Morphologically Normal-Appearing Adrenal Glands as a Prevalent Source of Aldosterone Production in Primary Aldosteronism

Approach to Endocrine Hypertension: A Case-Based Discussion

PURPOSE OF REVIEW

Hypertension remains a major chronic disease morbidity across the world, even in the twenty-first century, affecting ≈40% of the global population, adversely impacting the healthcare budgets in managing the high incidence of cardiovascular disease (CVD) complications and mortality because of elevated blood pressure (BP). However, evaluation and management of endocrine hypertension are not optimal in clinical practice. With three unique clinical case scenarios, we update the evidence base for diagnostic evaluation and management of endocrine hypertension in this review to inform appropriate day-to-day clinical practice decisions.

RECENT FINDINGS

Although most individuals with high BP suffer from essential hypertension (≈85%), some patients may have a clear underlying etiology (termed secondary hypertension), and a significant proportion of these patients have endocrine hypertension (≈10%) consequent to hormone excess from dysfunction of one or more endocrine glands. Even if a relatively common disease in the general population, the correct diagnosis and appropriate treatment of endocrine hypertension is often delayed because of poor awareness among clinicians, including primary care providers and physicians in the secondary care settings. An accurate and timely diagnosis of endocrine hypertension is crucial to potentially cure or at least properly manage these patients because the consequences of delays in diagnosis can be catastrophic, with markedly higher end-organ complications such as CVD, chronic kidney disease, and even premature mortality among sufferers.

Circulating miRNAs and Machine Learning for Lateralizing Primary Aldosteronism

BACKGROUND

Distinguishing between unilateral and bilateral primary aldosteronism, a major cause of secondary hypertension, is crucial due to different treatment approaches. While adrenal venous sampling is the gold standard, its invasiveness, limited availability, and often difficult interpretation pose challenges. This study explores the utility of circulating microRNAs (miRNAs) and machine learning in distinguishing between unilateral and bilateral forms of primary aldosteronism.

METHODS

MiRNA profiling was conducted on plasma samples from 18 patients with primary aldosteronism taken during adrenal venous sampling on an Illumina MiSeq platform. Bioinformatics and machine learning identified 9 miRNAs for validation by reverse transcription real-time quantitative polymerase chain reaction. Validation was performed on a cohort consisting of 108 patients with known subdifferentiation. A 30-patient subset of the validation cohort involved both adrenal venous sampling and peripheral, the rest only peripheral samples. A neural network model was used for feature selection and comparison between adrenal venous sampling and peripheral samples, while a deep-learning model was used for classification.

RESULTS

Our model identified 10 miRNA combinations achieving >85% accuracy in distinguishing unilateral primary aldosteronism and bilateral adrenal hyperplasia on a 30-sample subset, while also confirming the suitability of peripheral samples for analysis. The best model, involving 6 miRNAs, achieved an area under curve of 87.1%. Deep learning resulted in 100% accuracy on the subset and 90.9% sensitivity and 81.8% specificity on all 108 samples, with an area under curve of 86.7%.

CONCLUSIONS

Machine learning analysis of circulating miRNAs offers a minimally invasive alternative for primary aldosteronism lateralization. Early identification of bilateral adrenal hyperplasia could expedite treatment initiation without the need for further localization, benefiting both patients and health care providers.

Primary and "Pre-Primary" Aldosteronism in Resistant Hypertension: A Practical, Pragmatic, and Prudent Approach in Resource-Limited Milieu

Introduction Primary aldosteronism (PA), once considered rare, is now recognized as the most common cause of secondary hypertension, accounting for almost a quarter of resistant hypertension (RH) cases. Despite this, PA remains underdiagnosed, with an extremely low percentage of RH patients undergoing screening. Methods In a specialty diabetes-endocrinology clinic, the aldosterone:renin ratio (ARR) was assessed in 115 consecutive RH patients (ages 21-93 years; 47% male; 87% with type 2 diabetes). Fasting blood samples were drawn in a standing position after 30 minutes of walking. Adrenal imaging (CT/MRI) was performed for those with an ARR >20. Results ARR values ranged from 0.4 to 227 (ARR <10 (35%); 11-20 (19%), 21-40 (25%), and >40 (21%)), with corresponding stepwise decreasing plasma renin activity (PRA) (P= 1E-6) and increasing serum aldosterone (SA) (P= 8E-7). Increasing ARR tended to be associated with an increase in serum creatinine (R= 0.23; P= 0.03) and a decrease in estimated glomerular filtration rate (eGFR) (R= -0.24; P= 0.02) and an increase in urine albumin: creatinine ratio. The ARR> 40 group displayed the highest serum creatinine, lowest eGFR, higher urine albumin: creatinine ratio, highest serum sodium, lowest serum potassium, and highest (44%) abnormal adrenal imaging (bilateral hyperplasia diffuse/nodular; solitary adenoma), reflecting a later stage of the pathological spectrum. PA treatment with mineralocorticoid receptor antagonists (MRAs) had a salutary effect. Conclusions Our observations further reinforce that PA is not a binary condition, but exists as a spectrum disorder responsive to MRAs, even in patients with mildly elevated or normal aldosterone levels. Early disease detection/recognition ("renin-independent aldosterone production") can be facilitated by marking "pre-primary" aldosteronism (ARR 11-20), followed by monitoring progression (periodic rescreening) and optimizing treatment, with hopeful mitigation of end-organ damage in RH.

Multifocal, Asymmetric Bilateral Primary Aldosteronism Cannot be Excluded by Strong Adrenal Vein Sampling Lateralization: An International Retrospective Cohort Study

BACKGROUND

Primary aldosteronism (PA) has been broadly dichotomized into unilateral and bilateral forms. Adrenal vein sampling (AVS) lateralization indices (LI) ≥2 to 4 are the standard-of-care to recommend unilateral adrenalectomy for presumed unilateral PA. We aimed to assess the rates and characteristics of residual PA after AVS-guided adrenalectomy.

METHODS

We conducted an international, retrospective, cohort study of patients with PA from 7 referral centers who underwent unilateral adrenalectomy based on LI≥4 on baseline and/or cosyntropin-stimulated AVS. Aldosterone synthase (CYP11B2) immunohistochemistry and next generation sequencing were performed on available formalin-fixed paraffin-embedded adrenal tissue.

RESULTS

The cohort included 283 patients who underwent AVS-guided adrenalectomy, followed for a median of 326 days postoperatively. Lack of PA cure was observed in 16% of consecutive patients, and in 22 patients with lateralized PA on both baseline and cosyntropin-stimulated AVS. Among patients with residual PA postoperatively, 73% had multiple CYP11B2 positive areas within the resected adrenal tissue (versus 23% in those cured), wherein CACNA1D mutations were most prevalent (63% versus 33% in those cured). In adjusted regression models, independent predictors of postoperative residual PA included Black versus White race (odds ratio, 5.10 [95% CI, 1.45-17.86]), AVS lateralization only at baseline (odds ratio, 8.93 [95% CI 3.00-26.32] versus both at baseline and after cosyntropin stimulation), and CT-AVS disagreement (odds ratio, 2.75 [95% CI, 1.20-6.31]).

CONCLUSIONS

Multifocal, asymmetrical bilateral PA is relatively common, and it cannot be excluded by robust AVS lateralization. Long-term postoperative monitoring should be routinely pursued, to identify residual PA and afford timely initiation of targeted medical therapy.

Multiple radiologist review of adrenal CT still frequently misses lateralized surgical primary aldosteronism

Patients with primary aldosteronism (PA) have increased morbidity and mortality compared to those with essential hypertension. Accurate detection of lateralized PA is important so that affected patients can receive potentially curative adrenalectomy. However, around 40% of patients with lateralized PA have "normal" adrenal glands on computed tomography (CT). Additional independent review of imaging has been shown to improve diagnostic accuracy in many areas of imaging. Therefore, the authors sought to establish if multi-reader re-assessment of previously reported normal CT scans would result in increased detection of surgically remediable disease. The authors found that re-assessment of CT imaging by one, two, or three additional radiologists (or a combination thereof) slightly increased the detection of lateralized disease, but these differences were not statistically significant (p > .05). Readers had low inter-observer agreement (kappa = 0.17). If detection of a discrete nodule on CT was made a prerequisite for adrenal vein sampling (AVS), a second read by another reviewer would still result in an excess of missed cases (84.2%, 36.8%, and 65.8%, respectively, for each of the three independent reviewers). Therefore, a "normal" CT does not preclude the possibility of lateralized PA. Adrenal vein sampling should still be strongly considered wherever available and whenever surgery is considered for treatment of PA, irrespective of CT findings.

Primary Aldosteronism: State-of-the-Art Review

We are witnessing a revolution in our understanding of primary aldosteronism (PA). In the past 2 decades, we have learned that PA is a highly prevalent syndrome that is largely attributable to pathogenic somatic mutations, that contributes to cardiovascular, metabolic, and kidney disease, and that when recognized, can be adequately treated with widely available mineralocorticoid receptor antagonists and/or surgical adrenalectomy. Unfortunately, PA is rarely diagnosed, or adequately treated, mainly because of a lack of awareness and education. Most clinicians still possess an outdated understanding of PA; from primary care physicians to hypertension specialists, there is an urgent need to redefine and reintroduce PA to clinicians with a modern and practical approach. In this state-of-the-art review, we provide readers with the most updated knowledge on the pathogenesis, prevalence, diagnosis, and treatment of PA. In particular, we underscore the public health importance of promptly recognizing and treating PA and provide pragmatic solutions to modify clinical practices to achieve this.

Impact of dedicated multidisciplinary service on patient selection and outcomes for surgical treatment of primary aldosteronism

BACKGROUND

Primary aldosteronism is the most common surgically curable cause of endocrine hypertension. Management of the unilateral subtype of primary aldosteronism with adrenalectomy requires multidisciplinary input. It is unclear if a dedicated endocrine hypertension service confers better outcomes compared to standard care offered by individual clinicians.

METHODS

In this retrospective study, patients from the Monash University Endocrine Surgery Database were divided into either the endocrine hypertension service group, where patients were managed by a dedicated multidisciplinary team, or the standard group, where patients were managed by individual clinicians. The comparisons included patient selection for surgery, perioperative blood pressure control, and surgical cure rate.

RESULTS

Despite similar perioperative blood pressure, patients in the endocrine hypertension service group (n = 41) were on fewer antihypertensive medications (1 vs 2, P = .011) compared to the standard group (n = 55). A larger proportion of patients in the endocrine hypertension service group had either bilateral adrenal nodules or no adrenal lesions on computed tomography (41% vs 18%, P = .013). Patients in the standard group had larger adrenal lesions on computed tomography (median 15 mm vs 10 mm, P = .032). Postoperatively, the biochemical cure rate was higher in the endocrine hypertension service group at 6 to 12 months (97% vs 76%, P = .021).

CONCLUSION

Patients managed by endocrine hypertension service were more likely to be diagnosed with surgically curable primary aldosteronism without a unilateral adrenal adenoma on imaging, required fewer medications for perioperative blood pressure control, and experienced superior postoperative outcomes. Referral to a dedicated endocrine hypertension service is recommended for patients with primary aldosteronism who wish to pursue a surgical cure.

Pathophysiology of bilateral hyperaldosteronism

PURPOSE OF REVIEW

Renin-independent aldosterone production from one or both affected adrenal(s), a condition known as primary aldosteronism (PA), is a common cause of secondary hypertension. In this review, we aimed to summarize recent findings regarding pathophysiology of bilateral forms of PA, including sporadic bilateral hyperaldosteronism (BHA) and rare familial hyperaldosteronism.

RECENT FINDINGS

The presence of subcapsular aldosterone synthase (CYP11B2)-expressing aldosterone-producing micronodules, also called aldosterone-producing cell clusters, appears to be a common histologic feature of adrenals with sporadic BHA. Aldosterone-producing micronodules frequently harbor aldosterone-driver somatic mutations. Other potential factors leading to sporadic BHA include rare disease-predisposing germline variants, circulating angiotensin II type 1 receptor autoantibodies, and paracrine activation of aldosterone production by adrenal mast cells. The application of whole exome sequencing has also identified new genes that cause inherited familial forms of PA.

SUMMARY

Research over the past 10 years has significantly improved our understanding of the molecular pathogenesis of bilateral PA. Based on the improved understanding of BHA, future studies should have the ability to develop more personalized treatment options and advanced diagnostic tools for patients with PA.