Ectopic adrenocorticotropin (ACTH) and corticotropin-releasing hormone (CRH) production in the adrenal gland: basic and clinical aspects

Cortisol: Biosensing and detection strategies

Cortisol, a crucial steroid hormone synthesized by the adrenal glands, has diverse impacts on multiple physiological processes, such as metabolism, immune function, and stress management. Disruption in cortisol levels can result in conditions like Cushing's syndrome and Addison's disease. This review provides an in-depth exploration of cortisol, covering its structure, various forms in the body, detection methodologies, and emerging trends in cancer treatment and detection. Various techniques for cortisol detection, including electrochemical, chromatographic, and immunoassay methods were discussed and highlighted for their merits and applications. Electrochemical immunosensing emerges as a promising approach, which offered high sensitivity and low detection limits. Moreover, the review delves into the intricate relationship between cortisol and cancer, emphasizing cortisol's role in cancer progression and treatment outcomes. Lastly, the utilization of biomarkers, in-silico modeling, and machine learning for electrochemical cortisol detection were explored, which showcased innovative strategies for stress monitoring and healthcare advancement.

Case Report: Three Rare Cases of Ectopic ACTH Syndrome Caused by Adrenal Medullary Hyperplasia

Ectopic ACTH syndrome (EAS) accounts for 10-20% of endogenous Cushing's syndrome (CS). Hardly any cases of adrenal medullary hyperplasia have been reported to ectopically secrete adrenocorticotropic hormone (ACTH). Here we describe a series of three patients with hypercortisolism secondary to ectopic production of ACTH from adrenal medulla. Cushingoid features were absent in case 1 but evident in the other two cases. Marked hypokalemia was found in all three patients, but hyperglycemia and osteoporosis were present only in case 2. All three patients showed significantly elevated serum cortisol and 24-h urinary cortisol levels. The ACTH levels ranged from 19.8 to 103.0pmol/L, favoring ACTH-dependent Cushing's syndrome. Results of bilateral inferior petrosal sinus sampling (BIPSS) for case 1 and case 3 confirmed ectopic origin of ACTH. The extremely high level of ACTH and failure to suppress cortisol with high dose dexamethasone suppression test (HDDST) suggested EAS for patient 2. However, image studies failed to identify the source of ACTH secretion. Bilateral adrenalectomy was performed for rapid control of hypercortisolism. After surgery, cushingoid features gradually disappeared for case 2 and case 3. Blood pressure, blood glucose and potassium levels returned to normal ranges without medication for case 2. The level of serum potassium also normalized without any supplementation for case 1 and case 3. The ACTH levels of all three patients significantly decreased 3-6 months after surgery. Histopathology revealed bilateral adrenal medullary hyperplasia and immunostaining showed positive ACTH staining located in adrenal medulla cells. In summary, our case series reveals the adrenal medulla to be a site of ectopic ACTH secretion. Adrenal medulla-originated EAS makes the differential diagnosis of ACTH-dependent Cushing's syndrome much more difficult. Control of the hypercortisolism is mandatory for such patients.

60 YEARS OF POMC: Adrenal and extra-adrenal functions of ACTH

The pituitary adrenocorticotropic hormone (ACTH) plays a pivotal role in homeostasis and stress response and is thus the major component of the hypothalamo-pituitary-adrenal axis. After a brief summary of ACTH production from proopiomelanocortin (POMC) and on ACTH receptor properties, the first part of the review covers the role of ACTH in steroidogenesis and steroid secretion. We highlight the mechanisms explaining the differential acute vs chronic effects of ACTH on aldosterone and glucocorticoid secretion. The second part summarizes the effects of ACTH on adrenal growth, addressing its role as either a mitogenic or a differentiating factor. We then review the mechanisms involved in steroid secretion, from the classical Cyclic adenosine monophosphate second messenger system to various signaling cascades. We also consider how the interaction between the extracellular matrix and the cytoskeleton may trigger activation of signaling platforms potentially stimulating or repressing the steroidogenic potency of ACTH. Finally, we consider the extra-adrenal actions of ACTH, in particular its role in differentiation in a variety of cell types, in addition to its known lipolytic effects on adipocytes. In each section, we endeavor to correlate basic mechanisms of ACTH function with the pathological consequences of ACTH signaling deficiency and of overproduction of ACTH.

Role of ACTH in the Interactive/Paracrine Regulation of Adrenal Steroid Secretion in Physiological and Pathophysiological Conditions

In the normal human adrenal gland, steroid secretion is regulated by a complex network of autocrine/paracrine interactions involving bioactive signals released by endothelial cells, nerve terminals, chromaffin cells, immunocompetent cells, and adrenocortical cells themselves. ACTH can be locally produced by medullary chromaffin cells and is, therefore, a major mediator of the corticomedullary functional interplay. Plasma ACTH also triggers the release of angiogenic and vasoactive agents from adrenocortical cells and adrenal mast cells and, thus, indirectly regulates steroid production through modulation of the adrenal blood flow. Adrenocortical neoplasms associated with steroid hypersecretion exhibit molecular and cellular defects that tend to reinforce the influence of paracrine regulatory loops on corticosteroidogenesis. Especially, ACTH has been found to be abnormally synthesized in bilateral macronodular adrenal hyperplasia responsible for hypercortisolism. In these tissues, ACTH is detected in a subpopulation of adrenocortical cells that express gonadal markers. This observation suggests that ectopic production of ACTH may result from impaired embryogenesis leading to abnormal maturation of the adrenogonadal primordium. Globally, the current literature indicates that ACTH is a major player in the autocrine/paracrine processes occurring in the adrenal gland in both physiological and pathological conditions.

Role of ACTH and Other Hormones in the Regulation of Aldosterone Production in Primary Aldosteronism

The major physiological regulators of aldosterone production from the adrenal zona glomerulosa are potassium and angiotensin II; other acute regulators include adrenocorticotropic hormone (ACTH) and serotonin. Their interactions with G-protein coupled hormone receptors activate cAMP/PKA pathway thereby regulating intracellular calcium flux and CYP11B2 transcription, which is the specific steroidogenic enzyme of aldosterone synthesis. In primary aldosteronism (PA), the increased production of aldosterone and resultant relative hypervolemia inhibits the renin and angiotensin system; aldosterone secretion is mostly independent from the suppressed renin-angiotensin system, but is not autonomous, as it is regulated by a diversity of other ligands of various eutopic or ectopic receptors, in addition to activation of calcium flux resulting from mutations of various ion channels. Among the abnormalities in various hormone receptors, an overexpression of the melanocortin type 2 receptor (MC2R) could be responsible for aldosterone hypersecretion in aldosteronomas. An exaggerated increase in plasma aldosterone concentration (PAC) is found in patients with PA secondary either to unilateral aldosteronomas or bilateral adrenal hyperplasia (BAH) following acute ACTH administration compared to normal individuals. A diurnal increase in PAC in early morning and its suppression by dexamethasone confirms the increased role of endogenous ACTH as an important aldosterone secretagogue in PA. Screening using a combination of dexamethasone and fludrocortisone test reveals a higher prevalence of PA in hypertensive populations compared to the aldosterone to renin ratio. The variable level of MC2R overexpression in each aldosteronomas or in the adjacent zona glomerulosa hyperplasia may explain the inconsistent results of adrenal vein sampling between basal levels and post ACTH administration in the determination of source of aldosterone excess. In the rare cases of glucocorticoid remediable aldosteronism, a chimeric CYP11B2 becomes regulated by ACTH activating its chimeric CYP11B1 promoter of aldosterone synthase in bilateral adrenal fasciculate-like hyperplasia. This review will focus on the role of ACTH on excess aldosterone secretion in PA with particular focus on the aberrant expression of MC2R in comparison with other aberrant ligands and their GPCRs in this frequent pathology.

Chromaffin cells: the peripheral brain

Chromaffin cells probably are the most intensively studied of the neural crest derivates. They are closely related to the nervous system, share with neurons some fundamental mechanisms and thus were the ideal model to study the basic mechanisms of neurobiology for many years. The lessons we have learned from chromaffin cell biology as a peripheral model for the brain and brain diseases pertain more than ever to the cutting edge research in neurobiology. Here, we highlight how studying this cell model can help unravel the basic mechanisms of cell renewal and regeneration both in the central nervous system (CNS) and neuroendocrine tissue and also can help in designing new strategies for regenerative therapies of the CNS.

Acute and chronic stress increase DHEAS concentrations in rhesus monkeys

Most studies on the stress-responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis have focused on glucocorticoids, while few studies have investigated the adrenal secretion of dehydroepiandrosterone sulfate (DHEAS), which is unique to primates. Monkeys were chair-restrained for 2h per day for seven consecutive days, and blood samples were collected upon placement in the chair, and at 15, 30, 60 and 120 min later. Like cortisol, DHEAS concentrations increased throughout the initial session of chair restraint (acute stress). Unlike the cortisol response, which decreased after repeated exposure to the stressor, the DHEAS response was sustained throughout the seventh session of restraint (chronic stress) and response to the seventh session of restraint did not differ from the DHEAS response to the initial session. Like cortisol, DHEAS concentrations showed a diurnal rhythm with higher concentrations in the morning compared to the evening and a decrease in response to dexamethasone (DEX) administration. After repeated exposure to the stressor, the suppression of DHEAS in response to dexamethasone was more complete, suggesting an increase in negative feedback sensitivity. These data show that DHEAS concentrations increase in response to both acute and chronic (repeated) stress and provide another measure of HPA activity that parallels cortisol during acute responses to stress but diverges in chronic or repeated stress.

Adrenal Pheochromocytoma With Contralateral Adrenocortical Adenoma in a Cat

A 7-year-old, neutered male cat was presented with a 6-month history of progressive polyuria, polydipsia, polyphagia, aggression, and weight gain. Previous blood work, urinalysis, and radiographs did not delineate a cause for the clinical signs. An ultrasound revealed bilateral adrenal gland enlargement. A low-dose dexamethasone suppression test was consistent with hyperadrenocorticism. Based on these findings, bilateral adrenalectomy was attempted and successfully performed. Histopathology was consistent with a cortical adenoma in the right adrenal gland and a pheochromocytoma in the left adrenal gland. This association has never been reported in the cat.

Surgery for Cushing's syndrome: an historical review and recent ten-year experience

BACKGROUND

Cushing's syndrome (CS), due to multiple etiologies, is a disorder associated with the ravages of cortisol excess. The purpose of this review article is to provide a historical synopsis of surgery for CS, review a recent 10-year period of operative management at a tertiary care facility, and to outline a practical approach to diagnosis and management.

MATERIALS AND METHODS

From 1996 to 2005, 298 patients underwent 322 operative procedures for CS at Mayo Clinic, Rochester, Minnesota. A retrospective chart review was carried out. Data was gathered regarding demographics, preoperative assessment, procedures performed, and outcomes. Data are presented as counts and percentages. Five-year survival rates were calculated where applicable by the Kaplan-Meier method. Statistical analysis was carried out with SAS, version 9 (SAS Institute, Inc., Cary, NC).

RESULTS

Two-hundred thirty-one patients (78%) had ACTH-dependent CS and 67 patients (22%) had ACTH-independent CS. One-hundred ninety-six patients (66%) had pituitary-dependent CS and 35 patients (12%) had ectopic ACTH syndrome. Fifty-four patients (18%) had cortisol-secreting adenomas, 10 patients (3%) had cortisol-producing adrenocortical carcinomas, and 1% had other causes. Cure rates for first time pituitary operations (transsphenoidal, sublabial, and endonasal) were 80% and 55% for reoperations. Most benign adrenal processes could be managed laparoscopically. Five-year survival rates (all causes) were 90%, 51%, and 23% for adrenocortical adenomas, ectopic ACTH syndrome, and adrenocortical carcinomas, respectively.

CONCLUSIONS

Surgery for CS is highly successful for pituitary-dependent CS and most ACTH-independent adrenal causes. Bilateral total adrenalectomy can also provide effective palliation from the ravages of hypercortisolism in patients with ectopic ACTH syndrome and for those who have failed transsphenoidal surgery. Unfortunately, to date, adrenocortical carcinomas are rarely cured. Future successes with this disease will likely depend on a better understanding of tumor biology, more effective adjuvant therapies and earlier detection. Clearly, IPSS, advances in cross-sectional imaging, along with developments in transsphenoidal and laparoscopic surgery, have had the greatest impact on today's management of the complex patient with CS.

A case of catecholamine and glucocorticoid excess syndrome due to a corticotropin-secreting paraganglioma

We present a case of a 61-year-old female patient with ectopic corticotropin (ACTH) syndrome, hypopituitarism, and catecholamine excess due to a paraganglioma at the inferior pole of the left kidney. In this article we discuss the hormonal findings in the patient and its consequences, the pitfalls of the endocrine workup, and the results of our immunohistological and molecular studies in more detail.

Gene expression of phenylethanolamine N-methyltransferase in corticotropin-releasing hormone knockout mice during stress exposure

AIMS

Epinephrine (EPI) synthesizing enzyme phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28) is primarily localized in the adrenal medulla (AM). We have recently described existence of the PNMT gene expression in cardiac atria and ventricles and in sympathetic ganglia of adult rats and mice. The aim of the present work was to study regulation of the PNMT gene expression in corticotropin-releasing hormone knockout mice (CRH KO) and matched control wild-type mice (WT) under normal and stress conditions.

METHODS

Levels of the PNMT mRNA were determined by RT-PCR; PNMT immunoprotein and protein of transcription factor EGR-1 by Western Blot. Plasma EPI and corticosterone (CORT) levels were determined by radioenzymatic and RIA methods. Immobilization (IMMO) was used as a stressor.

RESULTS

Stress-induced increases in the PNMT mRNA and protein levels observed in WT mice were almost completely absent in CRH KO mouse adrenal medulla, stellate ganglia, and cardiac atria, while ventricular PNMT mRNA elevation was not CRH-dependent. Plasma EPI and CORT levels were markedly reduced in CRH KO compared to WT mice both before and after the stress. Levels of EGR-1, crucial transcription factor for regulation of the PNMT were highly increased in stressed WT and CRH KO mice in cardiac areas, but not in the adrenal medulla.

CONCLUSIONS

Data show that the CRH deficiency can markedly prevent immobilization-triggered induction of the PNMT mRNA and protein levels in the adrenal medulla and stellate ganglia. Reduced plasma epinephrine and corticosterone levels and adrenal medullary EGR-1 protein levels in CRH knockout versus WT mice during stress indicate that the HPA axis plays a crucial role in regulation of the PNMT gene expression in these organs. Cardiac atrial PNMT gene expression with stress is also dependent on intact HPA axis. However, in cardiac ventricles, especially after the single stress exposure, its expression is not impaired by CRH deficiency. Since cardiac EGR-1 protein levels in CRH KO mice are also not affected by the single stress exposure, we propose existence of different regulation of the PNMT gene expression, especially in the cardiac ventricles.Overall, our findings reveal that the PNMT gene expression is regulated through the HPA in both sympathoadrenal system and the heart and also via EGR-1 in the adrenal medulla, but apparently not in the heart. Regulation of the PNMT gene expression in various compartments of heart includes both corticosterone-dependent and independent mechanisms.

Multi-step approach in a complex case of Cushing's syndrome and medullary thyroid carcinoma

The diagnosis of Cushing's syndrome (CS) may sometimes be cumbersome. In particular, in ACTH-dependent CS it may be difficult to distinguish between the presence of an ACTH-secreting pituitary adenoma and ectopic ACTH and/or CRH secretion. In such instances, the etiology of CS may remain unknown despite extensive diagnostic workout, and the best therapeutic option for each patient has to be determined. We report here the case of a 54-yr-old man affected by ACTH-dependent CS in association with a left adrenal adenoma and medullary thyroid carcinoma (MTC). He presented with clinical features and laboratory indexes of hypercortisolism associated with elevated levels of calcitonin. Ectopic CS due to MTC was reported previously. In our case hypercortisolism persisted after surgical treatment of MTC. Thorough diagnostic assessment was performed, in order to define the aetiology of CS. He was subjected to basal and dynamic hormonal evaluation, including bilateral inferior petrosal sinus sampling. Extensive imaging evaluation was also performed. Overall, the laboratory data together with the results of radiological procedures suggested that CS might be due to inappropriate CRH secretion. However, the source of CRH secretion in this patient remained unknown. It was then decided to remove the left adenomatous adrenal gland. Cortisol level fell and has remained within the normal range nine months after surgery. This case well depicts the complexity of the diagnostic workout, which is needed sometimes to correctly diagnose and treat CS, and suggests that monolateral adrenalectomy may represent, at least temporarily, a reasonable therapeutic option in occult ACTH-dependent hypercortisolism.

Endogenous Ligands of PACAP/VIP Receptors in the Autocrine–Paracrine Regulation of the Adrenal Gland

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are the main endogenous ligands of a class of G protein-coupled receptors (Rs). Three subtypes of PACAP/VIP Rs have been identified and named PAC(1)-Rs, VPAC(1)-Rs, and VPAC(2)-Rs. The PAC(1)-R almost exclusively binds PACAP, while the other two subtypes bind with about equal efficiency VIP and PACAP. VIP, PACAP, and their receptors are widely distributed in the body tissues, including the adrenal gland. VIP and PACAP are synthesized in adrenomedullary chromaffin cells, and are released in the adrenal cortex and medulla by VIPergic and PACAPergic nerve fibers. PAC(1)-Rs are almost exclusively present in the adrenal medulla, while VPAC(1)-Rs and VPAC(2)-Rs are expressed in both the adrenal cortex and medulla. Evidence indicates that VIP and PACAP, acting via VPAC(1)-Rs and VPAC(2)-Rs coupled to adenylate cyclase (AC)- and phospholipase C (PLC)-dependent cascades, stimulate aldosterone secretion from zona glomerulosa (ZG) cells. There is also proof that they can also enhance aldosterone secretion indirectly, by eliciting the release from medullary chromaffin cells of catecholamines and adrenocorticotropic hormone (ACTH), which in turn may act on the cortical cells in a paracrine manner. The involvement of VIP and PACAP in the regulation of glucocorticoid secretion from inner adrenocortical cells is doubtful and surely of minor relevance. VIP and PACAP stimulate the synthesis and release of adrenomedullary catecholamines, and all three subtypes of PACAP/VIP Rs mediate this effect, PAC(1)-Rs being coupled to AC, VPAC(1)-Rs to both AC and PLC, and VPAC(2)-Rs only to PLC. A privotal role in the catecholamine secretagogue action of VIP and PACAP is played by Ca(2+). VIP and PACAP may also modulate the growth of the adrenal cortex and medulla. The concentrations attained by VIP and PACAP in the blood rule out the possibility that they act as true circulating hormones. Conversely, their adrenal content is consistent with a local autocrine-paracrine mechanism of action.

Urocortin 1, urocortin 3/stresscopin, and corticotropin-releasing factor receptors in human adrenal and its disorders

CONTEXT

Urocortin 1 (Ucn1) and urocortin 3 (Ucn3)/stresscopin are new members of the corticotropin-releasing factor (CRF) neuropeptide family. Ucn1 binds to both CRF type 1 (CRF1) and type 2 receptors (CRF2), whereas Ucn3 is a specific agonist for CRF2. Recently, direct involvement of the locally synthesized CRF family in adrenocortical function has been proposed.

OBJECTIVE, DESIGN, AND SETTING

We examined in situ expression of Ucn and CRF receptors in nonpathological human adrenal gland and its disorders using immunohistochemistry and mRNA in situ hybridization.

RESULTS

Ucn immunoreactivity was localized in the cortex and medulla of nonpathological adrenal glands. Ucn1 immunoreactivity was marked in the medulla, whereas Ucn3 was immunostained mostly in the cortex. Both CRF type 1 and CRF2 were expressed in the cortex, particularly in the zonae fasciculata and reticularis but very weakly or undetectably in the medulla. Immunohistochemistry in serial tissue sections with mirror images revealed that both Ucn3 and CRF2 were colocalized in more than 85% of the adrenocortical cells. mRNA in situ hybridization confirmed these findings above. In fetal adrenals, Ucn and CRF receptors were expressed in both fetal and definitive zones of the cortex. Ucn and CRF receptors were all expressed in the tumor cells of pheochromocytomas, adrenocortical adenomas, and carcinomas, but its positivity was less than that in nonpathological adrenal glands, suggesting that Ucn1, Ucn3, and CRF receptors were down-regulated in these adrenal neoplasms.

CONCLUSIONS

Ucn1, Ucn3, and CRF receptors are all expressed in human adrenal cortex and medulla and may play important roles in physiological adrenal functions.