Advances in the medical management of Cushing's syndrome

Background: Management of Cushing's syndrome, that is, excess cortisol secretion, has undergone considerable advances since the pioneering studies by Harvey Cushing. Surgery is clearly first choice for all etiologies of Cushing's syndrome, and medical therapy is largely administered in the interim between other therapeutic options. The limited use of medical therapy is a consequence of the lack of a truly efficacious compound to restrain adrenocorticotrophic hormone or cortisol secretion, but this will hopefully change in the near future as molecules developed over the past few years are tested. Conclusion: This paper illustrates present and perspective medical treatments for Cushing's syndrome

Role of the ubiquitin/proteasome system on ACTH turnover in rat corticotropes

Purpose: A large number of studies has investigated proopiomelanocortin processing in anterior pituitary corticotropes but little is known on proopiomelanocortin/ACTH degradation within these cells. The ubiquitin-proteasome system is an intracellular protein degradation pathway which has garnered considerable interest in recent times, given its role in maintenance of protein homeostasis. Aim of the present study was to evaluate the role of the ubiquitin-proteasome system in proopiomelanocortin/ACTH turnover in pituitary corticotropes. Methods: Rat anterior pituitary primary cultures were treated with 0.01\u2013100 nM MG132, a proteasome inhibitor, or 0.1\u2013100 nM K48R, an inhibitor of polyubiquitylation, for 4 and 24 h and ACTH concentrations in medium and cell lysates estimated by immunometric assay. Co-immunoprecipitation for ubiquitin and ACTH was carried out to establish ubiquitin-tagged protein products. Results: Inhibition of proteasome-mediated degradation with MG132 lead to an increase in ACTH concentrations, both as regards secretion and cell content. Likewise, inhibition of polyubiquitylation was associated with increased ACTH secretion and cell content. Ubiquitin/ACTH co-immunoprecipitation revealed that proopiomelanocortin was a target of ubiquitylation. Conclusions: We provide the first evidence that the ubiquitin-proteasome system is involved in proopiomelanocortin/ACTH degradation in corticotropes. Indeed, proopiomelanocortin is a target of ubiquitylation and modulation of ubiquitin-proteasome system affects ACTH turnover. This study shows that regulation of ACTH proteolytic degradation may represent a means to control ACTH secretion

Sexual Dimorphism in Cellular and Molecular Features in Human ACTH-Secreting Pituitary Adenomas.

Background. Cushing\u2019s disease presents gender disparities in prevalence and clinical course. Little is known, however, about sexual dimorphism at the level of the corticotrope adenoma itself. The aim of the present study was to evaluate molecular features of ACTH-secreting pituitary adenomas collected from female and male patients with Cushing\u2019s disease. (2) Methods. We analyzed 153 ACTH-secreting adenomas collected from 31 men and 122 women. Adenomas were established in culture and ACTH synthesis and secretion assessed in basal conditions as well as during incubation with CRH or dexamethasone. Concurrently, microarray analysis was performed on formalin-fixed specimens and differences in the expression profiles between specimens from male and female patients identified. (3) Results. ACTH medium concentrations in adenomas obtained from male patients were significantly lower than those observed in adenomas from female patients. This could be observed for baseline as well as modulated secretion. Analysis of corticotrope transcriptomes revealed considerable similarities with few, selected differences in functional annotations. Differentially expressed genes comprised genes with known sexual dimorphism, genes involved in tumour development and genes relevant to pituitary pathophysiology. (4) Conclusions. Our study shows for the first time that human corticotrope adenomas present sexual dimorphism and underlines the need for a gender-dependent analysis of these tumours. Differentially expressed genes may represent the basis for gender-tailored target therapy

Increased prevalence of prolonged QT interval in males with primary or secondary hypogonadism : a pilot study

P>Symptoms and signs of male hypogonadism span all organ systems, including the cardiovascular apparatus. The electrocardiographic QT interval reflects cardiac ventricular repolarization and, if prolonged, increases the risk of malignant arrhythmias. QT interval duration is similar in boys and girls during childhood, but shortens in males after puberty and experimental studies suggest that testosterone is a major contributor to shortening of QT interval in men. The aim of the present pilot study was to assess the duration of ventricular repolarization in adult males with primary or secondary hypogonadism. Standard ECG recordings were performed in 26 men (mean age 39.2 +/- 2.17 years) with pituitary or testicular hypogonadism and repeated in 15 patients during testosterone replacement. Twenty-six age-matched control men were also analysed. Measured QT intervals were corrected for heart rate according to Bazzett's formula (QTc = QT/root RR interval). The prevalence of prolonged QTc was considerably higher in hypogonadal patients (four of 26 men) than in control men (none, p < 0.05) and in the general, healthy population (< 2.5%). QTc interval normalized on hormone replacement therapy in the four patients presenting prolonged QTc in the hypogonadal state. Heart rate and left ventricular mass did not differ among the two groups and no known QT-prolonging factor was apparent in patients with abnormal QTc interval. In conclusion, a high number prolonged QT interval measurements was observed in hypogonadal men who may therefore be at increased risk for cardiac arrhythmias. This observation reveals an additional feature of male hypogonadism, which may benefit from testosterone replacement therapy

Usefulness of desmopressin testing to predict relapse during long-term follow-up in patients in remission from Cushing's disease

Recurrence of Cushing's disease after successful transsphenoidal surgery occurs in some 30% of the patients and the response to desmopressin shortly after surgery has been proposed as a marker for disease recurrence. The aim of the present study was to evaluate the response to desmopressin over time after surgery. We tested 56 patients with Cushing's disease in remission after transsphenoidal surgery with desmopressin for up to 20 years after surgery. The ACTH and cortisol response to desmopressin over time was evaluated in patients on long-term remission or undergoing relapse; an increase by at least 27\u2009pg/mL in ACTH levels identified responders. The vast majority of patients who underwent successful adenomectomy failed to respond to desmopressin after surgery and this response pattern was maintained over time in patients on long-term remission. Conversely, a response to desmopressin reappeared in patients who subsequently developed a recurrence of Cushing's disease, even years prior to frank hypercortisolism. It appears therefore that a change in the response pattern to desmopressin proves predictive of recurrence of Cushing's disease and may indicate which patients require close monitoring

Ubiquitin-Specific Protease 8 Mutant Corticotrope Adenomas Present Unique Secretory and Molecular Features and Shed Light on the Role of Ubiquitylation on ACTH Processing

Background: Somatic mutations in the ubiquitin-specific protease 8 (USP8) gene have recently been shown to occur in ACTH-secreting pituitary adenomas, thus calling attention to the ubiquitin system in corticotrope adenomas. Objectives: Assess the consequences of USP8 mutations and establish the role of ubiquitin on ACTH turnover in human ACTH-secreting pituitary adenomas. Methods: USP8 mutation status was established in 126 ACTH-secreting adenomas. Differences in ACTH secretion and POMC expression from adenoma primary cultures and in microarray gene expression profiles from archival specimens were sought according to USP8 sequence. Ubiquitin/ACTH coimmunoprecipitation and incubation with MG132, a proteasome inhibitor, were performed in order to establish whether ubiquitin plays a role in POMC/ACTH degradation in corticotrope adenomas. Results: USP8 mutations were identified in 29 adenomas (23%). Adenomas presenting USP8 mutations secreted greater amounts of ACTH and expressed POMC at higher levels compared to USP wild-type specimens. USP8 mutant adenomas were also more sensitive to modulation by CRH and dexamethasone in vitro. At microarray analysis, genes associated with endosomal protein degradation and membrane components were downregulated in USP8 mutant adenomas as were AVPR1B, IL11RA, and PITX2. Inhibition of the ubiquitin-proteasome pathway increased ACTH secretion and POMC itself proved a target of ubiquitylation, independently of USP8 sequence status. Conclusions: Our study has shown that USP8 mutant ACTH-secreting adenomas present a more "typical" corticotrope phenotype and reduced expression of several genes associated with protein degradation. Further, ubiquitylation is directly involved in intracellular ACTH turnover, suggesting that the ubiquitin-proteasome system may represent a target for treatment of human ACTH-secreting adenomas

No Untoward Effect of Long-Term Ketoconazole Administration on Electrocardiographic QT Interval in Patients with Cushing's Disease

Ketoconazole is listed among drugs that prolong QT interval and may increase the risk of torsade de pointes, a severe ventricular arrhythmia. This compound has recently been approved for treatment of Cushing's syndrome, a severe endocrine disorder. These patients harbour several risk factors for prolonged QT interval, for example hypokalaemia and left ventricular hypertrophy, but no study has evaluated whether administration of ketoconazole affects their QT interval. The aim of this study was to assess the QT interval in patients with Cushing's disease during long-term administration of ketoconazole. Electrocardiograms from 15 patients with Cushing's disease (12 women, 3 men, age: 37.8 \ub1 2.66 years) on ketoconazole treatment (100 mg-800 mg qd) for 1 month to 12 years were reviewed retrospectively. QT interval was measured and corrected for heart rate (QTc). Measurements before and during ketoconazole treatment were compared and any abnormal QTc value recorded. Concurrent medical therapies were also documented. On average, QTc was superimposable before and during ketoconazole treatment (393.2 \ub1 7.17 versus 403.3 \ub1 6.05 msec. in women; 424.3 \ub1 23.54 versus 398.0 \ub1 14.93 msec. in men, N.S.). QTc normalized on ketoconazole in one man with prolonged QTc prior to treatment; no abnormal QTc was observed in any other patient during the entire observation period, even during concurrent treatment with other QT-prolonging drugs. In conclusion, long-term ketoconazole administration does not appear to be associated with significant prolongation of QT interval in patients with Cushing's disease. ECG monitoring can follow recommendations drawn for other low-risk QT-prolonging drugs with attention to specific risk factors, for example hypokalaemia and drug interactions

Circadian blood pressure profile in patients with active Cushing's disease and after long-term cure

Hypertension is a major feature of Cushing's disease, with the attendant increase in the rate of cardiovascular events. The circadian blood pressure profile also impacts cardiovascular risk and a few studies have shown that patients with Cushing's syndrome do not present the expected nocturnal blood pressure decrease and, further, that this alteration persists in short-range disease remission. These studies were performed by conventional discontinuous ambulatory pressure monitoring, a technique not devoid of limitations. Aim of our study was the assessment of blood pressure and heart rate profile by beat-to-beat noninvasive monitoring in twelve patients with active Cushing's disease (9 women and 3 men, age 33.3 \ub1 2.36 years) and the assessment of its possible changes at short- (< 1 year) and long-term (2-3 years) follow-up after curative surgery. No nocturnal blood pressure dipping (i.e., decrease by 10% of daytime values) was observed in 50% of patients both during active hypercortisolism and within 1 year from surgery. Recovery of blood pressure dipping profile was detected at long-term follow-up in a minority of patients. Daytime heart rate was higher in patients with active Cushing's disease and decreased over time after cure. In conclusion, patients with Cushing's disease present absent nocturnal blood pressure dipping and abnormal heart rate values which do not resolve after short-term remission of hypercortisolism and show only partial improvement in the long run. These findings identify additional cardiovascular risk factors for patients cured of Cushing's disease

Gene expression profiling in human corticotrope tumors reveals distinct, neuroendocrine profiles

ACTH-secreting pituitary adenomas give rise to a severe endocrinological disorder, i.e., Cushing's disease, with multifaceted clinical presentation and treatment outcomes. Experimental studies suggested that disease variability is inherent to the pituitary tumor, thus pointing to the need for further studies into tumor biology. Aim of the present study was to evaluate transcriptome expression pattern in a large series of ACTH-secreting pituitary adenoma specimens, in order to identify molecular signatures of these tumors. Gene expression profiling of formalin-fixed paraffin-embedded specimens from 40 human ACTH-secreting pituitary adenomas revealed significant expression of genes involved in protein biosynthesis and ribosomal function, in keeping with neuroendocrine cell profile. Unsupervised cluster analysis identified three distinct gene profile clusters and several genes were uniquely overexpressed in a given cluster, accounting for different molecular signatures. Of note, gene expression profiles were associated with clinical features such as age and size of the tumor. Altogether, our study shows that corticotrope tumors are characterized by neuroendocrine gene expression profile and present subgroup-specific molecular features