The Mechanisms Underlying Autonomous Adrenocorticotropic Hormone Secretion in Cushing's Disease

Hypothalamic-Pituitary-Adrenal Axis and Epilepsy

Epilepsy is a recurrent, transient seizure disorder of the nervous system that affects the intellectual development, life and work, and psychological health of patients. People with epilepsy worldwide experience great suffering. Stressful stimuli such as infection, mental stress, and sleep deprivation are important triggers of epilepsy, and chronic stressful stimuli can lead to frequent seizures and comorbidities. The hypothalamic-pituitary-adrenal (HPA) axis is the most important system involved in the body's stress response, and dysfunction thereof is thought to be associated with core epilepsy symptoms and related psychopathology. This article explores the intrinsic relationships of corticotropin-releasing hormone, adrenocorticotropic hormone, and glucocorticoids with epilepsy in order to reveal the role of the HPA axis in the pathogenesis of epilepsy. We hope that this information will yield future possible directions and ideas for fully understanding the pathogenesis of epilepsy and developing antiepileptic drugs.

Gut liver brain axis in diseases: the implications for therapeutic interventions

Gut-liver-brain axis is a three-way highway of information interaction system among the gastrointestinal tract, liver, and nervous systems. In the past few decades, breakthrough progress has been made in the gut liver brain axis, mainly through understanding its formation mechanism and increasing treatment strategies. In this review, we discuss various complex networks including barrier permeability, gut hormones, gut microbial metabolites, vagus nerve, neurotransmitters, immunity, brain toxic metabolites, β-amyloid (Aβ) metabolism, and epigenetic regulation in the gut-liver-brain axis. Some therapies containing antibiotics, probiotics, prebiotics, synbiotics, fecal microbiota transplantation (FMT), polyphenols, low FODMAP diet and nanotechnology application regulate the gut liver brain axis. Besides, some special treatments targeting gut-liver axis include farnesoid X receptor (FXR) agonists, takeda G protein-coupled receptor 5 (TGR5) agonists, glucagon-like peptide-1 (GLP-1) receptor antagonists and fibroblast growth factor 19 (FGF19) analogs. Targeting gut-brain axis embraces cognitive behavioral therapy (CBT), antidepressants and tryptophan metabolism-related therapies. Targeting liver-brain axis contains epigenetic regulation and Aβ metabolism-related therapies. In the future, a better understanding of gut-liver-brain axis interactions will promote the development of novel preventative strategies and the discovery of precise therapeutic targets in multiple diseases.

Exploring the diversity of AVPR2 in Primates and its evolutionary implications

The current study focuses on the investigation of AVPR2 (VTR2C) protein-coupled receptor variants specific to different primate taxa. AVPR2 is activated by the neurohormone AVP, which modulates physiological processes, including water homeostasis. Our findings reveal positive selection at three AVPR2 sites at positions 190, 250, and 346. Variation at position 250 is associated with human Congenital Nephrogenic Diabetes Insipidus (cNDI), a condition characterized by excessive water loss. Other 13 functional sites with potential adaptive relevance include positions 185, 202, 204, and 252 associated with cNDI. We identified SH3-binding motifs in AVPR2's ICL3 and N-terminus domains, with some losses observed in clades of Cercopithecidae, Callitrichinae, and Atelidae. SH3-binding motifs are crucial in regulating cellular physiology, indicating that the differences may be adaptive. Co-evolution was found between AVPR2 residues and those in the AVP signal peptide/Neurophysin-2 and AQP2, other molecules in the same signaling cascade. No significant correlation was found between these Primates' taxon-specific variants and the bioclimatic variables of the areas where they live. Distinct co-evolving amino acid sequences in functional sites were found in Platyrrhini and Catarrhini, which may have adaptive implications involving glucocorticoid hormones, suggesting varied selective pressures. Further studies are required to confirm these results.

Neuromedin B receptor as a potential therapeutic target for corticotroph adenomas

PURPOSE

Cushing's disease (CD) results from autonomous adrenocorticotropic hormone (ACTH) secretion by corticotroph adenomas, leading to excessive cortisol production, ultimately affecting morbidity and mortality. Pasireotide is the only FDA approved tumor directed treatment for CD, but it is effective in only about 25% of patients, and is associated with a high rate of hyperglycemia. Neuromedin B (NMB), a member of the bombesin-like peptide family, regulates endocrine secretion and cell proliferation. Here, we assessed NMB and NMB receptor (NMBR) expression in human corticotroph adenomas and the effects of NMBR antagonist PD168368 on murine and human corticotroph tumors.

METHODS

To investigate NMB and NMBR expression, real-time qPCR and immunostaining on human pathological specimens of corticotroph, non-functional and somatotroph adenomas were performed. The effects of PD168368 on hormone secretion and cell proliferation were studied in vitro, in vivo and in seven patient-derived corticotroph adenoma cells. NMB and NMBR were expressed in higher extent in human corticotroph adenomas compared with non-functional or somatotroph adenomas.

RESULTS

In murine AtT-20 cells, PD168368 reduced proopiomelanocortin (Pomc) mRNA/protein expression and ACTH secretion as well as cell proliferation. In mice with tumor xenografts, tumor growth, ACTH and corticosterone were downregulated by PD168368. In patient-derived adenoma cells, PD168368 reduced POMC mRNA expression in four out of seven cases and ACTH secretion in two out of five cases. A PD168368-mediated cyclin E suppression was also identified in AtT-20 and patient-derived cells.

CONCLUSION

NMBR antagonist represents a potential treatment for CD and its effect may be mediated by cyclin E suppression.

Dexamethasone suppression for 18F-FDG PET/CT to localize ACTH-secreting pituitary tumors

BACKGROUND

18Fluorine-Fluoro-deoxy-glucose (18F-FDG) positron emission tomography (PET) is widely used for diagnosing various malignant tumors and evaluating metabolic activities. Although the usefulness of 18F-FDG PET has been reported in several endocrine diseases, studies on pituitary disease are extremely limited. To evaluate whether dexamethasone (DEX) suppression can improve 18F-FDG PET for the localization of adrenocorticotropic hormone-secreting adenomas in the pituitary gland in Cushing's disease (CD).

METHODS

We included 22 patients with CD who underwent PET imaging before and after DEX administration. We compared the success rates of PET before and after DEX suppression, magnetic resonance imaging (MRI), and bilateral inferior petrosal sinus sampling (BIPSS). We determined the final locations of adenomas based on intraoperative multiple-staged resection and tumor tissue identification using frozen sections. Standardized uptake value (SUV) were analyzed to confirm the change of intensity of adenomas on PET.

RESULTS

Twenty-two patients were included (age at diagnosis: 37 [13-56] years), and most were women (90.91%). Pituitary adenomas compared to normal pituitaries showed increased maximum SUV after DEX suppression but without statistical significance (1.13 versus. 1.21, z=-0.765, P = 0.444). After DEX suppression, the mean and maximum SUV of adenomas showed a positive correlation with nadir cortisol levels in high-dose DEX suppression test (Rho = 0.554, P = 0.007 and Rho = 0.503, P = 0.017, respectively). In reference sites, mean SUV of cerebellum was significantly decreased (7.65 vs. 6.40, P = 0.006*), but those of the thalamus and gray matter was increased after DEX suppression (thalamus, 8.70 vs. 11.20, P = 0.010*; gray matter, 6.25 vs. 7.95, P = 0.010*).

CONCLUSION

DEX suppression did not improve 18F-FDG PET/CT localization in patients with CD.

Elevated Serum Androstenedione Level in a Patient With Ectopic Adrenocorticotropic Hormone Syndrome

Background/Objective

Ectopic Cushing syndrome can be challenging to diagnose when its presentation is atypical. Herein, we highlight features of ectopic adrenocorticotropic hormone (ACTH) syndrome in a patient with worsening hypertension, hypokalemia, ACTH-dependent hypercortisolism, and disproportionate elevation in serum androstenedione levels.

Case Report

A 59-year-old woman presented with rapidly progressing hypertension, severe hypokalemia, confusion, and weakness. Her medical history included well-controlled hypertension receiving amlodipine 5 mg/day, which worsened 3 months prior to admission requiring losartan and spironolactone therapy, with twice daily potassium supplementation. Physical examination was notable for bruising, muscle wasting, thin extremities, facial fullness, and abdominal adiposity despite body mass index 17 kg/m2. Laboratory evaluation showed potassium 2.6 mEq/L (3.5-5.3), morning cortisol >50 mcg/dL (8-25), 24-hour urine cortisol 8369 mcg/day (<50), ACTH 308 pg/mL (<46), androstenedione 398 ng/dL (20-75), dehydroepiandrosterone sulfate 48 mcg/dL (≤430), and testosterone 11 ng/dL (≤4.5) levels. A 3.8-cm carcinoid right lung tumor was identified, and resection was performed with clean margins. Cortisol, androstenedione, and potassium levels rapidly normalized postoperatively and blood pressure returned to baseline, well-controlled on amlodipine.

Discussion

Our case illustrates disproportionate elevation in androstenedione levels despite normal dehydroepiandrosterone sulfate and testosterone in a woman with ectopic ACTH syndrome. Limited reports have observed similar discordance in androgen profiles in ectopic versus pituitary ACTH hypersecretion, potentially attributable to differential activation of androgen biosynthesis.

Conclusion

Adrenal androgen assessment may help differentiate pituitary versus ectopic ACTH secretion in which androstenedione is elevated, but studies are needed to determine whether disproportionate androstenedione elevation reliably predicts the origin of ACTH excess.

Activation of Mast Cells by Neuropeptides: The Role of Pro-Inflammatory and Anti-Inflammatory Cytokines

Mast cells (MCs) are tissue cells that are derived from bone marrow stem cells that contribute to allergic reactions, inflammatory diseases, innate and adaptive immunity, autoimmunity, and mental disorders. MCs located near the meninges communicate with microglia through the production of mediators such as histamine and tryptase, but also through the secretion of IL-1, IL-6 and TNF, which can create pathological effects in the brain. Preformed chemical mediators of inflammation and tumor necrosis factor (TNF) are rapidly released from the granules of MCs, the only immune cells capable of storing the cytokine TNF, although it can also be produced later through mRNA. The role of MCs in nervous system diseases has been extensively studied and reported in the scientific literature; it is of great clinical interest. However, many of the published articles concern studies on animals (mainly rats or mice) and not on humans. MCs are known to interact with neuropeptides that mediate endothelial cell activation, resulting in central nervous system (CNS) inflammatory disorders. In the brain, MCs interact with neurons causing neuronal excitation with the production of neuropeptides and the release of inflammatory mediators such as cytokines and chemokines. This article explores the current understanding of MC activation by neuropeptide substance P (SP), corticotropin-releasing hormone (CRH), and neurotensin, and the role of pro-inflammatory cytokines, suggesting a therapeutic effect of the anti-inflammatory cytokines IL-37 and IL-38.

Cortisol: Analytical and clinical determinants

Cortisol, the main human glucocorticoid, is synthesized from cholesterol in the adrenal cortex and predominantly metabolized by the liver. Interpretation of quantitative results from the analysis of serum, urine and saliva is complicated by variation in circadian rhythm, response to stress as well as the presence of protein-bound and free forms. Interestingly, cortisol is the only hormone routinely measured in serum, urine, and saliva. Preanalytical and analytical challenges arise in each matrix and are further compounded by the use of various stimulation and suppression tests commonly employed in clinical practice. Although not yet included in clinical guidelines, measurement of cortisol in hair may be of interest in specific situations. Immunoassays are the most widely used methods in clinical laboratories to measure cortisol, but they are susceptible to interference from synthetic and endogenous steroids, generally producing a variable overestimation of true cortisol results, especially in urine. Analysis by mass spectrometry provides higher specificity and allows simultaneous measurement of multiple steroids including synthetic steroids, thus reducing diagnostic uncertainty. An integrated review of cortisol in various disease states is also addressed.

Gene fusions are frequent in ACTH-secreting neuroendocrine neoplasms of the pancreas, but not in their non-pancreatic counterparts

Ectopic Cushing syndrome is a rare clinical disorder resulting from excessive adrenocorticotrophic hormone (ACTH) produced by non-pituitary neoplasms, mainly neuroendocrine neoplasms (NENs) of the lung, pancreas, and gastrointestinal tract, and other less common sites. The genetic background of ACTH-producing NENs has not been well studied. Inspired by an index case of ACTH-producing pancreatic NEN carrying a gene fusion, we postulated that ACTH-producing NENs might be enriched for gene fusions. We herein examined 21 ACTH-secreting NENs of the pancreas (10), lung (9), thymus (1), and kidney (1) using targeted RNA sequencing. The tumors were classified according to the most recent WHO classification as NET-G1/typical carcinoid (n = 4), NETG-2/atypical carcinoid (n = 14), and NET-G3 (n = 3). Overall, targeted RNA sequencing was successful in 11 cases (4 of 10 pancreatic tumors, 5 of 9 pulmonary tumors, and in the one renal and one thymic tumor). All four successfully tested pancreatic tumors revealed a gene fusion: two had a EWSR1::BEND2 and one case each had a KMT2A::BCOR and a TFG::ADGRG7 fusion, respectively. EWSR1 rearrangements were confirmed in both tumors with a EWSR1::BEND2 by FISH. Gene fusions were mutually exclusive with ATRX, DAXX, and MEN1 mutations (the most frequently mutated genes in NETs) in all four cases. Using RNA-based variant assessment (n = 16) or via the TSO500 panel (n = 5), no pathogenic BCOR mutations were detected in any of the cases. Taken together, gene fusions were detected in 4/4 (100%) pancreatic versus 0/7 (0%) non-pancreatic tumors, respectively. These results suggest a potential role for gene fusions in triggering the ACTH production in pancreatic NENs presenting with ectopic Cushing syndrome. While the exact mechanisms responsible for the ectopic ACTH secretion are beyond the scope of this study, overexpressed fusion proteins might be involved in promoter-mediated overexpression of pre-ACTH precursors in analogy to the mechanisms postulated for EWSR1::CREB1-mediated paraneoplastic phenomena in certain mesenchymal neoplasms. The genetic background of the ACTH-producing non-pancreatic NENs remains to be further studied.

Gene Mutations in Cushing's Syndrome

Background

Prolonged exposure to glucocorticoids can result in the development of Cushing's syndrome. Excess serum cortisol can occur due to several factors including exogenous steroids, pituitary and adrenal adenoma, and ectopic ACTH secretion.

Summary

The last 2 decades have seen significant progress in identifying new genetic and molecular mechanisms underlying hypercortisolemia. This has implicated mutations seen in a multitude of aberrant pathways that underpin the pathophysiology of Cushing's syndrome.

Key Messages

There is much overlap between the different, with mutations affecting well-understood molecular pathways such as the cAMP/PKA/MAPK and Wnt signalling systems. Further work should delineate the exact involvement of specific mutations in Cushing's syndrome and the effect of epigenetic/microenvironmental interactions. This could have implications for screening, as the identification of specific mutations may lead to earlier identification and subsequently improved prognosis.

The role of the type 7 adenylyl cyclase isoform in alcohol use disorder and depression

The translation of extracellular signals to intracellular responses involves a number of signal transduction molecules. A major component of this signal transducing function is adenylyl cyclase, which produces the intracellular "second messenger," cyclic AMP. What was initially considered as a single enzyme for cyclic AMP generation is now known to be a family of nine membrane-bound enzymes, and one cytosolic enzyme. Each member of the adenylyl cyclase family is distinguished by factors that modulate its catalytic activity, by the cell, tissue, and organ distribution of the family members, and by the physiological/behavioral functions that are subserved by particular family members. This review focuses on the Type 7 adenylyl cyclase (AC7) in terms of its catalytic characteristics and its relationship to alcohol use disorder (AUD, alcoholism), and major depressive disorder (MDD). AC7 may be part of the inherited system predisposing an individual to AUD and/or MDD in a sex-specific manner, or this enzyme may change in its expression or activity in response to the progression of disease or in response to treatment. The areas of brain expressing AC7 are related to responses to stress and evidence is available that CRF1 receptors are coupled to AC7 in the amygdala and pituitary. Interestingly, AC7 is the major form of the cyclase contained in bone marrow-derived cells of the immune system and platelets, and in microglia. AC7 is thus, poised to play an integral role in both peripheral and brain immune function thought to be etiologically involved in both AUD and MDD. Both platelet and lymphocyte adenylyl cyclase activity have been proposed as markers for AUD and MDD, as well as prognostic markers of positive response to medication for MDD. We finish with consideration of paths to medication development that may selectively modulate AC7 activity as treatments for MDD and AUD.

ACTH-secreting parotid acinic cell carcinoma unusually reported as a paraneoplastic syndrome

Paraneoplastic syndromes, induced by an immunological cross-reaction or hormone/peptide secretion, are an atypical presentation of tumors. Some tumors, such as small cell lung cancer and bronchial carcinoid, can be adrenocorticotropic hormone (ACTH) secreting tumors. Less commonly, parotid acinic cell carcinoma can be ACTH-secreting tumor leading to Cushing’s syndrome. Few literature cases have described ACTH related paraneoplastic syndrome of parotid adenocarcinoma. Because of the rarity of the condition, little is known about the management and prognosis of this phenomenon. In this report, we highlighted the case of a 59-year-old male with a past medical history of parotid adenocarcinoma treated with surgery, chemotherapy, and radiation therapy presented with clinical and biochemical signs of hyperaldosteronism. Abdominal ultra-sound, computed tomography, and magnetic resonance imaging showed hepatic mass. Liver biopsy with immunohistochemistry confirmed the presence of parotid adenocarcinoma secreting ACTH. He is on paclitaxel and carboplatin medication with good clinical response.

Genetic Basis of ACTH-Secreting Adenomas

Cushing's disease represents 60-70% of all cases of Cushing's syndrome, presenting with a constellation of clinical features associated with sustained hypercortisolism. Molecular alterations in corticotrope cells lead to the formation of ACTH-secreting adenomas, with subsequent excessive production of endogenous glucocorticoids. In the last few years, many authors have contributed to analyzing the etiopathogenesis and pathophysiology of corticotrope adenomas, which still need to be fully clarified. New molecular modifications such as somatic mutations of USP8 and other genes have been identified, and several case series and case reports have been published, highlighting new molecular alterations that need to be explored. To investigate the current knowledge of the genetics of ACTH-secreting adenomas, we performed a bibliographic search of the recent scientific literature to identify all pertinent articles. This review presents the most recent updates on somatic and germline mutations underlying Cushing's disease. The prognostic implications of these mutations, in terms of clinical outcomes and therapeutic scenarios, are still debated. Further research is needed to define the clinical features associated with the different genotypes and potential pharmacological targets.

A Comprehensive Approach to Predicting the Outcomes of Transsphenoidal Endoscopic Adenomectomy in Patients with Cushing’s Disease

Persistent and recurrent hypercortisolism after transsphenoidal endoscopic surgery (TSS) is considered to be an urgent issue prompting the search for Cushing’s disease (CD) remission predictors. The goal was to find a combination of predictors that can forecast the remission of CD after TSS. A total of 101 patients with CD who had undergone TSS were included. One year after surgery, CD remission status was evaluated. Preoperative pituitary magnetic resonance imaging (MRI) data, preoperative results of a high-dose dexamethasone suppression test (HDDST) and morning serum cortisol level collected 24 h after TSS (24 h MSeC) were compared in patients with and without remission of hypercortisolism. Remission one year after TSS was confirmed in 63 patients. CD remission predictors one year after TSS were: adenoma size ≥ 3 mm in the absence of invasive growth and the suppression of serum cortisol ≥ 74% in the HDDST, 24 h MSeC ≤ 388 nmol/L. A total of 38 patients had three favorable values of detected predictors; all of them had CD remission one year after TSS. With long-term follow-up, 36 of them remained in remission. Patients who had no one favorable predictor had no remission of hypercortisolism one year after TSS. Our data confirmed the prospects of using a combination of selected predictors to forecast CD remission after TSS.

Pathophysiology of Mild Hypercortisolism: From the Bench to the Bedside

Mild hypercortisolism is defined as biochemical evidence of abnormal cortisol secretion without the classical detectable manifestations of overt Cushing’s syndrome and, above all, lacking catabolic characteristics such as central muscle weakness, adipose tissue redistribution, skin fragility and unusual infections. Mild hypercortisolism is frequently discovered in patients with adrenal incidentalomas, with a prevalence ranging between 5 and 50%. This high variability is mainly due to the different criteria used for defining this condition. This subtle cortisol excess has also been described in patients with incidentally discovered pituitary tumors with an estimated prevalence of 5%. To date, the mechanisms responsible for the pathogenesis of mild hypercortisolism of pituitary origin are still not well clarified. At variance, recent advances have been made in understanding the genetic background of bilateral and unilateral adrenal adenomas causing mild hypercortisolism. Some recent data suggest that the clinical effects of glucocorticoid (GC) exposure on peripheral tissues are determined not only by the amount of the adrenal GC production but also by the peripheral GC metabolism and by the GC sensitivity. Indeed, in subjects with normal cortisol secretion, the combined estimate of cortisol secretion, cortisone-to-cortisol peripheral activation by the 11 beta-hydroxysteroid dehydrogenase enzyme and GC receptor sensitizing variants have been suggested to be associated with the presence of hypertension, diabetes and bone fragility, which are three well-known consequences of hypercortisolism. This review focuses on the pathophysiologic mechanism underlying both the different sources of mild hypercortisolism and their clinical consequences (bone fragility, arterial hypertension, subclinical atherosclerosis, cardiovascular remodeling, dyslipidemia, glucose metabolism impairment, visceral adiposity, infections, muscle damage, mood disorders and coagulation).

Consensus on diagnosis and management of Cushing's disease: a guideline update

Cushing's disease requires accurate diagnosis, careful treatment selection, and long-term management to optimise patient outcomes. The Pituitary Society convened a consensus workshop comprising more than 50 academic researchers and clinical experts to discuss the application of recent evidence to clinical practice. In advance of the virtual meeting, data from 2015 to present about screening and diagnosis; surgery, medical, and radiation therapy; and disease-related and treatment-related complications of Cushing's disease summarised in recorded lectures were reviewed by all participants. During the meeting, concise summaries of the recorded lectures were presented, followed by small group breakout discussions. Consensus opinions from each group were collated into a draft document, which was reviewed and approved by all participants. Recommendations regarding use of laboratory tests, imaging, and treatment options are presented, along with algorithms for diagnosis of Cushing's syndrome and management of Cushing's disease. Topics considered most important to address in future research are also identified.