ACTH after 15 min distinguishes between Cushing's disease and ectopic Cushing's syndrome: a proposal for a short and simple CRH test

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.

Ovine CRH Stimulation and 8 mg Dexamethasone Suppression Tests in 323 Patients With ACTH-Dependent Cushing's Syndrome

CONTEXT

Determining the etiology of adrenocorticotropin (ACTH)-dependent Cushing's syndrome (CS) is often difficult. The gold standard test, inferior petrosal sinus sampling (IPSS), is expensive and not widely available.

OBJECTIVE

Evaluate the performance of the corticotropin-releasing hormone stimulation test (CRH-ST) and the 8 mg high-dose dexamethasone suppression test (HDDST) in distinguishing Cushing's disease (CD) from ectopic ACTH syndrome (EAS).

METHODS

Retrospective review in a tertiary referral center. A total of 323 patients with CD or EAS (n = 78) confirmed by pathology or biochemical cure (n = 15) in 96% underwent CRH-ST and HDDST performed between 1986 and 2019. We calculated test sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value, and diagnostic accuracy (DA) for the diagnosis of CD, and determined optimal response criteria for each test, alone and in combination.

RESULTS

The CRH-ST performed better than the HDDST (DA 91%, 95% CI 87-94% vs 75%, 95% CI 69-79%). Optimal response criteria were a ≥40% increase of ACTH and/or cortisol during the CRH test and a ≥69% suppression of cortisol during the HDDST. A ≥40% cortisol increase during the CRH test was the most specific measure, PPV 99%. Seventy-four percent of subjects had concordant positive CRH test and HDDST results, yielding Se 93%, Sp 98%, DA 95%, and PPV 99%, with a pretest likelihood of 85%. A proposed algorithm diagnosed 64% of patients with CD with near perfect accuracy (99%), obviating the need for IPSS.

CONCLUSION

CRH is a valuable tool to correctly diagnose the etiology of ACTH-dependent CS. Its current worldwide unavailability impedes optimal management of these patients.

Non-Invasive Biochemical Testing of ACTH-dependent Cushing's Disease: Do We Still Need Petrosal Sinus Sampling?

Differentiating between a pituitary from an ectopic source of ACTH could be a real one of the major challenges of clinical endocrinology. The Bilateral inferior petrosal sinus sampling (BIPSS) is considered the gold standard for identifying the source of ACTH; however, is not available worldwide. After the SARS-CoV-2 pandemic, algorithms that include biochemical and imaging tests have gained importance as an alternative to BIPSS. This review summarizes the drawbacks in the differential diagnosis of ACTH-dependent Cushing; the evolution of diagnostic tests, and the evidence that exists on their performance. As well as a comparison between the advantages and disadvantages of invasive and non-invasive tests.

Machine learning models for differential diagnosis of Cushing's disease and ectopic ACTH secretion syndrome

BACKGROUND

Using machine learning (ML) to explore the noninvasive differential diagnosis of Cushing's disease (CD) and ectopic corticotropin (ACTH) secretion (EAS) model is the next hot research topic. This study was to develop and evaluate ML models for differentially diagnosing CD and EAS in ACTH-dependent Cushing's syndrome (CS).

METHODS

Two hundred sixty-four CD and forty-seven EAS were randomly divided into training and validation and test datasets. We applied 8 ML algorithms to select the most suitable model. The diagnostic performance of the optimal model and bilateral petrosal sinus sampling (BIPSS) were compared in the same cohort.

RESULTS

Eleven adopted variables included age, gender, BMI, duration of disease, morning cortisol, serum ACTH, 24-h UFC, serum potassium, HDDST, LDDST, and MRI. After model selection, the Random Forest (RF) model had the most extraordinary diagnostic performance, with a ROC AUC of 0.976 ± 0.03, a sensitivity of 98.9% ± 4.4%, and a specificity of 87.9% ± 3.0%. The serum potassium, MRI, and serum ACTH were the top three most important features in the RF model. In the validation dataset, the RF model had an AUC of 0.932, a sensitivity of 95.0%, and a specificity of 71.4%. In the complete dataset, the ROC AUC of the RF model was 0.984 (95% CI 0.950-0.993), which was significantly higher than HDDST and LDDST (both p < 0.001). There was no significant statistical difference in the comparison of ROC AUC between the RF model and BIPSS (baseline ROC AUC 0.988 95% CI 0.983-1.000, after stimulation ROC AUC 0.992 95% CI 0.983-1.000). This diagnostic model was shared as an open-access website.

CONCLUSIONS

A machine learning-based model could be a practical noninvasive approach to distinguishing CD and EAS. The diagnostic performance might be close to BIPSS.

Sensitivity of Different ACTH and Cortisol Concentration Values in Corticotropin-Releasing Hormone Based Tests in Cushing's Disease

PURPOSE

In Cushing's disease (CD) patients, the aim of the present study is to confirm sensitivity of several ACTH and cortisol concentration values in different time points, during corticotropin-releasing hormone (CRH) stimulation test and during CRH stimulation following dexamethasone suppression (DEX-CRH) test.

METHODS

We retrospectively analyzed cortisol and ACTH concentration increment during CRH and DEX-CRH tests in 23 patients with confirmed CD. Cortisol and ACTH concentrations were determined immediately before, 15 min and 30 min after CRH stimulation. We evaluated the sensitivity of different cutoff values including those reported in previous studies, in the diagnosis of CD.

RESULTS

During DEX-CRH test, 15 min serum cortisol concentration of 1.4 μg/dl (38 nmol/L) had a sensitivity of 90.9%, and serum cortisol concentration ≥1.27 μg/dl (35 nmol/L) had a sensitivity of 100%. For plasma ACTH, sensitivity of 100% was obtained using ACTH ≥3.5pmol/L (16 pg/ml) at 30 min. During CRH test, 35% increase from baseline in ACTH concentration had a sensitivity of 72.7%. Twenty percent increase in cortisol 30 minutes after stimulation yielded a sensitivity of 85.7%. The best sensitivity of ACTH and cortisol increment was obtained 15 min after stimulation, using 19% and 9% increase, respectively (sensitivity of 100% and 92.8%, respectively).

CONCLUSION

During CRH and DEX-CRH tests, the study findings agree with the good sensitivity of ACTH and cortisol cutoff values suggested in previous studies; yet, other cutoff values may give a higher diagnostic sensitivity.

Dynamic testing for differential diagnosis of ACTH-dependent Cushing Syndrome: a systematic review and meta-analysis

OBJECTIVE

Diagnostic accuracy of testing currently used for the differential diagnosis of Cushing's disease (CD) vs ectopic -ACTH secretion (EAS) is difficult to interpret. The present study aimed to identify and evaluate the diagnostic accuracy of corticotropin-releasing hormone (CRH) test, desmopressin test, and high-dose dexamethasone suppression test (HDDST) when used to establish a CD or EAS diagnosis.

DESIGN

This study is a systematic review of the literature and meta-analysis.

METHODS

MEDLINE, OVID, and Web of Science databases were searched for articles published between the years 1990-2021. Articles included described at least one test(s) (CRH, desmopressin, or HDDST) and the diagnostic reference standard(s) (histopathology, petrosal sinus sampling, surgical remission, imaging, and long-term follow-up) used to establish a CD or EAS diagnosis.

RESULTS

Sixty-two studies were included: 43 reported the use of HDDST, 32 CRH test, and 21 desmopressin test. CRH test was found to have the highest sensitivity in detecting CD (ACTH 86.9%, 95% confidence interval [CI] 82.1-90.6, cortisol 86.2%, 95%CI 78.3-91.5) and the highest specificity in detecting EAS (ACTH 93.9%, 95%CI 87-98.3, cortisol 89.4%, 95%CI 82.8-93.7). This resulted in a high diagnostic odds ratio (58, 95%CI 43.25-77.47), large area under the curve, and a receiver-operating characteristic (ROC) of 0.934. The diagnostic accuracy of HDDST and desmopressin test(s) was lower than that of the CRH test.

CONCLUSION

The meta-analysis indicates that a patient with a positive ACTH response after a CRH test is highly likely to have CD. Further studies analysing role of dynamic testing in addition to imaging are needed.

Biochemical testing to differentiate Cushing's disease from ectopic ACTH syndrome

The differential diagnosis of ACTH-dependent Cushing's syndrome is often a diagnostic challenge that has been debated in numerous studies. In this short article, we will discuss the performance and main drawbacks of the biochemical tests used for this diagnosis.

A noninvasive scoring model for the differential diagnosis of ACTH-dependent Cushing's syndrome: a retrospective analysis of 311 patients based on easy-to-use parameters

OBJECTIVES

The differential diagnosis of ACTH-dependent Cushing's disease (CS) is challenging. The gold standard approach bilateral inferior petrosal sinus sampling (BIPSS) is expensive and invasive, while other noninvasive tests, like the high-dose dexamethasone suppression test (HDDST), provide unsatisfactory diagnostic accuracy. This study aimed to find a new noninvasive practical approach with higher diagnostic accuracy to differently diagnose ACTH-dependent CS, which can be used in centers where BIPSS cannot be applied.

METHODS

264 Cushing's disease (CD) patients and 47 ectopic ACTH secretion syndrome (EAS) patients were analyzed in this single-center retrospective study (2011-2021). The multivariate logistic model was used to construct the scoring model.

RESULTS

Female (adjusted OR 3.030, 95%CI 1.229-7.471), hypokalemia (0.209, 0.076-0.576), ACTH (0.988, 0.982-0.994), MRI pituitary lesion positive (8.671, 3.521-21.352), and HDDST positive (2.768, 1.139-6.726) have a strong association with the differential diagnosis of ACTH-dependent CS and were included in the final multivariable logistic regression model. A -14-to-14-point noninvasive scoring model was built on the model. The AUC of the noninvasive scoring model was 0.915 (95% CI 0.869-0.960), significantly higher than the AUC of HDDST (0.756, 95% CI 0.685-0.825, P = 0.004). The optimal cutoff of the model was ≥0 to diagnose CD. The sensitivity of the noninvasive scoring model was 91.3% (95% CI 87.3%-94.1%), and the specificity was 80.9% (95% CI 67.5%-89.6%). When the model's sensitivity was 100.0%, the cutoff was ≥ -10 with a specificity of 19.2%; when the model's specificity was 100.0%, the cutoff was ≥ 13 with a sensitivity of 22.7%.

CONCLUSIONS

We developed a noninvasive scoring model to distinguish CD and EAS in ACTH-dependent CS patients with higher diagnostic utility than HDDST in the same cohort. The noninvasive scoring model might be applied in areas where BIPSS is unavailable, the CRH is hard to obtain, or the desmopressin stimulation is not widely applied. It also provided a triage tool for selecting patients that might benefit the most from a further BIPSS test.

Mechanism, diagnosis, and treatment of cyclic Cushing's syndrome: A review

Cushing's syndrome (CS) is caused by hypercortisolemia, leading to the occurrence of characteristic clinical symptoms. A small number of patients with CS have periodic and intermittent increases in cortisol levels, resulting in recurrent episodes of clinical symptoms. Such patients are known as having cyclic CS (CCS). The cortisol secretion cycle of patients with CCS is unpredictable, and laboratory tests often show negative results during the normal cortisol secretion period; therefore, the diagnosis and treatment of the disease are currently difficult. Although the pathogenesis of CCS remains uncertain, recent studies have suggested that it may be closely related to hypothalamic factors, feedback mechanisms, and tumor infarction. Our review summarizes the current state of research on the potential mechanisms, diagnosis, and treatment of CS and provides an outlook for future studies.

Consensus statement by the French Society of Endocrinology (SFE) and French Society of Pediatric Endocrinology & Diabetology (SFEDP) on diagnosis of Cushing's syndrome

Cushing's syndrome is defined by prolonged exposure to glucocorticoids, leading to excess morbidity and mortality. Diagnosis of this rare pathology is difficult due to the low specificity of the clinical signs, the variable severity of the clinical presentation, and the difficulties of interpretation associated with the diagnostic methods. The present consensus paper by 38 experts of the French Society of Endocrinology and the French Society of Pediatric Endocrinology and Diabetology aimed firstly to detail the circumstances suggesting diagnosis and the biologic diagnosis tools and their interpretation for positive diagnosis and for etiologic diagnosis according to ACTH-independent and -dependent mechanisms. Secondly, situations making diagnosis complex (pregnancy, intense hypercortisolism, fluctuating Cushing's syndrome, pediatric forms and genetically determined forms) were detailed. Lastly, methods of surveillance and diagnosis of recurrence were dealt with in the final section.

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.

Diurnal Salivary Cortisol Profiles in Patients with Cushing's Syndrome

BACKGROUND

Quantification of salivary cortisol is one of the highly sensitive and specific screening parameters for Cushing's syndrome (CS). However, only late-night salivary cortisol is part of the standard screening procedure. In this study, we aimed to analyze salivary cortisol day profiles in patients with different types of CS to test whether specific patterns might be relevant for diagnosis and subtyping.

MATERIAL AND METHODS

Among 428 patients including those with confirmed Cushing's syndrome (N=111, of those 75 with Cushing's disease, 27 patients with adrenal CS and nine patients with ectopic CS), autonomous cortisol secretion (N=39) or exclusion of CS (control group, N=278) salivary cortisol was measured five times a day.

RESULTS

At each of the five time points, salivary cortisol was significantly higher in patients with CS compared to the control group (p≤0.001). Using the entire profile instead of one single salivary cortisol at 11 p.m. improved diagnostic accuracy (85 vs. 91%) slightly. Patients with ACTH-dependent CS had higher salivary cortisol levels than patients with adrenal CS. Also, morning cortisol was significantly higher in patients with ectopic CS than in patients with Cushing's disease (p=0.04). Nevertheless, there was a strong overlap between diurnal profiles, and the diagnostic yield for subtyping was low.

DISCUSSION

The study results show that using diurnal salivary cortisol profiles for CS diagnosis results in a limited increase in diagnostic accuracy. With significant differences between Cushing subtypes, cortisol profiles are not useful in everyday clinical practice for subtyping of CS.

Outcome of CRH stimulation test and overnight 8 mg dexamethasone suppression test in 469 patients with ACTH-dependent Cushing's syndrome

OBJECTIVE

To evaluate diagnostic accuracy of the corticotropin-releasing hormone (CRH) stimulation test and the overnight 8 mg dexamethasone suppression test (DST) for the differentiation of Cushing's disease (CD) and ectopic Cushing's syndrome (ECS).

METHODS

Retrospective study in 6 European centers. Inclusion criteria: patients with a) overt adrenocorticotropin (ACTH)-dependent Cushing's syndrome at the time of dynamic testing, b) histopathological confirmed tumors and/or c) postoperative biochemical remission and/or adrenal insufficiency. Optimal cut-offs were calculated via receiver operating characteristic (ROC) analysis using CD as reference.

RESULTS

469 patients were analyzed [78% females; median age 43 years (IQR 19)]. CRH test and overnight 8 mg DST were performed in 420 [CD, n=394 (94%); ECS, n=26 (6%)] and 237 patients [228 CD (96%), 9 ECS (4%)]. Both tests were performed in 205 patients (44%). The post-CRH %-increase at 30 minutes of both ACTH (cut-off ≥31%, sensitivity 83%, specificity 85%, AUC 0.81) and cortisol (cut-off ≥12%, sensitivity 82%, specificity 89%, AUC 0.86) discriminated best between CD and ECS. A test duration of >60 minutes did not improve diagnostic performance of the CRH test. The optimal cortisol cut-off for the %-suppression during the 8 mg DST was ≥55% (sensitivity 80%, specificity 78%, AUC 0.75).

CONCLUSION

The CRH test has equivalent sensitivity but higher specificity than the 8 mg DST and is therefore the test of first choice. The diagnostic outcome of ACTH and cortisol is well comparable, however, sampling beyond 60 minutes post-CRH does not provide diagnostic benefits.

Consensus on diagnosis and management of Cushing's disease: a guideline update

Cushing's disease requires accurate diagnosis, careful treatment selection, and long-term management to optimise patient outcomes. The Pituitary Society convened a consensus workshop comprising more than 50 academic researchers and clinical experts to discuss the application of recent evidence to clinical practice. In advance of the virtual meeting, data from 2015 to present about screening and diagnosis; surgery, medical, and radiation therapy; and disease-related and treatment-related complications of Cushing's disease summarised in recorded lectures were reviewed by all participants. During the meeting, concise summaries of the recorded lectures were presented, followed by small group breakout discussions. Consensus opinions from each group were collated into a draft document, which was reviewed and approved by all participants. Recommendations regarding use of laboratory tests, imaging, and treatment options are presented, along with algorithms for diagnosis of Cushing's syndrome and management of Cushing's disease. Topics considered most important to address in future research are also identified.

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.

Cushing's disease

Cushing's disease (CD) is the most prevalent cause of endogenous hypercortisolism. CD is responsible for multiple co-morbidities and increased mortality. Accurate and prompt diagnosis and optimal treatment are essential to improve the prognosis of CD. However, the diagnosis of CD is probably one of the most difficult in endocrinology and, therefore, diagnostic workup should be performed in an experienced center. Transsphenoidal surgery performed by an expert surgeon is the only therapeutic option that can offer definitive cure and remains the first-line treatment in most patients. Second-line treatments include pharmacotherapy, pituitary radiotherapy and bilateral adrenalectomy. The second-line therapeutic strategy is complex, must be individualized and performed in a multidisciplinary expert center. Symptomatic treatments of persisting co-morbidities after remission, which are responsible for increased mortality and impaired quality of life is an important part of medical management.

Adrenal vein sampling for ACTH-producing pheochromocytomas

Adrenocorticotropic hormone (ACTH)-producing pheochromocytoma can cause a variety of clinical manifestations of excess catecholamine and corticosteroid. Anatomic localization of this source of ectopic ACTH is critical to facilitate unilateral adrenalectomy and prevent adrenal insufficiency due to bilateral adrenalectomy. Although nuclear scintigraphy remains the diagnostic gold standard, recent radiotracer supply shortages have necessitated alternative diagnostic paradigms to localize adrenal pheochromocytomas. We present a case where adrenal vein sampling (AVS) was utilized to lateralize an adrenal pheochromocytoma and discuss the approach and nuance as it differs from routine AVS for hyperaldosteronism or hypercortisolism.

The usefulness of the combined high-dose dexamethasone suppression test and desmopressin stimulation test in establishing the source of ACTH secretion in ACTH-dependent Cushing's syndrome

Bilateral inferior petrosal sinus sampling (BIPSS) is the current gold standard test for differentially diagnosing ACTH-dependent Cushing's syndrome (CS). However, BIPSS is an invasive procedure, and its availability is limited. We retrospectively analysed the 24-hour urinary free cortisol (UFC) level during the high-dose dexamethasone suppression test (HDDST) and plasma ACTH/cortisol levels after the desmopressin stimulation test (DDAVP test) in subjects with confirmed Cushing's disease (CD) (n = 92) and ectopic ACTH-dependent CS (EAS) (n = 16), and evaluated the positive predictive value (PPV) of the two combined-tests in the aetiological diagnosis of ACTH-dependent CS. The percent changes in UFC levels after the HDDST and in ACTH/cortisol levels after DDAVP administration relative to the corresponding basal levels and the area under the receiver operating characteristic (ROC) curve (AUC) were analysed. UFC suppression below 62.7% suggested a pituitary origin with a sensitivity (SE) of 80% (95% CI: 70-88) and a specificity (SP) of 80% (95% CI: 52-96). A threshold increase in the ACTH level after DDAVP stimulation of 44.6% identified CD with an SE of 91% (95% CI: 83-97) and an SP of 75% (95% CI: 48-93). The combination of both tests yielded an SE of 95.5% and PPV of 98.4% for CD, and significantly improved the efficiency of the differential diagnosis between CD and EAS. These dual non-invasive endocrine tests may substantially reduce the need for BIPSS in the etiological investigation of ACTH-dependent CS.

Inferior petrosal sinus sampling and stimulation with CRH: 15 years of experience in a tertiary hospital

BACKGROUND

Inferior petrosal sinus sampling (IPSS) is indicated in the diagnosis of adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome (CS), especially when the results of the initial diagnostic tests are discordant.

OBJECTIVE

To describe the patients who underwent this invasive functional test in a tertiary hospital.

METHODS

This was an observational study of a retrospective cohort of patients with ACTH-dependent CS and IPSS between 2004 and 2019. We determined their epidemiological, hormonal, radiological and functional characteristics, and evaluated their diagnostic capacity and optimal cut-off points to differentiate between Cushing's disease (CD) and ectopic Cushing's syndrome (ECS).

RESULTS

23 patients were evaluated, of which 65.2% were women with the average age of 42 (36-62) years. ACTH secretion of pituitary origin was evident in 82.6% of the patients and of ectopic origin in 17.4%. Plasma cortisol, urinary free cortisol, and ACTH levels were higher in patients with ECS. Regarding IPSS, the baseline central/peripheral ACTH gradient detected 89.5% of patients with CD and after stimulation with CRH, 100%. The optimal cut-off points in the diagnosis of CD were 2.06 at baseline and 2.49 after CRH stimulation.

CONCLUSION

IPSS with CRH stimulation is a test with a high diagnostic accuracy for correctly classifying patients with CD and ECS. The cut-off points of the gradients may be different from the classic ones. Therefore, we recommend that each center perform its own evaluation.

Method-Specific Cortisol and Dexamethasone Thresholds Increase Clinical Specificity of the Dexamethasone Suppression Test for Cushing Syndrome

BACKGROUND

The dexamethasone suppression test (DST) is the recommended first-tier test for suspected Cushing syndrome (CS). Missed dexamethasone intake or insufficient dexamethasone serum exposure may yield false positive results. Quantification of serum dexamethasone in DST samples may therefore improve test performance.

METHODS

Simultaneous quantification of dexamethasone and cortisol by liquid chromatography-tandem mass spectrometry in 400 DST serum samples (100 overt CS, 200 excluded CS, 100 adrenal incidentalomas with (possible) autonomous cortisol secretion, AI-ACS) randomly selected within the indication groups. The 2.5th percentile of dexamethasone in patients with excluded CS was considered the lower limit of normal (LLN).

RESULTS

Serum dexamethasone varied from undetectable to 20.2 ng/mL with a median of 4.8 ng/mL (95% CI 4.5-5.1 ng/mL). Dexamethasone was undetectable in only 16 patients (4%), suggesting non-compliance. The dexamethasone LLN was 1.8 ng/mL (4.6 nmol/L). Decreased glomerular filtration rate and diabetes mellitus were associated with higher serum dexamethasone concentration, while body mass index, sex, age, nicotine, and oral contraceptives had no significant effect. By excluding the 27 samples with dexamethasone <LLN and applying the method-specific cortisol cutoff of 2.4 µg/dL (66 nmol/L) to samples with suspected CS, the clinical specificity for CS increased from 67.5% to 92.4% while preserving 100% clinical sensitivity. Among 100 AI-ACS samples (defined by immunoassay), 4 samples had dexamethasone <1.8 ng/mL and 14 samples had cortisol <2.4 µg/dL, which excluded autonomous cortisol secretion.

CONCLUSIONS

Quantification of dexamethasone and method-specific cortisol cutoffs in DST samples may reduce the false positive rate and lower the proportion of patients requiring further workup.

Pitfalls in Performing and Interpreting Inferior Petrosal Sinus Sampling: Personal Experience and Literature Review

CONTEXT

Inferior petrosal sinus sampling (IPSS) helps differentiate the source of ACTH-dependent hypercortisolism in patients with inconclusive biochemical testing and imaging, and is considered the gold standard for distinguishing Cushing disease (CD) from ectopic ACTH syndrome. We present a comprehensive approach to interpreting IPSS results by examining several real cases.

EVIDENCE ACQUISITION

We performed a comprehensive review of the IPSS literature using PubMed since IPSS was first described in 1977.

EVIDENCE SYNTHESIS

IPSS cannot be used to confirm the diagnosis of ACTH-dependent Cushing syndrome (CS). It is essential to establish ACTH-dependent hypercortisolism before the procedure. IPSS must be performed by an experienced interventional or neuroradiologist because successful sinus cannulation relies on operator experience. In patients with suspected cyclical CS, it is important to demonstrate the presence of hypercortisolism before IPSS. Concurrent measurement of IPS prolactin levels is useful to confirm adequate IPS venous efflux. This is essential in patients who lack an IPS-to-peripheral (IPS:P) ACTH gradient, suggesting an ectopic source. The prolactin-adjusted IPS:P ACTH ratio can improve differentiation between CD and ectopic ACTH syndrome when there is a lack of proper IPS venous efflux. In patients who have unilateral successful IPS cannulation, a contralateral source cannot be excluded. The value of the intersinus ACTH ratio to predict tumor lateralization may be improved using a prolactin-adjusted ACTH ratio, but this requires further evaluation.

CONCLUSION

A stepwise approach in performing and interpreting IPSS will provide clinicians with the best information from this important but delicate procedure.

Case Report: A Challenging Localization of a Pulmonary Ectopic ACTH-Secreting Tumor in a Patient With Severe Cushing's Syndrome

BACKGROUND

Ectopic adrenocorticotropic syndrome (EAS) is a rare cause of endogenous ACTH-dependent Cushing's syndrome, usually associated with severe hypercortisolism as well as comorbidities. Tumor detection is still a challenge and often requires several imaging procedures. In this report, we describe a case of an ectopic ACTH secretion with a misleading localization of the responsible tumor due to a concomitant rectal carcinoma.

CASE PRESENTATION

A 49-year-old man was referred to our Endocrinology Unit due to suspicion of Cushing's syndrome. His medical history included metastatic rectal adenocarcinoma, diagnosed 5 years ago and treated with adjuvant chemotherapy, radiotherapy and surgical resection. During follow-up, a thoracic computed tomography scan revealed two pulmonary nodules located in the superior and middle lobes of the right lung with a diameter of 5 and 10 mm, respectively. However, these nodules remained radiologically stable thereafter and were not considered relevant. All biochemical tests were suggestive of EAS (basal ACTH levels: 88.2 ng/L, nv 0-46; basal cortisol levels: 44.2 µg/dl, nv 4.8-19.5; negative response to CRH test and high dose dexamethasone suppression test) and radiological localization of the ectopic ACTH-secreting tumor was scheduled. The CT scan revealed a dimensional increase of the right superior lung nodule (from 5 to 12 mm). [⁶⁸Ga]-DOTA-TOC PET/CT scan was negative, while [¹⁸F]-FDG-PET/CT showed a tracer accumulation in the superior nodule. After a multidisciplinary consultation, the patient underwent thoracic surgery that started with two atypical wedge resections of nodules. Frozen section analyses showed a neuroendocrine tumor on the right middle lobe nodule and a metastatic colorectal adenocarcinoma on the superior lesion. Then, a right superior nodulectomy and a right middle lobectomy with mediastinal lymphadenectomy were performed. The final histopathological examination confirmed a typical carcinoid tumor, strongly positive for ACTH. A post-surgical follow-up showed a persistent remission of Cushing's syndrome.

CONCLUSIONS

The present report describes a case of severe hypercortisolism due to EAS not detected by functional imaging methods, in which the localization of ACTH ectopic origin was puzzled by a concomitant metastatic rectal carcinoma. The multidisciplinary approach was crucial for the management of this rare disease.

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.

Factors Affecting Dexamethasone Suppression Test Results

Dexamethasone suppression tests are basic tools in diagnostics of hypercortisolemia. Low-dose tests play major role in screening and initial assessment. High-dose tests are aimed at more elaborate diagnostics, however their clinical value is questionable. Dexamethasone is a highly potent, synthetic steroid. It is metabolized by cytochrome P450 3A4 (CYP3A4), and so are various other xenobiotics. Due to wide spectrum of substances processed by CYP3A4, interferences and interactions are not uncommon. Physicians should be familiar with drugs modifying dexamethasone metabolism, and therefore the results of dynamic tests. Other important concerns are: drugs enhancing cortisol-binding globulin production, organ dysfunction, pseudo-Cushing states, pregnancy and other physiological conditions leading to elevated blood cortisol, cyclic Cushing disease. To properly assess and assist patients, it is crucial for health professionals to understand and be able to overcome such clinical dilemmas.

RELIABILITY OF THE CORTICOTROPIN RELEASING HORMONE STIMULATION TEST FOR DIFFERENTIATING BETWEEN ACTH DEPENDENT AND INDEPENDENT CUSHING SYNDROME

Context

It is a challenge to determine the origin of Cushing syndrome (CS), especially in patients with low-normal adrenocorticotropic hormone (ACTH) concentrations.

Objective

To evaluate the reliability of the corticotropin-releasing hormone (CRH) stimulation test in patients with CS whose origin of disease was not clearly identified using ACTH values, the high-dose dexamethasone suppression test (HDDST), and imaging in a single tertiary referral center.

Design and Methods

Twenty-one patients with CS who were admitted to the endocrinology-metabolism clinic between 2004 and 2016 whose ACTH concentrations were 5-20 pg/mL and needed CRH stimulation test were retrospectively assessed.

Results

Nine out of 21 patients were diagnosed as having Cushing's disease (CD) and 12/21 had adrenal CS. The CRH stimulation test had a sensitivity and specificity of 100% and 8%, and positive and negative predictive values of 100% and 45% according to the current diagnostic criteria, respectively. An increase in ACTH ≥115% at 15 minutes and cortisol ≥86% at 60 minutes after CRH were associated with the highest likelihood ratio. The sensitivity and specificity of ACTH was 67% and 83% (AUC=0.75±0.12, 95% CI: [0.5-0.9]; p=0.03), and for cortisol it was 75% and 78% (AUC=0.71±0.15, 95% CI: [0.5-0.9]; p=0.03). Cortisol suppression of more than 64% from basal level in the HDDST suggested CD with the highest likelihood ratio. When these cut-off values were used together, both tests were negative in the patients with CD.

Conclusion

The CRH stimulation test has low specificity to localize CS in patients with ACTH concentrations of 5-20 pg/mL according to the current diagnostic criteria. Different diagnostic criteria may be used in the CRH stimulation test and also in the HDDST in this group of patients.

Two types of ectopic Cushing syndrome or a continuum? Review

BACKGROUND

Two types of ectopic Cushing syndrome (ECS) are described: ECS associated with aggressive neoplasms, and ECS with indolent and occult tumors, however, there is a lack of studies that thoroughly review their characteristics.

METHODS

A systematic review was carried out on PUBMED of all the papers about the ECS, in order to better define the types of this subcategory of Cushing's syndrome, highlighting the differential aspects between these subgroups.

RESULTS

It was found that in 50% of cases the prototypic "aggressive" ECS is caused by small cell lung carcinomas (SCLC). In these cases, the clinical presentation may be atypical, predominating the signs and symptoms derived from the protein catabolism. Cortisol and ACTH levels are extremely high, the clinical presentation is abrupt (< 3-6 months) and the tumor is usually advanced, being impossible a curative treatment. On the other hand, "indolent" ECS is mainly represented by carcinoid tumors (CT). In these cases the clinical presentation overlaps enormously with that of Cushing's disease (CD). Cortisol and ACTH levels are slightly elevated, the clinical presentation is progressive (> 6 months) and the prognosis is usually good, and a curative treatment is possible in about 75% of the cases.

CONCLUSION

Although there is no absolute differentiation between the two extremes of ECS, a classification could be established in two groups, guided by its clinical and biochemical characteristics, and mainly by the type and stage of the ACTH-secreting tumor. However, a small percentage of tumors do not fit in this simple grouping, and may present both phenotypes or an intermediate one.

Diagnostic tests for Cushing's syndrome differ from published guidelines: data from ERCUSYN

OBJECTIVE

To evaluate which tests are performed to diagnose hypercortisolism in patients included in the European Registry on Cushing's syndrome (ERCUSYN), and to examine if their use differs from the current guidelines.

PATIENTS AND METHODS

We analyzed data on the diagnostic tests performed in 1341 patients with Cushing's syndrome (CS) who have been entered into the ERCUSYN database between January 1, 2000 and January 31, 2016 from 57 centers in 26 European countries. Sixty-seven percent had pituitary-dependent CS (PIT-CS), 24% had adrenal-dependent CS (ADR-CS), 6% had CS from an ectopic source (ECT-CS) and 3% were classified as having CS from other causes (OTH-CS).

RESULTS

Of the first-line tests, urinary free cortisol (UFC) test was performed in 78% of patients, overnight 1 mg dexamethasone suppression test (DST) in 60% and late-night salivary cortisol (LSaC) in 25%. Use of LSaC increased in the last five years as compared with previous years (P < 0.01). Use of HDDST was slightly more frequent in the last 5 years as compared with previous years (P < 0.05). Of the additional tests, late-night serum cortisol (LSeC) was measured in 62% and 48-h 2 mg/day low-dose dexamethasone suppression test (LDDST) in 33% of cases. ACTH was performed in 78% of patients. LSeC and overnight 1 mg DST supported the diagnosis of both PIT-CS and ADR-CS more frequently than UFC (P < 0.05).

CONCLUSIONS

Use of diagnostic tests for CS varies across Europe and partly differs from the currently available guidelines. It would seem pertinent that a European consensus be established to determine the best diagnostic approach to CS, taking into account specific inter-country differences with regard to the availability of diagnostic tools.

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.