An individualized approach to the management of Cushing disease

Structure and Function of Somatostatin and Its Receptors in Endocrinology

Somatostatin analogs, such as octreotide, lanreotide, and pasireotide, which function as somatostatin receptor ligands (SRLs), are the main drugs used for the treatment of acromegaly. These ligands are also used as important molecules for radiation therapy and imaging of neuroendocrine tumors. Somatostatin receptors (SSTRs) are canonical G protein-coupled proteins that play a role in metabolism, growth, and pathological conditions such as hormone disorders, neurological diseases, and cancers. Cryogenic electron microscopy combined with the protein structure prediction platform AlphaFold has been used to determine the 3-dimensional structures of many proteins. Recently, several groups published a series of papers illustrating the 3-dimensional structure of SSTR2, including that of the inactive/activated SSTR2-G protein complex bound to different ligands. The results revealed the residues that contribute to the ligand binding pocket and demonstrated that Trp8-Lys9 (the W-K motif) in somatostatin analogs is the key motif in stabilizing the bottom part of the binding pocket. In this review, we discuss the recent findings related to the structural analysis of SSTRs and SRLs, the relationships between the structural data and clinical findings, and the future development of novel structure-based therapies.

Paraneoplastic endocrine syndromes: a contemporary overview

INTRODUCTION

Endocrine paraneoplastic syndromes (ePNS) are caused by malignant cells that induce hormonal alterations unrelated to the tissue of origin of the neoplasm. The aim of this manuscript is to review the pathophysiology, diagnosis, and treatment of endocrine paraneoplastic syndromes (ePNS).

AREAS COVERED

We searched the PubMed/Medline, Embase, and Scielo databases, including 96 articles. The pathogenesis of ePNS involves mutations that activate hormonal genes. Hypercalcemia, the most common ePNS, is marker of poor prognosis in most cases. The syndrome of inappropriate antidiuresis causes euvolemic hyponatremia. Ectopic Cushing's syndrome is commonly associated with lung cancer. Paraneoplastic acromegaly is very rare and is associated with pancreatic and lung tumors. Paraneoplastic hypoglycemia usually requires surgical treatment. Other endocrine paraneoplastic syndromes include ectopic secretion of hormones such as calcitonin, renin, vasoactive intestinal polypeptide, fibroblast growth factor 23, paraneoplastic autoimmune hypophysitis, and others.

EXPERT OPINION

In addition to the local manifestations and metastasis of neoplasms, some secrete bioactive substances causing PNS. Recognizing and treating PNS early improves clinical outcomes. Larger-scale studies and clinical trials are needed to enhance their management and prognosis.

Pasireotide-induced hyperglycemia in Cushing's disease and Acromegaly: A clinical perspective and algorithms proposal

Pasireotide is an effective treatment for both Cushing's disease (CD) and acromegaly due to its ability to suppress adrenocorticotropic hormone and growth hormone, and to normalize insulin-like growth factor-1 levels, resulting in tumor shrinkage. However, it may also cause hyperglycemia as a side effect in some patients. The aim of this study was to review previous recommendations regarding the management of pasireotide-induced hyperglycemia in patients with CD and acromegaly and to propose efficient monitoring and treatment algorithms based on recent evidence and current guidelines for type 2 diabetes treatment. In about 25% of patients with CD and 50% of patients with acromegaly, pasireotide-induced hyperglycemia does not require drug therapy or can be managed with diet and oral antidiabetic agents. The risk of pasireotide-induced hyperglycemia is higher in patients with diabetes or prediabetes at baseline. Moreover, pasireotide used in the treatment of CD may lead to more frequent and difficult-to-treat glycemic disorders than those observed in acromegaly. Based on the pathomechanism of hyperglycemia, we suggest using metformin as the first-line therapy, followed by glucagon-like peptide-1 and/or sodium-glucose co-transporter-2 inhibitor, and finally insulin in patients with pasireotide-induced hyperglycemia. We propose algorithms for the management of glucose metabolic disorders caused by pasireotide treatment in patients with CD and acromegaly, including those with chronic kidney disease and at high cardiovascular risk.

Osilodrostat treatment in patients with Cushing's disease of Asian or non-Asian origin: a pooled analysis of two Phase III randomized trials (LINC 3 and LINC 4)

Cushing's disease is associated with increased morbidity and mortality. Osilodrostat, a potent oral 11β-hydroxylase inhibitor, provided rapid, sustained mean urinary free cortisol (mUFC) normalization in Cushing's disease patients in two Phase III studies (LINC 3, NCT02180217; LINC 4, NCT02697734). Here, we evaluate the efficacy and safety of osilodrostat in Cushing's disease in patients of Asian origin compared with patients of non-Asian origin. Pooled data from LINC 3 and LINC 4 were analyzed. Outcomes were evaluated separately for Asian and non-Asian patients. For the analysis, 210 patients were included; 56 (27%) were of Asian origin. Median (minimum-maximum) osilodrostat dose was 3.8 (1-25) and 7.3 (1-47) mg/day in Asian and non-Asian patients, respectively. mUFC control was achieved at weeks 48 and 72 in 64.3% and 68.1% of Asian and 68.2% and 75.8% of non-Asian patients. Improvements in cardiovascular and metabolic-related parameters, physical manifestations of hypercortisolism, and quality of life were similar in both groups. Most common adverse events (AEs) were adrenal insufficiency (44.6%) in Asian and nausea (45.5%) in non-Asian patients. AEs related to hypocortisolism and pituitary tumor enlargement occurred in more Asian (58.9% and 21.4%) than non-Asian patients (40.3% and 9.1%). Of Asian and non-Asian patients, 23.2% and 13.6%, respectively, discontinued because of AEs. Asian patients with Cushing's disease generally required numerically lower osilodrostat doses than non-Asian patients to achieve beneficial effects. Hypocortisolism-related AEs were reported in more Asian than non-Asian patients. Together, these findings suggest that Asian patients are more sensitive to osilodrostat than non-Asian patients.

Diagnostic Accuracy and Value of CXCR4-targeted PET/MRI Using 68Ga-Pentixafor for Tumor Localization in Cushing Disease

Background Gallium 68 (68Ga) pentixafor has emerged as a potential C-X-C chemokine receptor type 4 (CXCR4)-targeted radiotracer for neuroendocrine tumor, yet its application in Cushing disease remains uncertain. Purpose To assess the diagnostic accuracy and value of 68Ga-pentixafor PET/MRI in localizing adrenocorticotropic hormone (ACTH)-secreting pituitary tumors in Cushing disease. Materials and Methods A prospective single-center study was conducted from March 2023 to February 2024 in participants with Cushing disease scheduled for surgical pituitary tumor resection. All participants underwent preoperative 68Ga-pentixafor PET/MRI and contrast-enhanced MRI. Two radiologists and nuclear medicine physicians analyzed images. Surgical and histologic findings served as the reference standard. Diagnostic performance was compared using the McNemar test. The Wilcoxon signed rank test was used to compare the maximum standardized uptake value (SUVmax) between tumor and normal pituitary. Correlations between SUVmax and histopathologic or hormone characteristics were analyzed using the Spearman coefficient and logistic regression tests. Results A total of 43 participants (median age, 37 years [IQR, 31-49 years]; 35 female) were included, with 44 pituitary lesions identified after investigational imaging scans, 41 of which were confirmed as ACTH secreting. Sensitivity and diagnostic accuracy of 68Ga-pentixafor PET/MRI were 92.7% (38 of 41 lesions; 95% CI: 80.6, 97.5) and 88.6% (39 of 44 lesions; 95% CI: 76.0, 95.0), respectively, which were higher compared with that of contrast-enhanced MRI (78.0% [32 of 41 lesions; 95% CI: 63.3, 88.0] and 77.3% [34 of 44 lesions; 95% CI: 63.0, 87.2], respectively). Both techniques combined improved sensitivity to 100% (41 of 41 lesions; 95% CI: 91.4, 100.0) and accuracy to 95.5% (42 of 44 lesions; 95% CI: 84.9, 99.2) (P = .01). ACTH-secreting pituitary tumors exhibited a higher SUVmax than normal pituitary (3.9 vs 1.3, P < .001). The SUVmax exhibited a positive correlation with CXCR4 H-score (R = 0.5 [95% CI: 0.2, 0.7], P < .001) and ACTH levels (R = 0.4 [95% CI: 0.1, 0.6], P = .01). Conclusion 68Ga-pentixafor PET/MRI demonstrated high sensitivity in localizing ACTH-secreting pituitary tumors. 68Ga-pentixafor uptake was associated with CXCR4 expression and ACTH level. © RSNA, 2024 Supplemental material is available for this article.

Subtyping of Cushing's Syndrome: A Step Ahead

Cushing's Syndrome (CS) is a rare disease due to chronic endogenous cortisol secretion. In recent years, new developments have broadened the spectrum of differential diagnosis, traditionally categorized as adrenocorticotropic hormone (ACTH)-dependent and ACTH-independent forms. Moreover, increased awareness of the detrimental effects of cortisol on cardiometabolic health and the risk of cardiovascular events lead to increased diagnosis of mild forms, especially in the context of adrenal incidentalomas.This review provides an up-to-date narrative of the most recent literature regarding the challenges of CS diagnosis. After the description of the diagnostic tools available, the functional non-neoplastic hypercortisolism (formerly known as pseudo-Cushing state) is characterized, followed by the subtyping of the different conditions of hypercortisolism, including the differential diagnosis of ACTH-dependent forms and the management of adrenal hypercortisolism, with peculiar attention to the new genetic classification of adrenal CS, mild autonomous cortisol secretion, and bilateral adrenal adenomas.

An Update on the Genetic Drivers of Corticotroph Tumorigenesis

The genetic landscape of corticotroph tumours of the pituitary gland has dramatically changed over the last 10 years. Somatic changes in the USP8 gene account for the most common genetic defect in corticotrophinomas, especially in females, while variants in TP53 or ATRX are associated with a subset of aggressive tumours. Germline defects have also been identified in patients with Cushing's disease: some are well-established (MEN1, CDKN1B, DICER1), while others are rare and could represent coincidences. In this review, we summarise the current knowledge on the genetic drivers of corticotroph tumorigenesis, their molecular consequences, and their impact on the clinical presentation and prognosis.

Improved Clinical Outcomes During Long-term Osilodrostat Treatment of Cushing Disease With Normalization of Late-night Salivary Cortisol and Urinary Free Cortisol

Purpose

To assess whether simultaneous normalization of late-night salivary cortisol (LNSC) and mean urinary free cortisol (mUFC) in patients with Cushing disease treated with osilodrostat is associated with better clinical outcomes than control of mUFC or LNSC alone.

Methods

Pooled data from two phase III osilodrostat studies (LINC 3 and LINC 4) were analyzed. Both comprised a 48-week core phase and an optional open-label extension. Changes in cardiovascular/metabolic-related parameters, physical manifestations of hypercortisolism, and quality of life (QoL) were evaluated across the following patient subgroups: both LNSC and mUFC controlled, only mUFC controlled, only LNSC controlled, and neither controlled.

Results

Of 160 patients included in the analysis, 85.0% had both LNSC and mUFC uncontrolled at baseline. At week 72, 48.6% of patients had both LNSC and mUFC controlled; these patients generally exhibited greater improvements in cardiovascular/metabolic-related parameters than those with only mUFC controlled or both LNSC and mUFC uncontrolled: systolic/diastolic blood pressure, -7.4%/-4.9%, -6.0%/-5.5%, and 2.3%/0.8%, respectively; fasting plasma glucose, -5.0%, -4.8%, and 1.9%; glycated hemoglobin, -5.1%, -4.8%, and -1.3%. Weight, waist circumference, and body mass index improved with control of LNSC and/or mUFC; physical manifestations of hypercortisolism generally improved regardless of LNSC/mUFC control. Patients with both LNSC and mUFC controlled or only mUFC controlled had the greatest improvement from baseline to week 72 in QoL.

Conclusion

In osilodrostat-treated patients with Cushing disease, normalization of LNSC and mUFC led to improvements in long-term outcomes, indicating that treatment should aim for normalization of both parameters for optimal patient outcomes.

Clinical trial identifiers

NCT02180217 (LINC 3); NCT02697734 (LINC 4).

Conundrums of Diagnosis and Management of Cushing's Syndrome in Pregnancy

Pregnancy is rare in women with Cushing's syndrome (CS), due to hypercortisolism-induced gonadotropin suppression and anovulation. Diagnosis of CS is hampered by physiological cortisol level increases during normal pregnancy; importantly abnormal cortisol secretion circadian rhythm could be diagnostic. Active CS is associated with considerable maternal and fetal complications. Second trimester surgery (pituitary or adrenal) is the main treatment option, however observation in mild cases has been suggested. Medical treatment, although not approved for use in pregnancy, may be considered, after careful discussion and balancing any benefits with potential risks and side-effects.

High-throughput Screening for Cushing Disease: Therapeutic Potential of Thiostrepton via Cell Cycle Regulation

Cushing disease is a life-threatening disorder caused by autonomous secretion of ACTH from pituitary neuroendocrine tumors (PitNETs). Few drugs are indicated for inoperative Cushing disease, in particular that due to aggressive PitNETs. To explore agents that regulate ACTH-secreting PitNETs, we conducted high-throughput screening (HTS) using AtT-20, a murine pituitary tumor cell line characterized by ACTH secretion. For the HTS, we constructed a live cell-based ACTH reporter assay for high-throughput evaluation of ACTH changes. This assay was based on HEK293T cells overexpressing components of the ACTH receptor and a fluorescent cAMP biosensor, with high-throughput acquisition of fluorescence images. We treated AtT-20 cells with compounds and assessed ACTH concentrations in the conditioned media using the reporter assay. Of 2480 screened bioactive compounds, over 50% inhibition of ACTH secreted from AtT-20 cells was seen with 84 compounds at 10 μM and 20 compounds at 1 μM. Among these hit compounds, we focused on thiostrepton (TS) and determined its antitumor effects in both in vitro and in vivo xenograft models of Cushing disease. Transcriptome and flow cytometry analyses revealed that TS administration induced AtT-20 cell cycle arrest at the G2/M phase, which was mediated by FOXM1-independent mechanisms including downregulation of cyclins. Simultaneous TS administration with a cyclin-dependent kinase 4/6 inhibitor that affected the cell cycle at the G0/1 phase showed cooperative antitumor effects. Thus, TS is a promising therapeutic agent for Cushing disease. Our list of hit compounds and new mechanistic insights into TS effects serve as a valuable foundation for future research.

Hypopituitarism

Partial or complete deficiency of anterior or posterior pituitary hormone production leads to central hypoadrenalism, central hypothyroidism, hypogonadotropic hypogonadism, growth hormone deficiency, or arginine vasopressin deficiency depending on the hormones affected. Hypopituitarism is rare and likely to be underdiagnosed, with an unknown but rising incidence and prevalence. The most common cause is compressive growth or ablation of a pituitary or hypothalamic mass. Less common causes include genetic mutations, hypophysitis (especially in the context of cancer immunotherapy), infiltrative and infectious disease, and traumatic brain injury. Clinical features vary with timing of onset, cause, and number of pituitary axes disrupted. Diagnosis requires measurement of basal circulating hormone concentrations and confirmatory hormone stimulation testing as needed. Treatment is aimed at replacement of deficient hormones. Increased mortality might persist despite treatment, particularly in younger patients, females, and those with arginine vasopressin deficiency. Patients with complex diagnoses, pregnant patients, and adolescent pituitary-deficient patients transitioning to adulthood should ideally be managed at a pituitary tumour centre of excellence.

Medical treatment of functional pituitary adenomas, trials and tribulations

CONTEXT

Functioning pituitary adenomas (FPAs) include most frequently prolactinomas, somatotroph or corticotroph adenomas, while thyrotroph and gonadotroph adenomas are very rare. Despite their benign histological nature (aggressive tumors are rare and malignant ones exceptional), FPAs could cause significant morbidity and increased mortality due to complications associated with hormonal excess syndromes and/or mass effect leading to compression of adjacent structures. This mini review will focus on the increasing role of medical therapy in the multimodal treatment, which also includes transsphenoidal surgery (TSS) and radiotherapy.

EVIDENCE SYNTHESIS

Most patients with prolactinomas are treated only with medications, but surgery could be considered for some patients in a specialized pituitary center, if higher chances of cure. Dopamine agonists, especially cabergoline, are efficient in reducing tumor size and normalizing prolactin. TSS is the first-line treatment for all other FPAs, but most patients require complex adjuvant treatment, including a combination of therapeutic approaches. Medical therapy is the cornerstone of treatment in all patients after unsuccessful surgery or when surgery cannot be offered and includes somatostatin receptor ligands and dopamine agonists (almost all FPAs), growth hormone receptor antagonists (acromegaly), adrenal steroidogenesis inhibitors and glucocorticoid receptor blockers (Cushing's disease). Novel medical treatments, especially for acromegaly and Cushing's disease are under research.

CONCLUSIONS

An enlarged panel of effective drugs available with increased knowledge of predictive factors for response and/or adverse effects will enhance the possibility to offer a more individualized treatment. This would not only improve disease control and prognosis, but also quality of life.

Case report: Complete restoration of the HPA axis function in Cushing's disease with drug treatment

This report describes a rare case of a 20-year-old man with an ACTH- and prolactin-secreting invasive pituitary macroadenoma causing hyperprolactinemia and Cushing's disease. He was later found to have an AIP mutation. Treatment with cabergoline (1.5 mg weekly) normalized prolactin concentrations and induced a major shrinkage of the adenoma. Not only was urinary free cortisol normalized for more than 14 years, but also the treatment induced normal hypothalamo-pituitary-adrenal (HPA) axis function as illustrated by the reappearance of a normal cortisol/ACTH circadian rhythm, cortisol suppression to dexamethasone, and disappearance of the excessive and aberrant responses to CRH and desmopressin, respectively. This case is the first description of complete restoration of the physiological characteristics of the HPA axis by a medication during the treatment of Cushing's disease. Although exceptional, it illustrates that drugs targeting the pituitary adenoma can bring true complete remission of Cushing's disease.