Evaluation of diagnostic tests for ACTH-dependent Cushing's syndrome

Accuracy of the 10 μg desmopressin test for differential diagnosis of Cushing syndrome: a systematic review and meta-analysis

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.

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.

Enhancing Cushing's disease diagnosis: exploring the impact of desmopressin on ACTH gradient during BIPSS

Introduction

The differential diagnosis between Cushing's disease (CD) and ectopic ACTH syndrome (EAS) is complex, and bilateral inferior petrosal sinus sampling (BIPSS) is considered the gold-standard test. However, BIPSS with corticotropin-releasing hormone (CRH) stimulation is rarely available.

Objective

This retrospective cohort study aimed to assess the accuracy of the inferior petrosal sinus to peripheral ACTH gradient (IPS:P) before and after desmopressin stimulation for the differential diagnosis of ACTH-dependent Cushing's syndrome (CS), applying different cutoff values.

Methods

A total of 50 patients (48 with CD and 2 with EAS) who underwent BIPSS were included in this study. The sensitivity and specificity of IPS:P in BIPSS before and after desmopressin stimulation were evaluated. Various cutoff values for IPS:P were examined to determine their diagnostic accuracy.

Results

Using the traditional IPS:P cutoff, the sensitivity was 85.1% before stimulation, 89.6% after stimulation, and a combined sensitivity of 91.7%. Applying cutoff values of IPS:P >1.4 before and >2.8 after stimulation, the sensitivity was 87.2% and 89.6%, respectively, with a combined sensitivity of 91.7%. Receiver operating characteristic (ROC) curve analysis determined optimal cutoff values of 1.2 before stimulation and 1.57 after stimulation, resulting in a sensitivity of 93.6% and 93.8%, respectively, with a combined sensitivity of 97.9%. Specificity remained at 100% throughout all analyses. Among the 43 patients who responded positively to stimulation, 42 (97.7%) did so within the first three minutes, and all 43 (100%) did so within the first five minutes. None of the assessed clinical variables predicted the ACTH response to stimulation in BIPSS with statistical significance.

Discussion

ACTH stimulation with desmopressin during BIPSS improves the accuracy of IPS:P, making it a valuable tool for investigating ACTH-dependent Cushing's syndrome. Considering the low risk of complications, we recommend the use of desmopressin stimulation during BIPSS for the differential diagnosis of ACTH-dependent CS.

Emerging diagnostic methods and imaging modalities in cushing's syndrome

Endogenous Cushing's syndrome (CS) is a rare disease characterized by prolonged glucocorticoid excess. Timely diagnosis is critical to allow prompt treatment and limit long-term disease morbidity and risk for mortality. Traditional biochemical diagnostic modalities each have limitations and sensitivities and specificities that vary significantly with diagnostic cutoff values. Biochemical evaluation is particularly complex in patients whose hypercortisolemia fluctuates daily, often requiring repetition of tests to confirm or exclude disease, and when delineating CS from physiologic, nonneoplastic states of hypercortisolism. Lastly, traditional pituitary MRI may be negative in up to 60% of patients with adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas (termed "Cushing's disease" [CD]) whereas false positive pituitary MRI findings may exist in patients with ectopic ACTH secretion. Thus, differentiating CD from ectopic ACTH secretion may necessitate dynamic testing or even invasive procedures such as bilateral inferior petrosal sinus sampling. Newer methods may relieve some of the diagnostic uncertainty in CS, providing a more definitive diagnosis prior to subjecting patients to additional imaging or invasive procedures. For example, a novel method of cortisol measurement in patients with CS is scalp hair analysis, a non-invasive method yielding cortisol and cortisone values representing long-term glucocorticoid exposure of the past months. Hair cortisol and cortisone have both shown to differentiate between CS patients and controls with a high sensitivity and specificity. Moreover, advances in imaging techniques may enhance detection of ACTH-secreting pituitary adenomas. While conventional pituitary MRI may fail to identify microadenomas in patients with CD, high-resolution 3T-MRI with 3D-spoiled gradient-echo sequence has thinner sections and superior soft-tissue contrast that can detect adenomas as small as 2 mm. Similarly, functional imaging may improve the identification of ACTH-secreting adenomas noninvasively; Gallium-68-tagged corticotropin-releasing hormone (CRH) combined with PET-CT can be used to detect CRH receptors, which are upregulated on corticotroph adenomas. This technique can delineate functionality of adenomas in patients with CD from patients with ectopic ACTH secretion and false positive pituitary lesions on MRI. Here, we review emerging methods and imaging modalities for the diagnosis of CS, discussing their diagnostic accuracy, strengths and limitations, and applicability to clinical practice.

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.

Is Desmopressin Useful in the Evaluation of Cushing Syndrome?

The desmopressin test was first described 30 years ago. Based on the differential secretagogue properties of desmopressin on adrenocorticotropin (ACTH) release between normal and corticotroph tumor cells, this test was intended to facilitate the diagnosis of Cushing syndrome (CS). The distinct expression of the various arginine vasopressin receptors between normal pituitary, corticotroph tumors, or neuroendocrine tumors cells secreting ACTH ectopically suggested that this test could facilitate the etiological diagnosis of ACTH-dependent CS. In this review, we analyze the merits and pitfalls of desmopressin use in the diagnostic procedures of CS. Desmopressin response is not able to completely differentiate the various etiologies of CS; its wider availability has allowed its use for inferior petrosal sinus sampling confirmation of a pituitary source of ACTH excess. In addition, desmopressin can be useful to demonstrate adequate corticotroph tumor resection when its stimulatory effect is lost following pituitary surgery of patients with Cushing disease. Desmopressin response can also be a marker of the risk of longer-term postoperative recurrence. However, this review also highlights the lack of consensual criteria of normal or abnormal response to desmopressin in its various uses and requirement for further research on its usefulness.

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.

A Comprehensive Approach to Predicting the Outcomes of Transsphenoidal Endoscopic Adenomectomy in Patients with Cushing’s Disease

Persistent and recurrent hypercortisolism after transsphenoidal endoscopic surgery (TSS) is considered to be an urgent issue prompting the search for Cushing’s disease (CD) remission predictors. The goal was to find a combination of predictors that can forecast the remission of CD after TSS. A total of 101 patients with CD who had undergone TSS were included. One year after surgery, CD remission status was evaluated. Preoperative pituitary magnetic resonance imaging (MRI) data, preoperative results of a high-dose dexamethasone suppression test (HDDST) and morning serum cortisol level collected 24 h after TSS (24 h MSeC) were compared in patients with and without remission of hypercortisolism. Remission one year after TSS was confirmed in 63 patients. CD remission predictors one year after TSS were: adenoma size ≥ 3 mm in the absence of invasive growth and the suppression of serum cortisol ≥ 74% in the HDDST, 24 h MSeC ≤ 388 nmol/L. A total of 38 patients had three favorable values of detected predictors; all of them had CD remission one year after TSS. With long-term follow-up, 36 of them remained in remission. Patients who had no one favorable predictor had no remission of hypercortisolism one year after TSS. Our data confirmed the prospects of using a combination of selected predictors to forecast CD remission after TSS.

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.

Onset of Aortic Dissection Complicated with Cushing's Disease: A Case Report and Review of the Literature

Cushing's syndrome and Cushing's disease cause various metabolic disorders associated with high cortisol levels. Some reports have shown that Cushing's syndrome is complicated with dissecting aortic aneurysm and aortic dissection after long-term exposure to high cortisol levels. We herein report a rare case of aortic dissection complicated with Cushing's disease. Aortic dissection may occur even under relatively short periods of high cortisol conditions. This case suggests that hypercortisolemia should be treated as soon as possible in order to prevent aortic dissection in subjects with Cushing's disease.

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.

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.

Case Report: Three Rare Cases of Ectopic ACTH Syndrome Caused by Adrenal Medullary Hyperplasia

Ectopic ACTH syndrome (EAS) accounts for 10-20% of endogenous Cushing's syndrome (CS). Hardly any cases of adrenal medullary hyperplasia have been reported to ectopically secrete adrenocorticotropic hormone (ACTH). Here we describe a series of three patients with hypercortisolism secondary to ectopic production of ACTH from adrenal medulla. Cushingoid features were absent in case 1 but evident in the other two cases. Marked hypokalemia was found in all three patients, but hyperglycemia and osteoporosis were present only in case 2. All three patients showed significantly elevated serum cortisol and 24-h urinary cortisol levels. The ACTH levels ranged from 19.8 to 103.0pmol/L, favoring ACTH-dependent Cushing's syndrome. Results of bilateral inferior petrosal sinus sampling (BIPSS) for case 1 and case 3 confirmed ectopic origin of ACTH. The extremely high level of ACTH and failure to suppress cortisol with high dose dexamethasone suppression test (HDDST) suggested EAS for patient 2. However, image studies failed to identify the source of ACTH secretion. Bilateral adrenalectomy was performed for rapid control of hypercortisolism. After surgery, cushingoid features gradually disappeared for case 2 and case 3. Blood pressure, blood glucose and potassium levels returned to normal ranges without medication for case 2. The level of serum potassium also normalized without any supplementation for case 1 and case 3. The ACTH levels of all three patients significantly decreased 3-6 months after surgery. Histopathology revealed bilateral adrenal medullary hyperplasia and immunostaining showed positive ACTH staining located in adrenal medulla cells. In summary, our case series reveals the adrenal medulla to be a site of ectopic ACTH secretion. Adrenal medulla-originated EAS makes the differential diagnosis of ACTH-dependent Cushing's syndrome much more difficult. Control of the hypercortisolism is mandatory for such patients.

Case Report: An Unusual Case of Ectopic ACTH Syndrome Caused by Mediastinal Paraganglioma

Ectopic adrenocorticotrophic hormone (ACTH) syndrome is not common, which is more unusual when caused by paraganglioma. We herein present a 40-year-old Chinese male who was diagnosed with ACTH-dependent Cushing's syndrome. However, the localization of the ACTH source was troublesome due to the inconsistent results of the high-dose dexamethasone suppression test and the desmopressin stimulation test. Bilateral inferior petrosal sinus sampling was performed, and ectopic ACTH syndrome was diagnosed. After ⁶⁸Ga-DOTATATE-PET/CT and ¹⁸F-FDG-PET/CT were performed, it was localized in the anterior mediastinum. Post-operation histopathology demonstrated an ACTH-secreting mediastinal paraganglioma. The patient obtained complete clinical remission after a mediastinal tumorectomy.

Non-invasive Diagnostic Strategy in ACTH-dependent Cushing's Syndrome

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.

Treatment challenges in pediatric Cushing's disease: Review of the literature with particular emphasis on predictive factors for the disease recurrence

Cushing's disease (CD) is a rare endocrine condition caused by a corticotroph pituitary tumor that produces adrenocorticotropic hormone. The current state of knowledge of CD treatment is presented in this article including factors that can be helpful in predicting remission and/or recurrence of the disease. The primary goals in CD treatment are quick diagnosis and effective, prompt treatment as the persistent disease is associated with increased morbidity and mortality. Cooperation of a team consisting of experienced pediatrician/adult endocrinologist, neuroradiologist, transsphenoidal neurosurgeon and (if necessary) radiotherapist contribute to the best treatment effects.

Clinical investigation of pituitary incidentalomas: A two-center study

Recent advances in imaging technology resulted in an increase in pituitary incidentalomas (PIs) detection. PIs were reported to be present in 1.6% persons with magnetic resonance imaging of the brain. Whereas, there were few studies about PIs with detailed investigation. We aimed to investigate the clinical and endocrinological characteristics of PIs. We evaluated 65 patients diagnosed with PIs who underwent detailed clinical and endocrinological evaluations. Of the 65 patients, 33 (50.8%) had non-functional pituitary adenomas (NFPAs), 11 (16.9%) had Rathke's cleft cysts (RCCs), 7 (10.8%) had functional pituitary adenomas (FPAs), 6 (9.2%) had benign extra-pituitary tumors (BEPTs), and 8 (12.3%) had malignant tumors (MTs). Compared with patients with NFPAs, those with MTs were significantly younger and had a significantly lower body mass index, lower prevalence of hypertension, and lower prevalence of dyslipidemia. Patients with MTs had significantly higher prevalence of central diabetes insipidus than those with NFPAs. In addition, patients with NFPAs had significantly higher prevalence of pituitary apoplexy than those with FPAs, BEPTs, and MTs. In conclusion, our study demonstrated clinical and endocrinological characteristics of PIs. Highly detailed clinical and endocrinological investigations should be performed for PIs. In addition, MTs should be considered in the differential diagnosis for young and lean patients with central diabetes insipidus.

SELLA TURCICA 3T MAGNETIC RESONANCE IMAGING IN THE DIAGNOSIS OF CUSHING'S DISEASE IN CHILDREN: TWO CASE REPORTS

Objective:

To present two clinical cases of pediatric Cushing disease caused by adrenocorticotropic hormone secreting pituitary adenomas, which were diagnosed by magnetic resonance imaging using 3 Tesla technology.

Case description:

Two cases of Cushing disease in 9-year-old children are reported. Both children presented pituitary adenomas that were smaller than 5 mm at their largest diameter, and which were not seen by standard 1.5 Tesla resonance. One of the patients was submitted to bilateral and simultaneous catheterization of the inferior petrosal sinus, but the result was undetermined. In both cases, the pituitary adenoma was detected by 3 Tesla magnetic resonance imaging. Both patients underwent transsphenoidal surgery and were cured.

Comments:

Cushing disease presents high morbidity. Therefore, early diagnosis and prompt treatment are essential. It is usually caused by adenomas that are smaller than 5 mm in diameter. Surgery is the first line of treatment, and effective methods of locating the adenoma are necessary for greater therapeutic success. This report suggests that the 3 Tesla magnetic resonance imaging is more sensitive, and thus able to detect pituitary microadenomas (largest diameter <10 mm). This exam may be indicated as a low-morbidity diagnostic tool for finding pituitary microadenomas in Cushing disease that are not visualized by 1.5 Tesla magnetic resonance imaging.

A case of ectopic ACTH syndrome due to DDAVP-sensitive but V1b receptor-negative bronchial typical carcinoid with lymphatic metastasis and plasma ProGRP elevation

Ectopic ACTH syndrome (EAS) is a potentially fatal endocrine disease that results from a variety of neuroendocrine tumors (NETs), such as small cell lung cancer (SCLC) and bronchial typical carcinoid. Typical carcinoid is usually slow growing, not associated with plasma progastrin releasing peptide (ProGRP) elevation. Here, we report a 47-year-old female smoker with progressive typical carcinoid and plasma ProGRP elevation. Several types of Cushingoid features were found on physical examination. In addition, laboratory examination showed elevated plasma ACTH and serum cortisol levels. These findings indicated ACTH-dependent Cushing's syndrome. Moreover, the serum cortisol level was not suppressed by overnight high-dose dexamethasone treatment, suggesting the presence of an extra-pituitary tumor. Contrast-enhanced brain MRI revealed no pituitary adenoma, which also supported the idea that EAS occurred in the present case. Strikingly, chest computed tomographic (CT) scan showed a single 18-mm peripheral nodule in the right middle lobe of the lung. Tumor marker analysis revealed an elevation in plasma ProGRP. These data suggested a possibility that SCLC secreted ACTH and caused EAS in this patient. Of note, the plasma ACTH level was increased (1.7 fold) in l-desamino-8-D-arginine vasopressin (DDAVP) test, also suggesting the specific clinical feature in this case. After additional imaging examinations, we performed surgical resection with the suspicion of limited SCLC. As a result, pathological examination revealed a vasopressin receptor Ib (V1b) receptor-negative bronchial typical carcinoid with ACTH production and mediastinal lymphatic metastasis. In summary, we present a case of EAS caused by progressive bronchial typical carcinoid with plasma ProGRP elevation. We propose a novel subtype of lung typical carcinoid.

DIAGNOSIS OF ENDOCRINE DISEASE: The role of the desmopressin test in the diagnosis and follow-up of Cushing's syndrome

Desmopressin is a vasopressin analogue selective for type 2 vasopressin receptors that mediate renal water retention. In contrast to the native hormone arginine vasopressin, a well-known ACTH secretagogue, desmopressin, exerts minimal or no activity on ACTH excretion. However, in a substantial proportion of patients with ACTH-dependent Cushing's syndrome (CS), desmopressin elicits an ACTH and cortisol response, which contrasts with the minimal responses obtained in healthy subjects. The mechanism underlying this paradoxical response involves upregulation of vasopressin type 3 and/or the aberrant expression of type 2 receptors by neoplastic ACTH-producing cells. This makes desmopressin administration a suitable test enabling the distinction between neoplastic from functional (formerly termed 'pseudo-Cushing syndrome') ACTH-dependent cortisol excess. Several studies have now established an adjunctive role of desmopressin in the initial diagnostic workup of CS. Despite some early data indicating that this test may also have a role in distinguishing between Cushing's disease (CD) and ectopic ACTH secretion, subsequent studies failed to confirm this observation. The ability of the paradoxical response to desmopressin to depict the presence of neoplastic ACTH-secreting cells was also exploited in the follow-up of patients with CD undergoing surgery. Loss of the desmopressin response, performed in the early postoperative period, was a good predictor for a favorable long-term outcome. Moreover, during follow-up, reappearance of desmopressin paradoxical response was an early indicator for recurrence. In conclusion, the desmopressin test is a valid tool in both the diagnosis and follow-up of patients with CD and should be more widely applied in the workup of these patients.

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.

Ectopic ACTH syndrome caused by desmopressin-responsive thymic neuroendocrine tumor

A 32-year-old Chinese woman with rapid weight gain and progressive edema was found to have typical Cushingoid features. Her endocrine data were consistent with a diagnosis of ACTH-dependent Cushing's syndrome. To differentiate ectopic ACTH syndrome (EAS) from Cushing's disease (CD), various dynamic endocrine and imaging tests were performed. Her ACTH response was negative to corticotropin-releasing hormone (CRH) and positive to desmopressin. Magnetic resonance imaging of the pituitary showed no mass lesion. Computed tomography scan of the chest revealed a large mass (21 × 15 mm) in the anterior mediastinum, where positron emission tomography showed accumulation of [(18)F] fluorodeoxyglucose. Selective venous sampling showed marked step-up in ACTH level in the internal thoracic vein but not in the cavernous sinus after CRH stimulation. These data are compatible with the diagnosis of EAS. The resected tumor was pathologically consistent with thymic neuroendocrine tumor (NET) positive for ACTH by immunohistochemistry and abundant V1b receptor gene expression by RT-PCR. Postoperatively, her circulating ACTH/cortisol levels became normalized, and responded to stimulation with CRH but not with desmopressin. Her Cushingoid appearance gradually disappeared, and she was free from recurrence 5 years after surgery. This is a rare case of desmopressin-responsive EAS caused by thymic NET with predominant V1b gene expression, which was successfully localized by imaging modalities combined with selective venous sampling.

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.

A case of ectopic ACTH syndrome treated with intermittent administration of dopamine agonists

ACTH-dependent Cushing's syndrome includes Cushing's disease and ectopic ACTH syndrome (EAS). The differential diagnosis of Cushing's disease from EAS in cases of ACTH-dependent Cushing's syndrome is a challenging problem. We report here a case of EAS with an unknown source of ACTH secretion. Extensive imaging procedures, involving computed tomography (neck to pelvis), pituitary magnetic resonance imaging, and whole-body (18)F-fluorodeoxyglucose-positron emission tomography, failed to reveal the source of ACTH secretion. Intermittent administration of bromocriptine, a short-acting and nonselective dopamine agonist, has afforded adequate suppression of plasma ACTH and cortisol levels over the long term.

LEARNING POINTS

Tumor excision is the primary treatment for EAS. However, when surgery is impossible, medical therapy is needed to treat hypercortisolism.In cases where the source of ACTH secretion is unknown, inhibitors of steroidogenesis, such as metyrapone, mitotane, ketoconazole, and etomidate, are mostly used to suppress cortisol secretion.Medications that suppress ACTH secretion are less effective, therefore less popular, as standard treatments.In the present case, short-term treatment with dopamine agonists was effective for the long-term suppression of both ACTH and cortisol levels.

Pathophysiology and treatment of subclinical Cushing's disease and pituitary silent corticotroph adenomas [Review]

Pituitary adrenocorticotropic hormone (ACTH)-secreting tumor presents with a variety of clinical features. We outlined the features of ACTH release and characteristics of corticotroph adenoma cells. We especially focused on the corticotroph adenomas in patients with no clinical features of Cushing's disease. Subclinical Cushing's disease is defined by ACTH-induced mild hypercortisolism without typical features of Cushing's disease. Silent corticotroph adenomas (SCAs) are defined by normal cortisol secretion and ACTH-immunopositive staining without autonomous ACTH secretion. Clinicians who are not well-informed about the disease may sometimes confuse SCAs (because of their clinically silent nature) with "subclinical Cushing's disease". The recent criteria for diagnosing subclinical Cushing's disease in Japan are presented. Cortisol measurement was recently standardized in Japan, so plasma cortisol cutoff level should be reconsidered for the diagnosis. In patients with uncontrolled diabetes and hypertension despite appropriate treatment, subclinical Cushing's disease may be efficiently detected. Subclinical Cushing's disease may be associated with metabolic change. In subclinical Cushing's disease, mild hypercortisolism due to autonomous secretion of ACTH contributes to metabolic change and treatment of subclinical hypercortisolism can reverse this change.

Cushing's disease presenting with gastrointestinal perforation: a case report

Gastrointestinal perforation is a complication associated with steroid therapy or hypercortisolism, but it is rarely observed in patients with Cushing's disease in clinical practice, and only one case has been reported as a presenting symptom. Herein, we report a rare case of Cushing's disease in which a patient presented with gastrointestinal perforation as a symptom. A 79-year-old man complained of discomfort in the lower abdomen for 6 months. Based on the endocrinological and gastroenterological examinations, he was diagnosed with Cushing's disease with a perforation of the descending colon. After consultation with a gastroenterological surgeon, it was decided that colonic perforation could be conservatively observed without any oral intake and treated with parenteral administration of antibiotics because of the mild systemic inflammation and lack of abdominal guarding. Despite the marked elevated levels of serum cortisol, oral medication was not an option because of colonic perforation. Therefore, the patient was submitted to endonasal adenomectomy to normalize the levels of serum cortisol. Subsequently, a colostomy was successfully performed. Despite its rarity, physicians should be aware that gastrointestinal perforation may be associated with hypercortisolism, especially in elderly patients, and immediate diagnosis and treatment of this life-threatening condition are essential. If a perforation can be conservatively observed, endonasal adenomectomy prior to laparotomy is an alternative treatment option for hypercortisolism.

Reliability of the diagnostic tests for Cushing's syndrome performed in a tertiary referral center

The study aimed to retrospectively evaluate the reliability of the diagnostic and location tests in Cushing's Syndrome (CS). Eighty-seven patients diagnosed with CS between 1995 and 2007 by Endocrinology Metabolism Department of Cerrahpasa Medical School were included in the study. The control group consisted of 91 patients who presented to the outpatient clinic because of obesity. The diagnostic tests were as follows: 1 mg dexamethasone suppression test (DST), 24-h urinary free cortisol (UFC), midnight cortisol level (MCL), ACTH level and overnight 8 mg DST. The sensitivity and specificity of UFC were 81 and 66 % respectively for the cut-off point of 50 μg/day, whereas they were 64 and 76 % respectively for the cut-off point of 100 μg/day. For the cut-off value of 1.8/μg/dL for MCL and 1 mDST, the sensitivity rates were 100 and 98 %, while the specificity rates were 88 and 33 %, respectively. Among the location tests, the sensitivity and specificity of ACTH under 10 pg/mL for adrenal CS were 92 and 94 % respectively. The sensitivity and specificity of ACTH higher than 30 pg/mL for ACTH-dependent CS were 69 and 100 % respectively. The sensitivity rates of 8 mg DST for 50 and 60 % suppressions were 83 and 79 % respectively, whereas the specificity rates were 75 and 88 % respectively. 1 mg DST (cut-off <1.8 μg/dL) and UFC (50 μg/24 h) are appropriate tests for screening CS. Overnight 8 mg DST with 60 % suppression for Cushing's Disease (CD) and ACTH levels <10 pg/mL for adrenal CS, ACTH levels >30 pg/mL for ACTH dependency were identified as the best tests for the differential diagnosis of the subtypes.

Evaluation of the diagnostic criteria for Cushing's disease in Japan

Adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome is caused by an ACTH-producing tumor, as is the case with Cushing's disease and ectopic ACTH syndrome (EAS). Diagnosis and differential diagnosis of Cushing's disease from EAS in ACTH-dependent Cushing's syndrome are thus challenging problems in clinical endocrinology. The diagnostic criteria for Cushing's disease in Japan, established by the working group of the Japan Ministry of Health, Labour and Welfare, were originally reported in 2003 and revised in 2007 and 2010. In addition, criteria for subclinical Cushing's disease were established in Japan in 2010. In this review, we evaluate the usefulness and accuracy of the most recent diagnostic criteria. Previous data suggest that as an initial test of Cushing's syndrome, 0.5 mg dexamethasone is more sensitive than 1 mg in the overnight dexamethasone suppression test (DST). Here, we recommend 0.5 mg plus a plasma cortisol cut-off level of 3 µg/dL as a suitable low-dose overnight DST for screening of all cases of ACTH-dependent Cushing's syndrome in Japan. Recently, standardization of cortisol measurements by the ID-LC/MS/MS method using seven assay kits with standard plasma material containing synthetic hydrocortisone-d4 was carried out in Japan. The resulting relative standard deviation was within 10%. The cut-off value remains valid even after standardization of plasma cortisol measurements. Although the recent diagnostic criteria achieve higher diagnostic specificity, care should be taken since data for Cushing's disease partially overlaps with some cases of EAS. Overall, therefore, this review suggests that the accuracy of each diagnostic test should be considered.

Obstructive sleep apnea syndrome causes a pseudo-Cushing's state in Japanese obese patients with type 2 diabetes mellitus

Activation of the hypothalamic-pituitary-adrenal axis has been reported in some patients with the obstructive sleep apnea syndrome (OSAS). In current study, we investigated whether OSAS affect the screening test for subclinical Cushing's disease using 0.5 mg overnight dexamethasone suppression test (DST) in Japanese obese diabetic patients with OSAS. Among Japanese obese patients with type 2 diabetes mellitus who had been hospitalized in our department, we selected 20 patients with moderate to severe untreated OSAS (apnea-hypoxia index, AHI, of ≥15 events/hour). All patients underwent 0.5 mg DST. The same test was repeated in patients with positive response of it within a few days after continuous positive airway pressure (CPAP) therapy. We found that five patients showed positive response of DST (25%). Three of these patients continued to use CPAP, and they showed normal response of DST after CPAP therapy. Serum cortisol after 0.5 mg DST measured before CPAP therapy correlated significantly with fasting serum cortisol level (r=0.764, p<0.0001), but not with various clinical parameters, including AHI (p=0.784), body mass index (p=0.984), waist circumference (p=0.957), HbA1c (p=0.261), fasting plasma glucose (p=0.420) and HOMA-IR (p=0.500). Our study show that OSAS causes a pseudo-Cushing's syndrome in obese patients with type 2 diabetes mellitus, which phenomena can be reversed by CPAP therapy.

Plasma corticotrophin response to desmopressin in patients with Cushing's disease correlates with the expression of vasopressin receptor 2, but not with that of vasopressin receptor 1 or 3, in their pituitary tumours

OBJECTIVES

Most patients with Cushing's disease (CD) respond to corticotrophin-releasing hormone (CRH) or desmopressin with increased corticotrophin (ACTH) and cortisol levels. Although the vasopressin receptor subtype located on normal corticotrophs is the V3 receptor (V3R), desmopressin is a selective V2 receptor (V2R) agonist and it is unclear whether corticotrophinomas exhibit aberrant V2R expression. Furthermore, no studies have determined the relationship between the in vivo response of CD patients to desmopressin and vasopressin receptor expression, or between the response to CRH and CRH receptor (CRHR) expression. Therefore, the aim of this study was to investigate the expression of vasopressin receptors (V1R, V2R, and V3R) and CRHR on corticotroph tumours and its possible relation to the in vivo response.

DESIGNS

A prospective study of 29 patients with CD.

METHODS

Patients underwent desmopressin and CRH stimulation tests before surgery. The expression of vasopressin receptors and CRHR on corticotrophinomas was determined by immunocytochemistry.

RESULTS

Most of the corticotrophinomas exhibited abundant expression of V1R, V3R, and CRHR, whereas the expression of V2R varied greatly and was lower in macroadenomas than in microadenomas. Both the percentage increment of ACTH and net area under the curve (AUC) of ACTH in the desmopressin stimulation test were found to be correlated with tumour volume. After adjustment for tumour volume, a positive correlation was found between the percentage increment of ACTH and the degree of V2R expression, but not between that of V1R or V3R. No relationship between the level of expression of CRHR on tumour tissues and the percentage increment or netAUC of ACTH to CRH was observed in CD patients.

CONCLUSIONS

We concluded that V2R was expressed on corticotrophinomas and that the level of its expression correlated well with the ACTH response to desmopressin in CD patients, although abundant expression of V1R and V3R was also found in almost all corticotroph tumours. Further studies are needed to elucidate the role of these receptors in the pathogenesis of CD.

ACTH response to desmopressin in a patient with acromegaly; expression of corticotropin-releasing factor, urocortins and vasopressin V1b receptor in GH-producing pituitary adenoma

GH-producing pituitary adenomas frequently co-produce other certain anterior pituitary hormones, such as prolactin (PRL). In contrast, GH-producing adenomas which express all of corticotropin-releasing factor (CRF), urocorin1 (Ucn1) and urocortin3 (Ucn3) have not been reported. A 39-year-old woman was admitted for evaluation of the pituitary tumor. The diagnosis of acromegaly was confirmed by elevated serum GH and IGF-I levels, and the absence of GH suppression by oral glucose tolerance test. ACTH response to desmopressin (DDAVP) was observed (plasma ACTH levels increased from 13.9 to 50.4 pg/ml at 90 min). Although it is known that ACTH response to DDAVP is considerably useful for the diagnosis of ACTH-dependent Cushing's syndrome, the diagnosis of Cushing's disease was not supported by the criteria. The patient underwent transsphenoidal resection of the pituitary tumor. Immunohistological examination confirmed a GH- and PRL-producing adenoma, whereas ACTH was negative. ACTH response to DDAVP disappeared after tumor removal. To determine the cause of preoperative ACTH response to DDAVP, we examined expression of CRF family peptides and vasopressin V1b receptor in the pituitary adenoma by immunohistochemistry. Immunohistochemistry revealed positive immunostaining for CRF, Ucn1, Ucn3 and vasopressin V1b receptor in the adenoma. These observations raised the possibility that DDAVP caused an ACTH response, perhaps via the paracrine effects of tumor-derived CRF and Ucn1. When ACTH response to DDAVP is observed in patients with pituitary tumor, not only the direct effect of DDAVP on ACTH secretion, but also a possible involvement of CRF and/or urocortins expressed in the pituitary adenoma, should be considered.

Differential gene expression profiles of POMC-related enzymes, transcription factors and receptors between non-pituitary and pituitary ACTH-secreting tumors

The differential gene expression of proopiomelanocortin (POMC)-related processing enzymes, transcription factors, and receptors responsible for ACTH secretion between non-pituitary and pituitary ACTH-secreting tumors remains obscure. This study was attempted to determine the gene expression profiles of transcription factors (Tpit, NeuroD1 and IKZF1), proprotein convertase (PC) 1/3 and PC2, and several key receptors linked to ACTH secretion, including corticotrophin releasing hormone receptor (CRHR1), vasopressin receptor 1b (V1bR), somatostatin receptor (SSTR) subtype-2, -5 and dopamine receptor type 2 (D2R) in non-pituitary and pituitary ACTH-secreting tumors. Surgical tissue specimens from carcinoid tumors causing ectopic ACTH syndrome (EAS: n=4) and pituitary tumors causing Cushing's disease (CD: n=13), were subjected to real-time RT-PCR for measurements of each mRNA levels. POMC and CRHR1 mRNA levels in CD were far greater than those in EAS, whereas IKZF1, PC2, SSTR-2 and -5 mRNA levels in EAS were significantly greater than those in CD. NeuroD1, Tpit, PC1/3, V1bR and D2R mRNA levels were comparable between EAS and CD. In conclusion, differential gene expression profiles revealed more abundant mRNA expression in EAS than in CD of 1) IKZF1 with its potential implication of cell differentiation and hormone secretion, 2) PC2 with its possible enhanced processing activity of mature ACTH, and 3) SSTR-2 and -5 with their potential therapeutic application of more selective agonists in EAS patients.

ACTH and cortisol responses to ghrelin and desmopressin in patients with Cushing's disease and adrenal enlargement

BACKGROUND

Overexpression of ghrelin and vasopressin (V3) receptors demonstrated on corticotrophe adenomas accounts for exaggerated ACTH and cortisol responses to ghrelin and desmopressin (DDAVP) in patients with Cushing's disease (CD).

AIM

In this study we have compared ACTH and cortisol responsiveness to DDAVP and ghrelin in CD patients with and without adrenal enlargement.

SUBJECTS AND METHODS

Ghrelin and DDAVP tests were performed in 15 patients with CD (7 with and 8 without signs of adrenal enlargement) with CRH test in 8 patients. In 7 age and sex-matched healthy subjects, ghrelin test was performed. Plasma ACTH and serum cortisol concentrations were measured after ghrelin, DDAVP and CRH. Growth hormone was measured after stimulation with ghrelin.

RESULTS

Significantly higher baseline and peak ACTH and cortisol concentrations after ghrelin were observed in all patients with CD compared to healthy control subjects. Patients with CD and adrenal enlargement had significantly lower baseline and peak ACTH concentrations after stimulation with ghrelin compared to CD patients without adrenal enlargement, while cortisol levels at baseline and after ghrelin administration were similar. Three out of seven patients with CD and adrenal enlargement did not respond to DDAVP while they responded well to CRH and ghrelin.

CONCLUSION

Patients with CD and adrenal enlargement pose special diagnostic problems. They may have lower baseline ACTH levels and may not respond to DDAVP while they respond to ghrelin and CRH. Despite increased endogenous cortisol levels in CD, cortisol responses to ghrelin and CRH are preserved in patients with CD and adrenal enlargement.

Cushing's syndrome: why is diagnosis so difficult?

Practicing and perfecting the art of medicine demands recognition that uncertainty permeates all clinical decisions. When delivering clinical care, clinicians face a multiplicity of potential diagnoses, limitations in diagnostic capacity, and "sub-clinical" disease identified by tests rather than by clinical manifestations. In addition, clinicians must recognize the rapid changes in scientific knowledge needed to guide decisions. Cushing's syndrome is one of several disorders in which there may be considerable difficulty and delay in diagnosis. This article describes a current model of clinical reasoning, some of its challenges, and the application of the principles of clinical epidemiology to meet some of those challenges.

Clinical features and management of ectopic ACTH syndrome at a single institute in Japan

Ectopic ACTH syndrome (EAS) is a diagnostic challenge because it is often indistinguishable from Cushing's disease. We describe our series of EAS patients referred to us during 1992-2009. Among 16 cases (9 females / 7 males), with mean age of 58.4 ± 19.0yr, the ectopic source was identified in ten (proven EAS), whereas unidentified in six (occult/unknown EAS). Their salient clinical manifestations included Cushingoid feature (88%), skin pigmentation (88%), profound hypokalemia (88%), hypertension (75%), diabetes/impaired glucose tolerance (75%), hyperlipidemia (69%), and severe infection (44%). Dynamic endocrine tests revealed markedly elevated plasma ACTH levels (211 ± 116pg/mL) and cortisol levels (60.9 ± 30.1µg/dL) which showed resistance to overnight high-dose (8mg) dexamethasone suppression test in 15 (94%) and unresponsiveness to CRH stimulation in 12 (75%). No ACTH gradient during inferior petrosal sampling was noted in 13 of 15 (87%). Imaging tests by CT/MRI identified the tumors in 8 of 16 (50%), in 4 of 11 (36%) and 4 of 6 (66.7%) octreotide-responders by somatostatin receptor scintigraphy, but in only one of 9 (11.1%) by FDG-PET scan. Six cases deceased, including small cell carcinoma (2) and adenocarcinoma (1) of lung, neuroendocrine carcinoma of pancreas (1) and stomach (1), and olfactory neuroblastoma (1), whereas 4 cases survived after removal of the tumors, including bronchial carcinoid tumor (3) and thymic hyperplasia (1). Six occult/unknown EAS patients survived for 67.5 months after medical treatment with metyrapone to control hypercortisolism. Thus, various endocrine tests combined with imaging studies are required to correctly localize the tumors. Control of hypercortisolemia by metyrapone, even if tumor is unrecognized, is critical for better prognosis, and the long-term follow-up by repeated endocrine and imaging tests is mandatory.

Evaluation of plasma, salivary, and urinary cortisol levels for diagnosis of Cushing's syndrome

As a screening test for Cushing's syndrome, the evaluation of late-night cortisol levels is indispensable. We evaluated the usefulness and accuracy of plasma, urinary, and salivary cortisol levels measured late at night for the diagnosis of Cushing's syndrome. High cortisol levels (> 5 microg/dL) during the night are indicative of Cushing's syndrome, although night plasma cortisol levels are not readily reproducible because of the stressful situation. There was no correlation between plasma and urinary cortisol levels late at night, and late-night urinary cortisol levels provided weak information for the diagnosis of Cushing's syndrome. By contrast, late-night plasma and salivary cortisol levels showed a positive correlation, and salivary cortisol sampling was found to be useful for the diagnosis of Cushing's syndrome, because more than 0.4 microg/dL of late-night salivary cortisol levels gave a sensitivity of 86% and a specificity of 100% in our hospital. This method is also useful for the diagnosis of early or mild stage Cushing's syndrome, so-called subclinical Cushing's syndrome. Inherent differences between assays make it difficult to define optimal diagnostic criteria. However, the relative levels of salivary cortisol ratio, which is presented as a relative level, compared with the mean levels of healthy subjects in each institute, is useful for the screening of Cushing's syndrome as the cut-off level of 1.5 shows both high sensitivity and specificity in subclinical and overt Cushing's syndrome. Late-night salivary cortisol measurement is therefore a primary method of choice in the screening of patients suspected of having Cushing's syndrome.

Development and validation of a 0.5 mg dexamethasone suppression test as an initial screening test for the diagnosis of ACTH-dependent Cushing's syndrome

For the diagnosis of Cushing' s syndrome (CS), the overnight 1 mg dexamethasone suppression test (DST) has been widely used as a standard low-dose DST. However, it is evident that 1 mg DST may not be sensitive enough to detect CS when the cortisol cut-off concentration is 5 microg/dL. Therefore, we developed and validated 0.5 mg DST as a new screening method for diagnosis of ACTH-dependent CS. To compare 0.5 mg DST with 1 mg DST, 110 patients with ACTH-dependent CS were enrolled, including 88 with Cushing' s disease (CD), 8 with subclinical CD and 14 with ectopic ACTH syndrome, as well as 134 control subjects. Subjects were given either 0.5 mg or 1 mg dexamethasone orally at 23:00 on different days, with blood samples collected the following morning between 8:00 and 9:00 to determine plasma cortisol concentration. The area under the receiver operator characteristics curve observing the 0.5 mg DST was higher than that of the 1 mg DST. The most sensitive and specific cut-off value of plasma cortisol concentration using 0.5 mg DST was found to be 3.05 microg/dL with 99.1% sensitivity and 98.4% specificity, identical to the 3 microg/dL cut-off currently used in the Japanese guideline for diagnosis of subclinical CD. In conclusion, 0.5 mg DST is a sensitive and specific screening test for diagnosis of ACTH-dependent CS. We recommend 0.5 mg DST with a cortisol cut-off concentration of 3 microg/dL to be used as the initial step in diagnosing ACTH-dependent CS.