Cardiovascular complications of Cushings syndrome: Impact on morbidity and mortality

Unusual infections and thrombotic events in Cushing's syndrome

The diagnosis of Cushing's syndrome requires a high degree of suspicion, especially in patients in whom typical features are overshadowed by other ailments. These include, among others, widespread opportunistic infections or sepsis and venous or arterial thromboembolism.This Review will summarize available data on patients presenting with severe infections or thrombotic events and the best approach to diagnosis.

Anesthetic considerations in cancer care

PURPOSE OF REVIEW

Cancer burden remains a global medical and financial challenge. Advances in surgical management have resulted in increased oncological surgeries that often involve anesthetic administration. This review aims to inform on anesthetic considerations when caring for cancer patients in the perioperative period.

RECENT FINDINGS

There are various retrospective studies and, more recently, several randomized controlled trials that have explored whether the choice of anesthesia (total intravenous anesthesia vs. inhaled anesthetic) results in a significant difference in cancer outcomes, mortality, cancer recurrence, and metastasis. To date, no definitive proof has been made, and the current conclusion remains that the anesthetic technique does not influence survival or overall long-term outcomes.

SUMMARY

Comprehensive risk assessment is essential in cancer patients before elective surgeries due to a variety of concerns such as malnutrition, aspiration risk, postradiation airway compromise, and antineoplastic systemic effects. Oncologic patients' exposure to chemotherapy and radiation causes immunosuppression and multiorgan toxicity that places them at increased perioperative risk for morbidity and mortality. Other concerns include the challenges of adequate pain management and pre-existing chronic pain.

Cushing syndrome

Cushing syndrome (CS) is a constellation of signs and symptoms caused by excessive exposure to exogenous or endogenous glucocorticoid hormones. Endogenous CS is caused by increased cortisol production by one or both adrenal glands (adrenal CS) or by elevated adrenocorticotropic hormone (ACTH) secretion from a pituitary tumour (Cushing disease (CD)) or non-pituitary tumour (ectopic ACTH secretion), which stimulates excessive cortisol production. CS is associated with severe multisystem morbidity, including impaired cardiovascular and metabolic function, infections and neuropsychiatric disorders, which notably reduce quality of life. Mortality is increased owing to pulmonary emboli, infection, myocardial infarction and cerebrovascular accidents. The clinical presentation is variable and because some CS signs and symptoms are common in the general population, the diagnosis might not be considered until many features have accumulated. Guidelines recommend screening patients with suspected CS with 24-h urine cortisol, bedtime salivary cortisol and/or 1 mg dexamethasone suppression test. Subsequently, determining the aetiology of CS is important as it affects management. The first-line therapy for all aetiologies of endogenous CS is surgical resection of the causal tissue, including corticotroph adenoma or ectopic tumour for ACTH-dependent CS or unilateral or bilateral adrenalectomy for adrenal CS. Second-line therapies include steroidogenesis inhibitors for any cause of CS, pituitary radiation (with or without steroidogenesis inhibitors) for CD, and bilateral adrenalectomy for ACTH-dependent causes of CS.

Mineralocorticoid Effects in Cushing's Disease: A Case Report

Cushing's syndrome is a rare disease caused due to prolonged exposure to excess glucocorticoids. Although rare, diagnosing Cushing's syndrome is clinically significant as it allows tailored and timely management and significant reduction or even prevention of the comorbidities caused by cortisol excess. This report delineates the presentation of a 44-year-old female with refractory secondary hypertension and severe hypokalaemia, initially thought to be caused by hyperaldosteronism. Upon a more careful physical examination, the presence of moon facies, acanthosis nigricans and violaceous abdominal striae raised suspicion of hypercortisolism. Laboratory tests confirmed the suspicion with increased cortisol and adrenocorticotropic hormone (ACTH) levels. Furthermore, imaging findings led to the final diagnosis of Cushing's disease due to an ACTH-secreting pituitary macroadenoma. The patient underwent successful transsphenoidal surgery, resulting in substantial clinical improvement, evidenced by significant weight loss and hypertension with decreased need for drugs. When left untreated, patients with Cushing's disease have a higher mortality rate than the general population. This case underscores the critical importance of keeping in mind secondary endocrine causes in the context of resistant hypertension especially with complex metabolic disturbances and recognizing the most characteristic features of this disease.

Cardiovascular risk and glucocorticoids: a Dutch National Registry of growth hormone treatment in adults with growth hormone deficiency analysis

PURPOSE

Patients with hypopituitarism are at increased cardiovascular risk, in part because of growth hormone deficiency (GHD), but probably also because of the overuse of glucocorticosteroids in concomitant adrenal insufficiency (AI). We hypothesized that patients with hypopituitarism that were on glucocorticosteroid replacement therapy for concomitant AI would have worse cardiovascular outcomes than those without.

METHODS

Retrospective nationwide cohort study. GHD patients from the Dutch National Registry of Growth Hormone Treatment in adults were grouped by the presence (AI; N = 1836) or absence (non-AI; N = 750) of concomitant AI, and differences between groups were analyzed for baseline characteristics and cardiovascular risk, at baseline and during GHRT.

RESULTS

At baseline, AI patients had higher levels of total and LDL cholesterol (both p < 0.01). During GHRT, AI patients were more likely to use cardiovascular drugs (p ≤ 0.01), but we did not find worse outcomes for blood pressure, body composition, lipid and glucose metabolism. The risk of developing peripheral arterial disease (HR 2.22 [1.06-4.65]) and non-fatal cerebrovascular events (HR 3.47 [1.60-7.52]) was higher in AI patients, but these differences disappeared in the models adjusted for baseline differences.

CONCLUSION

We found no clear evidence to support our hypothesis that patients with hypopituitarism and concomitant AI have worse cardiovascular outcomes than non-AI patients. This suggests that glucocorticoid replacement therapy in AI may be safer than previously thought. However, cardiovascular burden, events and medication use at baseline and during GHRT (in unadjusted models) were higher in AI; so the lack of power, the important role of (adjusting for) other risk factors, and the inability to distinguish between glucocorticoid treatment regimens may have influenced the outcomes.

Cardiac disease in Cushing's syndrome. Emphasis on the role of cardiovascular magnetic resonance imaging

BACKGROUND

Cushing's Syndrome (CS) is associated with increased cardiovascular morbidity and mortality. In endogenous CS, cardiovascular mortality remains increased for up to 15 years post remission of hypercortisolism. Similarly, patients with exogenous CS have 4-fold increased incidence of cardiovascular events, regardless of pre-existing cardiovascular disease (CVD).

OBJECTIVE

To present the pathophysiology, prognosis, clinical and imaging phenotype of cardiac disease in CS.

METHODS

A Pubmed search for cardiac disease in CS over the last 20 years was conducted using combinations of relevant terms. Preclinical and clinical studies, as well as review papers reporting on subclinical heart failure (HF), cardiomyopathy, coronary heart disease (CHD), and cardiovascular imaging were selected.

RESULTS

Cardiac disease in CS is associated with direct mineralocorticoid and glucocorticoid receptor activation, increased responsiveness to angiotensin II, ectopic epicardial adiposity, arterial stiffness and endothelial dysfunction, as well as with diabetes mellitus, hypertension, hyperlipidemia, obesity and prothrombotic diathesis. Subclinical HF and cardiomyopathy are principally related to direct glucocorticoid (GC) effects and markedly improve or regress post hypercortisolism remission. In contrast, CHD is related to both direct GC effects and CS comorbidities and persists post cure. In patients without clinical evidence of CVD, echocardiography and cardiac magnetic resonance (CMR) imaging reveal left ventricular hypertrophy, fibrosis, diastolic and systolic dysfunction, with the latter being underestimated by echocardiography. Finally, coronary microvascular disease is encountered in one third of cases.

CONCLUSION

Cardiovascular imaging is crucial in evaluation of cardiac involvement in CS. CMR superiority in terms of reproducibility, operator independency, unrestricted field of view and capability of tissue characterisation makes this modality ideal for future studies.

Unique Gene Expression Signature in Periadrenal Adipose Tissue Identifies a High Blood Pressure Group in Patients With Cushing Syndrome

BACKGROUND

Cushing syndrome (CS) is a rare disease caused by excess cortisol levels with high cardiovascular morbidity and mortality. Hypertension in CS promotes hypercortisolism-associated cardiovascular events. Adipose tissue is a highly plastic tissue with most cell types strongly affected by the excess cortisol exposure. We hypothesized that the molecular and cellular changes of periadrenal adipose tissue in response to cortisol excess impact systemic blood pressure levels in patients with CS.

METHODS

We investigated gene expression signatures in periadrenal adipose tissue from patients with adrenal CS collected during adrenal surgery.

RESULTS

During active CS we observed a downregulation of gene programs associated with inflammation in periadrenal adipose tissue. In addition, we observed a clustering of the patients based on tissue gene expression profiles into 2 groups that differed in blood pressure levels (CS low blood pressure and CS high blood pressure). The 2 clusters showed significant differences in gene expression pattens of the renin-angiotensin-aldosterone-system. Renin was the strongest regulated gene compared with control patients and its expression correlated with increased blood pressure observed in our patients with CS. In the CS high blood pressure group, systemic renin plasma levels were suppressed indicative of an abnormal blood pressure associated with periadrenal adipose tissue renin-angiotensin-aldosterone-system activation.

CONCLUSIONS

Here, we show for the first time a relevant association of the local renin-angiotensin-aldosterone-system and systemic blood pressure levels in patients with CS. Patients from the CS high blood pressure group still had increased blood pressure levels after 6 months in remission, highlighting the importance of local tissue effects on long-term systemic effects observed in CS.

Gut microbial dysbiosis in patients with Cushing's disease in long-term remission. Relationship with cardiometabolic risk

Background

Patients with Cushing's disease (CD) in remission maintain an increased cardiovascular risk. Impaired characteristics of gut microbiome (dysbiosis) have been associated with several cardiometabolic risk factors.

Methods

Twenty-eight female non-diabetic patients with CD in remission with a mean ± SD) age of 51 ± 9 years, mean ( ± SD) BMI, 26 ± 4, median (IQR) duration of remission, 11(4) years and 24 gender-, age, BMI-matched controls were included. The V4 region of the bacterial 16S rDNA was PCR amplified and sequenced to analyse microbial alpha diversity (Chao 1 index, observed number of species, Shannon index) and beta diversity analysis through the Principal Coordinates Analysis (PCoA) of weighted and unweighted UniFrac distances. Inter-group difference in microbiome composition was analysed using MaAsLin2.

Results

The Chao 1 index was lower in CD as compared with controls (Kruskal-Wallis test, q = 0.002), indicating lower microbial richness in the former. Beta diversity analysis showed that faecal samples from CS patients clustered together and separated from the controls (Adonis test, p<0.05). Collinsella, a genus form of the Actinobacteria phylum was present in CD patients only, whereas Sutterella, a genus from Proteobacteria phylum, was scarcely detectable/undetectable in CD patients as well as Lachnospira, a genus of the Lachnospiraceae family of the Firmicutes phylum. In CS, the Chao 1 index was associated with fibrinogen levels and inversely correlated with both triglyceride concentrations and the HOMA-IR index (p<0.05).

Conclusions

Patients with CS in remission have gut microbial dysbiosis which may be one of the mechanisms whereby cardiometabolic dysfunctions persist after "cure".

Neutrophilia with subclinical Cushing's disease: A case report and literature review

The increase in the level of neutrophils following subclinical Cushing's disease is an uncommon clinical phenomenon that is characterized by insignificant biochemical or clinical evidence of hypercortisolism. In this study, we reported a 37-year-old female patient who presented with palpitations and fatigue, and showed increased neutrophils that were unaffected by anti-infection therapy. The patient was suspected of having a urinary tract infection because of occasionally with urinary frequency, urgency, increased procalcitonin, leukocytosis, and an increased proportion of neutrophils. The ineffectiveness of anti-infection therapy ruled out the possibility of urinary tract infection. Further examination of the bone marrow excluded the possibility of blood disease. However, the levels of blood cortisol and adrenocorticotropic hormone (ACTH) increased, and a magnetic resonance imaging examination revealed lesions in the sphenoidal sinus and sella area of the sphenoidal bone, which confirmed the relationship between increased glucocorticoids and increased neutrophils. This was further confirmed by follow-up surgery and pathological examination, which revealed silent corticotropin adenomas, which are characterized by the lack of biochemical or clinical evidence of hypercortisolism with positive immunostaining for ACTH.

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.

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.

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.

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.

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.

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.

Glucose and lipid metabolism abnormalities in Cushing's syndrome

Prolonged excess of glucocorticoids (GCs) has adverse systemic effects leading to significant morbidities and an increase in mortality. Metabolic alterations associated with the high level of the GCs are key risk factors for the poor outcome. These include GCs causing excess gluconeogenesis via upregulation of key enzymes in the liver, a reduction of insulin sensitivity in skeletal muscle, liver and adipose tissue by inhibiting the insulin receptor signalling pathway, and inhibition of insulin secretion in beta cells leading to dysregulated glucose metabolism. In addition, chronic GC exposure leads to an increase in visceral adipose tissue, as well as an increase in lipolysis resulting in higher circulating free fatty acid levels and in ectopic fat deposition. Remission of hypercortisolism improves these metabolic changes, but very often does not result in full resolution of the abnormalities. Therefore, long-term monitoring of metabolic variables is needed even after the resolution of the excess GC levels.

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.

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.

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.