Prevalence of Cortisol Cosecretion in Patients With Primary Aldosteronism: Role of Metanephrine in Adrenal Vein Sampling

CONTEXT

Adrenal venous sampling (AVS) is the gold standard procedure for subtype diagnosis in patients with primary aldosteronism (PA). Cortisol is usually adopted for the normalization of aldosterone levels in peripheral and adrenal samples. However, asymmetrical cortisol secretion can potentially affect the lateralization index, leading to subtype misdiagnosis.

OBJECTIVE

We aimed to assess the prevalence of asymmetrical cortisol secretion in patients undergoing AVS and whether variations in adrenal vein cortisol might influence AVS interpretations. We then evaluated the use of metanephrines for the normalization of aldosterone levels for lateralization index.

METHODS

We retrospectively included 101 patients with PA who underwent AVS: 49 patients underwent unstimulated AVS, while 52 patients underwent both unstimulated and cosyntropin-stimulated AVS. Eighty-eight patients had bilateral successful AVS according to metanephrine ratio. We assessed the prevalence of asymmetrical cortisol secretion through the cortisol to metanephrine (C/M) lateralization index (LI). We then evaluated whether the use of aldosterone to metanephrine (A/M) LI can improve the diagnostic accuracy of AVS compared with aldosterone to cortisol (A/C) LI.

RESULTS

Asymmetrical cortisol secretion is present in 18% of patients with PA. Diagnosis with A/M LI and A/C LI is discordant in 14% of patients: 9% had a diagnosis of unilateral PA with A/M LI instead of bilateral PA with A/C LI and 5% had a diagnosis of bilateral PA with A/M LI instead of unilateral PA.

CONCLUSION

The assessment of metanephrine levels in AVS is useful for the determination of selectivity and lateralization, allowing an accurate diagnosis, especially in patients with asymmetrical cortisol secretion.

Prediction of hyperaldosteronism subtypes when adrenal vein sampling is unilaterally successful

OBJECTIVE

Adrenal venous sampling (AVS) is the gold standard to discriminate patients with unilateral primary aldosteronism (UPA) from bilateral disease (BPA). AVS is technically demanding and in cases of unsuccessful cannulation of adrenal veins, the results may not always be interpreted. The aim of our study was to develop diagnostic models to distinguish UPA from BPA, in cases of unilateral successful AVS and the presence of contralateral suppression of aldosterone secretion.

DESIGN

Retrospective evaluation of 158 patients referred to a tertiary hypertension unit who underwent AVS. We randomly assigned 110 patients to a training cohort and 48 patients to a validation cohort to develop and test the diagnostic models.

METHODS

Supervised machine learning algorithms and regression models were used to develop and validate two prediction models and a simple 19-point score system to stratify patients according to their subtype diagnosis.

RESULTS

Aldosterone levels at screening and after confirmatory testing, lowest potassium, ipsilateral and contralateral imaging findings at CT scanning, and contralateral ratio at AVS, were associated with a diagnosis of UPA and were included in the diagnostic models. Machine learning algorithms correctly classified the majority of patients both at training and validation (accuracy: 82.9-95.7%). The score system displayed a sensitivity/specificity of 95.2/96.9%, with an AUC of 0.971. A flow-chart integrating our score correctly managed all patients except 3 (98.1% accuracy), avoiding the potential repetition of 77.2% of AVS procedures.

CONCLUSIONS

Our score could be integrated in clinical practice and guide surgical decision-making in patients with unilateral successful AVS and contralateral suppression.

Intratumoral heterogeneity of the tumor cells based on in situ cortisol excess in cortisol-producing adenomas; ∼An association among morphometry, genotype and cellular senescence∼

Cortisol-producing adrenocortical adenomas (CPAs) are associated with ACTH-independent Cushing's syndrome and histologically composed of two cellular subtypes: compact (lipid-poor) and clear (lipid-rich) tumor cells. However, the details of hormonal and biological activities of these tumor cells have remained unknown, especially in CPAs. CPAs frequently harbored unique histological features different from those of aldosterone-producing adenomas (APAs) including a senescent phenotype. Therefore, we explored the association between morphological features and the immunoreactivity of steroidogenic enzymes in CPAs with different genotypes and compared them with cellular senescence markers as well as clinicopathological factors of the cases. Hormonal activities (3βHSD, CYP21A, CYP17A1, CYP11B1 and DHEA-ST) and cellular senescence markers (p16, p21 and Ki-67) within different morphological features (clear and compact) were evaluated in 40 CPAs. CPA genotypes (PRKACA, GNAS and CTNNB1) were examined by Sanger sequencing and then compared them with the factors above. p21 immunoreactivity was significantly positively correlated with that of CYP21A (p = 0.0110), CYP17A1 (p = 0.0356) and DHEA-ST (p = 0.0420) but inversely with tumor size (p = 0.0015). CYP21A (p = 0.0016), CYP11B1 (p = 0.0001), CYP17A1 (p < 0.0001) and p16 (p = 0.0137) immunoreactivity were all significantly higher in compact cells than those in clear cells. CYP17A1 (p = 0.0056) and 3βHSD (p = 0.0437) immunoreactivity was significantly higher in PRKACA-mutated than wild type CPAs. p16 immunoreactivity and serum DHEA-S level were both significantly higher in GNAS-mutated than PRKACA-mutated (p = 0.0250) and wild type (p = 0.0180) CPAs. Results of our present study did demonstrate that compact tumor cells were hormonally active and more senescent than clear tumor cells in CPAs. PRKACA- and GNAS-mutated tumor cells were more hormonally active and senescent than those without mutations despite the similar morphological features. We herein proposed a novel histological classification of the tumor cell subtypes based on in situ cortisol excess, genotypes and the status of cell senescence in CPAs.

Development and Validation of Prediction Models for Subtype Diagnosis of Patients With Primary Aldosteronism

CONTEXT

Primary aldosteronism (PA) comprises unilateral (lateralized [LPA]) and bilateral disease (BPA). The identification of LPA is important to recommend potentially curative adrenalectomy. Adrenal venous sampling (AVS) is considered the gold standard for PA subtyping, but the procedure is available in few referral centers.

OBJECTIVE

To develop prediction models for subtype diagnosis of PA using patient clinical and biochemical characteristics.

DESIGN, PATIENTS AND SETTING

Patients referred to a tertiary hypertension unit. Diagnostic algorithms were built and tested in a training (N = 150) and in an internal validation cohort (N = 65), respectively. The models were validated in an external independent cohort (N = 118).

MAIN OUTCOME MEASURE

Regression analyses and supervised machine learning algorithms were used to develop and validate 2 diagnostic models and a 20-point score to classify patients with PA according to subtype diagnosis.

RESULTS

Six parameters were associated with a diagnosis of LPA (aldosterone at screening and after confirmatory testing, lowest potassium value, presence/absence of nodules, nodule diameter, and computed tomography results) and were included in the diagnostic models. Machine learning algorithms displayed high accuracy at training and internal validation (79.1%-93%), whereas a 20-point score reached an area under the curve of 0.896, and a sensitivity/specificity of 91.7/79.3%. An integrated flowchart correctly addressed 96.3% of patients to surgery and would have avoided AVS in 43.7% of patients. The external validation on an independent cohort confirmed a similar diagnostic performance.

CONCLUSIONS

Diagnostic modelling techniques can be used for subtype diagnosis and guide surgical decision in patients with PA in centers where AVS is unavailable.

Primary Aldosteronism and Obstructive Sleep Apnea: Casual Association or Pathophysiological Link?

The coexistence of aldosterone oversecretion and obstructive sleep apnea is frequently observed, especially in patients with resistant hypertension, obesity, and metabolic syndrome. Since aldosterone excess and sleep apnea are both independently associated with an increased risk of cardiovascular disease, to investigate whether their coexistence might be attributed to common predisposing conditions, such as metabolic disorders, or to an actual pathophysiological interconnection appears of great importance. Fluid overload and metabolic abnormalities relating to aldosterone oversecretion may be implicated in obstructive sleep apnea development. Nocturnal intermittent hypoxia may in turn exacerbate renin-angiotensin-aldosterone system activity, thus leading to hyperaldosteronism. Furthermore, fat tissue excess and adipocyte secretory products might predispose to both sleep apnea and aldosterone oversecretion in subjects with obesity. Consistent with these evidences, obstructive sleep apnea frequently affects patients with primary aldosteronism. Conversely, whether primary aldosteronism is more prevalent in individuals affected by obstructive sleep apnea compared to the general population remains controversial.

OR03-04 The Study of Cell Senescence in Cortisol-Producing Adrenocortical Adenomas

Introduction Aging is associated with the pathogenesis of many endocrine disorders such as cardiovascular diseases and diabetes. Cell senescence has been reported as one of their mechanisms. In addition, stress responsiveness has been reported to be associated with cell senescence. In addition, some genetic abnormalities such as mitochondrial DNA (mtDNA) damages or telomere shortening, have been detected in some endocrine disorders. Cortisol is a well-known stress-induced hormone and closely associated with aging. We previously reported that cortisol-producing adenoma (CPA) more abundantly expressed cell senescent markers such as p16 and p21 than other hormone-producing adrenocortical adenomas. However, the detailed pathophysiology of cell senescence and its association with histological features in CPAs have remained virtually unknown. Therefore, we analyzed cell senescent markers (telomere length, mtDNA copy number, mtDNA deletion and p16 and p21 immunoreactivity) and analyzed their correlation with clinicopathological factors in CPA patients.

Methods & Materials Forty CPA cases was immunohistochemically evaluated. Twenty CPA, ten adjacent ZF and six non-functional adenoma (NFA) were examined for mtDNA abnormalities. mtDNA deletion was evaluated by nested-PCR and mtDNA copy number and telomere length were measured using real-time PCR.

Results p21 immunoreactivity was significantly higher in CPA than that of adjacent ZF (P=0.0001) and significantly inversely correlated with tumor size (P=0.0004). Telomere length was much longer in CPA than that in adjacent ZF(P=0.0038), and NFA (P=0.0018). mtDNA copy number of NFA was significantly higher than that of CPA and adjacent ZF (P=0.0038). mtDNA copy number of compact cells was significantly higher than that of clear cells (P=0.0432). mtDNA copy number of compact cells was positively correlated with urinary free cortisol (UFC) (P=0.0428) and plasma cortisol (F) (P=0.0609). mtDNA copy number of clear cells were inversely correlated with F (0.0497). 4977 bp mtDNA deletion was more frequently detected in CPA (54%) and in adjacent ZF (50%) than in NFA (17%).

Discussion Results of our present study did reveal that CPA harbored more senescent phenotype as demonstrated by abundant p16 and p21, marked telomere shortening, frequent mtDNA 4977bp deletion and relatively low mtDNA copy number, possibly caused by long-term exposure of excessive cortisol in situ compared to NFA. In addition, clear tumor cells could represent more senescent histological phenotype because of their lower mtDNA copy numbers. This is the first study to demonstrate that compact tumor cells were biologically more active than clear tumor cells and could reflect clinical cortisol biosynthesis, resulting in marked functional intratumoral heterogeneity in CPAs.

The spectrum of low-renin hypertension

Low-renin hypertension (LRH) is a frequent condition in patients with arterial hypertension, accounting for 30% of patients. Monogenic forms can cause LRH in a minority of cases. However, in the large majority of patients, LRH is caused by the combined effects of congenital and acquired factors, comprising dietary habits. Several genetic variants have been proposed as co-factors in the pathogenesis of LRH with normal-low serum aldosterone. Emerging evidences support the hypothesis that a large proportion of LRH with normal-high serum aldosterone is associated with subclinical primary aldosteronism (PA). The recent identification of aldosterone-producing cell clusters (APCCs) as the possible cause of subclinical PA, further supported the concept of a continuous spectrum of autonomous aldosterone secretion, from subclinical forms towards overt PA. In this review we describe the main aspects of LRH, focusing on molecular basis, clinical risk profile and patients' management.

Primary Aldosteronism and Obstructive Sleep Apnea: A Cross-Sectional Multi-Ethnic Study

The association between primary aldosteronism (PA) and obstructive sleep apnea (OSA) has been a matter of debate. 2016 Endocrine Society guideline recommends screening for PA all hypertensive patients with OSA. We designed a multicenter, multiethnic, cross-sectional study to evaluate the prevalence of PA in patients with OSA and the prevalence of OSA in unselected patients with PA. Two hundred and three patients with OSA (102 whites and 101 Chinese) were screened for PA, and 207 patients with PA (104 whites, 100 Chinese, and 3 of African descent) were screened for OSA by cardiorespiratory polygraphy. Eighteen patients with OSA (8.9%) had PA (11.8% of white and 5.9% of Chinese ethnicity). In patients without other indications for PA screening, the prevalence of PA dropped to 1.5%. The prevalence of OSA in patients with PA was 67.6%, consistent in both white and Chinese patients. A correlation between aldosterone levels and apnea/hypopnea index was observed in white patients with PA (R²=0.225, P=0.016) but not in Chinese patients. Multinomial logistic regression confirmed a significant and independent association between plasma aldosterone levels and moderate to severe OSA diagnosis in white patients (odds ratio, 1.002; P=0.002). In conclusion, aldosterone levels may contribute to the severity of OSA in white patients with hyperaldosteronism, but patients with OSA are not at high risk of PA. Results of the present study challenge the current recommendation of the Endocrine Society guideline that all patients with OSA should be screened for PA, irrespective of the grade of hypertension.

A surface on the G protein beta-subunit involved in interactions with adenylyl cyclases

Receptor activation of heterotrimeric G proteins dissociates G alpha from the G betagamma complex, allowing both to regulate effectors. Little is known about the effector-interaction regions of G betagamma. We had used molecular modeling to dock a peptide encoding the region of residues 956-982 of adenylyl cyclase (AC) 2 onto Gbeta to identify residues on Gbeta that may interact with effectors. Based on predictions from the model, we synthesized peptides encoding sequences of residues 86-105 (Gbeta 86-105) and 115-135 (Gbeta 115-135) from Gbeta. The Gbeta 86-105 peptide inhibited G betagamma stimulation of AC2 and blocked G betagamma inhibition of AC1 and by itself inhibited calmodulin-stimulated AC1, thus displaying partial agonist activity. Substitution of Met-101 with Asn in this peptide resulted in the loss of both the inhibitory and partial agonist activities. Most activities of the Gbeta 115-135 peptide were similar to those of Gbeta 86-105 but Gbeta 115-135 was less efficacious in blocking G betagamma inhibition of AC1. Substitution of Tyr-124 with Val in the Gbeta 115-135 peptide diminished all of its activities. These results identify the region encoded by amino acids 84-143 of Gbeta as a surface that is involved in transmitting signals to effectors.