Roles of clinical criteria, computed tomography scan, and adrenal vein sampling in differential diagnosis of primary aldosteronism subtypes

Diagnosis and treatment of primary aldosteronism

A few simple rules can allow physicians to successfully identify many patients with arterial hypertension caused by PA among the so-called essential hypertensive patients. The hyperaldosteronism and the hypokalemia can be cured with adrenalectomy in practically all of these patients. Moreover, in a substantial proportion of them, the blood pressure can be normalized or markedly lowered if a unilateral cause of PA is discovered. Hence, the screening for PA can be rewarding both for the patient and for the clinician, particularly in those cases where hypertension is severe and/or resistant to treatment, in which the removal of an APA can allow blood pressure to be brought under control despite withdrawal of, or a prominent reduction in, the number and doses of antihypertensive medications.

A comprehensive review of the clinical aspects of primary aldosteronism

Primary aldosteronism is much more common than previously thought. The high prevalence of primary aldosteronism, the damage this condition does to the heart, blood vessels and kidneys (which causes a high rate of cardiovascular events), along with the notion that a timely diagnosis followed by an appropriate therapy can correct the arterial hypertension and hypokalemia, justify efforts to search for primary aldosteronism in many patients with hypertension. Most centers can use a cost-effective strategy to screen for patients with primary aldosteronism. By contrast, the identification of primary aldosteronism subtypes, which involves adrenal-vein sampling, should only be undertaken at tertiary referral centers that have experience in performing and interpreting this test. The identification of a curable form of primary aldosteronism can be beneficial for the patient. In some subgroups of patients with hypertension who are at high risk of primary aldosteronism or can benefit most from an accurate diagnosis, an aggressive diagnostic approach is necessary.

Diagnosis and treatment of primary aldosteronism

Primary aldosteronism is the most common form of secondary hypertension. The detection of primary aldosteronism is of particular importance, not only because it provides an opportunity for a targeted treatment (surgical for APA and medical with mineralocorticoid receptor antagonists for BAH), but also because it has been extensively demonstrated that patients affected by PA are more prone to cardiovascular events and target organ damage than essential hypertensives. According to the Endocrine Society Guidelines diagnosis of PA is made following a rigorous flow-chart comprising screening, confirmation/exclusion testing and subtype diagnosis. In the present review we describe briefly the published diagnostic strategies of the Guidelines, highlighting new evidence that has become recently available and discuss issues that still need to be addressed by future research.

Evaluation of primary aldosteronism

PURPOSE OF REVIEW

The purpose of this review is to briefly summarize current knowledge on diagnosis and treatment of primary aldosteronism, the most frequent cause of endocrine hypertension.

RECENT FINDINGS

The prevalence of primary aldosteronism increases with the severity of hypertension, from 2% in patients with grade 1 hypertension to 20% among resistant hypertensives. The detection of primary aldosteronism is of particular importance, not only because it provides an opportunity for a targeted treatment but also because it has been extensively demonstrated that patients affected by primary aldosteronism are more prone to cardiovascular events and target organ damage than patients with essential hypertension. The diagnosis of primary aldosteronism is a three-step process; screening, confirmation and subtype diagnosis.

SUMMARY

We review, the strategies to correctly identify primary aldosteronism, highlighting the central role of the new guidelines and the diagnostic aspects still under debate.

Aldosterone-producing adenoma and other surgically correctable forms of primary aldosteronism

Surgically correctable forms of primary aldosteronism are characterized by unilateral aldosterone hypersecretion and renin suppression, associated with varying degrees of hypertension and hypokalemia. Unilateral aldosterone hypersecretion is caused by an aldosterone-producing adenoma (also known as Conn's adenoma and aldosteronoma), primary unilateral adrenal hyperplasia and rare cases of aldosterone-producing adrenocortical carcinoma. In these forms, unilateral adrenalectomy can cure aldosterone excess and hypokalemia, but not necessarily hypertension. The prevalence of primary aldosteronism in the general population is not known. Its prevalence in referred hypertensive populations is estimated to be between 6 and 13%, of which 1.5 to 5% have an aldosterone-producing adenoma or primary unilateral adrenal hyperplasia. Taking into account referral biases, the prevalence of surgically correctable primary aldosteronism is probably less than 1.5% in the hypertensive population and less than 0.3% in the general adult population. Surgically correctable primary aldosteronism is sought in patients with hypokalemic, severe or resistant forms of hypertension. Recent recommendations suggest screening for primary aldosteronism using the aldosterone to renin ratio. Patients with a raised ratio then undergo confirmatory suppression tests. The differential diagnosis of hypokalemic hypertension with low renin includes mineralocorticoid excess, with the mineralocorticoid being cortisol or 11-deoxycorticosterone, apparent mineralocorticoid excess, pseudo-hypermineralocorticoidism in Liddle syndrome or exposure to glycyrrhizic acid. Once the diagnosis is confirmed, adrenal computed tomography is performed for all patients. If surgery is considered, taking into consideration the clinical context and the desire of the patient, adrenal vein sampling is performed to detect whether or not aldosterone hypersecretion is unilateral. Laparoscopic surgery for unilateral aldosterone hypersecretion is associated with a morbidity of about 8%, with most complications being minor. It generally results in the normalization of aldosterone secretion and kalemia, and in a large decrease in blood pressure, but normotension without treatment is only achieved in half of all cases. Normotension following adrenalectomy is more frequent in young patients with recent hypertension than in patients with long-standing hypertension or a family history of hypertension.

Adipokines and cardiometabolic profile in primary hyperaldosteronism

CONTEXT

Primary aldosteronism (PA) has been recently associated with an unfavorable cardiometabolic profile. However, whether pro- and antiinflammatory adipokines levels can vary in PA is unknown.

OBJECTIVE

We evaluated the circulating levels of resistin, leptin, and adiponectin, echocardiographic left ventricle (LV) parameters, and the prevalence of metabolic syndrome (SM) in subjects with PA.

PATIENTS

Seventy-five subjects with established diagnosis of PA and 232 consecutive individuals with known or suspected hypertension were enrolled.

MAIN OUTCOME MEASURES

Plasma adipokine levels and echocardiographic parameters were calculated. Prevalence of SM was also estimated.

RESULTS

Among the 75 PA subjects, 37 patients were affected by aldosterone-producing adenoma and 38 by idiopathic hyperaldosteronism; 40 subjects were affected by essential hypertension (EH) and SM (EH SM+); 152 subjects were affected by EH without SM (EH SM-); and 40 subjects were normotensive (NT). Subjects with PA had the highest plasma resistin levels among the four groups (P < 0.01). Plasma resistin concentration was significantly higher in PA subjects when compared with EH SM+ individuals (P < 0.01) and EH SM- subjects (P < 0.01). PA subjects showed the higher LV mass and left atrium than EH individuals, irrespectively of the presence of SM (P < 0.01 for both). Plasma resistin levels was significantly correlated with ejection fraction and LV end-diastolic volume. The prevalence of SM was higher in PA subjects than in those with EH (25.4 vs. 20.3%).

CONCLUSIONS

Our data suggest that elevated aldosterone levels is associated with elevated circulating resistin levels and cardiac morphological changes independently of the presence of SM.

PET and PET/CT in endocrine tumours

Functional information provided by PET tracers together with the superior image quality and the better data quantification by PET technology had a changing effect on the significance of nuclear medicine in medical issues. Recently introduced hybrid PET/CT systems together with the introduction of novel PET radiopharmaceuticals have contributed to the fact that nuclear medicine has become a growing diagnostic impact on endocrinology. In this review imaging strategies, different radiopharmaceuticals including the basic mechanism of their cell uptake, and the diagnostic value of PET and PET/CT in endocrine tumours except differentiated thyroid carcinomas will be discussed.

Adrenal venous sampling in primary aldosteronism: a low dilution of adrenal venous blood is crucial for a correct interpretation of the results

OBJECTIVE

In primary aldosteronism, adrenal venous sampling (AVS) is essential for subtype differentiation as it evaluates aldosterone secretion from both adrenals. Selectivity of adrenal sampling is assessed by the ratio of cortisol concentrations in adrenal venous blood and inferior vena cava blood (C(adrenal)/C(ivc)). Since the criteria for selective adrenal sampling differ among the reported literature, we performed a study to evaluate the influence of different selectivity criteria on AVS results.

DESIGN AND METHODS

Reports of AVS were screened retrospectively. All AVS were performed with cosyntrophin infusion. Reports containing samples with C(adrenal)/C(ivc)>or=10 taken from both adrenals and at least one other adrenal sample characterised by C(adrenal)/C(ivc)>or=1.1 were enrolled. For each individual, we chose reference samples that were defined by the highest C(adrenal)/C(ivc) achieved from each adrenal. The significance of the remaining samples with C(adrenal)/C(ivc)>or=1.1 was analysed in regard to their respective reference samples. We assessed the impact of analysed samples on identification of lateralisation of aldosterone secretion that is crucial for decisions concerning adrenalectomy.

RESULTS

AVS reports of 87 patients were enrolled. A total of 225 adrenal samples were analysed and divided into five groups according to C(adrenal)/C(ivc):1.1-1.99, 2-2.99, 3-4.99, 5-9.99 and >or=10. By comparing reference with analysed samples, a concordant assessment with respect to lateralisation of aldosterone secretion was observed in 39, 52, 72, 85 and 94% of the respective groups of analysed samples.

CONCLUSION

AVS provides consistent information when adrenal samples with high cortisol concentrations are used.

Adrenal venous sampling: where is the aldosterone disappearing to?

Adrenal venous sampling (AVS) is generally considered to be the gold standard in distinguishing unilateral and bilateral aldosterone hypersecretion in primary hyperaldosteronism. However, during AVS, we noticed a considerable variability in aldosterone concentrations among samples thought to have come from the right adrenal glands. Some aldosterone concentrations in these samples were even lower than in samples from the inferior vena cava. We hypothesized that the samples with low aldosterone levels were unintentionally taken not from the right adrenal gland, but from hepatic veins. Therefore, we sought to analyze the impact of unintentional cannulation of hepatic veins on AVS. Thirty consecutive patients referred for AVS were enrolled. Hepatic vein sampling was implemented in our standardized AVS protocol. The data were collected and analyzed prospectively. AVS was successful in 27 patients (90%), and hepatic vein cannulation was successful in all procedures performed. Cortisol concentrations were not significantly different between the hepatic vein and inferior vena cava samples, but aldosterone concentrations from hepatic venous blood (median, 17 pmol/l; range, 40–860 pmol/l) were markedly lower than in samples from the inferior vena cava (median, 860 pmol/l; range, 460–4510 pmol/l). The observed difference was statistically significant (P < 0.001). Aldosterone concentrations in the hepatic veins are significantly lower than in venous blood taken from the inferior vena cava. This finding is important for AVS because hepatic veins can easily be mistaken for adrenal veins as a result of their close anatomic proximity.

Cardiovascular and cerebrovascular comorbidities of hypokalemic and normokalemic primary aldosteronism: results of the German Conn's Registry

CONTEXT

Primary aldosteronism (PA) is associated with vascular end-organ damage.

OBJECTIVE

Our objective was to evaluate differences regarding comorbidities between the hypokalemic and normokalemic form of PA.

DESIGN AND SETTING

This was a retrospective cross-sectional study collected from six German centers (German Conn's registry) between 1990 and 2007.

PATIENTS

Of 640 registered patients with PA, 553 patients were analyzed.

MAIN OUTCOME MEASURES

Comorbidities depending on hypokalemia or normokalemia were examined.

RESULTS

Of the 553 patients (61 +/- 13 yr, range 13-96), 56.1% had hypokalemic PA. The systolic (164 +/- 29 vs. 155 +/- 27 mm Hg; P < 0.01) and diastolic (96 +/- 18 vs. 93 +/- 15 mm Hg; P < 0.05) blood pressures were significantly higher in hypokalemic patients than in those with the normokalemic variant. The prevalence of cardiovascular events (angina pectoris, myocardial infarction, chronic cardiac insufficiency, coronary angioplasty) was 16.3%. Atrial fibrillation occurred in 7.1% and other atrial or ventricular arrhythmia in 5.2% of the patients. Angina pectoris and chronic cardiac insufficiency were significantly more prevalent in hypokalemic PA (9.0 vs. 2.1%, P < 0.001; 5.5 vs. 2.1%, P < 0.01). Overall, cerebrovascular comorbidities were not different between hypokalemic and normokalemic patients, however, stroke tended to be more prevalent in normokalemic patients.

CONCLUSIONS

Our data indicate a high prevalence of comorbidities in patients with PA. The hypokalemic variant is defined by a higher morbidity than the normokalemic variant regarding some cardiovascular but not cerebrovascular events. Thus, PA should be sought not only in hypokalemic but also in normokalemic hypertensives because high-excess morbidity occurs in both subgroups.

Adrenal endothelin-1 levels are not associated with aldosterone secretion in primary aldosteronism

BACKGROUND

Endothelin-1 (ET-1) may function as an aldosterone secretagogue and, in turn, aldosterone can upregulate ET-1 expression. Hence, the existence of a feedforward loop involving ETs and aldosterone has been speculated in primary aldosteronism (PA). In the present study, we sought to examine ET-1 secretion from the adrenal glands in patients with PA.

DESIGN

We determined ET-1 levels in blood samples obtained during adrenal venous sampling of patients affected by PA (n=17). Furthermore, we examined the mRNA expression of the ET system in tissue samples from aldosterone-producing adenomas (APAs, n=9) and control normal adrenals (n=3).

METHODS

Blood ET-1 levels were determined by RIA. Tissue mRNA expression of the ET system was assayed with Affymetrix microarrays.

RESULTS

ET-1 levels did not differ between inferior vena cava and adrenal vein blood in both bilateral adrenal hyperplasia and APA patients. Moreover, cortisol-normalized ET-1 levels did not show lateralized adrenal ET-1 secretion in APAs. Through gene expression profiling with microarray performed in a distinct set of APA individuals (n=9), we confirmed the adrenal expression of a complete ET system, but we did not detect a significant upregulation of ET components within the APA tissue compared with normal adrenals.

CONCLUSIONS

The present data argue against the hypothesis of increased ET-1 secretion from APAs and do not support a general role for adrenal ET-1 in the vascular pathophysiology of PA.

What are the keys to successful adrenal venous sampling (AVS) in patients with primary aldosteronism?

Adrenal venous sampling (AVS) is the criterion standard to distinguish between unilateral and bilateral adrenal disease in patients with primary aldosteronism. The keys to successful AVS include appropriate patient selection, careful patient preparation, focused technical expertise, defined protocol, and accurate data interpretation. The use of AVS should be based on patient preferences, patient age, clinical comorbidities, and the clinical probability of finding an aldosterone-producing adenoma. AVS is optimally performed in the fasting state in the morning. AVS is an intricate procedure because the right adrenal vein is small and may be difficult to locate - the success rate depends on the proficiency of the angiographer. The key factors that determine the successful catheterization of both adrenal veins are experience, dedication and repetition. With experience, and focusing the expertise to 1 or 2 radiologists at a referral centre, the AVS success rate can be as high as 96%. A centre-specific, written protocol is mandatory. The protocol should be developed by an interested group of endocrinologists, radiologists and laboratory personnel. Safeguards should be in place to prevent mislabelling of the blood tubes in the radiology suite and to prevent sample mix-up in the laboratory.

Adrenalectomy improves arterial stiffness in primary aldosteronism

BackgroundAldosterone has been shown to substantially contribute to the accumulation of different types of collagen fibers and growth factors in the arterial wall, which increase wall stiffness. We previously showed that arterial wall stiffness is increased in primary aldosteronism (PA) independently of concomitant hypertension. This study was aimed at assessing the effects of specific treatment of PA on the arterial stiffness.MethodsTwenty-nine patients with confirmed PA (15 with aldosterone-producing adenoma treated by unilateral laparoscopic adrenalectomy, 14 treated with spironolactone (mainly idiopathic aldosteronism) were investigated by Sphygmocor applanation tonometer (using measurement of carotid-femoral pulse wave velocity (PWV) and augmentation index (AI)) at the time of the diagnosis and then approximately 1 year after the specific treatment.ResultsThe office blood pressure (BP) decreased from 167 +/- 18/96 +/- 9 to 136 +/- 12/80 +/- 7 mm Hg after adrenalectomy (P = 0.001), and from 165 +/- 21/91 +/- 13 to 151 +/- 22/88 +/- 8 mm Hg (not significant (n.s.)) on spironolactone. The mean 24-h BP decreased from 150 +/- 18/93 +/- 11 mm Hg to 126 +/- 17/80 +/- 10 mm Hg after adrenalectomy (P < 0.01), and from 155 +/- 16/94 +/- 12 to 139 +/- 18/88 +/- 8 mm Hg (n.s.) on spironolactone. The PWV significantly decreased after surgery from 9.5 +/- 2.7 m/s to 7.6 +/- 2 m/s (P = 0.001), and the AI (recalculated for heart rate 75/min) decreased significantly from 27 +/- 10 to 19 +/- 9% (P < 0.01). On the other hand, we did not find significant change of arterial stiffness indices in patients treated with spironolactone (PWV: 9.3 +/- 1.6 m/s vs. 8.8 +/- 1.3 m/s (n.s.); AI: 25 +/- 9% vs. 25 +/- 8% (n.s.)).ConclusionsSurgical but not conservative treatment of PA led to a significant decrease of BP and arterial stiffness parameters.American Journal of Hypertension (2008). doi:10.1038/ajh.2008.243American Journal of Hypertension (2008); 21, 10, 1086-1092. doi 10.1038/ajh.2008.243.

Diagnosis and management of primary aldosteronism

PURPOSE OF REVIEW

To illustrate the steps for clinical management of primary aldosteronism from screening evaluation to surgical and/or medical treatment.

RECENT FINDINGS

It is now widely accepted that primary aldosteronism represents the most common form of endocrine hypertension and its early diagnosis is crucial for hypertensive patients who can be cured by the surgical removal of an aldosterone-secreting adenoma or benefit from a specific medical treatment with mineralocorticoid receptor antagonists. Recent evidence indicates that hyperaldosteronism is indeed associated with detrimental consequences on cardiovascular system, renal function and glucose metabolism.

SUMMARY

The diagnostic protocol for primary aldosteronism requires multistep evaluation and should begin with a screening test, followed when appropriate, by confirmatory test and functional and anatomical evaluation. Finally, although it is technically difficult and the cut-off levels for acceptance of the success are not standardized, the subtype forms should be identified using a selective adrenal venous sampling.