Improvement of hypercortisolism by β-blocker therapy in subclinical Cushing's syndrome associated with ACTH-independent macronodular adrenocortical hyperplasia

Clinical, pathophysiologic, genetic and therapeutic progress in Primary Bilateral Macronodular Adrenal Hyperplasia

Patients with primary bilateral macronodular adrenal hyperplasia (PBMAH) usually present bilateral benign adrenocortical macronodules at imaging and variable levels of cortisol excess. PBMAH is a rare cause of primary overt Cushing's syndrome, but may represent up to one third of bilateral adrenal incidentalomas with evidence of cortisol excess. The increased steroidogenesis in PBMAH is often regulated by various G-protein coupled receptors aberrantly expressed in PBMAH tissues; some receptor ligands are ectopically produced in PBMAH tissues creating aberrant autocrine/paracrine regulation of steroidogenesis. The bilateral nature of PBMAH and familial aggregation, led to the identification of germline heterozygous inactivating mutations of the ARMC5 gene, in 20-25% of the apparent sporadic cases and more frequently in familial cases; ARMC5 mutations/pathogenic variants can be associated with meningiomas. More recently, combined germline mutations/pathogenic variants and somatic events inactivating the KDM1A gene were specifically identified in patients affected by GIP-dependent PBMAH. Functional studies demonstrated that inactivation of KDM1A leads to GIP-receptor (GIPR) overexpression and over or down-regulation of other GPCRs. Genetic analysis is now available for early detection of family members of index cases with PBMAH carrying identified germline pathogenic variants. Detailed biochemical, imaging, and co-morbidities assessment of the nature and severity of PBMAH is essential for its management. Treatment is reserved for patients with overt or mild cortisol/aldosterone or other steroid excesses taking in account co-morbidities. It previously relied on bilateral adrenalectomy; however recent studies tend to favor unilateral adrenalectomy, or less frequently, medical treatment with cortisol synthesis inhibitors or specific blockers of aberrant GPCR.

An Overview of the Heterogeneous Causes of Cushing’s Syndrome due to Primary Macronodular Adrenal Hyperplasia (PMAH)

Primary macronodular adrenal hyperplasia (PMAH) is considered a rare cause of adrenal Cushing syndrome, is pituitary ACTH-independent, generally results from bilateral adrenal macronodules (>1 cm), and is often associated with variable cortisol secretion, resulting in a heterogeneous clinical presentation. Recent advances in the molecular pathogenesis of PMAH have offered new insights into the comprehension of this heterogeneous and complex adrenal disorder. Different molecular mechanisms involving the actors of the cAMP/protein kinase A pathway have been implicated in the development of PMAH, including germline and/or somatic molecular defects such as hyperexpression of the G-protein aberrant receptors and pathogenic variants of MC2R, GNAS, PRKAR1A, and PDE11A. Nevertheless, since 2013, the ARMC5 gene is believed to be a major genetic cause of PMAH, accounting for more than 80% of the familial forms of PMAH and 30% of apparently sporadic cases, except in food-dependent Cushing syndrome in which ARMC5 is not involved. Recently, 2 independent groups have identified that the tumor suppressor gene KDM1A is responsible for PMAH associated specifically with food-dependent Cushing syndrome. Consequently, PMAH has been more frequently genetically associated than previously assumed. This review summarizes the most important aspects, including hormone secretion, clinical presentation, radiological imaging, and molecular mechanisms, involved in familial Cushing syndrome associated with PMAH.

Cushing´s syndrome due to bilateral adrenal cortical disease: Bilateral macronodular adrenal cortical disease and bilateral micronodular adrenal cortical disease

Cushing´s syndrome (CS) secondary to bilateral adrenal cortical disease may be caused by bilateral macronodular adrenal cortical disease (BMACD) or by bilateral micronodular adrenal cortical disease (miBACD). The size of adrenal nodules is a key factor for the differentiation between these two entities (>1cm, BMACD and <1cm; miBACD). BMACD can be associated with overt CS, but more commonly it presents with autonomous cortisol secretion (ACS). Surgical treatment of BMACD presenting with CS or with ACS and associated cardiometabolic comorbidities should be the resection of the largest adrenal gland, since it leads to hypercortisolism remission in up to 95% of the cases. Medical treatment focused on the blockade of aberrant receptors may lead to hypercortisolism control, although cortisol response is frequently transient. miBACD is mainly divided in primary pigmented nodular adrenocortical disease (PPNAD) and isolated micronodular adrenocortical disease (i-MAD). miBACD can present at an early age, representing one of the main causes of CS at a young age. The high-dose dexamethasone suppression test can be useful in identifying a paradoxical increase in 24h-urinary free cortisol, that is a quite specific in PPNAD. Bilateral adrenalectomy is generally the treatment of choice in patients with overt CS in miBACD, but unilateral adrenalectomy could be considered in cases with asymmetric disease and mild hypercortisolism. This article will discuss the clinical presentation, genetic background, hormonal and imaging features and treatment of the main causes of primary bilateral adrenal hyperplasia associated with hypercortisolism.

Bilateral Adrenal Hyperplasia: Pathogenesis and Treatment

Bilateral adrenal hyperplasia is a rare cause of Cushing’s syndrome. Micronodular adrenal hyperplasia, including the primary pigmented micronodular adrenal dysplasia (PPNAD) and the isolated micronodular adrenal hyperplasia (iMAD), can be distinguished from the primary bilateral macronodular adrenal hyperplasia (PBMAH) according to the size of the nodules. They both lead to overt or subclinical CS. In the latter case, PPNAD is usually diagnosed after a systematic screening in patients presenting with Carney complex, while for PBMAH, the diagnosis is often incidental on imaging. Identification of causal genes and genetic counseling also help in the diagnoses. This review discusses the last decades’ findings on genetic and molecular causes of bilateral adrenal hyperplasia, including the several mechanisms altering the PKA pathway, the recent discovery of ARMC5, and the role of the adrenal paracrine regulation. Finally, the treatment of bilateral adrenal hyperplasia will be discussed, focusing on current data on unilateral adrenalectomy.

Hidden hypercortisolism: a too frequently neglected clinical condition

PURPOSE

Classic Cushing's syndrome (CS) is a severe disease characterized by central obesity, hypertension, easy bruising, striae rubrae, buffalo hump, proximal myopathy and hypertricosis. However, several CS cases have also been reported with unusual or camouflaged manifestations. In recent years, several authors investigated the prevalence of "hidden hypercortisolism" (HidHyCo) among subjects affected with bone fragility, hypertension and type 2 diabetes mellitus (DM2). The prevalence of the HidHyCo is estimated to be much higher than that of classic CS. However, similarly to classic CS, HidHyCo is known to increase the risk of fractures, cardiovascular disease and mortality.

METHODS

We reviewed all published cases of unusual presentations of hypercortisolism and studies specifically assessing the HidHyCo prevalence in diabetic, osteoporotic and hypertensive patients.

RESULTS

We found 49 HidHyCo cases, in whom bone fragility, hypertension and diabetes were the presenting manifestations of an otherwise silent hypercortisolism. Amongst these cases, 34.7%, 32.7%, 6.1% and 19.0%, respectively, had bone fragility, hypertension, DM2 or hypertension plus DM2 as the sole clinical manifestations of HidHyCo. Overall, 25% of HidHyCo cases were of pituitary origin, and bone fragility was the very prevalent first manifestation among them. In population studies, it is possible to estimate that 1-4% of patients with apparent primary osteoporosis has a HidHyCo and the prevalence of this condition among diabetics ranges between 3.4 and 10%.

CONCLUSION

These data indicate that patients with resistant or suddenly worsening hypertension or DM2 or unexplainable bone fragility should be screened for HidHyCo using the most recently approved sensitive cut-offs.

Mifepristone Treatment in Four Cases of Primary Bilateral Macronodular Adrenal Hyperplasia (BMAH)

CONTEXT

Primary bilateral macronodular adrenal hyperplasia (BMAH) is a rare form of adrenal Cushing syndrome conventionally treated with adrenalectomy. Medical treatment is often reserved for patients not eligible for surgery. However, to date there have been few studies about the efficacy of mifepristone for the treatment of BMAH associated with hypercortisolism.

OBJECTIVE

To describe a series of patients with hypercortisolism due to BMAH treated with mifepristone from multiple medical practices.

DESIGN

We retrospectively assessed four patients treated with mifepristone for hypercortisolism due to BMAH who had either failed unilateral adrenalectomy, declined surgery, or were poor surgical candidates.

RESULTS

Mifepristone induced clinical improvement and remission of the signs and symptoms of hypercortisolism in all described patients with BMAH. The median treatment duration at the time of efficacy response assessment was 5 months (range: 3 to 18 months). Improvement in cardiometabolic parameters was observed as early as 2 weeks after treatment was started. All patients achieved improvements in glycemic control and hypertension and had significant weight loss. The most common adverse event observed with mifepristone therapy was fatigue. Increases in TSH level occurred in two patients.

CONCLUSION

Mifepristone can be an effective medical alternative to surgery in patients with hypercortisolism due to BMAH.

Unilateral Adrenalectomy for Primary Bilateral Macronodular Adrenal Hyperplasia: Analysis of 71 Cases

Objective Primary bilateral macronodular adrenal hyperplasia (PBMAH) is characterized by benign bilateral enlarged adrenal masses, causing Cushing’s syndrome (CS). The aim of the current article is to define the role of unilateral adrenalectomy (UA) in treating patients with CS related to PBMAH.

Methods A PubMed database search was conducted to identify articles reporting UA to treat PBMAH. We also report cases of PBMAH from our medical center treated by UA.

Results A total number of 71 cases of PBMAH (62 cases reported in the literature and 9 cases from our center) are presented. Most patients were women (73.2%) and most UA involved the left side (64.3%). In most cases, the resected gland was the larger one. Following UA, 94.4% of cases had remission of hypercortisolism. Recurrence rate of CS was 19.4% and hypoadrenalism occurred in 29.6%. After UA, when the size of the remained adrenal gland was equal or greater than 3.5 cm, CS persisted in 21.4% of cases, and recurrence occurred in 27.3% of cases (after 20±9.2 months). However, when the size of the remained gland was less than 3.5 cm, CS resolved in all cases and recurrence occurred in 21.2% of cases after a long period (65.6±52.1 months). High levels of urinary free cortisol (UFC) were not correlated with post-surgical CS recurrence or persistence.

Conclusions UA leads to beneficial outcomes in patients with CS related to PBMAH, also in cases with pre-surgical elevated UFC or contralateral large gland.

Aberrant G-protein coupled hormone receptor in adrenal diseases

The regulation of cortisol or aldosterone production when ACTH of pituitary origin or the renin-angiotensin systems are suppressed in primary adrenal Cushing's syndrome or in primary aldosteronism is exerted by diverse genetic and molecular mechanisms. In addition to recently identified mutations in various genes implicated in the cyclic AMP or ion channel pathways, steroidogenesis is not really autonomous as it is frequently regulated by the aberrant adrenocortical expression of diverse hormone receptors, particularly G-protein coupled hormone receptors (GPCR) which can substitute for the normal function of ACTH or angiotensin-II. In addition, paracrine or autocrine production of ligands for the aberrant GPCR such as ACTH or serotonin is found in some adrenal tumors or hyperplasias and participates in a complex regulatory loop causing steroid excess. Targeted therapies to block the aberrant ligands or their receptors could become useful in the future, particularly for patients with bilateral source of steroid excess.

Cell-to-cell communication in bilateral macronodular adrenal hyperplasia causing hypercortisolism

It has been well established that, in the human adrenal gland, cortisol secretion is not only controlled by circulating corticotropin but is also influenced by a wide variety of bioactive signals, including conventional neurotransmitters and neuropeptides, released within the cortex by various cell types such as chromaffin cells, neurons, cells of the immune system, adipocytes, and endothelial cells. These different types of cells are present in bilateral macronodular adrenal hyperplasia (BMAH), a rare etiology of primary adrenal Cushing's syndrome, where they appear intermingled with adrenocortical cells in the hyperplastic cortex. In addition, the genetic events, which cause the disease, favor abnormal adrenal differentiation that results in illicit expression of paracrine regulatory factors and their receptors in adrenocortical cells. All these defects constitute the molecular basis for aberrant autocrine/paracrine regulatory mechanisms, which are likely to play a role in the pathophysiology of BMAH-associated hypercortisolism. The present review summarizes the current knowledge on this topic as well as the therapeutic perspectives offered by this new pathophysiological concept.

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.

A marked difference in the vasopressin responsiveness between the adrenal glands in a patient with adrenocorticotropin-independent macronodular adrenal hyperplasia

We herein present the case of a 53-year-old patient with adrenocorticotropin-independent macronodular adrenocortical hyperplasia (AIMAH), which is a rare form of Cushing syndrome. He had hypercortisolemia and bilateral macronodular adrenal glands with a left side predominance. The administration of vasopressin significantly increased the plasma cortisol level (1.9-fold). Following left adrenalectomy, the patient's hypercortisolemia significantly improved and vasopressin responsiveness was lost, suggesting that the responsiveness originated from the resected left adrenal gland. The marked difference in vasopressin responsiveness between the adrenals corresponded with their asymmetrical size and function. Evaluating the differences in the vasopressin sensitivity may therefore be helpful for understanding the progression of AIMAH.

Aberrant cortisol responses to physiological stimuli in patients presenting with bilateral adrenal incidentalomas

Aberrant receptors have been implicated in the pathogenesis of several types of adrenal tumours. So far the presence of aberrant receptors has been investigated in patients with massively enlarged adrenals due to ACTH-independent macronodular adrenal hyperplasia (AIMAH) and unilateral adrenal adenomas associated with overt or subclinical Cushing's syndrome. The likelihood of aberrant responses in patients presenting with bilateral adrenal incidentalomas (BI) presenting as discrete solitary bilateral adenomas has not been thoroughly addressed. This is an observational cross-sectional prospective study conducted in a secondary/tertiary care centre. We studied 33 patients; 28 with incidentally discovered bilateral discrete adrenal adenomas and five with massive bilateral adrenal macronodular hyperplasia. We probed responses to physiological stimuli, namely upright posture and meal; in a subgroup of menopausal women the presence of aberrant gonadotropin receptors was assessed by the LHRH test. Abnormal responses obtained in tests performed with no dexamethasone suppression were always repeated and confirmed under dexamethasone suppression. Aberrant cortisol responses were confirmed in 10 patients; 9 to posture, 1 to meal (along with a positive response to posture) and 1 to LHRH tests. Patients who responded to any test compared to those who tested negative had larger adenomas, higher post-LDDST and midnight cortisol and a trend for lower ACTH levels. Patients without subclinical hypercortisolism (SH) did not respond to any test while 50% of patients with SH had an aberrant response (P = 0.002). A greater prevalence of aberrant responses was noted in patients with bilateral macronodular hyperplasia compared to those with solitary bilateral adenomas (80 vs. 21.4%, P = 0.02). Aberrant cortisol responses, primarily to posture testing, are present in a substantial proportion of patients with bilateral adrenal incidentalomas. Such cortisol responses are observed only in patients with subclinical hypercortisolism and especially in those patients with larger adrenal lesions.

Long-term efficacy of trilostane for Cushing's syndrome due to adrenocorticotropin-independent bilateral macronodular adrenocortical hyperplasia

A 66-year-old man with Cushing's syndrome due to adrenocorticotropin-independent bilateral macronodular adrenocortical hyperplasia (AIMAH) was treated for 7 years with trilostane, a 3β-hydroxysteroid dehydrogenase inhibitor. Administration of trilostane reduced the serum cortisol level to around the upper limit of normal for 7 years, and symptoms of excessive glucocorticoid production (such as moon face and obesity) were gradually improved. On the other hand, the size of both adrenal glands gradually increased despite treatment with trilostane. Though trilostane therapy could not prevent adrenal growth, it did suppress cortisol secretion over the long term, so it might be a reasonable option for AIMAH in addition to adrenalectomy.