Functional imaging in ectopic Cushing syndrome

Cushing's syndrome as a paraneoplastic feature of renal cell carcinoma: A case report

Cushing's syndrome has been believed to be a paraneoplastic syndrome of renal cell carcinomas. However, there appears to be a dearth of compelling evidence to substantiate this notion. The only eligible documentation of Cushing's syndrome due to ectopic adrenocorticotropic hormone secretion by renal cancer in English literature dates back to 1988, and it pertains to a deceased patient discovered during an autopsy. Here, we present the first case of Cushing's syndrome as a paraneoplastic feature of renal cancer which showed complete resolution following surgical removal of the tumor. Additionally, we conduct review of the literature on this particular subject.

Review of the Pathophysiologic and Clinical Aspects of Hypokalemia in Children and Young Adults: an Update

This article examines the regulatory function of the skeletal muscle, renal, and adrenergic systems in potassium homeostasis. The pathophysiologic bases of hypokalemia, systematic approach for an early diagnosis, and therapeutic strategy to avert life-threatening complications are highlighted. By promoting skeletal muscle uptake, intense physical exercise (post), severe trauma, and several toxins produce profound hypokalemia. Hypovolemia due to renal and extra-renal fluid losses and ineffective circulation activate secondary aldosteronism causing urinary potassium wasting. In addition to hypokalemic alkalosis, primary aldosteronism causes low-renin hypertension. Non-aldosterone mineralocorticoid activation leading to low-renin and low-aldosterone hypertension occurs in Liddle's syndrome and apparent mineralocorticoid excess. Although there is enzymatic inhibition of cortisol synthesis in congenital adrenal hyperplasia, precursors of aldosterone produce low-renin hypokalemic hypertension. In addition to the glucocorticoid effect, hypercortisolism activates mineralocorticoid receptors in Cushing's syndrome. Genetic mutations involving furosemide-sensitive Na+-K+-2Cl- co-transporters and thiazide-sensitive Na+-Cl- transporters result in (non-hypertensive) salt-wasting nephropathy. Proximal and distal renal tubular acidosis is associated with hypokalemia. Eating disorders causing hypokalemia include bulimia, laxative abuse, and diuretic misuse. Low urinary potassium (<15 mmol/day) and/or low urinary chloride (<20 mol/L) suggest a gastrointestinal pathology. Co-morbidity of hypokalemia with chronic pulmonary and cardiovascular diseases may increase the fatality rate.

Value of [68Ga]Ga-somatostatin receptor PET/CT in the grading of pulmonary neuroendocrine (carcinoid) tumours and the detection of disseminated disease: single-centre pathology-based analysis and review of the literature

BACKGROUND

Although most guidelines suggest performing a positron emission tomography/computed tomography (PET/CT) with somatostatin receptor (SSTR) ligands for staging of pulmonary carcinoid tumours (PC), only a limited number of studies have evaluated the role of this imaging tool in this specific patient population. The preoperative differentiation between typical carcinoid (TC) and atypical carcinoid (AC) and the extent of dissemination (N/M status) are crucial factors for treatment allocation and prognosis of these patients. Therefore, we performed a pathology-based retrospective analysis of the value of SSTR PET/CT in tumour grading and detection of nodal and metastatic involvement of PC and compared this with the previous literature and with [18F]FDG PET/CT in a subgroup of patients.

METHODS

SSTR PET/CT scans performed between January 2007 and May 2020 in the context of PC were included. If available, [18F]FDG PET/CT images were also evaluated. The maximum standardized uptake (SUVmax) values of the primary tumour, of the pathologically examined hilar and mediastinal lymph node stations, as well as of the distant metastases, were recorded. Tumoural SUVmax values were related to the tumour type (TC versus AC) for both SSTR and [18F]FDG PET/CT in diagnosing and differentiating both tumour types. Nodal SUVmax values were compared to the pathological status (N+ versus N-) to evaluate the diagnostic accuracy of SSTR PET/CT in detecting lymph node involvement. Finally, a mixed model analysis of all pathologically proven distant metastatic lesions was performed.

RESULTS

A total of 86 SSTR PET/CT scans performed in 86 patients with PC were retrospectively analysed. [18F]FDG PET/CT was available in 46 patients. Analysis of the SUVmax values in the primary tumour showed significantly higher SSTR uptake in TC compared with AC (median SUVmax 18.4 vs 3.8; p = 0.003) and significantly higher [18F]FDG uptake in AC compared to TC (median SUVmax 5.4 vs 3.5; p = 0.038). Receiver operating characteristic (ROC) curve analysis resulted in an area under the curve (AUC) of 0.78 for the detection of TC on SSTR PET/CT and of 0.73 for the detection of AC on [18F]FDG PET/CT. A total of 267 pathologically evaluated hilar and mediastinal lymph node stations were analysed. ROC analysis of paired SSTR/[18F]FDG SUVmax values for the detection of metastasis of TC in 83 lymph node stations revealed an AUC of 0.91 for SSTR PET/CT and of 0.74 for [18F]FDG PET/CT (difference 0.17; 95% confidence interval - 0.03 to 0.38; p = 0.10). In a sub-cohort of 10 patients with 12 distant lesions that were pathologically examined due to a suspicious aspect on SSTR PET/CT, a positive predictive value (PPV) of 100% was observed.

CONCLUSION

Our findings confirm the higher SSTR ligand uptake in TC compared to AC and vice versa for [18F]FDG uptake. More importantly, we found a good diagnostic performance of SSTR PET/CT for the detection of hilar and mediastinal lymph node metastases of TC. Finally, a PPV of 100% for SSTR PET/CT was found in a small sub-cohort of patients with pathologically investigated distant metastatic lesions. Taken together, SSTR PET/CT has a very high diagnostic value in the TNM assessment of pulmonary carcinoids, particularly in TC, which underscores its position in European guidelines.

A Rapidly Progressive Case of Ectopic Adrenocorticotropic Hormone (ACTH) Syndrome

Patient: Female, 74-year-old

Final Diagnosis: ACTH-dependent Cushing’s syndrome • ectopic ACTH syndrome

Symptoms: Edema • general fatigue • recurrent mechanical fall

Medication: —

Clinical Procedure: —

Specialty: Critical Care Medicine • Endocrinology and Metabolic • Family Medicine • General and Internal Medicine • Nephrology • Oncology

Neuroendocrine neoplasia and bone (Review)

This is a narrative review focusing on neuroendocrine neoplasia (NEN) and bone status, in terms of metastases and osteoporosis/fractures. One fifth of NEN have skeletal dissemination, this affinity being regulated by intrinsic tumor factors such as the C-X-C chemokine receptor 4 (CXCR4). Bone colonization impairs the patient quality of life, representing a surrogate of reduced survival. Patients with NEN without bone metastases may exhibit low bone mineral density, perhaps carcinoid-related osteoporosis, yet not a standardized cause of osteoporosis. Case-finding strategies to address bone health in NEN with a good prognosis are lacking. Contributors to fractures in NEN subjects may include: menopausal status and advanced age, different drugs, induced hypogonadism, malnutrition, malabsorption (due to intestinal resection, carcinoid syndrome), hypovitaminosis D, impaired glucose profile (due to excessive hormones such as glucagon, somatostatinoma or use of somatostatin analogues), various corticoid regimes, and high risk of fall due to sarcopenia. Pheocromocytoma/paraganglioma involve bone through malignant forms (bone is an elective site) and potential secondary osteoporosis due to excessive hormonal content and increased sympathetic activity which is a key player of bone microarchitecture/quality as reflected by low Trabecular Bone Score. Glucocorticoid osteoporosis is related to NEN-associated ectopic Cushing syndrome. Currently, there are a lack of studies to emphasis that excessive gut-derivate serotonin in NENs with carcinoid syndrome is a specific activator of bone loss thus a contributor to carcinoid-related osteoporosis.

New types of localization methods for adrenocorticotropic hormone-dependent Cushing's syndrome

The management of endogenous Cushing's syndrome (CS) typically involves two key steps: (i) confirmation of autonomous hypercortisolism and (ii) localization of the cause to guide treatment. Adrenocorticotropic hormone (ACTH)-dependent CS is most commonly due to a pituitary corticotrope tumor which may be so small as to evade detection on conventional magnetic resonance imaging (MRI). Although biochemical testing (e.g., corticotropin stimulation; dexamethasone suppression) can provide an indication of the likely origin of ACTH excess, bilateral inferior petrosal sinus catheterization offers greater accuracy to distinguish pituitary-driven CS [Cushing's Disease (CD)] from the ectopic ACTH syndrome [EAS, e.g., due to a bronchial or pancreatic neuroendocrine tumor (NET)]. In patients with CD, 40-50% may not have a pituitary adenoma (PA) readily visualized on standard clinical MRI. In these subjects, alternative MR sequences (e.g., dynamic, volumetric, fluid attenuation inversion recovery) and higher magnetic field strength (7T > 3T > 1.5T) may aid tumor localization but carry a risk of identifying coincidental (non-causative) pituitary lesions. Molecular imaging is therefore increasingly being deployed to detect small ACTH-secreting PA, with hybrid imaging [e.g., positron emission tomography (PET) combined with MRI] allowing precise anatomical localization of sites of radiotracer (e.g., ¹¹C-methionine) uptake. Similarly, small ACTH-secreting NETs, missed on initial cross-sectional imaging, may be detected using PET tracers targeting abnormal glucose metabolism (e.g., ¹⁸F-fluorodeoxyglucose), somatostatin receptor (SSTR) expression (e.g., ⁶⁸Ga-DOTATATE), amine precursor (e.g., ¹⁸F-DOPA) or amino acid (e.g., ¹¹C-methionine) uptake. Therefore, modern management of ACTH-dependent CS should ideally be undertaken in specialist centers which have an array of cross-sectional and functional imaging techniques at their disposal.