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The objective of this study was to determine whether measurements of human CRH in the inferior petrosal sinuses could distinguish patients with Cushing's syndrome from those with pseudo-Cushing states or normal physiology. Twenty-five patients with Cushing's disease, 17 patients with the syndrome of ectopic ACTH, 7 patients with Cushing's syndrome of adrenal origin, 6 patients with pseudo-Cushing states, and 11 volunteers believed to have normal hypothalamic-pituitary-adrenal axes were studied. Basal plasma human CRH and ACTH were measured at two time points in the petrosal sinuses and in a peripheral vein. Most subjects were studied after the administration of intravenous diazepam or midazolam and fentanyl, but because of the known inhibitory effects of such sedation on CRH secretion, 2 normal volunteers and 3 patients with pseudo-Cushing states were studied without sedation. Human CRH levels were near or below the detection limit of the assay in all subjects. Although the normal volunteers and patients with pseudo-Cushing states who were studied without sedation had significantly greater inferior petrosal sinus ACTH levels than those who received sedation, there were no differences in measured human CRH levels for any of the groups. We conclude that inferior petrosal sinus human CRH levels are not easily measured in the inferior petrosal sinuses and cannot be used to determine whether individual patients may have hypersecretion of CRH causing their ACTH secretion.

Cushing's syndrome (CS) may be difficult to distinguish from pseudo-Cushing states (PCS) based on physical findings or urinary glucocorticoid excretion. As the lack of diurnal variation in serum cortisol is characteristic of CS, we studied whether diurnal cortisol determinations could discriminate CS from PCS. Two hundred and sixty-three patients were evaluated: 240 had CS, and 23 had PCS. Urine was collected for 24 h for measurement of cortisol and 17-hydroxycorticosteroids (17OHCS). Blood was drawn at 2300, 2330, 0000, 0030, and 0100 h and at 0600, 0630, 0700, 0730, and 0800 h the next morning for serum cortisol determination. The main outcome measure was the sensitivity of these parameters for the diagnosis of CS at 100% specificity. A midnight cortisol value greater than 7.5 microg/dL correctly identified 225 of 234 patients with CS and all PCS patients. This sensitivity (96%) was superior to that obtained for any other measure, including urinary cortisol (45%), 17OHCS (22%), any other individual cortisol time point (10-92%), the morning (23%) or the evening (93%) cortisol mean, and the ratio (11%) of morning to evening values. We conclude that at 100% specificity, a single serum cortisol value above 7.5 microg/dL at midnight discriminates CS from PCS with higher sensitivity than 24-h urinary cortisol or 17OHCS, or other individual or combined measures of serum cortisol.

The dexamethasone-suppressed CRH test (Dex-CRH test) differentiates patients with Cushing's syndrome (CS) from those with pseudo-Cushing states, who have decreased ACTH responses to CRH because of negative feedback exerted by chronic hypercortisolism. Normal subjects, however, have not been studied with the Dex-CRH test, raising concern that this test might not separate patients with CS from patients with normal adrenal function. To determine whether the criterion that separates CS from pseudo-Cushing states also would differentiate patients with Cushing's disease (CD) from individuals with eucortisolism, we studied 20 healthy volunteers during low-dose (2 mg/day) dexamethasone suppression, and then during the Dex-CRH test (CRH stimulation test performed 2 h after completion of low-dose dexamethasone suppression), and contrasted their results with those of 20 patients with surgically proven mild CD [urine free cortisol (UFC) < 1000 nmol/day). Basal UFC was significantly greater in patients with CD (P < 0.001) but within the normal range (55-250 nmol/day) in 4 patients. During low-dose dexamethasone suppression, a UFC less than 100 nmol/day (36 micrograms/day) was found in all but 1 volunteer subject, and a urine 17-hydroxycorticosteroid excretion less than 14.6 mumol/day (5.3 mg/day) was found in all but 2 subjects. During the Dex-CRH test, plasma cortisol less than 38 nmol/L was found in all 20 normal volunteers until 30 min after CRH administration. By contrast, the 15-min CRH-stimulated plasma cortisol exceeded 38 nmol/L in all patients with CD (P < 0.001). Plasma dexamethasone measured just before CRH administration was similar in normal volunteers (13.0 +/- 6.1 mumol/L) and patients with CD (16.4 +/- 6.4 mumol/L). We conclude that cortisol measurements obtained during the Dex-CRH test are suppressed in normal volunteers below those found in mild CD. These results suggest that the Dex-CRH test may be useful in the evaluation of CS in patients without significant hypercortisoluria. However, its value in patients with episodic hormonogenesis has not been tested.

Objective: In both normal volunteers and patients with Cushing's disease, one dominant inferior petrosal sinus (IPS) contains higher concentrations of AVP and ACTH than the contralateral (non-dominant) IPS, but ovine corticotrophin-releasing hormone (oCRH)-stimulated AVP in the petrosal sinuses is greater in Cushing's disease than in normal volunteers. To distinguish whether greater oCRH-releasable AVP might be specifically related to the presence of a pituitary corticotrophinoma, or be due to hypercortisolism per se, we compared IPS AVP in patients with Cushing's disease with those of patients with other causes of Cushing's syndrome., Patients: Twenty-three patients with Cushing's disease, 16 patients with the syndrome of ectopic ACTH and seven patients with Cushing's syndrome of adrenal origin., Measurements: AVP and ACTH, measured both before and 3, 5 and 10 minutes after oCRH in the petrosal sinuses, and in a peripheral vein., Results: In all three groups, AVP concentrations were lateralized such that most of the AVP was found in one, dominant IPS. oCRH significantly increased IPS ACTH only in patients with Cushing's disease (p < 0.001), whereas it significantly increased dominant IPS AVP levels in all three patient groups (P < 0.01). However, neither dominant nor non-dominant IPS AVP (basal or oCRH-stimulated) were significantly different among patients with Cushing's disease, ectopic ACTH or Cushing's syndrome of adrenal origin. Basal and oCRH-stimulated IPS AVP were negatively correlated with urine free cortisol., Conclusions: Inferior petrosal sinus AVP levels are similar in all forms of Cushing's syndrome, and thus the higher inferior petrosal sinus AVP levels in patients with Cushing's disease compared with normal volunteers are unlikely to be related specifically to the presence of the pituitary corticotrophinoma. While AVP may play a role in pituitary corticotroph tumourigenesis or may be secreted by some pituitary corticotroph tumours, the observation that CRH-stimulated inferior petrosal sinus AVP levels are higher in Cushing's disease than in normal volunteers appears most likely to be related to the low endogenous CRH levels induced by hypercortisolism, rather than a consequence of Cushing's disease itself. We hypothesize that low endogenous CRH leads to increased sensitivity of central nervous system CRH receptors to exogenous CRH, and thus to greater ovine CRH-stimulated AVP.

In patients with Cushing's disease (CD), basal inferior petrosal sinus arginine vasopressin (AVP) concentrations are greater than peripheral levels and are further increased by the administration of CRH. AVP has an interpetrosal sinus gradient similar to that for ACTH, leading to the hypotheses that petrosal sinus AVP might either be derived from the corticotroph adenoma or be important for adenoma formation. To determine whether petrosal sinus AVP is truly increased in patients with CD, we compared inferior petrosal sinus and peripheral venous AVP and ACTH levels in 23 patients with CD and 9 healthy volunteers before and after iv ovine CRH. In both groups, AVP and ACTH showed interpetrosal lateralization, such that greater levels of both hormones were found at each time point in a single dominant petrosal sinus. When both hormones exhibited lateralization (an intersinus gradient > 1.5), ACTH and AVP always lateralized together. In patients with CD, the ACTH interpetrosal sinus lateralization correctly identified the side of the pituitary containing the tumor in 75% of evaluable patients, whereas the AVP interpetrosal sinus lateralization identified 63% (P = NS). Ovine CRH stimulated AVP in both the dominant and nondominant petrosal sinuses in patients with CD. Although basal AVP in the dominant petrosal sinus was not significantly different in patients with CD and normal volunteers (144 +/- 85 vs. 13.0 +/- 4.3 pmol/L; P = 0.058), dominant petrosal sinus AVP was significantly elevated in patients with CD compared to normal volunteers at 3 min (269 +/- 122 vs. 45.1 +/- 30.0 pmol/L; P < 0.05) and 5 min (315 +/- 120 vs 40.2 +/- 23.6 pmol/L; P < 0.05) after ovine CRH administration. Peripheral venous AVP levels were similar in all groups. We conclude that lateralization of AVP secretion occurs in both patients with CD and normal volunteers, but there is greater CRH-stimulated AVP secretion in the inferior petrosal sinuses of patients with CD.

Patients with Cushing syndrome have elevated 24 h urinary free cortisol excretion and loss of diurnal rhythm of plasma cortisol, however, morning total plasma cortisol concentrations are often similar to those of normal individuals. To test the hypothesis that an elevated morning plasma free cortisol could distinguish patients with Cushing syndrome from those without the disorder, we measured plasma free cortisol levels at 08:00 in 20 patients with surgically-confirmed mild Cushing syndrome, 19 patients with pseudo-Cushing states, and 9 normal volunteers. We then determined the sensitivity, specificity and diagnostic accuracy of plasma free cortisol for the diagnosis of hypercortisolism and for the diagnosis of Cushing syndrome. Plasma free cortisol was compared to 08:00 total plasma cortisol and to basal 24 hour urinary free cortisol. Morning plasma free cortisol was significantly elevated in patients with mild Cushing syndrome (58 +/- 6 nmol/L; mean +/- SE) compared to plasma free cortisol in patients with pseudo-Cushing states (36 +/- 6 nmol/L) (p < 0.005) and normal volunteers (22 +/- 4 nmol/L) (p < 0.0005). Total morning cortisol was significantly greater in patients with mild Cushing syndrome (470 +/- 28 nmol/L) than in normal volunteers (310 +/- 33 nmol/L, p < 0.05) but was not different from patients with pseudo-Cushing states (410 +/- 47 nmol/L, p = NS). Urinary free cortisol was also significantly greater in mild Cushing syndrome (540 +/- 50 nmol/d) than in patients with pseudo-Cushing states (430 +/- 41 nmol/d, p < 0.05) or normal volunteers (160 +/- 28 nmol/d, p < 0.0001). However, there was considerable overlap of plasma free cortisol, plasma total cortisol and urinary free cortisol between the three groups precluding these tests alone from being useful to distinguish patients with mild Cushing syndrome from patients with pseudo-Cushing states. To achieve 100% sensitivity for the diagnosis of Cushing syndrome, the specificity for plasma free cortisol, plasma total cortisol and urinary free cortisol was 0.11, 0.32 and 0.32, respectively. We conclude that plasma free cortisol is of limited value in the differential diagnosis of hypercortisolism.

To evaluate the sleep disturbances of patients with Cushing syndrome and to examine the relationship between the sleep disturbances and plasma levels of delta-sleep-inducing peptide-like immunoreactivity (DSIP-LI), we performed three polysomnographic/endocrinological studies in patients with Cushing syndrome. In study 1, polysomnography was studied in 12 patients and 12 matched normal volunteers. In addition, DSIP-LI was measured every 30 min for 24 h in 9 patients with Cushing syndrome and 12 normal volunteers. The percentage of time spent in delta sleep (stages 3 and 4) was significantly reduced in patients with Cushing syndrome (5.8 +/- 1.4%; mean +/- SEM) compared to normal volunteers (14.0 +/- 2.5%) (p < 0.01). REM sleep indices, however, were not significantly different between the two groups. There was a significant negative correlation between amount of delta sleep and 08.00 h DSIP-LI (r = -0.43, p < 0.05), which is against the notion of a causal relationship between DSIP-LI and delta sleep. The circadian rhythm of plasma DSIP-LI was found to be similar in Cushing patients and normal volunteers. In study 2, we measured plasma levels of delta-sleep-inducing peptide-like immunoreactivity (DSIP-LI) at 08.00 h in 65 patients with Cushing syndrome and 49 normal volunteers. The 08.00 h DSIP-LI concentrations of 797 +/- 57 pmol/l (mean +/- SEM) in the patients with Cushing syndrome were significantly reduced compared to the level of 1,062 +/- 99 pmol/l found in the normal volunteers (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Objective: To develop criteria for interpreting results of the metyrapone test for the differential diagnosis of the adrenocorticotropin (ACTH)-dependent Cushing syndrome and to compare its diagnostic accuracy with that of the high-dose dexamethasone suppression test., Design: Retrospective cohort study., Setting: Inpatient research ward., Patients: 186 patients believed to have the ACTH-dependent Cushing syndrome who had the metyrapone test, the dexamethasone test, and a surgical procedure to remove the source of excessive ACTH., Measurements: The sensitivity, specificity, and diagnostic accuracy were determined for the metyrapone test using urine excretion of hydroxysteroid and plasma levels of 11-deoxycortisol. For the dexamethasone suppression test, urine excretions of 17-hydroxysteroid (17-OHS) and free cortisol were used., Main Results: 156 patients had pituitary disease, 15 had ectopic ACTH secretion, and 15 had no diagnosis after pituitary surgery. Of those 15 patients, 14 were ultimately classified as having pituitary disease on the basis of follow-up, and 1 was found to have ACTH-independent Cushing syndrome. After administration of metyrapone, stimulation of 17-OHS excretion greater than 70% or of a plasma 11-deoxycortisol level greater than 400-fold did not result in the misclassification of any of the patients with surgically confirmed cases of ectopic ACTH secretion. When these criteria were combined, the percentage of correct predictions (122 of 186 [71%; 95% CI, 62% to 79%]) was higher than that for either steroid alone (116 of 186 [62%; CI, 52% to 71%]) for excretion of 17-OHS and that for plasma 11-deoxycortisol (82 of 186 [44%; CI, 34% to 54%]). When the criteria for both the metyrapone test and the dexamethasone test were combined, the percentage of correct predictions (153 of 186 [82%; CI, 75% to 87%]) was higher than that obtained when the criteria for either test alone were used (P = 0.001). Similar results were found when the 15 patients with indeterminate surgery were assigned to the appropriate group on the basis of follow-up. When the criteria for both the metyrapone and dexamethasone tests were combined to identify patients with the pituitary Cushing syndrome, the sensitivity and diagnostic accuracy improved to 88% and 89%, respectively., Conclusions: The metyrapone test, which can be done in 48 hours, has a sensitivity and specificity for the diagnosis of the Cushing syndrome identical to that of the standard 6-day high-dose dexamethasone suppression test. Combining both tests results in greater accuracy than that obtained with either test alone.

Glucocorticoids mainly act through binding to cytosolic receptors that translocate to the nucleus after ligand binding, and dimerize to affect gene transcription in multiple fashions. The liganded receptors may interact with DNA at specific glucocorticoid responsive-elements, may physically hinder the ability of other transcription-regulating proteins to interact with their own DNA response-elements, and may form intranuclear complexes with the transcription factor c-jun, thus changing the number of c-jun/c-fos heterodimers that bind at AP-1 sites. By these, and perhaps other, mechanisms, physiologic concentrations of glucocorticoids regulate normal tissue metabolism, and supraphysiologic concentrations cause Cushing's syndrome. Cushing's syndrome leaves virtually no body tissue untouched. Left untreated, it results in progressive adiposity, myopathy, dermopathy (atrophy, stria, purpura, and hirsutism), psychopathy, glucose intolerance, hypercholesterolemia, hypertension, atherosclerosis, immunosuppression, and, ultimately, death. The physiology underlying each of these effects of hypercortisolism has been reviewed. The differences in the presentation of Cushing's syndrome in children and adults have also been discussed. The goal of the clinician must be to identify individuals with Cushing's syndrome as early in the course of the disease as possible so as to avoid the devastating complications that result from prolonged hypercortisolism. In patients for whom screening tests are equivocal, or only intermittently elevated, it may be necessary to re-evaluate the patient over time to establish that the patient has hypercortisolism. Some clinical guidelines for which patients to screen for hypercortisolism have been presented. Once hypercortisolism is established, patients with mild hypercortisolism (urine free cortisol less than four-fold above the upper limit of normal) should undergo tests to differentiate true Cushing's syndrome from a pseudo-Cushing state.

To determine whether petrosal sinus sampling is useful to distinguish patients with mild or intermittent Cushing's disease from normal subjects and individuals with pseudo-Cushing states, we performed bilateral inferior petrosal sinus sampling for ACTH before and after the administration of CRH in 7 eucortisolemic volunteers, 8 hypercortisolemic patients with pseudo-Cushing states, and 40 patients with ACTH-dependent Cushing's disease whose urinary free cortisol excretion was within the range found in patients with, pseudo-Cushing states (< 1000 nmol/day; < 360 micrograms/day). The ACTH level, the ratio of the inferior petrosal sinus ACTH to the peripheral venous ACTH concentration (the IPS:P ratio), and the greater ratio of right to left or left to right petrosal sinuses (the R:L ratio) were compared in patients with and without Cushing's disease. Maximal petrosal ACTH values were significantly elevated in patients with Cushing's disease compared to patients with pseudo-Cushing states before CRH administration (P < 0.001), but not after CRH. Maximal petrosal plasma ACTH values after the administration of CRH as high as 808 pmol/L (3670 pg/mL) and 469 pmol/L (2130 pg/mL) were found in patients with pseudo-Cushing states and in normal volunteers, respectively, whereas maximal petrosal ACTH levels as low as 10 pmol/L (46 pg/mL) were observed in patients with surgically proven Cushing's disease. Maximal and minimal IPS:P ratios were significantly greater in patients with Cushing's disease than in subjects without Cushing's disease before, but not after, CRH treatment. R:L ratios did not differ among groups either before or after CRH. All of the subjects without Cushing's disease showed large R:L gradients, consistent with the notion of one dominant petrosal sinus containing a greater percentage of pituitary effluent. The ACTH concentrations, IPS:P ratios, and R:L ratios exhibited great overlap between those with and without Cushing's disease, which resulted in a diagnostic accuracy of 81% at best for the diagnosis of Cushing's disease. We conclude that petrosal sinus sampling is of limited usefulness in distinguishing either normal individuals or patients with pseudo-Cushing states from those with mild Cushing's disease. This limited usefulness must be recognized when interpreting the results of petrosal sinus sampling in patients with mild or intermittent hypercortisolism who may have a pseudo-Cushing state. Because of these limitations, petrosal sinus sampling should be reserved for patients with clear clinical and biochemical evidence of Cushing's syndrome.

Objective: The biochemical and phenotypic presentation of mild hypercortisolism in Cushing's syndrome is often indistinguishable from that seen in pseudo-Cushing's states such as depression. Both dexamethasone suppression and corticotropin-releasing hormone (CRH) stimulation tests have been used individually to distinguish these conditions, but neither approach has achieved a diagnostic accuracy greater than 85%. Therefore, we sought to develop a combined dexamethasone-CRH test that would take advantage of the altered sensitivity of patients with Cushing's syndrome to both dexamethasone and CRH and would achieve greater accuracy in the diagnosis of Cushing's syndrome., Design: Prospective cohort study., Setting: Tertiary care research hospital., Patients: A total of 58 adults referred for evaluation of mild hypercortisolism (urine free cortisol level < 1000 nmol/d). The diagnosis of Cushing's syndrome was confirmed at surgery in 39 patients. The diagnosis of a pseudo-Cushing's state was made in 19 patients on the basis of extended follow-up (mean, 28 months) without progression of cushingoid features., Intervention: The low-dose dexamethasone suppression test, the CRH stimulation test, and the CRH stimulation test started 2 hours after completion of low-dose dexamethasone suppression (the dexamethasone-CRH test) were performed in all patients., Main Outcome Measures: Sensitivity, specificity, and accuracy of the three procedures for diagnosis of Cushing's syndrome were calculated from plasma corticotropin, plasma cortisol, urine free cortisol, and urine 17-hydroxycorticosteroid values., Results: The low-dose dexamethasone suppression test had 74% specificity, 69% sensitivity, and 71% diagnostic accuracy, using the standard criterion (17-hydroxycorticosteroid excretion level > 11.0 mumol/d on the second day of dexamethasone administration). With a urine free cortisol criterion for Cushing's syndrome of greater than 100 nmol/d, the low-dose dexamethasone suppression test had 100% specificity, 56% sensitivity, and 71% diagnostic accuracy. The CRH stimulation test without dexamethasone pretreatment had 100% specificity, 64% sensitivity, and 76% diagnostic accuracy. The diagnostic accuracy of the dexamethasone-CRH test for Cushing's syndrome was significantly greater than the accuracy of either the low-dose dexamethasone test or the CRH test alone (P < .01). A plasma cortisol concentration greater than 38 nmol/L measured 15 minutes after the administration of CRH correctly identified all cases of Cushing's syndrome and all cases of pseudo-Cushing's states (100% specificity, sensitivity, and diagnostic accuracy)., Conclusion: The dexamethasone-CRH test is a more accurate test to distinguish Cushing's syndrome from pseudo-Cushing's states in patients with mild hypercortisolism.