An association of primary aldosteronism and adrenaline-secreting phaeochromocytoma

Coexistence of Pheochromocytoma and Primary Aldosteronism due to Multiple Aldosterone-producing Micronodules in the Ipsilateral Adrenal Gland

A 46-year-old woman was referred for hypertension and a right adrenal tumor. Primary aldosteronism (PA) was suspected because of the high plasma aldosterone concentration-to-plasma renin activity ratio. However, a subsequent evaluation revealed coexistent PA and pheochromocytoma. We performed laparoscopic right adrenalectomy. Histology of the resected adrenal gland confirmed pheochromocytoma and multiple aldosterone-producing adrenocortical micronodules. Following adrenalectomy, the urinary catecholamine levels normalized, and hyperaldosteronism improved but persisted. Hypertension also improved but persisted and was normalized with spironolactone. The clinical course indicated that the PA lesions were likely bilateral. This was a histologically proven case of coexistent pheochromocytoma and PA due to multiple aldosterone-producing micronodules.

Left adrenal aldosteronism coexisting with left paraaortic paraganglioma presenting as bilateral adrenal and left paraaortic tumors- comprehensive adrenal evaluation aiding perfect management: a case report

BACKGROUND

Coexistence of a catecholamine-secreting tumor and an adrenal cortical tumor is quite rare which makes both diagnosis and management challenging. The purpose of this article is to describe the presence of this condition, share a stepwise approach for preoperative evaluation, and review the related literature.

CASE PRESENTATION

A 44-year-old male patient had a history of hypertension and aggravating hypokalemia for years. Abdominal computed tomography incidentally found concomitant bilateral adrenal and left para-aortic tumors. Comprehensive adrenal hormone tests revealed a high aldosterone renin ratio and mildly elevated 24-h urine vanillylmandelic acid and norepinephrine levels. Subsequently, a metaiodobenzylguanidine scan showed uptake over the left para-aortic tumor, and NP-59 adrenal scintigraphy showed uptake over the left adrenal tumor. Further confirmatory tests, including captopril suppression, irbesartan suppression, and saline infusion, all confirmed the diagnosis of hyperaldosteronism. Adrenal venous sampling following 2 months of preparation with an alpha blocker demonstrated a left aldosterone-producing adrenal adenoma. Combining hormonal analysis, imaging studies, and adrenal venous sampling, the patient was diagnosed with left adrenal aldosteronoma, right adrenal nonfunctional tumor, and left para-aortic paraganglioma (PGL). Accordingly, laparoscopic left adrenalectomy and left PGL excision were performed smoothly under alpha blocker maintenance. The pathology report confirmed left adrenal cortical adenoma and left para-aortic PGL. Postoperatively, the blood pressure, biochemical tests, and adrenal hormone assays returned to normal, and related symptoms disappeared and were relatively stable during the follow-up period of two years.

CONCLUSIONS

This is the first case of left para-aortic PGL coexisting with an ipsilateral aldosterone-producing adenoma presenting as a left para-aortic tumor associated with bilateral adrenal tumors. Awareness of the rarity of this coexistence can avoid unexpected disasters during the process of evaluation and management.

Concomitant Pheochromocytoma and Primary Aldosteronism: A Case Series and Literature Review

Context

The detection and management of concomitant pheochromocytoma (PHEO) and primary aldosteronism (PA) is not well understood.

Objective

To investigate varying presentations and outcomes of cases with coexisting PHEO and PA to provide an approach to its diagnosis and management.

Methods

We conducted a retrospective case series of adult patients with concomitant PHEO and PA at Mayo Clinic from 2000-2020 and an additional review of cases before 2000 and from the medical literature. Clinical, biochemical, radiologic, and histologic parameters were measured.

Results

Fifteen patients (53% men, median age 53 years) were diagnosed with concomitant PHEO and PA. The majority presented with hypertension (13, 87%) and hypokalemia (13, 87%), and 6 (40%) presented with symptoms suggestive of catecholamine excess. All patients who underwent preoperative workup for catecholamine excess (14, 93%) were found to have biochemical levels above the upper limits of normal. Adrenal vein sampling (AVS) was performed in 9 patients (60%), where 5 (56%) were diagnosed with bilateral PA, and 4 (44%) with unilateral PA. Patients underwent either unilateral (12, 80%) or bilateral (3, 20%) adrenalectomy. Biochemical improvement or resolution of catecholamine excess was confirmed in all cases with documented measurements. Recurrence of PHEO was not observed. Six patients (40%) displayed persistent PA postoperatively.

Conclusion

Concomitant PHEO and PA is a rare but likely underreported condition. Hypertension with or without hypokalemia should prompt evaluation for PA, while any indeterminate adrenal mass should be assessed for PHEO. Coexisting disease warrants consideration of AVS to determine the laterality of PA to ensure appropriate management.

Primary Aldosteronism: Changing Definitions and New Concepts of Physiology and Pathophysiology Both Inside and Outside the Kidney

In the 60 years that have passed since the discovery of the mineralocorticoid hormone aldosterone, much has been learned about its synthesis (both adrenal and extra-adrenal), regulation (by renin-angiotensin II, potassium, adrenocorticotrophin, and other factors), and effects (on both epithelial and nonepithelial tissues). Once thought to be rare, primary aldosteronism (PA, in which aldosterone secretion by the adrenal is excessive and autonomous of its principal regulator, angiotensin II) is now known to be the most common specifically treatable and potentially curable form of hypertension, with most patients lacking the clinical feature of hypokalemia, the presence of which was previously considered to be necessary to warrant further efforts towards confirming a diagnosis of PA. This, and the appreciation that aldosterone excess leads to adverse cardiovascular, renal, central nervous, and psychological effects, that are at least partly independent of its effects on blood pressure, have had a profound influence on raising clinical and research interest in PA. Such research on patients with PA has, in turn, furthered knowledge regarding aldosterone synthesis, regulation, and effects. This review summarizes current progress in our understanding of the physiology of aldosterone, and towards defining the causes (including genetic bases), epidemiology, outcomes, and clinical approaches to diagnostic workup (including screening, diagnostic confirmation, and subtype differentiation) and treatment of PA.

Autocrine/paracrine regulatory mechanisms in adrenocortical neoplasms responsible for primary adrenal hypercorticism

A wide variety of autocrine/paracrine bioactive signals are able to modulate corticosteroid secretion in the human adrenal gland. These regulatory factors, released in the vicinity of adrenocortical cells by diverse cell types comprising chromaffin cells, nerve terminals, cells of the immune system, endothelial cells, and adipocytes, include neuropeptides, biogenic amines, and cytokines. A growing body of evidence now suggests that paracrine mechanisms may also play an important role in the physiopathology of adrenocortical hyperplasias and tumors responsible for primary adrenal steroid excess. These intra-adrenal regulatory systems, although globally involving the same actors as those observed in the normal gland, display alterations at different levels, which reinforce the capacity of paracrine factors to stimulate the activity of adrenocortical cells. The main modifications in the adrenal local control systems reported by now include hyperplasia of cells producing the paracrine factors and abnormal expression of the latter and their receptors. Because steroid-secreting adrenal neoplasms are independent of the classical endocrine regulatory factors angiotensin II and ACTH, which are respectively suppressed by hyperaldosteronism and hypercortisolism, these lesions have long been considered as autonomous tissues. However, the presence of stimulatory substances within the neoplastic tissues suggests that steroid hypersecretion is driven by autocrine/paracrine loops that should be regarded as promising targets for pharmacological treatments of primary adrenal disorders. This new potential therapeutic approach may constitute an alternative to surgical removal of the lesions that is classically recommended in order to cure steroid excess.

Expression and functional role of urotensin-II and its receptor in the adrenal cortex and medulla: novel insights for the pathophysiology of primary aldosteronism

CONTEXT

The involvement of urotensin II, a vasoactive peptide acting via the G protein-coupled urotensin II receptor, in arterial hypertension remains contentious.

OBJECTIVE

We investigated the expression of urotensin II and urotensin II receptor in adrenocortical and adrenomedullary tumors and the functional effects of urotensin II receptor activation.

DESIGN

The expression of urotensin II and urotensin II receptor was measured by real time RT-PCR in aldosterone-producing adenoma (n = 22) and pheochromocytoma (n = 10), using histologically normal adrenocortical (n = 6) and normal adrenomedullary (n = 5) tissue as control. Urotensin II peptide and urotensin II receptor protein were investigated with immunohistochemistry and immunoblotting. To identify urotensin II-related and urotensin II receptor-related pathways, a whole transcriptome analysis was used. The adrenocortical effects of urotensin II receptor activation were also assessed by urotensin II infusion with/without the urotensin II receptor antagonist palosuran in rats.

RESULTS

Urotensin II was more expressed in pheochromocytoma than in aldosterone-producing adenoma tissue; the opposite was seen for the urotensin II receptor expression. Urotensin II receptor activation in vivo in rats enhanced (by 182 +/- 9%; P < 0.007) the adrenocortical expression of immunoreactive aldosterone synthase.

CONCLUSIONS

Urotensin II is a putative mediator of the effects of the adrenal medulla and pheochromocytoma on the adrenocortical zona glomerulosa. This pathophysiological link might account for the reported causal relationship between pheochromocytoma and primary aldosteronism.

Coexistence of aldosterone-producing adrenocortical adenoma and pheochromocytoma in an ipsilateral adrenal gland

A 40-year-old female, diagnosed as essential hypertension, demonstrated a 2 cm mass in left adrenal gland by computed tomography without abnormal endocrinological findings. (131)I-adosterol and (123)I-metaiodobenzylguanidine (MIBG) scintigraphy at 39 years of age showed no abnormal accumulation. Follow up (131)I-adosterol scintigraphy performed one year later showed apparently abnormal uptake and slightly elevated uptake in left adrenal gland. Her physical examination was unremarkable except for mild hypertension. Routine blood chemistry was normal except for hypokalemia. Endocrinological date revealed suppressed plasma renin activity, and elevated plasma aldosterone concentration, and noradrenalin levels. Serial T2-weighted magnetic resonance imaging clearly demonstrated two distinct tumors. Furthermore, selective adrenal venous sampling with intravenous ACTH infusion indicated aldosterone-producing adrenocortical adenoma (APA) in left adrenal gland. During operation of adrenal tumor, blood pressure elevated markedly and complication of pheochromocytoma (PC) was suspected. Immunohistochemical findings after left adrenolectomy revealed that the adrenal mass was compatible with APA and PC. Risk of operation against undiagnosed PC is very high and, therefore, it must be diagnosed before surgery. Herein, we present an extremely rare case of the simultaneous occurrence of both APA and PC in an ipsilateral adrenal gland.

New concepts in adrenal vein sampling for aldosterone in the diagnosis of primary aldosteronism

Improved diagnostic techniques and adoption of a systematic and thorough diagnostic workup can lead to identification of the surgically correctable forms of primary aldosteronism (PA) far more frequently than expected. Adrenalectomy can provide long-term normalization of blood pressure and correction of PA in most patients with an aldosterone-producing adenoma. Forms needing surgical correction are generally held to be less common than forms requiring medical therapy; however, this can be a misconception arising from the lack of systematic use of adrenal vein sampling (AVS). Currently AVS still remains the "gold standard" for identifying unilateral causes of PA that are surgically curable. The criteria for selecting patients to undergo AVS, the technique for performing AVS, and the criteria for analyzing and interpreting its results are summarized here.

Surgically correctable hypertension caused by primary aldosteronism

Surgically correctable forms of primary aldosteronism are generally held to be less common than forms requiring medical therapy. However, with the availability of improved diagnostic techniques and the adoption of a systematic and thorough diagnostic work-up they can be identified more commonly than expected. Adrenal vein sampling (AVS) for measurement of cortisol and aldosterone has emerged as the 'gold standard' diagnostic test for identifying unilateral causes of primary aldosteronism that are amenable to surgical cure. Adrenalectomy can provide long-term normalisation of blood pressure and correction of primary aldosteronism in about 55% of patients with an aldosterone-producing adenoma and can markedly ameliorate blood pressure control in the rest. This chapter summarises the diagnostic work-up suggested for identifying these forms and examines the other diseases mimicking mineralocorticoid excess that enter into the differential diagnosis of surgically curable primary aldosteronism.

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.

A Patient with Concurrent Primary Hyperaldosteronism and Adrenal Insufficiency

A 73-year-old man with history of longstanding primary hyperaldosteronism developed adrenal insufficiency after he ruptured an abdominal aortic aneurysm and had a prolonged hypotensive episode. The patient presented as a diagnostic dilemma with recurrent hypotensive episodes and hypokalemia. A cosyntropin (Cortrosyn) stimulation test demonstrated a blunted cortisol response while at the same time having a suppressed plasma renin activity level and an elevated plasma aldosterone value. Diagnosis of Addison disease and concurrent primary hyperaldosteronism resulted in the patient's being treated with an unusual combination of prednisone and spironolactone followed by marked improvement in his symptoms.

Proadrenomedullin-derived peptides in the paracrine control of the hypothalamo-pituitary-adrenal axis

Adrenomedullin (ADM) and proadrenomedullin N-terminal 20 peptide (PAMP) are widely distributed in various body tissues and organs, including the hypothalamo-pituitary-adrenal (HPA) axis. ADM and PAMP inhibit in vitro release of ACTH from pituitary corticotropes, and findings suggest that this effect may become relevant when an exceedingly high ACTH secretion must be counteracted. ADM directly supresses angiotensin-II- and K+-stimulated aldosterone secretion from ZG cells, acting through calcitonin gene-related peptide (CGRP) type 1 ADM(22-52)-sensitive receptors, the activation of which is likely to impair Ca2+ influx. In contrast, ADM stimulates medullary chromaffin cells to release catecholamines, which in turn enhance aldosterone secretion acting in a paracrine manner. Also this effect of ADM occurs via CGRP1 receptors, which are coupled with the adenylate cyclase-dependent cascade. There is indication that in vivo these two opposite effects of ADM on ZG may interact with each other when normal aldosterone secretion has to be restored. ADM exerts a mitogenic effect on rat ZG, acting via CGRP1 receptors that activate the tyrosine kinase-dependent mitogen-activated protein kinase cascade. These findings, along with the demonstration of a high level of ADM gene expression in adrenocortical adenomas and carcinomas, may suggest a role for ADM as adrenocortical growth stimulator and tumor promoter. PAMP, like ADM, suppresses aldosterone response of ZG cells to Ca2+-dependent agonists, but, in contrast with ADM, it inhibits catecholamine release by adrenal medulla. Both effects of PAMP are mediated by PAMP(12-20)-sensitive receptors, whose signaling mechanism is likely to involve the blockade of voltage-gated Ca2+ channels. The concentrations attained by ADM and PAMP in the blood rule out the possibility that they act as true circulating hormones. Conversely, their content in the hypothalamo-pituitary complex and adrenal gland is consistent with a paracrine mechanism of action, which may play an important role in pathophysiological conditions where the function of the HPA axis has to be reset.

Secretin, glucagon, gastric inhibitory polypeptide, parathyroid hormone, and related peptides in the regulation of the hypothalamus- pituitary-adrenal axis

Secretin, glucagon, gastric inhibitory polypeptide (GIP), and parathyroid hormone (PTH) belong, together with vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase (AC)-activating polypeptide, to a family of peptides (the VIP-secretin-glucagon family), which also includes growth hormone-releasing hormone and exendins. All the members of this peptide family possess a remarkable amino-acid sequence homology, and bind to G-protein-coupled receptors, whose signaling mechanism primarily involves AC/protein kinase A and phospholipase C/protein kinase C cascades. VIP and pituitary AC-activating polypeptide play a role in the regulation of the hypothalamus-pituitary-adrenal (HPA) axis, and in this review we survey findings that also other members of the VIP-secretin-glucagon family may have the same function. Secretin and secretin receptors are expressed in the hypothalamus and pituitary gland, and secretin inhibits adrenocorticotropic hormone (ACTH) release. No evidence is available for the presence of secretin receptors in adrenal glands, but secretin selectively depresses the glucocorticoid response to ACTH of dispersed zona fasciculata-reticularis (ZF/R) cells. Glucagon and glucagon-like peptide-1 are contained in the hypothalamus, and all the components of the HPA axis are provided with glucagon and glucagons-like-1 receptors. These peptides exert a short-term inhibitory effect on stress-induced pituitary ACTH release and depress the ZF/R cell response to ACTH by inhibiting the AC/protein kinase A cascade; they also stimulate hypothalamic arginine-vasopressin release. GIP receptors are present in the ZF/R of the normal adrenals, and are particularly abundant in some types of adrenocortical adenomas and hyperplasias. GIP, through the activation of the AC/protein kinase A cascade, evokes a sizeable glucocorticoid secretagogue effect, leading to the identification of a food/GIP-dependent Cushing's syndrome. PTH and PTH-related protein are expressed in the hypothalamus and pituitary gland, and PTH and PTH-related protein receptors in all the components of the HPA axis. Both peptides enhance ACTH and arginine-vasopressin release, as well as stimulate aldosterone and glucocorticoid secretion of dispersed zona glomerulosa and ZF/R cells, respectively. The involvement of growth hormone-releasing hormone and exendins in the functional regulation of the HPA axis has not yet been extensively investigated.

Pheochromocytoma and sub-clinical Cushing's syndrome during pregnancy: diagnosis, medical pre-treatment and cure by laparoscopic unilateral adrenalectomy

The coexistence of pheochromocytoma and primary adrenal Cushing's syndrome of the same adrenal gland has rarely been reported. We describe here the case of a female patient presenting with mild Cushing's stigmata, hypertension and diabetes mellitus in whom we diagnosed a pheochromocytoma of the left adrenal gland with coexisting non-ACTH-dependent cortisol hypersecretion. While hormonal work-up was still in progress, the patient became pregnant and wanted to carry her pregnancy to full-term. A laparoscopic adrenalectomy in the 17th week of gestation was decided upon and the patient accordingly prepared for surgery by pre-treatment with phenoxybenzamine. Successful surgery--the first ever reported laparoscopic resection of a pheochromocytoma in pregnancy--without perioperative complications was performed under general anesthesia, with the patient receiving peri- and post-operative hydrocortisone substitution. Pathohistological examination revealed a pheochromocytoma with positive immunostaining for interleukin-6 (IL-6) and negative immunostaining for ACTH, vasoactive intestinal polypeptide (VIP) and cytochrome P450, and with no signs of malignancy. A paracrine stimulation of the ipsilateral adrenal cortex by IL-6 produced by the pheochromocytoma, leading to cortical hyperplasia and subclinical Cushing's syndrome, is suggested by the positive immunostaining for IL-6 and the MRI findings. Post-operatively, secondary adrenal insufficiency ensued, necessitating continuing hydrocortisone replacement over 12 months. Hypertension resolved after surgery, and diabetes after the uncomplicated vaginal delivery at term.

Hyper- and hypoaldosteronism

Aldosterone participates in blood volume and serum potassium homeostasis, which in turn regulate aldosterone secretion by the zona glomerulosa of the adrenal cortex. Autonomous aldosterone hypersecretion leads to hypertension and hypokalemia. Improved screening techniques have led to a re-evaluation of the frequency of primary aldosteronism among adults with hypertension, recognizing that normokalemic cases are more frequent than was previously appreciated. The genetic basis of glucocorticoid remediable aldosteronism has been elucidated and adequately explains most of the pathophysiologic features of this disorder. A new form of familial aldosteronism has been described, familial hyperaldosteronism type II; linkage analysis and direct mutation screening has shown that this disorder is unrelated to mutations in the genes for aldosterone synthase or the angiotensin II receptor. The features of aldosterone hypersecretion may be due to non-aldosterone-mediated mineralocorticoid excess. These include two causes of congenital adrenal hyperplasia (11 beta-hydroxylase deficiency and 17 alpha-hydroxylase deficiency), the syndrome of apparent mineralocorticoid excess (AME) due to 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) deficiency, primary glucocorticoid resistance, Liddle's syndrome due to activating mutations of the renal epithelial sodium channel, and exogenous sources of mineralocorticoid, such as licorice, or drugs, such as carbenoxolone. The features of mineralocorticoid excess are also often seen in Cushing's syndrome. Hypoaldosteronism may lead to hypotension and hyperkalemia. Hypoaldosteronism may be due to inadequate stimulation of aldosterone secretion (hyporeninemic hypoaldosteronism), defects in adrenal synthesis of aldosterone, or resistance to the ion transport effects of aldosterone, such as are seen in pseudohypoaldosteronism type I (PHA I). PHA I is frequently due to mutations involving the amiloride sensitive epithelial sodium channel. Gordon's syndrome (PHA type II) is due to resistance to the kaliuretic but not sodium reabsorptive effects of aldosterone for which the genetic basis is still unknown. This review aims to provide a survey of the clinical disorders of aldosterone excess and deficiency and their clinical management, with a focus on primary aldosteronism and isolated aldosterone deficiency.

Role of tachykinins in the regulation of the hypothalamo-pituitary-adrenal axis

Tachykinins are a family of neuropeptides, which act by binding to three main subtypes of G protein-coupled receptors, named NK1, NK2 and NK3. Tachykinins are contained in both nerve fibers and secretory cells of the hypothalamo-pituitary-adrenal (HPA) axis, and evidence indicates that they take part in the functional control of it. Tachykinins involved in this function include substance P (SP), neuropeptide K and its derivative neurokinin A (NKA), and neurokinin B, which preferentially bind to NK1, NK2 and NK3 receptors, respectively. NK1 agonists exert an inhibitory effect on the hypothalamo pituitary CRH/ACTH system, while NK2 and perhaps NK3 agonists stimulate it, thereby controlling the secretion and growth of the adrenal cortex via circulating ACTH. Intra-adrenal tachykinins may also affect the cortex function. Their direct action on adrenocortical cells is doubtful and probably pharmacologic in nature, but several investigations suggest that tachykinins indirectly stimulate the cortex by acting on medullary chromaffin cells, which in turn exert a paracrine control on adrenocortical cells. SP enhances aldosterone production of zona glomerulosa by eliciting catecholamine secretion; neuropeptide K and NKA raise glucocorticoid production of zonae fasciculata and reticularis through the activation of the intramedullary CRH/ACTH system. The relevance of these effects of tachykinins under basal conditions is questionable, although there are indications that SP is involved in the maintenance of a normal growth and steroidogenic capacity of rat zona glomerulosa, and that SP and NKA play an important role in the stimulation of the adrenal growth during the fetal life. In contrast, evidence has been provided that the role of tachykinins, and especially of SP, could become very relevant under paraphysiological (e.g., physical or inflammatory stresses) or pathological conditions (e.g., ACTH-secreting pituitary tumors), when an excess of steroid-hormone production has to be counteracted.

Role of VIP, PACAP, and related peptides in the regulation of the hypothalamo-pituitary-adrenal axis

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are members of a family of regulatory peptides that are widely distributed in the body and share numerous biologic actions. The two peptides display a remarkable amino acid-sequence homology, and bind to a class of G protein-coupled receptors, named PACAP/VIP receptors (PVRs), whose signaling mechanism mainly involves the activation of adenylate-cyclase and phospholipase-C cascades. A large body of evidence suggests that VIP and PACAP play a role in the control of the hypothalamo--pituitary-adrenal (HPA) axis, almost exclusively acting in a paracrine manner, since their blood concentration is very low. VIP and PACAP are contained in both nerve fibers and neurons of the hypothalamus, and VIP, but not PACAP, is also synthesized in the pituitary gland. Both peptides are expressed in the adrenal gland, and especially in medullary chromaffin cells. All the components of the HPA axis are provided with PVRs. VIP and PACAP enhance pituitary ACTH secretion, VIP by eliciting the hypothalamic release of CRH and potentiating its secretagogue action, and PACAP by directly stimulating pituitary corticotropes. Through this central mechanism, VIP and PACAP may increase mineralo- and glucocorticoid secretion of the adrenal cortex. VIP but not PACAP also exerts a weak direct secretagogue action on adrenocortical cells by activating both PVRs and probably a subtype of ACTH receptors. VIP and PACAP raise aldosterone production via a paracrine indirect mechanism involving the stimulation of medullary chromaffin cells to release catecholamines, which in turn enhance the secretion of zona glomerulosa cells via a beta-adrenoceptor-mediated mechanism. PACAP appears to be able to evoke a glucocorticoid response through the activation, at least in the rat, of the intramedullary CRH/ACTH system. The relevance of these effects of VIP and PACAP under basal conditions is questionable, although there are indications that endogenous VIP is involved in the maintenance of the normal growth and steroidogenic capacity of rat adrenal cortex. However, indirect evidence suggests that these peptides might play a relevant role under paraphysiological conditions (e.g., in the mediation of HPA axis responses to cold and inflammatory stresses) or may be somehow involved in the pathogenesis of Cushing disease or some case of hyperaldosteronism associated with secreting pheochromocytomas.

Morphological and functional studies of the paracrine interaction between cortex and medulla in the adrenal gland

Within the last years it has become evident that besides the hypothalamo-pituitary-adrenal axis, extrapituitary mechanisms exist that regulate the activity of the adrenal cortex. In this context, intra-adrenal regulatory mechanisms play an important role. Several secretory products from adrenomedullary cells are able to influence adrenocortical steroidogenesis. Since the main blood flow within the adrenal is directed centripetally from the cortex to the medulla, chromatin cells should act on cortical cells in a paracrine manner. The morphological prerequisite for this regulatory pathway is seen in the close apposition of the two tissues. Within the mammalian adrenal, the two endocrine tissues are interwoven to an astonishing degree with cortical cells located within the medulla and vice versa. It is concluded from morphological and functional studies that paracrine interactions between cortex and medulla play an important role in the regulation of adrenocortical steroidogenesis.

PCR-SSCP analysis of the p53 gene in tumours of the adrenal gland

1. Mutations of the p53 tumour suppressor gene are relatively common in the aetiology of a wide spectrum of tumour types, both sporadic and familial. 2. The majority of mutations of the p53 gene are reported to be in the highly conserved region of exons 5-8. 3. Alterations in exons 4, 5 and 7 of the p53 gene in patients with functional adrenal tumours, including aldosterone-producing adenomas, have recently been described. 4. In the present study PCR-SSCP was used to examine the exons 4-9 of the p53 gene in paired peripheral blood leucocyte and tumour DNA in a variety of adrenal tumours, including aldosterone-producing carcinoma and adenoma (both familial and sporadic), phaeochromocytoma and incidentaloma. 5. No evidence was found for mutations in exons 4-9 of the p53 gene in these varieties of adrenal tumours.