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BACKGROUND: Cushing's syndrome (CS) poses diagnostic challenges, particularly in distinguishing pituitary-dependent Cushing's syndrome, Cushing's disease (CD), from the ectopic ACTH syndrome (EAS). This study evaluated the diagnostic value of the desmopressin stimulation test (DST) in patients with ACTH-dependent CS in helping this discrimination. METHODS: Twenty-three ACTH-dependent CS patients underwent sequential DST, bilateral inferior petrosal sinus sampling (BIPSS), and transsphenoidal surgery (TSS). Two definitions of a positive DST results were applied. Diagnostic performance was assessed using sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and likelihood ratios. To avoid bias from predetermined criteria, we generated univariate receiver-operating characteristic (ROC) curves, plotting sensitivity against 1-specificity at various percentage cortisol and ACTH response levels. RESULTS: Against BIPSS, DST demonstrated robust sensitivity (Definition 1: 90.0%, Definition 2: 76.2%) and overall accuracy (Definition 1: 87.0%, Definition 2: 73.9%). PPV was high (Definition 1: 95.0%, Definition 2: 94.1%), but NPV indicated potential false negatives. Compared to TSS, DST showed good sensitivity (Definition 1: 90.9-77.3%) and PPV (100.0%) but limited NPV (16.7%). The likelihood ratios emphasized the diagnostic value of the test. Notably, against TSS, DST showed perfect discriminatory power (AUC 1.000 for percent ACTH, 0.983 for percent cortisol). CONCLUSION: The desmopressin test shows promise in accurately identifying the underlying cause of ACTH-dependent CS, potentially reducing the reliance on invasive procedures and providing a practical solution for managing complex cases. Further research with larger cohorts is required to validate the utility of the DST in routine clinical practice.
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CONTEXT: Once hypercortisolemia is confirmed, differential diagnosis between Cushing's syndrome (CS) due to neoplastic endogenous hypercortisolism and non-neoplastic hypercortisolism (NNH, pseudo-Cushing's syndrome) is crucial. Due to worldwide corticotropin-releasing hormone (CRH) unavailability, accuracy of alternative tests to dexamethasone (Dex)-CRH, is clearly needed. OBJECTIVE: Assess the diagnostic accuracy of Dex-CRH test, desmopressin stimulation test, midnight serum cortisol (MSC), and late-night salivary cortisol (LNSC) levels to distinguish CS from NNH. METHODS: Articles through March 2022 were identified from Scopus, Web of Science, MEDLINE, EMBASE, and PubMed. All steps through the systematic review were performed independently and in duplicate and strictly adhered to the updated PRISMA-DTA checklist. DATA SYNTHESIS: A total of 24 articles (1900 patients) were included. Dex-CRH had a pooled sensitivity and specificity of 91% (95%CI 87-94%; I2 0%) and 82% (73-88%; I2 50%), desmopressin test 86% (81-90%; I2 28%) and 90% (84-94%; I2 15%), MSC 91% (85-94%; I2 66%) and 81% (70-89%; I2 71%), and LNSC 80% (67-89%; I2 57%) and 90% (84-93%; I2 21%), respectively. Summary receiver operating characteristics areas under the curve were Dex-CRH 0.949, desmopressin test 0.936, MSC 0.942, and LNSC 0.950 without visual or statistical significance. The overall risk of studies bias was moderate. CONCLUSION: Dex-CRH, the desmopressin stimulation test, and MSC have similar diagnostic accuracy, with Dex-CRH and MSC having slightly higher sensitivity, and the desmopressin test being more specific. LNSC was the least accurate, probably due to high heterogeneity, intrinsic variability, different assays, and lack of consistent reported cutoffs. When facing this challenging differential diagnosis, the results presented here should increase clinicians' confidence when deciding which test to perform.
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Síndrome de Cushing , Humanos , Síndrome de Cushing/diagnóstico , Hidrocortisona/sangre , Hidrocortisona/metabolismo , Diagnóstico Diferencial , Hormona Liberadora de Corticotropina/metabolismo , Dexametasona , Desamino Arginina VasopresinaRESUMEN
CONTEXT: Current guidelines for distinguishing Cushing's disease (CD) from ectopic ACTH secretion (EAS) are questionable, as they use pituitary MRI as first-line investigation for all patients, CRH testing is no longer available and they suggest performing inferior petrosal sinus sampling (BIPPS), an invasive and rarely available investigation, in many patients. OBJECTIVE: To establish non-invasive personalized diagnostic strategies based on the probability of EAS estimated from simple baseline parameters. DESIGN: Retrospective study. SETTING: University hospitals. PATIENTS: 247 CD and 36 EAS patients evaluated between 2001 and 2023 in 2 French hospitals. A single-center cohort of 105 Belgian patients served for external validation. RESULTS: 24h-urinary free cortisol (UFC) had the highest area under ROC curve for discrimination of CD from EAS (0·96 [95% CI, 0·92-0·99] in the primary study and 0·99 [95% CI, 0·98-1·00] in the validation cohort). The addition of clinical, imaging and biochemical parameters did not improve EAS prediction over UFC alone, with only BIPPS showing a modest improvement (c-statistic index 0·99 [95% CI, 0·97-1·00]). 3 groups were defined based on baseline UFC: < 3 (group one), 3-10 (group 2) and > 10 x the upper limit of normal (group 3), and were associated with 0%, 6·1% and 66·7% prevalence of EAS, respectively. Diagnostic approaches performed in our cohort support the use of pituitary MRI alone in group one, MRI first followed by neck-to-pelvis CT-scan (npCT) when negative in group 2, and npCT first followed by pituitary MRI when negative in group 3. When not combined with the CRH test, the desmopressin test has limited diagnostic value. CONCLUSION: UFC accurately predicts EAS and can serve to define personalized and non-invasive diagnostic algorithms.
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We evaluated the accuracy of the 10 µg desmopressin test in differentiating Cushing disease (CD) from non-neoplastic hypercortisolism (NNH) and ectopic ACTH syndrome (EAS). A systematic review of studies on diagnostic test accuracy in patients with CD, NNH, or EAS subjected to the desmopressin test obtained from LILACS, PubMed, EMBASE, and CENTRAL databases was performed. Two reviewers independently selected the studies, assessed the risk of bias, and extracted the data. Hierarchical and bivariate models on Stata software were used for meta-analytical summaries. The certainty of evidence was measured using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation Working Group) approach. In total, 14 studies were included: 3 studies on differentiated CD versus NNH and 11 studies on differentiated CD versus EAS. Considering ΔACTH in 8 studies involving 429 patients, the pooled sensitivity for distinguishing CD from EAS was 0.85 (95% confidence interval [CI]: 0.80-0.89, I2 = 17.6%) and specificity was 0.64 (95% CI: 0.49-0.76, I2 = 9.46%). Regarding Δcortisol in 6 studies involving 233 participants, the sensitivity for distinguishing CD from EAS was 0.81 (95% CI: 0.74-0.87, I2 = 7.98%) and specificity was 0.80 (95% CI: 0.61-0.91, I2 = 12.89%). The sensitivity and specificity of the combination of ΔACTH > 35% and Δcortisol > 20% in 5 studies involving 511 participants were 0.88 (95% CI: 0.79-0.93, I2 = 35%) and 0.74 (95% CI: 0.55-0.87, I2 = 27%), respectively. The pooled sensitivity for distinguishing CD from NNH in 3 studies involving 170 participants was 0.88 (95% CI: 0.79-0.93) and the specificity was 0.94 (95% CI: 0.86-0.97). Based on the desmopressin test for differentiating CD from EAS, considering ΔACTH, Δcortisol, or both percent increments, 15%, 19%, or 20% of patients with CD, respectively, would be incorrectly classified as having EAS. For CD versus NNH, 11% of patients with CD would be falsely diagnosed as having NNH, whereas 7% of patients with NNH would be falsely diagnosed as having CD. However, in all hierarchical plots, the prediction intervals were considerably wider than the confidence intervals. This indicates low confidence in the estimated accuracy, and the true accuracy is likely to be different. Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=85634, identifier CRD42018085634; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=68317, identifier CRD42017068317.
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Síndrome de ACTH Ectópico , Síndrome de Cushing , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT) , Humanos , Síndrome de Cushing/diagnóstico , Desamino Arginina Vasopresina , Diagnóstico Diferencial , Síndrome de ACTH Ectópico/diagnóstico , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/diagnósticoRESUMEN
Ectopic adrenocorticotrophic hormone (ACTH) secretion (EAS) is a rare cause of ACTH-dependent Cushing's syndrome (CS), most often caused by a thoracic neuroendocrine tumor (NET). Large-cell neuroendocrine carcinomas (LCNEC) with EAS are rare and usually present a more severe ACTH secretion and hypercortisolism. We report a 44-year-old non-smoker man, who presented clinical and biochemical evidence of ACTH-dependent CS. Desmopressin 10 µg i.v. produced a 157% increase in ACTH and a 25% increase in cortisol from baseline; there was no stimulation of ACTH or cortisol during the corticotropin-releasing hormone (CRH) test and no suppression with high dose dexamethasone. Pituitary MRI identified a 5 mm lesion, but inferior petrosal venous sinus sampling under desmopressin did not identify a central ACTH source. Thorax and abdominal imaging identified a left lung micronodule. Surgery confirmed a lung LCNEC with strongly positive ACTH immunohistochemistry (IHC) in the primary and lymph node metastasis. The patient was in CS remission after surgery and adjuvant chemotherapy but developed a recurrence 9.5 years later, with LCNEC pulmonary left hilar metastases, ectopic CS, and positive ACTH IHC. This is the first report of LCNEC, with morphologic feature of carcinoid tumor of the lung with ectopic ACTH stimulated by desmopressin. Long delay prior to metastatic recurrence indicates relatively indolent NET. This case report indicates that response to desmopressin, which usually occurs in Cushing's disease or benign NETs, can occur in malignant LCNEC.
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The authors report a case of hypernatremia in a patient with a history of dementia. This case highlights the challenges and scope of taking care of such patients. It also highlights the hardships in diagnosing and caring for patients with inadequate documentation of past diagnoses and treatments.
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PURPOSE: The clinical and hormonal overlap between neoplastic (CS) and non-neoplastic (NNH/pCS) hypercortisolism is a challenge. Various dynamic tests have been proposed to allow an early discrimination between these conditions, but to date there is no agreement on which of them should be used. AIM: To provide an overview of the available tests and to obtain a quantitative synthesis of their diagnostic performance in discriminating NNH/pCS from CS. METHODS: The included articles, published between 1990 and 2022, applied one or more second line tests to differentiate NNH/pCS from CS patients. For the NNH/pCS group, we admitted the inclusion of patients presenting clinical features and/or biochemical findings suggestive of hypercortisolism despite apparent lack of a pCS-related condition. RESULTS: The electronic search identified 339 articles. After references analysis and study selection, we identified 9 studies on combined dexamethasone-corticotropin releasing hormone (Dex-CRH) test, 4 on Desmopressin test and 3 on CRH test; no study on Dex-Desmopressin met the inclusion criteria. Dex-CRH test provided the highest sensitivity (97%, 95 CI% [88%; 99%]). CRH tests showed excellent specificity (99%, 95% CI [0%; 100%]), with low sensitivity. Although metaregression analysis based on diagnostic odds ratio failed to provide a gold standard, CRH test (64.77, 95% CI [0.15; 27,174.73]) seemed to lack in performance compared to the others (Dex-CRH 138.83, 95% CI [49.38; 390.32] and Desmopressin 110.44, 95% CI [32.13; 379.63]). DISCUSSION: Both Dex-CRH and Desmopressin tests can be valid tools in helping discrimination between NNH/pCS and CS. Further studies are needed on this topic, possibly focusing on mild Cushing's Disease and well-characterized NNH/pCS patients. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022359774 , identifier CRD42022359774.
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Síndrome de Cushing , Humanos , Diagnóstico Diferencial , Síndrome de Cushing/diagnóstico , Desamino Arginina Vasopresina , Hospitalización , Oportunidad RelativaRESUMEN
CONTEXT: Diagnostic accuracy of testing currently used for the differential diagnosis of Cushing disease (CD) vs ectopic adrenocorticotropic hormone secretion (EAS) is difficult to interpret. OBJECTIVE: The present study aimed to identify and evaluate the diagnostic accuracy of the corticotropin-releasing hormone (CRH) test, the desmopressin test, and the high-dose dexamethasone suppression test (HDDST) when used to establish a CD or EAS diagnosis. METHODS: This study is a systematic review of the literature and meta-analysis. MEDLINE, OVID, and Web of Science databases were searched for articles published between 1990 and 2021. Articles included described at least 1 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 the HDDST; 32, the CRH test; and the 21, the desmopressin test. The CRH test was found to have the highest sensitivity in detecting CD (ACTH 86.9%, 95% 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 of 0.934. The diagnostic accuracy of the HDDST and desmopressin test 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 analyzing role of dynamic testing in addition to imaging are needed.
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Síndrome de ACTH Ectópico , Síndrome de Cushing , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT) , Humanos , Síndrome de Cushing/diagnóstico , Desamino Arginina Vasopresina , Hidrocortisona , Diagnóstico Diferencial , Síndrome de ACTH Ectópico/diagnóstico , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/diagnóstico , Hormona Adrenocorticotrópica , Hormona Liberadora de CorticotropinaRESUMEN
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.
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Síndrome de ACTH Ectópico , Síndrome de Cushing , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT) , Humanos , Síndrome de ACTH Ectópico/diagnóstico , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/diagnóstico , Síndrome de Cushing/diagnóstico , Hormona Adrenocorticotrópica , Diagnóstico Diferencial , Muestreo de Seno Petroso , Hormona Liberadora de CorticotropinaRESUMEN
The treatment of choice for Cushing's disease (CD) is trans-sphenoidal surgery (TSS). However, TSS is not always curative and, even when curative it is associated with a substantial rate of recurrence. Published recurrence rates vary between 5 and 20%; half of these recurrences appear within 5-years and the remaining half within or even after 10 years post-surgery. A low or undetectable cortisol in the immediate post-op period is regarded as the best criterion of remission. However, low post-op cortisol levels do not accurately predict long-term remission. Moreover, there are no other robust predictors providing certainty about the long-term outcomes. Interestingly, several studies have shown that the desmopressin test performed in the early post-op period may have some promise in predicting more precisely the risk of recurrence. In view of the lack of robust ways to predict long-term outcomes, current guidelines suggest that every patient in remission should be monitored for the possibility of recurrence. The methods used to detect recurrence are similar to those used to assess the cortisol secretory status and include assessment of: (i) abnormal circadian rhythm by late night salivary cortisol (LNSC) or midnight serum cortisol; (ii) impaired cortisol feedback by the dexamethasone suppression test and; (iii) increased 24-h bioavailable cortisol by urinary free cortisol. The timing of evaluation begins when HPA axis recovers, and then annually or sooner in case of clinical suspicion. Currently LNSC is regarded as the earliest and most sensitive biochemical alteration in detecting recurrence; a major caveat for LNSC, however, is its great variability. In practice, the diagnosis of recurrence is a challenge due to the fact that recurrence is usually a slow process with apparent clinical manifestations that may be delayed and alterations of classical biomarkers that may be delayed as well.
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Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT) , Humanos , Hidrocortisona , Sistema Hipotálamo-Hipofisario , Desamino Arginina Vasopresina , Estudios Retrospectivos , Sistema Hipófiso-Suprarrenal , Biomarcadores , Dexametasona , RecurrenciaRESUMEN
Cyclic Cushing's syndrome (also known as intermittent or periodic) is a disease characterized by periods of transient hypercortisolemia shifting into periods of normo- and/or hypocortisolemia. Diagnosis of cyclic Cushing's syndrome is based on at least three periods of confirmed hypercortisolemia interspersed by two periods of normocortisolemia. Cyclic Cushing's syndrome is one of the greatest challenges in modern endocrinology due to its diverse clinical picture, unpredictable duration and frequency of phases, and various etiologies. We discuss a diagnostic algorithm for periodic hypercortisolemia with special regard to hair cortisol analysis and desmopressin stimulation test which both seem to be helpful in finding the correct answer.
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Síndrome de Cushing/diagnóstico , Animales , Síndrome de Cushing/metabolismo , Cabello/química , Cabello/metabolismo , Humanos , Hidrocortisona/química , Hidrocortisona/metabolismoRESUMEN
CONTEXT: Inferior petrosal sinus sampling (IPSS) is used to diagnose Cushing's disease (CD) when dexamethasone-suppression and CRH tests, and pituitary magnetic resonance imaging (MRI), are negative or give discordant results. However, IPSS is an invasive procedure and its availability is limited. OBJECTIVE: To test a noninvasive diagnostic strategy associated with 100% positive predictive value (PPV) for CD. DESIGN: Retrospective study. SETTING: Two university hospitals. PATIENTS: A total of 167 patients with CD and 27 patients with ectopic ACTH-syndrome investigated between 2001 and 2016. MAIN OUTCOME MEASURE(S): Performance of a strategy involving the CRH and desmopressin tests with pituitary MRI followed by thin-slice whole-body computed tomography (CT) scan in patients with inconclusive results. RESULTS: Using thresholds of a cortisol increase > 17% with an ACTH increase > 37% during the CRH test and a cortisol increase > 18% with an ACTH increase > 33% during the desmopressin test, the combination of both tests gave 73% sensitivity and 98% PPV of CD. The sensitivity and PPV for pituitary MRI were 71% and 99%, respectively. CT scan identified 67% EAS at presentation with no false-positives. The PPV for CD was 100% in patients with positive responses to both tests, with negative pituitary MRI and CT scan. The Negative Predictive Value was 100% in patients with negative responses to both tests, with negative pituitary MRI and positive CT scan. Using this strategy, IPPS could have been avoided in 47% of patients in whom it is currently recommended. CONCLUSIONS: In conjunction with expert radiologic interpretation, the non-invasive algorithm studied significantly reduces the need for IPSS in the investigation of ACTH-dependent Cushing's syndrome.
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Síndrome de ACTH Ectópico/diagnóstico , Técnicas de Apoyo para la Decisión , Tumores Neuroendocrinos/complicaciones , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/diagnóstico , Hipófisis/patología , Síndrome de ACTH Ectópico/sangre , Síndrome de ACTH Ectópico/etiología , Síndrome de ACTH Ectópico/cirugía , Adolescente , Hormona Adrenocorticotrópica/sangre , Hormona Adrenocorticotrópica/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Algoritmos , Desamino Arginina Vasopresina/administración & dosificación , Diagnóstico Diferencial , Femenino , Humanos , Hidrocortisona/sangre , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Tumores Neuroendocrinos/sangre , Tumores Neuroendocrinos/patología , Muestreo de Seno Petroso/efectos adversos , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/sangre , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/patología , Hipersecreción de la Hormona Adrenocorticotrópica Pituitaria (HACT)/cirugía , Pruebas de Función Hipofisaria/métodos , Hipófisis/diagnóstico por imagen , Hipófisis/efectos de los fármacos , Hipófisis/cirugía , Valor Predictivo de las Pruebas , Estudios Retrospectivos , Tomografía Computarizada por Rayos X , Adulto JovenRESUMEN
Diabetes insipidus (DI) is characterized by hypoosmotic polyuria related to deficiency of arginine-vasopressin (AVP) secretion (centraldiabetesinsipidus, CDI) or renalinsensitivity to AVP (nephrogenicdiabetesinsipidus, NDI). We report a case of a child with congenital NDI.
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Diabetes Insípida Nefrogénica/congénito , Electrólitos/análisis , Insuficiencia de Crecimiento , Niño , Humanos , PoliuriaRESUMEN
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.
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Síndrome de Cushing/diagnóstico , Técnicas de Diagnóstico Endocrino , Adolescente , Adulto , Anciano , Hormona Liberadora de Corticotropina , Desamino Arginina Vasopresina , Dexametasona , Femenino , Humanos , Masculino , Persona de Mediana Edad , Neuroimagen , Estudios Retrospectivos , Adulto JovenRESUMEN
OBJECTIVE: To assess the utility of the desmopressin (DDAVP) test in the diagnosis and follow-up of a cyclical Cushing's disease (CCS) case. MATERIAL AND METHODS: Laboratory tests included morning and midnight serum cortisol levels, 24h urine free cortisol excretion, midnight salivary cortisol levels, serum cortisol levels after low (1 mg) and high (8 mg) dexamethasone, plasma ACTH and serum cortisol levels after DDAVP. Magnetic resonance imaging (MRI) was used to assess the presence of a pituitary adenoma. The resected tumor specimen was studied by histological, immunohistochemical and cell biology techniques. RESULTS: A patient was referred to our unit with a diagnosis of Cushing's syndrome (CS) for further evaluation and treatment. However, no biochemical evidence of hypercortisolism was observed in the follow-up evaluations. Furthermore, the typical features of CS fluctuated throughout this period. A consistent positive response to the DDAVP stimulation test was observed during the diagnostic work-up, even when overt clinical features of CS were not apparent, raising suspicion for CCS. After two years of follow-up a definitive diagnosis of hypercortisolism was established. An MRI scan revealed a pituitary adenoma, as the source of ACTH production. After transphenoidal surgery, clinical signs of CS resolved and the response to DDAVP became negative. DDAVP induced a significant increase in ACTH levels in cultured pituitary adenoma cells, consistent with the in vivo DDAVP test results. CONCLUSIONS: Our case illustrates the utility of the DDAVP test in the evaluation of patients with suspected CCS. The DDAVP test could facilitate the management of CCS by shortening the time of diagnosis.