% of primary aldosteronism cases. Moreover, reports have described a rare syndrome of primary aldosteronism characterized by histologic features intermediate between adrenal adenoma and adrenal hyperplasia, which often is unilaterally localized (also referred to earlier literature as “intermediate aldosteronism”) (see Etiology). (See the images below.)
Clinically, the distinction between the 2 major causes of primary aldosteronism is vital because the treatment of choice for each is markedly different. While the treatment of choice for aldosteronomas is surgical extirpation, the treatment of choice for IAH is medical therapy with aldosterone antagonists. (See Treatment and Medication.)
Entities known to cause aldosteronism include the following (see the image below):
Aldosterone-producing adenomas (APAs) 
Aldosterone-producing renin-responsive adenomas (AP-RAs; also abbreviated as RRAs)
Bilateral idiopathic adrenal (glomerulosa) hyperplasia or IAH (also known as primary adrenal hyperplasia or PAH)
Familial forms of primary aldosteronism
Ectopic secretion of aldosterone (The ovaries and kidneys are the 2 organs described in the literature that in the setting of neoplastic disease, can be ectopic sources of aldosterone, but this is a rare occurrence.)
Pure aldosterone-producing adrenocortical carcinomas (very rare; physiologically behave as APAs)
Aldosterone, by inducing renal reabsorption of sodium at the distal convoluted tubule (DCT), enhances secretion of potassium and hydrogen ions, causing hypernatremia, hypokalemia, and alkalosis. (See Prognosis, Workup, and Treatment.)
Genetic-familial primary aldosteronism
Three distinct genetic-familial varieties of primary aldosteronism exist. Sutherland and colleagues first described the type 1 variety of familial primary aldosteronism, glucocorticoid-remediable aldosteronism (GRA), in 1966. In GRA, HTN responds clinically to small doses of glucocorticoids in addition to other antihypertensive agents. The type 1 form of familial primary aldosteronism is due to an aberrantly formed chimeric gene product that combines the glucocorticoid-responsive (inhibitable) promoter of the 11beta-hydroxylase gene (CYP11B1) with the coding region of the aldosterone synthetase gene (CYP11B2). Under ambient glucocorticoid levels, the promoter is not fully transcriptionally silenced, and this leads to overexpression of aldosterone synthetase, with subsequent increased synthesis and secretion of aldosterone. (See Etiology and Workup.)
The type 2 variant of familial primary aldosteronism (which is not glucocorticoid sensitive) was first described in 1991. Although the exact genetic abnormality for type 2 primary aldosteronism has not been identified, data suggest that the locus for this disease is on band 7p22.
The type 3 variant of familial primary aldosteronism is due to KCNJ5 (potassium inwardly rectifying channel, subfamily J, member 5) potassium channel mutations. This type was described by Lifton’s group in 2011.
The most important factors that predict the pathophysiologic association of hypokalemia with primary aldosteronism are (1) aldosterone hypersecretion, which acts on the cortical collecting duct to stimulate potassium secretion into the tubular fluid, thus enhancing renal/urinary potassium wasting ; (2) adequate intravascular volume, which enables adequate water delivery (tubular flow rate) to the renal distal convoluted tubules (DCTs) and collecting ducts to enable renal potassium loss; and (3) adequate dietary sodium intake, which, in turn, increases total body potassium, renal/ tubular sodium delivery, and, thus, enhances renal potassium loss via the countercurrent transport system.
The absence of 1 or more of the physiologic circumstances described above may explain the absence of frank hypokalemia in many patients with proven primary aldosteronism.
The associated metabolic alkalosis in primary aldosteronism is due to increased renal hydrogen ion loss mediated by hypokalemia and aldosterone.
Almost 20% of patients with primary aldosteronism have impaired glucose tolerance resulting from the inhibitory effect of hypokalemia on insulin action and secretion; however, diabetes mellitus is no more common than in the general population.
The cardinal anomaly causing primary aldosteronism syndrome is autonomous (nonsuppressible) aldosterone production. In addition to nonsuppressible aldosterone production, suppressed and poorly stimulative levels of plasma renin are coexisting with only mildly expanded intravascular and extravascular fluid volume. Normal regulation of aldosterone secretion is mediated to varying degrees by renin, serum potassium and sodium levels, intravascular volume status, and corticotropin.
Regulation of aldosterone production by these factors may be altered in various ways, depending on the subtype of primary aldosteronism. Generally, aldosterone-producing adenomas (APAs) and GRA remain corticotropin responsive, while idiopathic adrenal hyperplasia (IAH) and aldosterone-producing renin-responsive adenomas (RRAs) maintain responsiveness to the renin-angiotensin system (RAS).
In glucocorticoid-remediable aldosteronism (GRA), the RAS is suppressed, and aldosterone is regulated by corticotropin because of the chimeric gene fusion of a corticotropin-sensitive promoter with the coding regions of the aldosterone synthetase gene (which normally does not have such a promoter). Thus, ambient corticotropin levels pathologically overstimulate aldosterone synthesis inappropriately.
In patients with GRA, the administration of dexamethasone (or any other glucocorticoid) at doses sufficient to suppress excessive corticotropin production results in a reduction in aldosterone synthesis and natriuresis and the eventual correction of the biochemical anomalies of primary aldosteronism. Histologic studies in this disease have shown specific hyperplasia of the zona fasciculata, with concomitant atrophy of the zona glomerulosa.
The exact cause of sporadic primary aldosteronism due to an adenoma or hyperplasia is unclear. The existence of trophic factors (eg, endothelins, cytokines) has been postulated in cases of hyperplasia. Somatic mutations of genes leading to growth advantage in the adrenal adenomatous tissue are a possible, but unproven, cause.
In familial forms of primary aldosteronism, the molecular basis of GRA is known. GRA is due to a mutation that results from a hybrid gene product. The 11beta-hydroxylase and aldosterone synthetase genes that are normally located close to each other on chromosome 8 cross over to create a novel hybrid gene product. This hybrid gene consists of the regulatory corticotropin-responsive sequence of the 11beta-hydroxylase gene (CYP11B1) fused to the structural component of the aldosterone synthetase gene (CYP11B2).
Most sporadic aldosteronomas arise from the zona fasciculata, and they often have surrounding glandular hyperplasia close to the adenoma. This suggests that a proliferative response of cells to some presently unidentified paracrine/autocrine factor occurs. Within this zone of hyperplasia, a clonal change in a single cell is believed to take place, thus providing the nidus for the developing adenoma.
The genetic basis of type 2 familial aldosteronism is unclear; however, the locus for this disease has been mapped on 7p22 (band 11q13). This syndrome can histologically manifest as hyperplasia or adenomas.
The genetic basis for type 3 familial aldosteronism has recently been deciphered. Mutations in the KCNJ5 potassium channel-coding gene results in loss of ion selectivity, cell membrane depolarization, increased Ca2+ entry in adrenal glomerulosa cells, and increased aldosterone synthesis.
The existence of tertiary aldosteronism as a separate entity remains controversial. The entity is presumed to result from chronic elevations in plasma renin levels and secondary aldosteronism, which eventually establishes a state of autonomous, unregulated aldosteronism with a histologic picture of mixed hyperplasia and adenomas in the affected adrenocortical tissue. This clinicopathologic picture is considered to be the irreversible end-result of prolonged neurohumoral effects on vascular resistance and “terminal” hypertrophy of the aldosterone-producing adrenocortical tissue.
Few well-described cases exist, but in most, the adrenal glands are hyperplastic, often with nodular hyperplasia (which can cause diagnostic confusion). Virtually all of the cases described are in the setting of renal artery stenosis, which complicates further the attribution of the hypertensive state to chronic “inappropriate” aldosterone excess.
Initially, renin levels are elevated, which is typical of secondary aldosteronism. When the tertiary (autonomous) phase develops, the biochemical profile changes to a low-renin/high-aldosterone state. The paradigm is analogous to the pathogenesis of tertiary hyperparathyroidism.
Occurrence in the United States
The exact prevalence of primary aldosteronism is unclear, but estimates suggest that 5-15% of essential hypertension (HTN) cases may be due to primary aldosteronism. The prevalence of primary aldosteronism is probably higher in patients who have a low serum potassium level, in patients who are elderly, and in patients who have HTN that is resistant to single medication use.
No evidence demonstrates that primary aldosteronism, in its more common forms, occurs in relative excess in any part of the world.
Race-, sex-, and age-related demographics
Primary aldosteronism occurs worldwide. Several reports suggest a higher prevalence in African Americans, persons of African origin, and, potentially, other blacks. This appears to be particularly true of the idiopathic adrenal hyperplasia (IAH) variant of the disease.
Aldosterone-producing adenomas (APAs) are more common in women than in men, with a female-to-male ratio of 2:1. The typical patient with an APA is a woman aged 30-50 years.
Accumulating data for IAH suggest different demographics for this condition, with the idiopathic disease being 4 times more prevalent in men than in women and peaking in the sixth decade of life.
The morbidity and mortality associated with primary aldosteronism, especially Conn syndrome, are primarily related to hypokalemia and hypertension (HTN).[9, 10] Hypokalemia, especially if severe, causes cardiac arrhythmias, which can be fatal.
Complications from chronic HTN include myocardial infarction, cerebrovascular disease, and congestive heart failure. Treatment can also lead to complications, such as drug reactions and complications from surgery.
Evidence exists to show that chronic aldosteronism in and of itself, in the absence of elevated blood pressure (eg, as occurs in secondary aldosteronism), is also associated with increased risk for cardiac injury, including ischemic, hypertrophic, and fibrotic injury. Furthermore, studies have shown that patients with primary aldosteronism are more likely to have or develop left ventricular hypertrophy, stroke, and acute coronary syndromes than are patients with similar degrees of HTN from other causes. Of course, patients with HTN due to primary aldosteronism are also at risk of developing the entire spectrum of complications of chronic HTN, including hypertensive nephropathy and retinopathy.
Rossi GP, Ragazzo F, Seccia TM, Maniero C, Barisa M, Calò LA, et al. Hyperparathyroidism can be useful in the identification of primary aldosteronism due to aldosterone-producing adenoma. Hypertension. 2012 Aug. 60(2):431-6. [Medline].
Dluhy RG, Lifton RP. Glucocorticoid-remediable aldosteronism. Endocrinol Metab Clin North Am. 1994 Jun. 23(2):285-97. [Medline].
Funder JW. The genetic basis of primary aldosteronism. Curr Hypertens Rep. 2012 Apr. 14(2):120-4. [Medline].
Young DB. Quantitative analysis of aldosterone's role in potassium regulation. Am J Physiol. 1988 Nov. 255(5 Pt 2):F811-22. [Medline].
Stowasser M, Klemm SA, Tunny TJ, et al. Plasma aldosterone response to ACTH in subtypes of primary aldosteronism. Clin Exp Pharmacol Physiol. 1995 Jun-Jul. 22(6-7):460-2. [Medline].
Litchfield WR, New MI, Coolidge C, et al. Evaluation of the dexamethasone suppression test for the diagnosis of glucocorticoid-remediable aldosteronism. J Clin Endocrinol Metab. 1997 Nov. 82(11):3570-3. [Medline]. [Full Text].
Mulatero P, Stowasser M, Loh KC, Fardella CE, Gordon RD, Mosso L, et al. Increased diagnosis of primary aldosteronism, including surgically correctable forms, in centers from five continents. J Clin Endocrinol Metab. 2004 Mar. 89(3):1045-50. [Medline].
Born-Frontsberg E, Reincke M, Rump LC, et al. Cardiovascular and cerebrovascular comorbidities of hypokalemic and normokalemic primary aldosteronism: results of the German Conn's Registry. J Clin Endocrinol Metab. 2009 Apr. 94(4):1125-30. [Medline].
Bernini G, Galetta F, Franzoni F, Bardini M, Taurino C, Bernardini M, et al. Arterial stiffness, intima-media thickness and carotid artery fibrosis in patients with primary aldosteronism. J Hypertens. 2008 Dec. 26(12):2399-405. [Medline].
Apostolopoulou K, Künzel HE, Gerum S, Merkle K, Schulz S, Fischer E, et al. Gender differences in anxiety and depressive symptoms in patients with primary hyperaldosteronism: A cross-sectional study. World J Biol Psychiatry. 2012 May 8. [Medline].
Cruz DN, Perazella MA. Hypertension and hypokalemia: unusual syndromes. Conn Med. 1997 Feb. 61(2):67-75. [Medline].
Cesari M, Letizia C, Angeli P, Sciomer S, Rosi S, Rossi GP. Cardiac Remodeling in Patients With Primary and Secondary Aldosteronism: A Tissue Doppler Study. Circ Cardiovasc Imaging. 2016 Jun. 9 (6):[Medline].
Hall JE, Granger JP, Smith MJ Jr. Role of renal hemodynamics and arterial pressure in aldosterone "escape". Hypertension. 1984. 6:1183.
Yokota N, Bruneau BG, Kuroski de Bold ML, et al. Atrial natriuretic factor significantly contributes to the mineralocorticoid escape phenomenon. Evidence for a guanylate cyclase-mediated pathway. J Clin Invest. 1994 Nov. 94(5):1938-46. [Medline]. [Full Text].
Schiffrin EL, Chrétien M, Seidah NG, et al. Response of human aldosteronoma cells in culture to the N-terminal glycopeptide of pro-opiomelanocortin and gamma 3-MSH. Horm Metab Res. 1983 Apr. 15(4):181-4. [Medline].
[Guideline] Funder JW, Carey RM, Fardella C, Gomez-Sanchez CE, Mantero F, Stowasser M, et al. Case detection, diagnosis, and treatment of patients with primary aldosteronism: an endocrine society clinical practice guideline. J Clin Endocrinol Metab. 2008 Sep. 93(9):3266-81. [Medline].
Quamme GA. Control of magnesium transport in the thick ascending limb. Am J Physiol. 1989 Feb. 256(2 Pt 2):F197-210. [Medline].
Seiler L, Rump LC, Schulte-Mönting J, Slawik M, Borm K, Pavenstädt H, et al. Diagnosis of primary aldosteronism: value of different screening parameters and influence of antihypertensive medication. Eur J Endocrinol. 2004 Mar. 150(3):329-37. [Medline].
Tzanela M, Effremidis G, Vassiliadi D, et al. The aldosterone to renin ratio in the evaluation of patients with incidentally detected adrenal masses. Endocrine. 2007 Oct. 32(2):136-42. [Medline].
Diederich S, Mai K, Bahr V, et al. The simultaneous measurement of plasma-aldosterone- and -renin-concentration allows rapid classification of all disorders of the renin-aldosterone system. Exp Clin Endocrinol Diabetes. 2007 Jul. 115(7):433-8. [Medline].
Wu VC, Chang HW, Liu KL, et al. Primary aldosteronism: diagnostic accuracy of the losartan and captopril tests. Am J Hypertens. 2009 Aug. 22(8):821-7. [Medline].
Burton TJ, Mackenzie IS, Balan K, Koo B, Bird N, Soloviev DV, et al. Evaluation of the sensitivity and specificity of (11)C-metomidate positron emission tomography (PET)-CT for lateralizing aldosterone secretion by Conn's adenomas. J Clin Endocrinol Metab. 2012 Jan. 97(1):100-9. [Medline].
Otsuka F, Otsuka-Misunaga F, Koyama S, et al. Hormonal characteristics of primary aldosteronism due to unilateral adrenal hyperplasia. J Endocrinol Invest. 1998 Sep. 21(8):531-6. [Medline].
Stowasser M, Bachmann AW, Tunny TJ. Production of 18-oxo-cortisol in subtypes of primary aldosteronism. Clin Exp Pharmacol Physiol. 1996 Jun-Jul. 23(6-7):591-3. [Medline].
Hamlet SM, Gordon RD, Gomez-Sanchez CE, et al. Adrenal transitional zone steroids, 18-oxo and 18-hydroxycortisol, useful in the diagnosis of primary aldosteronism, are ACTH-dependent. Clin Exp Pharmacol Physiol. 1988 Apr. 15(4):317-22. [Medline].
McAlister FA, Lewanczuk RZ. Primary hyperaldosteronism and adrenal incidentaloma: an argument for physiologic testing before adrenalectomy. Can J Surg. 1998 Aug. 41(4):299-305. [Medline].
Georgiades CS, Hong K, Geschwind JF, et al. Adjunctive use of C-arm CT may eliminate technical failure in adrenal vein sampling. J Vasc Interv Radiol. 2007 Sep. 18(9):1102-5. [Medline].
Young WF, Stanson AW, Grant CS, et al. Primary aldosteronism: adrenal venous sampling. Surgery. 1996 Dec. 120(6):913-9; discussion 919-20. [Medline].
Webb R, Mathur A, Chang R, Baid S, Nilubol N, Libutti SK, et al. What is the Best Criterion for the Interpretation of Adrenal Vein Sample Results in Patients with Primary Hyperaldosteronism?. Ann Surg Oncol. 2011 Nov 3. [Medline].
Young WF, Stanson AW, Thompson GB, et al. Role for adrenal venous sampling in primary aldosteronism. Surgery. 2004 Dec. 136(6):1227-35. [Medline].
Naruse M, Naruse K, Yoshimoto T, et al. Dopaminergic regulation of aldosterone secretion: its pathophysiologic significance in subsets of primary aldosteronism. Hypertens Res. 1995 Jun. 18 Suppl 1:S59-64. [Medline].
Carey RM. Primary aldosteronism. Horm Res. 2009 Jan. 71 Suppl 1:8-12. [Medline].
Hood SJ, Taylor KP, Ashby MJ, et al. The spironolactone, amiloride, losartan, and thiazide (SALT) double-blind crossover trial in patients with low-renin hypertension and elevated aldosterone-renin ratio. Circulation. 2007 Jul 17. 116(3):268-75. [Medline]. [Full Text].
Ronconi V, Turchi F, Appolloni G, di Tizio V, Boscaro M, Giacchetti G. Aldosterone, Mineralocorticoid Receptor and the Metabolic Syndrome: Role of the Mineralocorticoid Receptor Antagonists. Curr Vasc Pharmacol. 2011 Oct 21. [Medline].
Minowada S, Fujimura T, Takahashi N, et al. Computed tomography-guided percutaneous acetic acid injection therapy for functioning adrenocortical adenoma. J Clin Endocrinol Metab. 2003 Dec. 88(12):5814-7. [Medline]. [Full Text].
Sukor N, Gordon RD, Ku YK, et al. Role of unilateral adrenalectomy in bilateral primary aldosteronism: a 22-year single center experience. J Clin Endocrinol Metab. 2009 Jul. 94(7):2437-45. [Medline].
Celen O, O'Brien MJ, Melby JC, et al. Factors influencing outcome of surgery for primary aldosteronism. Arch Surg. 1996 Jun. 131(6):646-50. [Medline].
Waldmann J, Maurer L, Holler J, Kann PH, Ramaswamy A, Bartsch DK, et al. Outcome of surgery for primary hyperaldosteronism. World J Surg. 2011 Nov. 35(11):2422-7. [Medline].
Letavernier E, Peyrard S, Amar L, et al. Blood pressure outcome of adrenalectomy in patients with primary hyperaldosteronism with or without unilateral adenoma. J Hypertens. 2008 Sep. 26(9):1816-23. [Medline].
Milsom SR, Espiner EA, Nicholls MG, et al. The blood pressure response to unilateral adrenalectomy in primary aldosteronism. Q J Med. 1986 Dec. 61(236):1141-51. [Medline].
Giacchetti G, Turchi F, Boscaro M, Ronconi V. Management of primary aldosteronism: its complications and their outcomes after treatment. Curr Vasc Pharmacol. 2009 Apr. 7(2):244-49. [Medline].
Baguet JP, Steichen O, Mounier-Vehier C, Gosse P. SFE/SFHTA/AFCE consensus on primary aldosteronism, part 1: Epidemiology of PA, who should be screened for sporadic PA?. Ann Endocrinol (Paris). 2016 Apr 15. 86 (20):1002-8. [Medline]. [Full Text].
Steichen O, Amar L, Chaffanjon P, Kraimps JL, Menegaux F, Zinzindohoue F. SFE/SFHTA/AFCE consensus on primary aldosteronism, part 6: Adrenal surgery. Ann Endocrinol (Paris). 2016 Jun 10. [Medline]. [Full Text].
Pechère-Bertschi A, Herpin D, Lefebvre H. SFE/SFHTA/AFCE consensus on primary aldosteronism, part 7: Medical treatment of primary aldosteronism. Ann Endocrinol (Paris). 2016 Jun 14. [Medline]. [Full Text].