Glucose and lipid metabolism abnormalities in Cushing's syndrome

Role of Glucocorticoids in Metabolic Dysfunction-Associated Steatotic Liver Disease

PURPOSE OF THE REVIEW

To summarize published data on the association between glucocorticoids and metabolic dysfunction-associated steatotic liver disease (MASLD), focusing on the possible pathophysiological links and related treatment considerations.

RECENT FINDINGS

Glucocorticoids, commonly used for managing many inflammatory and autoimmune diseases, may contribute to the development and progression of MASLD. Glucocorticoids may induce hyperglycemia and hyperinsulinemia, thus increasing systemic and hepatic insulin resistance, a hallmark of MASLD pathogenesis. Furthermore, glucocorticoids increase adipose tissue lipolysis, and hepatic de novo lipogenesis and decrease hepatic fatty acid β-oxidation, thus promoting MASLD development. Preclinical evidence also suggests that glucocorticoids may adversely affect hepatic inflammation and fibrosis. 11beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and 5α-reductase are implicated in the link between glucocorticoids and MASLD, the former enzyme increasing and the latter reducing the glucocorticoid action on the liver. Treatment considerations exist due to the pathogenic link between glucocorticoids and MASLD. Since iatrogenic hypercortisolism is common, glucocorticoids should be used at the minimum daily dose to control the subjective disease. Furthermore, the pharmacologic inhibition of 11β-HSD1 has provided favorable results in MASLD, both in preclinical studies and early MASH clinical trials. Glucocorticoids are closely linked to MASLD pathophysiology, with specific clinical and therapeutic implications.

Polymeric Microneedles for Health Care Monitoring: An Emerging Trend

Bioanalyte collection by blood draw is a painful process, prone to needle phobia and injuries. Microneedles can be engineered to penetrate the epidermal skin barrier and collect analytes from the interstitial fluid, arising as a safe, painless, and effective alternative to hypodermic needles. Although there are plenty of reviews on the various types of microneedles and their use as drug delivery systems, there is a lack of systematization on the application of polymeric microneedles for diagnosis. In this review, we focus on the current state of the art of this field, while providing information on safety, preclinical and clinical trials, and market distribution, to outline what we believe will be the future of health monitoring.

Myricanol improves metabolic profiles in dexamethasone induced lipid and protein metabolism disorders in mice

Myricanol (MY) is one of the main active components from bark of Myrica Rubra. It is demonstrated that MY rescues dexamethasone (DEX)-induced muscle dysfunction via activating silent information regulator 1 (SIRT1) and increasing adenosine 5'-monophosphate-activated protein kinase (AMPK) phosphorylation. Since SIRT1 and AMPK are widely involved in the metabolism of nutrients, we speculated that MY may exert beneficial effects on DEX-induced metabolic disorders. This study for the first time applied widely targeted metabolomics to investigate the beneficial effects of MY on glucose, lipids, and protein metabolism in DEX-induced metabolic abnormality in mice. The results showed that MY significantly reversed DEX-induced soleus and gastrocnemius muscle weight loss, muscle fiber damage, and muscle strength loss. MY alleviated DEX-induced metabolic disorders by increasing SIRT1 and glucose transporter type 4 (GLUT4) expressions. Additionally, myricanol prevented muscle cell apoptosis and atrophy by inhibiting caspase 3 cleavages and muscle ring-finger protein-1 (MuRF1) expression. Metabolomics showed that MY treatment reversed the serum content of carnitine ph-C1, palmitoleic acid, PS (16:0_17:0), PC (14:0_20:5), PE (P-18:1_16:1), Cer (t18:2/38:1(2OH)), four amino acids and their metabolites, and 16 glycerolipids in DEX mice. Kyoto encyclopedia of genes and genomes (KEGG) and metabolic set enrichment analysis (MSEA) analysis revealed that MY mainly affected metabolic pathways, glycerolipid metabolism, lipolysis, fat digestion and absorption, lipid and atherosclerosis, and cholesterol metabolism pathways through regulation of metabolites involved in glutathione, butanoate, vitamin B6, glycine, serine and threonine, arachidonic acid, and riboflavin metabolism. Collectively, MY can be used as an attractive therapeutic agent for DEX-induced metabolic abnormalities.

Adipose tissue in cortisol excess: What Cushing's syndrome can teach us?

Endogenous Cushing's syndrome (CS) is a rare condition due to prolonged exposure to elevated circulating cortisol levels that features its typical phenotype characterised by moon face, proximal myopathy, easy bruising, hirsutism in females and a centripetal distribution of body fat. Given the direct and indirect effects of hypercortisolism, CS is a severe disease burdened by increased cardio-metabolic morbidity and mortality in which visceral adiposity plays a leading role. Although not commonly found in clinical setting, endogenous CS is definitely underestimated leading to delayed diagnosis with consequent increased rate of complications and reduced likelihood of their reversal after disease control. Most of all, CS is a unique model for systemic impairment induced by exogenous glucocorticoid therapy that is commonly prescribed for a number of chronic conditions in a relevant proportion of the worldwide population. In this review we aim to summarise on one side, the mechanisms behind visceral adiposity and lipid metabolism impairment in CS during active disease and after remission and on the other explore the potential role of cortisol in promoting adipose tissue accumulation.

Thromboxane A2 Modulates de novo Synthesis of Adrenal Corticosterone in Mice via p38/14-3-3γ/StAR Signaling

Prostanoids are endogenous lipid bioactive mediators that play essential roles in physiological processes such as glucocorticoid secretion. Here, it is found that the thromboxane (Tx)A2 receptor (TP) is highly expressed in the adrenal cortex of mice. Both global and adrenocortical-specific deletion of the TP receptor lead to increased adiposity in mice by elevating corticosterone synthesis. Mechanistically, the TP receptor deletion increases the phosphorylation of steroidogenic acute regulatory protein (StAR) and corticosterone synthesis in adrenal cortical cells by suppressing p-p38-mediated phosphorylation of 14-3-3γ adapter protein at S71. The activation of the p38 in the adrenal cortical cells by forced expression of the MKK6EE gene attenuates hypercortisolism in TP-deficient mice. These observations suggest that the TxA2/TP signaling regulates adrenal corticosterone homeostasis independent of the hypothalamic-pituitary-adrenal axis and the TP receptor may serve as a promising therapeutic target for hypercortisolism.

Blood glucose and lipids are associated with sarcoidosis: findings from observational and mendelian randomization studies

BACKGROUND

Several researches have demonstrated that patients with sarcoidosis accompanied with the abnormality in blood glucose and/or lipids, however, the causal relationship between them remains uncertain. To elucidate the potential association and causality of blood glucose and lipids with sarcoidosis, we conducted a propensity score matching (PSM)-based observational study combined with mendelian randomization (MR) analysis.

METHODS

All subjects in this study were retrospectively collected from Tongji Hospital during 2010 and 2023. 1:1 PSM was employed to control the potential confounders as appropriate. Univariable and multivariable logistic regression analyses were performed to estimate the associations of sarcoidosis with fasting glucose, high density lipoprotein cholesterol (HDLC), low density lipoprotein cholesterol (LDLC), total cholesterol (TC), and total triglyceride (TG). The further subtype analysis was also conducted. Afterwards, a bidirectional MR analysis based on public data deeply explored the causality among the 5 candidate traits and sarcoidosis, for which the inverse-variance weighted (IVW) method was utilized as the main inferring approach.

RESULTS

In the observational study, a total number of 756 subjects were enrolled, with 162 sarcoidosis patients and 594 non-sarcoidosis participants, while 160 pairs of subjects were matched after PSM. Multivariable logistic regression analysis indicated that HDLC (OR: 0.151; 95% CI: 0.056-0.408; P < 0.001) and TC (OR: 3.942; 95% CI: 2.644-5.877; P < 0.001) were strongly associated with sarcoidosis. Subtype analysis showed that low HDLC was independently correlated to risk of lesions in bronchus and lungs, and mediastinal lymph nodes, while high TC was to cervical lymph nodes. In MR analysis, high fasting glucose, low HDLC, and high TC were identified as the causal factors of sarcoidosis.

CONCLUSION

HDLC and TC had the potential to influence the risk of sarcoidosis, which could be regarded as predictors and may provide new diagnostic and therapeutic targets for sarcoidosis.

Practical therapeutic approach in the management of diabetes mellitus secondary to Cushing's syndrome, acromegaly and neuroendocrine tumours

Cushing's syndrome, acromegaly and neuroendocrine disorders are characterized by an excess of counterregulatory hormones, able to induce insulin resistance and glucose metabolism disorders at variable degrees and requiring immediate treatment, until patients are ready to undergo surgery. This review focuses on the management of diabetes mellitus in endocrine disorders related to an excess of counterregulatory hormones. Currently, the landscape of approved agents for treatment of diabetes is dynamic and is mainly patient-centred and not glycaemia-centred. In addition, personalized medicine is more and more required to provide a precise approach to the patient's disease. For this reason, we aimed to define a practical therapeutic algorithm for management of diabetes mellitus in patients with glucagonoma, pheochromocytoma, Cushing's syndrome and acromegaly, based on our practical experience and on the physiopathology of the specific endocrine disease taken into account. This document is addressed to all specialists who approach patients with diabetes mellitus secondary to endocrine disorders characterized by an excess of counterregulatory hormones, in order to take better care of these patients. Care and control of diabetes mellitus should be one of the primary goals in patients with an excess of counterregulatory hormones requiring immediate and aggressive treatment.

Lithium treatment mitigates the diabetogenic effects of chronic cortico-therapy

BACKGROUND AND PURPOSE

Glucocorticoids (GCs) are the main treatment for autoimmune and inflammatory disorders and are also used as immunosuppressive therapy for patients with organ transplantation. However, these treatments have several side effects, including metabolic disorders. Indeed, cortico-therapy may induce insulin resistance, glucose intolerance, disrupted insulin and glucagon secretion, excessive gluconeogenesis, leading to diabetes in susceptible individuals. Recently, lithium has been shown to alleviate deleterious effects of GCs in various diseased conditions.

EXPERIMENTAL APPROACH

In this study, using two rat models of GC-induced metabolic disorders, we investigated the effects of Lithium Chloride (LiCl) in the mitigation of deleterious effects of GCs. Rats were treated either with corticosterone or dexamethasone, and with or without LiCl. Animals were then assessed for glucose tolerance, insulin sensitivity, in vivo and ex vivo glucose-induced insulin secretion and hepatic gluconeogenesis.

KEY RESULTS

We showed that in rats chronically treated with corticosterone, lithium treatment markedly reduced insulin resistance. In addition, in rats treated with dexamethasone, lithium administration improved glucose tolerance, associated with enhanced insulin secretion in vivo. Moreover, liver gluconeogenesis was reduced upon LiCl treatment. The improvement of insulin secretion in vivo appeared to be due to an indirect regulation of β cell function, since the ex vivo assessment of insulin secretion and β cell mass in islets from animals treated with LiCl revealed no difference compared to untreated animals.

CONCLUSION AND IMPLICATIONS

Collectively, our data provide evidences for the beneficial effects of lithium to mitigate the adverse metabolic effects of chronic cortico-therapy.

Ectopic lipid metabolism in anterior pituitary dysfunction

Over the past decades, adapted lifestyle and dietary habits in industrialized countries have led to a progress of obesity and associated metabolic disorders. Concomitant insulin resistance and derangements in lipid metabolism foster the deposition of excess lipids in organs and tissues with limited capacity of physiologic lipid storage. In organs pivotal for systemic metabolic homeostasis, this ectopic lipid content disturbs metabolic action, thereby promotes the progression of metabolic disease, and inherits a risk for cardiometabolic complications. Pituitary hormone syndromes are commonly associated with metabolic diseases. However, the impact on subcutaneous, visceral, and ectopic fat stores between disorders and their underlying hormonal axes is rather different, and the underlying pathophysiological pathways remain largely unknown. Pituitary disorders might influence ectopic lipid deposition indirectly by modulating lipid metabolism and insulin sensitivity, but also directly by organ specific hormonal effects on energy metabolism. In this review, we aim to I) provide information about the impact of pituitary disorders on ectopic fat stores, II) and to present up-to-date knowledge on potential pathophysiological mechanisms of hormone action in ectopic lipid metabolism.

Long-term morbidity and mortality in patients with Cushing's syndrome

Increased multisystem morbidity and mortality in patients with Cushing's syndrome comprise clinical problems and challenges, both at the time of diagnosis and in remission. Relevant comorbidities and clinical problems include hypertension, diabetes, overweight, myopathy and a high risk for acute complications such as infections and venous thrombembolism. Although there are therapy recommendations for most of these comorbidities, there is a lack of large, prospective studies to confirm and optimise them. Mortality is especially high during active disease and within the first year after diagnosis, as a result of cardiovascular events, infections and suicide. All in all, interdisciplinary therapy management is important for reducing morbidity and mortality over the long-term.

Surgery and perioperative management of patients with Cushing's disease

Transsphenoidal surgery (TSS) is the initial treatment modality of first choice in Cushing's disease (CD). With microscopic TSS and endoscopic TSS, two operative techniques with equally favourable remission rates and operative morbidity are available. On average, remission is achieved with primary TSS in 80% of patients with microadenomas and 60% of patients with macroadenomas. The current literature indicates that remission rates in repeat TSS for microadenomas can also exceed 70%. Experience with TSS in CD plays an important role in the success rate and centralization in Pituitary Centres of Excellence has been proposed. Microadenoma stage, imaging-visible adenoma, confirmation of ACTH-positive adenoma on histopathology and noninvasiveness are positive predictors for postoperative remission. In postoperative management, a steroid-sparing protocol with early postoperative assessment of remission status is recommended. Convincing evidence suggests that prolonged postoperative prophylactic antithrombotic measures can significantly reduce the risk of postoperative thromboembolic events in CD. Prevention or successful treatment of cortisol withdrawal syndrome remains an unsolved issue that should be a focus of future research. The further development and broad availability of functional imaging hold promise for improved preoperative detection of microadenomas. Intraoperative identification of microadenomas by specific fluorescent targeting could be a promising future avenue for the treatment of patients with negative imaging.

Clinical presentation and etiology of Cushing's syndrome: Data from ERCUSYN

This review presents the data on clinical presentation at diagnosis in 1564 patients included in the European Registry on Cushing's syndrome (ERCUSYN), of whom 1045 (67%) had pituitary-dependent Cushing's syndrome (CS) (PIT-CS), 385 (25%) had adrenal dependent CS (ADR-CS) and 89 (5%) had ectopic adrenocorticotropic hormone syndrome (ECT-CS). The most frequent symptoms in the overall series were weight gain (83%), hypertension (79%), skin alterations (76%) and myopathy (70%). Diabetes mellitus was present in 32% and depression in 35% of patients. Skin alterations, menstrual irregularities and reduced libido were more prevalent in PIT-CS patients compared to ADR-CS patients, whereas patients with ECT-CS more frequently had diabetes mellitus, myopathy, hirsutism and vertebral fractures compared to the other etiologies, consistent with a more severe clinical scenario. Reduced libido and bone fractures were more prevalent in men compared to women. Quality of life was poor at diagnosis, irrespective of the etiology of CS, and also associated with the presence of depression at baseline. A delay of 2 years between the onset of symptoms and diagnosis was also observed, with a high number of specialists consulted, who often missed the correct diagnosis. To develop strategies aimed at shortening the time elapsed to diagnosis, it is important to rapidly start treatment and reduce the burden of the disease on patient psychophysical health and longevity.

The diagnosis and management of Cushing's syndrome in pregnancy

Endogenous Cushing's syndrome (CS) is rarely encountered during pregnancy. Clinical and biochemical changes in healthy pregnancy overlap with those seen in pregnancy complicated by CS; the diagnosis is therefore challenging and can be delayed. During normal gestation, adrenocorticotrophic hormone, corticotrophin-releasing hormone, cortisol, and urinary free cortisol levels rise. Dexamethasone administration fails to fully suppress cortisol in pregnant women without CS. Localisation may be hindered by non-suppressed adrenocorticotrophic hormone levels in a large proportion of those with adrenal CS; smaller corticotroph adenomas may go undetected as a result of a lack of contrast administration or the presence of pituitary hyperplasia; and inferior petrosal sinus sampling is not recommended given the risk of radiation and thrombosis. Yet, diagnosis is essential; active disease is associated with multiple insults to both maternal and foetal health, and those cured may normalise the risk of maternal-foetal complications. The published literature consists mostly of case reports or small case series affected by publication bias, heterogeneous definitions of maternal or foetal outcomes or lack of detail on severity of hypercortisolism. Consequently, conclusive recommendations, or a standardised management approach for all, cannot be made. Management is highly individualised: the decision for surgery, medical control of hypercortisolism or adoption of a conservative approach is dependent on the timing of diagnosis (respective to stage of gestation), the ability to localise the tumour, severity of CS, pre-existing maternal comorbidity, and, ultimately, patient choice. Close communication is a necessity with the patient placed at the centre of all decisions, with risks, benefits, and uncertainties around any investigation and management carefully discussed. Care should be delivered by an experienced, multidisciplinary team, with the resources and expertise available to manage such a rare and challenging condition during pregnancy.

Aggressive corticotroph tumors and carcinomas

Pituitary tumors are generally benign, although in rare cases aggressive pituitary tumors (APTs) and carcinomas present important diagnostic and therapeutic challenges and are associated with a high mortality rate. Almost half of these APTs and carcinomas are corticotroph tumors, suggesting a specific prognosis. Clinical, pathological and molecular prognostic markers are limited and do not allow early management of these tumors. Temozolomide remains the first-line treatment once a diagnosis of aggressive pituitary tumor or carcinoma has been made. Novel alternative treatments exist, including immune checkpoint inhibitors, which can be used in the case of temozolomide treatment failure. The aim of this review is to present the clinical, pathological and molecular characteristics of aggressive corticotroph tumors and carcinomas, and to describe the results obtained with currently available treatments.

Pituitary MRI in Cushing's disease - an update

Pituitary MRI is essential in the diagnosis of ACTH-dependent Cushing's syndrome, but its results are inconsistent. The demonstration of a sellar image compatible with the diagnosis of corticotropinoma varies from 40% to 90%, depending on the centre where the imaging is performed. In fact, the expertise of the neuroradiologist, use of a Tesla 3.0 MRI and choice of sequences are fundamental. The T2 and 3D gradient echo sequences after gadolinium injection are the most informative and today allow the detection of macro- and microadenomas in almost all cases. The diagnosis of numerous picoadenomas (<3-4 mm) is more challenging. The 2D and 3D spin echo or delayed T1 SE or FLAIR sequences after gadolinium can be used as a complement or to confirm a suspicious image. Characterization of corticotropinomas remains problematic. However, the correct assessment of so-called incidentalomas by recognizing artifacts, anatomical variants and frequent Rathke's cleft cysts eliminates around 90% of the incidentalomas that mimic pituitary adenomas, as repetitively reported in the literature. For the time being, there is reason to believe that hybrid imaging combining PET and MRI such as 11C-methionine PET coregistered with volumetric MRI will solve the diagnosis of corticotropinomas in the near future.

Role of radiosurgery in the treatment of Cushing's disease

Radiotherapy is a useful adjuvant treatment for patients with Cushing's disease that is not cured by surgery. In particular, Gamma Knife radiosurgery (GKRS) has been increasingly used worldwide as the preferred radiation technique in patients with persistent or recurrent Cushing's disease. The most widely accepted criterion for hormonal remission after GKRS is normalization of urinary free cortisol (UFC) levels. When a clear biological target is not identified, irradiation of the whole pituitary gland can be considered. The 5-year probability of remission is 65%-75%. Normalization of hypercortisolism usually occurs within 3 years from GKRS treatment and control of tumor growth is optimal, approaching more than 90%. No clear predictor of a favorable outcome has emerged up to now, except for the experience of the treating team. In the largest series, development of partial or complete hypopituitarism occurred between 15% and 36%. Severe side effects of GKRS, such as optic neuropathy and oculomotor palsy, are uncommon but have been documented in patients previously exposed to radiation. Recurrence of disease has been reported in as high as 16%-18% of the patients who achieved normalization of UFC levels in the two largest series, whereas smaller series did not describe late failure of GKRS. The reason for this discrepancy is unclear, as is the relationship between hormonal and tumoral recurrence. Another unresolved issue is whether treatment with adrenal blocking drugs can jeopardize the results of GKRS. GKRS is an effective second-line treatment in patients with Cushing's disease not cured by surgery. Hypopituitarism is the most frequent side effect of GKRS, whereas severe neurologic complications are uncommon in radiation-naïve patients.

Hypothalamic-pituitary-adrenal axis recovery after treatment of Cushing's syndrome

After successful treatment for Cushing's syndrome (CS), secondary adrenal insufficiency develops as a result of the prior suppression of the hypothalamic-pituitary-adrenal (HPA) axis by excess cortisol in the body. Until the recovery of the HPA axis, glucocorticoid replacement therapy is required to enable normal functioning of the body and prevent adrenal crisis. Significant variation in the median time of recovery of the HPA axis is found in various cohorts of CS patients ranging from several weeks to years. Despite the use of physiological glucocorticoid replacement, after cure for CS, patients often experience symptoms of glucocorticoid withdrawal syndrome (GWS). The optimal glucocorticoid regimen to reduce GWS needs to be established and requires an individualized approach aiming to avoid overtreatment at one side and minimize the risk of undertreatment and possible adrenal crisis and GWS on the other side.

The corticotroph cells from early development to tumorigenesis

During development, highly specialized differentiated cells, such as pituitary secretory cells, acquire their identity and properties through a series of specification events exerted by transcription factors to implement a unique gene expression program and epigenomic state. The investigation of these developmental processes informs us on the unique features of a cell lineage, both to explain these features and also to outline where these processes may fail and cause disease. This review summarizes present knowledge on the developmental origin of pituitary corticotroph and melanotroph cells and on the underlying molecular mechanisms. At the onset, comparison of gene expression programs active in pituitary progenitors compared to those active in differentiated corticotrophs or melanotrophs indicated dramatic differences in the control of, for example, the cell cycle. Tpit is the transcription factor that determines terminal differentiation of pro-opiomelanocortin (POMC) lineages, both corticotrophs and melanotrophs, and its action involves this switch in cell cycle control in parallel with activation of cell-specific gene expression. There is thus far more to making a corticotroph cell than just activating transcription of the POMC gene. Indeed, Tpit also controls implementation of mechanisms for enhanced protein translation capacity and development of extensive secretory organelles. The corticotroph cell identity also includes mechanisms responsible for homotypic cell-cell interactions between corticotrophs and for privileged heterotypic cell interactions with pituitary cells of other lineages. The review also summarizes current knowledge on how a pioneer transcription factor, Pax7, remodels the epigenome such that the same determination transcription factor, Tpit, will implement the melanotroph program of gene expression. Finally, this canvas of regulatory mechanisms implementing POMC lineage identities constitutes the background to understand alterations that characterize corticotroph adenomas of Cushing's disease patients. The integration of all these data into a unified scheme will likely yield a scheme to globally understand pathogenic mechanisms in Cushing's disease.

Long-term follow-up and predictors of recurrence of Cushing's disease

Transsphenoidal surgery is the first-line treatment for Cushing's disease to selectively remove the tumor. The rate of postoperative remission is estimated around 70%-80% in expert centers. However, the long-term remission rate is lower because of recurrence during follow-up that can be observed in 15% to 25% of the patients depending on the studies and duration of follow-up. There is no significant predictive factor of recurrence before surgery, but postoperative corticotroph insufficiency and its duration has been found to be a protective factor for recurrence in many studies. The persistence of a positive response to desmopressin after surgery is associated with a higher rate of recurrence. Long term monitoring for recurrence with annual clinical and hormonal investigations after the hypothalamic-pituitary-adrenal axis postoperative recovery is advised. The biological tests used for the diagnosis of Cushing's syndrome (24 h-urinary-free cortisol [UFC], late-night salivary or serum cortisol, 1 mg dexamethasone suppression test) can be used to screen for recurrence. Several studies report that increased late night cortisol and alterations of dynamic testing can be observed before the increased 24 h-UFC. For this reason it is suggested that late-night salivary cortisol would be a very sensitive tool to diagnose recurrence, pending the realization of several assays in case of borderline or discrepant result. This review will summarize the knowledge about recurrence of Cushing's disease after pituitary surgery and the current recommendations for its monitoring and diagnosis.

Distinguishing Cushing's disease from the ectopic ACTH syndrome: Needles in a haystack or hiding in plain sight?

In the context of ACTH-dependent Cushing's syndrome, ectopic ACTH secretion from a neuroendocrine tumour is not uncommon, and needs to be carefully differentiated from pituitary-dependent Cushing's syndrome, Cushing's disease, in order to optimise therapy. Some cases may be quite obvious, while in others the diagnosis may be difficult to confirm and the source of ACTH problematic, as many clinical and biochemical tests may overlap with Cushing's disease. Imaging is essential, but needs to be interpreted in the light of both anatomical as well as functional imaging modalities. In this review we summarise some of the main diagnostic problems, and emphasise the multimodal and interdisciplinary nature of the diagnostic pathways.

Medical management of Cushing's disease: When and how?

Transsphenoidal surgery is the first-line treatment of Cushing's disease. However, medical treatment can be given in a high proportion of patients with this rare condition. This is especially the case in severe hypercortisolism for which medical treatment will be given for a short period of time to prepare the patient for surgery, or on a long-term basis after failed transsphenoidal surgery, or when waiting for the maximal beneficial effect of radiation techniques. These different situations all require that hypercortisolism be perfectly controlled. Severe hypercortisolism is frequently treated by a block and replace approach during which a substitutive treatment is given after the induction of adrenal insufficiency. Mild hypercortisolism, the most frequent situation, is usually treated with a titration approach with a progressive dose increase. This approach requires certainty of eucortisolism because patients may be treated for a prolonged period. This review details the main situations during which medical treatment should be considered, as well as the way in which to monitor them to avoid the long-term consequences of mild hypo- or hypercortisolism.

Long-term effects of glucocorticoid excess on the brain

The metabolic and cardiovascular clinical manifestations in patients with Cushing's syndrome (CS) are generally well known. However, recent studies have broadened the perspective of the effects of hypercortisolism, showing that both endogenous and exogenous glucocorticoid excess alter brain functioning on several time scales. Consequently, cognitive deficits and neuropsychological symptoms are highly prevalent during both active CS and CS in remission, as well as during glucocorticoid treatment. In this review, we discuss the effects of endogenous hypercortisolism and exogenously induced glucocorticoid excess on the brain, as well as the prevalence of cognitive and neuropsychological deficits and their course after biochemical remission. Furthermore, we propose possible mechanisms that may underly neuronal changes, based on experimental models and in vitro studies. Finally, we offer recommendations for future studies.

Genetics of Cushing's disease

Corticotroph tumours are primarily sporadic monoclonal neoplasms and only rarely found in genetic syndromes. Recurrent mutations in the ubiquitin specific protease 8 (USP8) gene are found in around half of cases. Mutations in other genes such as USP48 and NR3C1 are less frequent, found in less than ~20% of cases. TP53 and ATXR mutations are reported in up to one out of four cases, when focusing in USP8 wild type or aggressive corticotroph tumours and carcinomas. At present, USP8 mutations are the primary driver alterations in sporadic corticotroph tumours, TP53 and ATXR mutations may indicate transition to more aggressive tumour phenotype. Next generation sequencing efforts have identified additional genomic alterations, whose role and importance in corticotroph tumorigenesis remains to be elucidated.

Diagnostic workup of Cushing's syndrome

Cushing's syndrome (CS) is a rare but detrimental endocrine disorder. Early diagnosis and prompt treatment are essential since the duration of hypercortisolism has an adverse impact on the extent of comorbidities and overall survival. The diagnostic approach involves a stepwise process that includes (1) screening and confirming the diagnosis and (2) establishing the aetiology of CS. The tests currently used to confirm the diagnosis of CS include urinary free cortisol measurements, the dexamethasone suppression test and late- night salivary cortisol or midnight serum cortisol measurements. None of these tests are ideal; all have pitfalls and require careful interpretation. Following confirmation of CS, measurement of ACTH discriminates between ACTH-dependent and non-ACTH dependent causes of CS. Adrenal imaging provides clues for the aetiology of non-ACTH dependent forms. Differentiation between the ACTH-dependent forms that involve pituitary corticotroph adenomas and ectopic ACTH sources is more complex and include pituitary MRI imaging, the high dose dexamethasone suppression test, the CRH test, bilateral inferior petrosal sinus sampling and, when required imaging modalities to detect ectopic ACTH secreting lesions. This review, which is part of a special issue on "Update of Cushing's syndrome: 100 years after Minnie G" will provide an update on our current diagnostic workup for the confirmation and differential diagnosis of CS.