Dynamic testing in Cushing's syndrome

Indication to dynamic and invasive testing in Cushing's disease according to different neuroradiological findings

PURPOSE

Dynamic testing represents the mainstay in the differential diagnosis of ACTH-dependent Cushing's syndrome. However, in case of undetectable or detectable lesion < 6 mm on MRI, bilateral inferior petrosal sinus sampling (BIPSS) is suggested by current guidelines. Aim of this study was to analyze the performance of CRH, desmopressin and high-dose dexamethasone suppression test (HDDST) in the differential diagnosis of ACTH-dependent Cushing's syndrome as well as the impact of invasive and noninvasive tests on surgical outcome in patients affected by Cushing's disease (CD).

METHODS

Retrospective analysis on 148 patients with CD and 26 patients with ectopic ACTH syndrome.

RESULTS

Among CD patients, negative MRI/lesion < 6 mm was detected in 97 patients (Group A); 29 had a 6-10 mm lesion (Group B) and 22 a macroadenoma (Group C). A positive response to CRH test, HDSST and desmopressin test was recorded in 89.4%, 91·4% and 70.1% of cases, respectively. Concordant positive response to both CRH/HDDST and CRH/desmopressin tests showed a positive predictive value of 100% for the diagnosis of CD. Among Group A patients with concordant CRH test and HDDST, no difference in surgical outcome was found between patients who performed BIPSS and those who did not (66.6% vs 70.4%, p = 0.78).

CONCLUSIONS

CRH, desmopressin test and HDDST have high accuracy in the differential diagnosis of ACTH-dependent CS. In patients with microadenoma < 6 mm or non-visible lesion, a concordant positive response to noninvasive tests seems sufficient to diagnose CD, irrespective of MRI finding. In these patients, BIPSS should be reserved to discordant tests.

Second-Line Tests in the Diagnosis of Adrenocorticotropic Hormone-Dependent Hypercortisolism

Cushing’s syndrome (CS) is a rare disease caused by chronic and excessive cortisol secretion. When adrenocorticotropin hormone (ACTH) is measurable, autonomous adrenal cortisol secretion could be reasonably ruled out in a differential diagnosis of CS. ACTH-dependent CS accounts for 80%–85% of cases and involves cortisol production stimulated by uncontrolled pituitary or ectopic ACTH secretion. Pituitary adenoma is not detected in up to one-third of cases with pituitary ACTH secretion, whereas cases of CS due to ectopic ACTH secretion may be associated with either malignant neoplasia (such as small cell lung carcinoma) or less aggressive neuroendocrine tumors, exhibiting only the typical symptoms and signs of CS. Since the differential diagnosis of ACTH-dependent CS may be a challenge, many strategies have been proposed. Since none of the available tests show 100% diagnostic accuracy, a step-by-step approach combining several diagnostic tools and a multidisciplinary evaluation in a referral center is suggested. In this review, we present a clinical case to demonstrate the diagnostic work-up of ACTH-dependent CS. We describe the most commonly used dynamic tests, as well as the applications of conventional or nuclear imaging and invasive procedures.

Human Corticotropin-Releasing Hormone Tests: 10 Years of Real-Life Experience in Pituitary and Adrenal Disease

CONTEXT

The human corticotropin-releasing hormone (CRH) test (hCRHtest) is used to differentiate Cushing disease (CD) from ectopic adrenocorticotropin (ACTH) secretion (EAS), to assess autonomous cortisol secretion by the adrenal glands, and to characterize pseudo-Cushing syndrome (CS) or adrenal insufficiency (AI).

MAIN OUTCOME MEASURE

The main outcome measure of this study was to assess the diagnostic accuracy of the hCRHtest.

METHODS

We measured ACTH and cortisol levels; collected the peak values (peakACTH and peakcortisol), and calculated the percentage increases (∆%ACTH and ∆%cortisol) after an intravenous bolus of 100 μg hCRH.

DESIGN AND SETTING

This cross-sectional study of hCRH tests from 2010 to 2019 took place in a referral university hospital center.

PATIENTS

We enrolled 200 patients: 86 CD, 15 EAS, 18 adrenal CS, 25 mild adrenal autonomous cortisol secretion, 31 pseudo-CS, and 25 suspected AI.

RESULTS

The hCRHtest was performed mainly for the differential diagnosis of ACTH-dependent CS or adrenal lesions (P = .048). PeakACTH and peakcortisol were higher in CD, and ∆%ACTH and ∆%cortisol were able to differentiate CD from EAS with a sensitivity and specificity greater than 80%. In patients with low (< 10 pg/mL) or indeterminate (10-20 pg/mL) basalACTH levels, an absent or reduced peakACTH response was able to differentiate adrenal from ACTH-dependent forms. PeakACTH and peakcortisol after hCRHtest were lower in pseudo-CS than in CD, but ∆%ACTH and ∆%cortisol were similar. The role of hCRHtest in patients with AI was limited.

CONCLUSIONS

The hCRHtest test is the mainstay of the differential diagnosis of ACTH-dependent CS. It is also useful for pointing to a diagnosis of CD in the event of bilateral adrenal masses, and in patients with low basalACTH.

Cushing's syndrome: Overview of clinical presentation, diagnostic tools and complications

Cushing's syndrome (CS) is a severe condition that results from chronic exposure to elevated circulating cortisol levels; it is a rare but potentially life-threating condition, especially when not timely diagnosed and treated. Even though the diagnosis can be straightforward in florid cases due to their typical phenotype, milder forms can be missed. Despite the availability of different screening tests, the diagnosis remains challenging as none of the available tools proved to be fully accurate. Due to the ubiquitous effect of cortisol, it is easy understandable that its excess leads to a variety of systemic complications including hypertension, metabolic syndrome, bone damages and neurocognitive impairment. This article discusses clinical presentation of CS with an eye on the most frequent cortisol-related comorbidities and discuss the main pitfalls of first- and second-line tests in endogenous hypercortisolism diagnostic workup.

Evaluation and Treatment of Adrenal Dysfunction in the Primary Care Environment

Adrenal insufficiency (Addison's disease) and Cushing's syndrome are rare disorders characterized by abnormal secretion of adrenal hormones. All patients with adrenal insufficiency and many with Cushing's syndrome require life-long therapy with the potential to impact the quality of life. Management requires gain of a significant amount of knowledge related to treatment, self-care, and how to react quickly in critical situations. Knowledge deficits related to management may cause patients to become critically ill and may even cause death. Ongoing patient/family teaching is crucial for proper disease management and sustaining the quality of life.

Plasma Steroid Metabolome Profiling for Diagnosis and Subtyping Patients with Cushing Syndrome

BACKGROUND

Diagnosis of Cushing syndrome requires a multistep process that includes verification of hypercortisolism followed by identification of the cause of adrenocortical hyperfunction. This study assessed whether pituitary, ectopic, and adrenal subtypes of Cushing syndrome were characterized by distinct plasma steroid profiles that might assist diagnosis.

METHODS

In this retrospective cross-sectional study, mass spectrometric measurements of a panel of 15 plasma steroids were applied to 222 patient samples tested for Cushing syndrome. Disease was excluded in 138 and confirmed in 51 patients with pituitary Cushing syndrome, 12 with ectopic adrenocorticotropin secretion, and 21 with adrenal disease. Another 277 age- and sex-matched hypertensive and normotensive volunteers were included for comparison.

RESULTS

Compared with patients without disease, the largest increases in plasma steroids among patients with Cushing syndrome were observed for 11-deoxycortisol (289%), 21-deoxycortisol (150%), 11-deoxycorticosterone (133%), corticosterone (124%), and cortisol (122%). Patients with ectopic disease showed the most prominent increases, but there was considerable variation for other steroids according to subtype. Patients with adrenal disease had the lowest concentrations of androgens, whereas those with ectopic and pituitary disease showed the lowest concentrations of aldosterone. Plasma 18-oxocortisol was particularly low in ectopic disease. With the use of 10 selected steroids, subjects with and without different Cushing syndrome subtypes could be discriminated nearly as closely as with the use of salivary and urinary free cortisol, dexamethasone-suppressed cortisol, and plasma adrenocorticotropin (9.5% vs 5.8% misclassification).

CONCLUSIONS

Patients with different subtypes of Cushing syndrome show distinctive plasma steroid profiles that may offer a supplementary single-test alternative for screening purposes.

Second-line tests in the differential diagnosis of ACTH-dependent Cushing's syndrome

INTRODUCTION

Diagnosing Cushing's syndrome (CS) can be a challenge, especially in ACTH-dependent CS, when it comes to detecting the origin of ACTH secretion.

MATERIALS AND METHODS

Retrospective data were collected on 170 patients with ACTH-dependent CS (149 CD, 21 EAS) referring to two endocrinology units, focusing on three non-invasive tests: dexamethasone 8 mg overnight challenge (HDDST); corticotrophin-releasing hormone (CRH) assay and the desmopressin (DDAVP) test.

RESULTS

Patients with EAS were slightly older and had higher ACTH, serum and urinary cortisol levels than patients with CD (p < 0.01). CD patients had a stronger ACTH and cortisol response after CRH injection (p < 0.0001), and a more pronounced reduction in cortisol levels after HDDST (p < 0.0001). A threshold percentage ACTH increase after CRH stimulation of 72.4 % was able to identify CD with a sensitivity (SE) of 76 % (95 % CI 68-83) and a specificity (SP) of 100 % (95 % CI 83-100). As for HDDST, a cortisol suppression >52.7 % below the basal level suggested a pituitary origin with a SE of 88 % (95 % CI 81-93) and a SP of 90 % (95 % CI 68-99). There were no cases of EAS with positive responses to both these tests. Increases in ACTH and cortisol levels after the DDAVP test were also higher in CD than in EAS (p < 0.01), though the SE and SP were lower.

CONCLUSIONS

Patients with CD showed a stronger response to HDDST and CRH, and the adopted cut-offs showed a good SE and SP in discriminating them from patients with EAS. Concordant tests indicated CD when positive, whereas no response to either test was highly suggestive of EAS. The DDAVP test was of limited utility in the diagnostic phase. In conclusion, the choice of tests may play an important part in the differential diagnosis of ACTH-dependent CS.

ACTH Antagonists

Adrenocorticotropin (ACTH) acts via a highly selective receptor that is a member of the melanocortin receptor subfamily of type 1 G protein-coupled receptors. The ACTH receptor, also known as the melanocortin 2 receptor (MC2R), is unusual in that it is absolutely dependent on a small accessory protein, melanocortin receptor accessory protein (MRAP) for cell surface expression and function. ACTH is the only known naturally occurring agonist for this receptor. This lack of redundancy and high degree of ligand specificity suggests that antagonism of this receptor could provide a useful therapeutic aid and a potential investigational tool. Clinical situations in which this could be useful include (1) Cushing's disease and ectopic ACTH syndrome - especially while preparing for definitive treatment of a causative tumor, or in refractory cases, or (2) congenital adrenal hyperplasia - as an adjunct to glucocorticoid replacement. A case for antagonism in other clinical situations in which there is ACTH excess can also be made. In this article, we will explore the scientific and clinical case for an ACTH antagonist, and will review the evidence for existing and recently described peptides and modified peptides in this role.

Cushing's disease, pseudo-Cushing states and the dexamethasone test: a historical and critical review

The dexamethasone (DXM) test has been widely used for diagnosing Cushing's disease (CD). The purpose of this paper is to review its diagnostic merit based on calculation of data extracted from earlier publications. Studies presenting individual values for patients with CD and normal subjects were identified through PubMed searches and references in pertinent studies. Calculation of the retrieved data demonstrated huge variation in the relative suppressibility, negative suppression being common. Furthermore, in almost each study retrieved, the pre and post DXM values were closely correlated. Finally, the generally accepted view that DXM causes less suppression in Cushing's disease than in euadrenal controls appears unfounded. A central issue in the definition of so-called "pseudo-Cushing's states" is failure to suppress cortisol secretion with DXM. From analysis of the literature it appears quite possible that this does not reflect a specific endocrine deficit, but a physiological "stress" reaction. The above issues question the diagnostic value of the test, in particular in clinically and biochemically borderline cases.

Do patients with type 2 diabetes mellitus have an increased prevalence of Cushing's syndrome?

Many clinical features are common for patients with type 2 diabetes mellitus (T2DM) and Cushing's syndrome (CS) such as central obesity, hypertension and dyslipidaemia. Patients with CS often have T2DM. Because T2DM is much more frequent than CS, it is possible that some patients with T2DM have increased production of cortisol and thus represent patients with CS. The aim of this review was to evaluate the prevalence of CS in patients with T2DM. A search was performed in PubMed and Medline. We found seven prospective studies, two case-control studies and two cross-sectional studies. The difficulties in diagnosing subclinical CS is discussed. The most frequent tests for diagnosing CS, late-night salivary cortisol, 1-mg dexamethasone suppression test and urinary free cortisol are discussed and put in relation to the results of the literature found. The observed prevalence of CS in patients with T2DM varies widely between the different studies, ranging from 0-9.4%. This may be due to patient selection, differences in test methodology (including choice of test), cutoff values and different cortisol assays. The true prevalence of CS in T2DM has not been determined. We need more studies investigating the prevalence of CS in T2DM patients. There is a need for developing more specific tests for diagnosing CS in patients with only slightly elevated cortisol secretion and subclinical CS. We suggest that examination for hypercortisolism should only be performed in T2DM patients with a cushingoid appearance and hypertension or truncal obesity or dyslipidaemia.

Utility of salivary cortisol measurements in Cushing's syndrome and adrenal insufficiency

CONTEXT

The measurement of cortisol in saliva is a simple, reproducible, and reliable test to evaluate the normal and disordered control of the hypothalamic-pituitary-adrenal (HPA) axis. There are a variety of simple methods to obtain saliva samples without stress, making this a robust test applicable to many different experimental and clinical situations.

EVIDENCE ACQUISITION

Ovid Medline and PubMed from 1950 to present were searched using the following strategies: [<saliva or salivary>and<cortisol or hydrocortisone>and<Cushing or Cushing's>] and [<saliva or salivary>and<cortisol or hydrocortisone>and<adrenal insufficiency or hypoadrenalism or hypopituitarism or Addison's disease>]. The bibliographies of all relevant citations were evaluated for any additional appropriate citations.

EVIDENCE SYNTHESIS

Measurement of an elevated late-night (2300 to 2400 h) salivary cortisol has a greater than 90% sensitivity and specificity for the diagnosis of endogenous Cushing's syndrome. Late-night salivary cortisol measurements are also useful to monitor patients for remission and/or recurrence after pituitary surgery for Cushing's disease. Because it is a surrogate for plasma free cortisol, the measurement of salivary cortisol may be useful during an ACTH stimulation test in patients with increased plasma binding protein concentrations due to increased estrogen, or decreased plasma binding protein concentrations during critical illness. Most reference laboratories now offer salivary cortisol testing.

CONCLUSIONS

It is expected that the use of the measurement of salivary cortisol will become routine in the evaluation of patients with disorders of the HPA axis.

Changes in adenosine 5'-monophosphate-activated protein kinase as a mechanism of visceral obesity in Cushing's syndrome

OBJECTIVE

Features of the metabolic syndrome such as central obesity with insulin resistance and dyslipidemia are typical signs of Cushing's syndrome and common side effects of prolonged glucocorticoid treatment. AMP-activated protein kinase (AMPK), a key regulatory enzyme of lipid and carbohydrate metabolism as well as appetite, is involved in the development of the deleterious metabolic effects of excess glucocorticoids, but no data are available in humans. In the current study, we demonstrate the effect of high glucocorticoid levels on AMPK activity of human adipose tissue samples from patients with Cushing's syndrome.

METHODS

AMPK activity and mRNA expression of genes involved in lipid metabolism were assessed in visceral adipose tissue removed at abdominal surgery of 11 patients with Cushing's syndrome, nine sex-, age-, and weight-matched patients with adrenal incidentalomas, and in visceral adipose tissue from four patients with non-endocrine-related abdominal surgery.

RESULTS

The patients with Cushing's syndrome exhibited a 70% lower AMPK activity in visceral adipose tissue as compared with both incidentalomas and control patients (P = 0.007 and P < 0.001, respectively). Downstream targets of AMPK fatty acid synthase and phosphoenol-pyruvate carboxykinase were up-regulated in patients with Cushing's syndrome. AMPK activity was inversely correlated with 0900 h serum cortisol and with urinary free cortisol.

CONCLUSIONS

Our data suggest that glucocorticoids inhibit AMPK activity in adipose tissue, suggesting a novel mechanism to explain the deposition of visceral adipose tissue and the consequent central obesity observed in patients with iatrogenic or endogenous Cushing's syndrome.