An evaluation of the distinction of ectopic and pituitary ACTH dependent Cushing's syndrome by clinical features, biochemical tests and radiological findings

The efficiency of various laboratory and radiological investigations in the differentiation of ectopic from pituitary dependent Cushing's syndrome was studied, based on findings in 23 patients with verified Cushing's disease and seven patients with the ectopic ACTH syndrome. Clinical features strongly favouring the ectopic type were male sex and history for less than 18 months. Basal biochemical features strongly indicating the ectopic syndrome included plasma K+ less than 3.0 mmol/l and HCO3 greater than 30 mmol/l; serum cortisol at 9 a.m. or midnight of greater than 800 nmol/l; urine free cortisol greater than 1300 nmol/24 hours; plasma ACTH greater than 100 ng/l. In the high-dose dexamethasone suppression test, suppression by less than 50 per cent of 9 a.m. serum cortisol, urine free cortisol or 17-oxogenic steroids was usually indicative of an ectopic source of ACTH. A mean suppressed value of greater than 450 nmol/l for the 9 a.m. and midnight cortisol combined occurred in all of those with the ectopic syndrome, but in none of the 23 patients with Cushing's disease. For urine free cortisol, a mean suppressed value of less than 1000 nmol/24 hours was found in all patients with Cushing's disease, but in none of those in the ectopic group. In the metyrapone test, there was an increase of less than or equal to 3-fold in 11-deoxycortisol at 24 hours in patients with ectopic ACTH; the increase was greater than 3-fold in all but one of the patients with Cushing's disease. Failure to respond to either dexamethasone or metyrapone was found in only one of the patients with Cushing's disease (Patient 16); in the ectopic group, all patients except Patient D failed to respond to either test. It is concluded that patients presenting with clinically obvious Cushing's syndrome along with measurable plasma ACTH can be reliably divided by conventional tests into those that are driven from the pituitary and those driven by ectopic ACTH.     

Cushing's Syndrome: AN EVALUATION OF THE CLINICAL USEFULNESS OF URINARY FREE CORTISOL AND OTHER URINARY STEROID MEASUREMENTS IN DIAGNOSIS

Urinary free cortisol excretion has been measured in a groupof 40 patients with Cushing's syndrome and in 34 patients inwhom this diagnosis was suspected on clinical grounds, but inwhom it was later disproved. Measurements were made in the basal state, during dexamethasonesuppression, and after metyrapone (when free cortisol and 11-deoxycortisolwere measured together) and the results compared with thoseof 17 oxogenic steroid measurements. In the basal state no normal or ‘suspected’ patientexcreted more than 106 µg/24 h of free cortisol whilethe lowest value seen in any patient with Cushing's syndromewas 110 µg/24 h. In 25 per cent of the patients with hyperadrenalism17 OGS excretion was within the normal range. Three patientswith ectopic ACTH produc tion all excreted more than 1000 µgof free cortisol in 24 h and in two of the three 17 OGS excretionwas greater than 100 mg/ h. During low-dose dexamethasone suppression (2 mg daily) freecortisol excretion fell to very low levels in normal and suspectedsubjects but failed to do so in patients with Cushing's syndrome,although a few patients did show suppression almost to withinthe normal range. In no patient with Cushing's syndrome did17 OGS excretion fall to less than 5 mg/24 h. However, it alsofailed to do this in 43 per cent of the ‘suspected’subjects. High-dose dexamethasone suppression (8 mg/day) failed to providea clear differentiation between patients with pituitary-dependentdisease and those with autonomous adrenal lesions or ACTH-producingtumours in terms of change in either free cortisol or 17 OGSexcretion. On metyrapone testing 96 per cent of pituitary-dependent patientsshowed a definite rise in 17 OGS excretion. We have not yetseen such a response in a patient with a non-pituitary-dependentlesion. Measurement of free F+S excretion was not ¹Present address: Department of Medicine, University Hospitalof South Manchester, Withington     

Corticotropin-releasing hormone, proopiomelanocortin, and glucocorticoid receptor gene expression in adrenocorticotropin-producing tumors in vitro.

To differentiate between ectopic ACTH syndrome and Cushing's disease, gene expression of corticotropin-releasing hormone (CRH), proopiomelanocortin (POMC), and glucocorticoid receptor was examined in 10 pituitary adenomas (Cushing's disease) and in 10 ectopic ACTH-producing tumors. CRH increased plasma ACTH levels in all patients with Cushing's disease and in five patients with ectopic ACTH syndrome whose tumors contained CRH and CRH mRNA. In five CRH nonresponders, CRH was not detected in tumors that contained no CRH mRNA or that contained only long-size CRH mRNA. Dexamethasone (Dex) decreased plasma ACTH levels in all patients with Cushing's disease and in three patients with ectopic ACTH-producing bronchial carcinoid. These tumors contained glucocorticoid receptor mRNA. CRH increased and Dex decreased ACTH release and POMC mRNA levels in pituitary adenoma and bronchial carcinoid cells. PMA increased POMC mRNA levels only in carcinoid cells. These results reveal characteristics of ectopic ACTH-producing tumors: long-size CRH mRNA and PMA-induced POMC gene expression. In addition, there are two ectopic ACTH syndrome subtypes: tumors containing ACTH with CRH (CRH responder) and tumors without CRH. Dex decreases ACTH release and POMC mRNA levels in some bronchial carcinoids. Therefore, CRH and Dex tests have limited usefulness in differentiating between Cushing's disease and ectopic ACTH syndrome.     

NOCTURNAL 8mg DEXAMETHASONE SUPPRESSION TEST: A PRACTICAL AND ACCURATE TEST FOR IDENTIFICATION OF THE CAUSE OF ENDOGENOUS CUSHING'S SYNDROME

SUMMARY The efficacy of a nocturnal 8mg dexamethasone suppression test (nocturnal DST) was compared with that of the standard high-dose dexamethasone suppression test (standard DST) in identifying the cause of endogenous Cushing's syndrome in 10 proven cases with Cushing's disease, 20 with adrenal tumours, and one with ectopic ACTH syndrome. The nocturnal test compared serum cortisol concentration at 8am before and after administration of a single dose of 8mg dexamethasone at 11pm. Suppression of serum cortisol level to <50% of the baseline value indicated a diagnosis of Cushing's disease, while a lack of suppression below that limit indicated one of the other two causes of Cushing's syndrome: glucocorticoid-secreting adrenal tumour or ectopic ACTH syndrome. The nocturnal DST had a sensitivity of 90%, a specificity of 100%, an accuracy of 96.8%, a positive predictive value of 100%, and a negative predictive value of 95.5%. These values are comparable to the efficacy of the standard DST in distinguishing Cushing's disease from glucocorticoid-secreting adrenocortical tumour or ectopic ACTH syndrome. Furthermore, this rapid test does not require hospitalisation or urine collection like the standard DST. The nocturnal 8mg dexamethasone suppression test is practical, fairly reliable, and an effective alternative with which to identify the cause of endogenous Cushing's syndrome.     

Corticotropin releasing factor as an aid in the diagnosis of Cushing syndrome

6 patients with Cushing's syndrome were investigated with regard to the effect of synthetic ovine corticotropin-releasing factor (o-CRF), administered as an intravenous bolus of 100 micrograms, on peripheral plasma concentrations of ACTH and cortisol. The purpose of this study was to evaluate the usefulness of this "CRF test" in the differential diagnosis of Cushing's syndrome as compared with conventional diagnostic procedures. 100 micrograms CRF caused a rise in plasma ACTH and cortisol in patients with bilateral adrenal hyperplasia (n = 3). However, in patients with cortisol-producing adrenal adenoma (n = 2) and ectopic ACTH overproduction (n = 1), no increase in plasma cortisol and ACTH was induced by exogenous CRF. We conclude from these findings that the CRF test will prove a valuable diagnostic tool to differentiate pituitary from extrapituitary forms of endogenous hypercortisolism in patients with Cushing's syndrome.     

Medical treatment for Cushing's syndrome

Systemic cortisol plays an important role in the metabolism of glucose, lipids and proteins, as well as in the regulation of electrolyte balance. It is well known that the development of the microvascular disease of various organs such as the heart and kidney, in patients with diabetes mellitus, hyperlipidemia and hypertension of which disorders are frequently associated with Cushing's syndrome. Thus, we should treat Cushing's syndrome as soon as possible, since many complications, including cardiovascular diseases and infections, will soon occur when the definite diagnosis is delayed. Adrenalectomy is essential for treatment for Cushing's syndrome even in the patients with pituitary or ectopic ACTH-producing tumor. Some case can not be treated with surgical procedures because of worsened conditions with several complications of infection and diabetes. Then we choose medical treatment. Medical adrenalectomy is achieved by using with mitotane which is usually used for adrenocortical cancer. We commonly treat the patients with Cushing's syndrome due to adrenal tumor and pituitary or ectopic ACTH producing tumor by using metyrapone which mainly inhibits 11-hydroxylase. Metyrapone is also recommended to treat the patients who are not well differentiated Cushing's disease from ectopic ACTH syndrome. We rarely use trilostane which is an inhibitor against 3beta-hydroxysteroid dehydrogenase (3beta-HSD). Replacement therapy with hydrocortisone should be considered if adrenal failure will occur during treatment with those drugs.     

Ectopic ACTH syndrome

Although the clinical and biochemical discrimination of true Cushing syndrome from the Cushing phenotype is sometime difficult, four diagnostic studies are currently used: late-night serum and salivary cortisol level, urine free cortisol level, low-dose dexamethasone suppression, and the dexamethasone-CRH test. Using these tests, 90% of patients with Cushing syndrome are diagnosed. Once the diagnosis of the Cushing syndrome is firmly established, the next step is differential diagnosis of the subtype. Furthermore, the differentiation of pituitary and ectopic ACTH-dependent Cushing syndrome should be carried out using measurement of ACTH. Finally, bilateral petrosal sinus sampling for ACTH with CRH administration might be a powerful tool for a diagnosis for ectopic ACTH syndrome. A variety of benign and malignant tumors of non-pituitary tissues have been associated with the ectopic ACTH syndrome. The tumors most commonly associated with ACTH syndrome arise from neuroendocrine tissues, however, the pathogenesis of the ectopic ACTH syndrome remains unknown.     

Diagnosis and pathophysiology of Cushing's syndrome

Cushing's syndrome is the consequence of a sustained overproduction of cortisol (hydrocortisone) by the adrenal cortex. This may be due to excessive secretion of cortisol by functioning adrenocortical tumors or to "nontumorous" adrenocortical hyperfunction. The latter may be a result of stimulation of the adrenal cortex by increased release of corticotropin (ACTH) from a small pituitary tumor or from nonpituitary nonadrenal tumor. Carcinoids or carcinomas of the lung or pancreas, and even pheochromocytomas have caused the syndrome of ectopic ACTH production. The problems involved in the diagnosis of Cushing's syndrome are establishing its presence and determining the underlying cause. Treatment is then dependent upon the underlying pathogenetic lesion.     

An unusual cause of Cushing's syndrome: primary pigmented nodular adrenal dysplasia

We report a case of Cushing's syndrome due to primary pigmented nodular adrenal dysplasia (PPNAD) and discuss the diagnostic process and management of this rare case. The diagnosis of PPNAD is discussed in the context of other causes of Cushing's syndrome. Eighty-five per cent of cases of Cushing's syndrome are due to a pituitary corticotrophic tumour (Cushing's disease). Rarer causes include cortisol secreting adrenal adenoma and ectopic ACTH secretion. In the routine investigation of Cushing's disease it is not unusual to find bilateral adrenal nodules on the CT scan. We present a case of Cushing's syndrome in which this radiographic finding was present and yet the biochemical diagnosis was one of ACTH independent disease. Histology revealed PPNAD.     

Safety and efficacy of increasing wintertime vitamin D and calcium intake by milk fortification

We studied the safety and efficacy of milk fortified with vitaminD₃ and calcium. Over the winter, we conducted a double-blind,placebo-controlled trial of fortified milk (12µg vitaminD₃ and 1525 mg calcium per litre) compared to unfortified milk(0.3µg vitamin D₃ and 1270 mg calcium per litre) in 102adults (aged 17–54 years). Serum 25-hydroxyvitamin D [25(OH)D],ionized calcium, and creatinine were measured at baseline andafter intervention. Fortification reduced the seasonal declinein serum 25(OH)D concentrations by >50%. In the fortifiedgroup, serum 25(OH)D decreased by 15nmol/l from 77±35nmol/l to 62±26 nmol/l (p<0.001). In the control group,serum 25(OH)D fell by 31 nmol/l from 85±39 nmol/l to54±25 nmol/l (p<0.001). We suggest that milk enrichedwith vitamin D be provided in high-latitude European countriesto diminish the wintertime fall in serum 25(OH)D.     

The low-dose corticotropin stimulation test in acute traumatic and non-traumatic brain injury: incidence of hypo-responsiveness and relationship to outcome

Objective To investigate adrenal responses to the low-dose corticotropin (ACTH) stimulation test in acute traumatic or non-traumatic brain injury (BI) and to assess its value in predicting outcome.Design Prospective study.Setting Intensive care unit (ICU) in a university hospital.Patients and participants Seventy-five patients with acute BI, with a median age of 45 years were investigated. BI was due to trauma (n=51), ischemic stroke (n=17), subarachnoid hemorrhage (n=4) or intracerebral hemorrhage (n=3).Interventions Blood was taken on day 16 (median) after admission to the ICU to determine baseline cortisol and ACTH. Thereafter, a low-dose stimulation test (LDST) was performed: 1 µg of tetracosactrin was injected and 30 min later a second blood specimen was obtained to measure stimulated cortisol. Patients having a stimulated cortisol below 500 nmol/l were defined as non-responders to the LDST.Measurements and results Median baseline and stimulated cortisol were 491 nmol/l and 690 nmol/l, respectively. The median increment in cortisol was 154 nmol/l (range 5–579 nmol/l). Mean ACTH was 46±21 pg/ml. Ten (13%) patients were non-responders to the LDST; these had a higher mortality rate compared to patients with adequate cortisol production (70 vs 32%, p=0.034). Logistic regression analysis revealed that APACHE II (p<0.001), Glasgow Coma Scale (GCS) (p=0.04) and age (p=0.02) were independent outcome predictors. In contrast, the increment in cortisol (p=0.26) did not add to outcome prediction.Conclusions Adrenal hypo-responsiveness in the setting of acute traumatic or non-traumatic BI is not an independent outcome predictor in the presence of high APACHE II, low GCS and older age.     

Plasma cortisol levels before and during "low-dose" hydrocortisone therapy and their relationship to hemodynamic improvement in patients with septic shock

OBJECTIVES: To compare cortisol levels during "low-dose" hydrocortisone therapy to basal and ACTH-stimulated endogenous levels and to assess whether clinical course and the need for catecholamines depend on cortisol levels and/or pretreatment adrenocortical responsiveness. DESIGN AND SETTING: Prospective observational study in a medical ICU of a university hospital. PATIENTS: Twenty consecutive patients with septic shock and a cardiac index of 3.5 l/min or higher, started on "low-dose" hydrocortisone therapy (100 mg bolus, 10 mg/h for 7 days and subsequent tapering) within 72 h of the onset of shock. MEASUREMENTS AND RESULTS: Basal total and free plasma cortisol levels ranged from 203 to 2169 and from 17 to 372 nmol/l. In 11 patients cortisol production was considered "inadequate" because there was neither a response to ACTH of at least 200 nmol/l nor a baseline level of at least 1000 nmol/l. Following the initiation of hydrocortisone therapy total and free cortisol levels increased 4.2- and 8.5-fold to median levels of 3,587 (interquartile range 2,679-5,220) and 1,210 (interquartile range 750-1,846) nmol/l on day 1, and thereafter declined to median levels of 1,310 nmol/l and 345 nmol/l on day 7. Patients with "inadequate" steroid production could be weaned from vasopressor therapy significantly faster, although their plasma free cortisol concentrations during the hydrocortisone treatment period did not differ. CONCLUSIONS: (a) During proposed regimens of "low-dose" hydrocortisone therapy, initially achieved plasma cortisol concentrations considerably exceed basal and ACTH stimulated levels. (b) Cortisol concentrations decline subsequently, despite continuous application of a constant dose. (c) "Inadequate" endogenous steroid production appears to sensitize patients to the hemodynamic effects of a "therapeutic rise" in plasma cortisol levels.     

Biochemical evaluation of adrenal dysfunction: the laboratory perspective.

In this study, we reviewed the diagnostic efficiency of laboratory tests that are performed for assessment of patients with Cushing's syndrome or adrenal insufficiency. Baseline laboratory data from patients subsequently diagnosed with adrenal dysfunction were analyzed for tests performed between 1987 and 1989 at our institution. Results were analyzed for 36 patients diagnosed with pituitary-dependent Cushing's syndrome, 15 with ectopic Cushing's syndrome, 12 with adrenal-dependent Cushing's syndrome, 20 with primary adrenal insufficiency, and 7 with secondary adrenal insufficiency. Tests reviewed were plasma cortisol, plasma corticotropin, urinary free cortisol, urinary 17-ketosteroids, urinary ketogenic steroids, low-dose and high-dose dexamethasone suppression, and metyrapone stimulation. Our findings suggest that a substantial proportion of diagnoses could be based on the results of three tests--plasma corticotropin, plasma cortisol, and urinary free cortisol. We present a nomogram that combines the results of plasma corticotropin and plasma cortisol testing to enhance the diagnostic efficiency of these tests.     

Parallel assays of beta-endorphin and ACTH in Cushing's patients undergoing petrosal sinus sampling

This study explores the possibility of improving endocrinologic testing during petrosal sinus catheterization by determining both beta-endorphin and corticotropin (ACTH). We studied 14 patients with Cushing's disease, two with adrenal tumor, and three with ectopic tumors secreting ACTH. In patients with Cushing's disease, beta-endorphin concentrations paralleled those of ACTH in all basal plasma samples collected either from petrosal sinuses or peripheral veins. Individual responses of beta-endorphin and ACTH to corticotropin releasing hormone (CRH) were closely related to the presence of a corticotroph adenoma. In such patients, a consistently higher concentration of beta-endorphin over ACTH was observed in all samples collected either from petrosal sinuses or peripheral veins; the ratios were unchanged after the administration of CRH. In patients with ectopic ACTH secretion, the mean ratio of beta-endorphin over ACTH (with both values expressed in pmol/L) was significantly higher (3.5) than that of patients with Cushing's disease (2.9) or Cushing's syndrome due to adrenal tumor (2.7).     

Cortisol secretion in patients with type 2 diabetes: relationship with chronic complications

OBJECTIVE: The presence of an enhanced cortisol secretion in patients with type 2 diabetes is debated. In type 2 diabetic subjects, cortisol secretion was found to be associated with the complications and metabolic control of diabetes. We evaluated cortisol secretion in 170 type 2 diabetic subjects and in 71 sex-, age-, and BMI-matched nondiabetic subjects. RESEARCH DESIGN AND METHODS: In all subjects, we evaluated ACTH at 8:00 a.m. in basal conditions and serum cortisol levels at 12:00 p.m. (F24) and at 9:00 a.m. after a 1-mg overnight dexamethasone suppression test and 24-h urinary free cortisol (UFC). In diabetic patients, we evaluated the presence of chronic complications (incipient nephropathy, asymptomatic neuropathy, background retinopathy, and silent macroangiopathy). Patients were subdivided according to the absence (group 1, n = 53) or presence (group 2, n = 117) of diabetes complications. RESULTS: In group 2, UFC (125.2 +/- 4.6 nmol/24 h) and F24 (120.6 +/- 4.1 nmol/l) were higher than in group 1 (109.2 +/- 6.8 nmol/24 h, P = 0.057, and 99.7 +/- 6.1 nmol/l, P = 0.005, respectively) and in nondiabetic patients (101.7 +/- 5.9 nmol/24 h, P = 0.002, and 100.3 +/- 5.3 nmol/l, P = 0.003, respectively). In diabetic patients, the number of complications was associated with F24 (R = 0.345; P < 0.0001) and diabetes duration (R = 0.39; P < 0.0001). Logistic regression analysis showed that the presence of diabetes complications was significantly associated with F24, sex, duration of diabetes, and glycated hemoglobin. CONCLUSIONS: In type 2 diabetic subjects, hypothalamic-pituitary-adrenal activity is enhanced in patients with diabetes complications and the degree of cortisol secretion is related to the presence and number of diabetes complications.     

定位诊断困难的支气管类癌致库欣综合征一例及文献复习

  目的  探讨库欣综合征病因为支气管类癌所致异位促肾上腺皮质激素(adrenocorticotropic hormone, ACTH)综合征的定位诊断方法。  方法  报道1例定位诊断困难的49岁女性库欣综合征患者, 收集其临床资料, 对其定位诊断过程和方法进行回顾性分析。  结果  患者曾经被误诊为库欣病并接受经蝶窦垂体手术。库欣综合征的症状在垂体手术后仍持续存在。经过6个月的随访和数周的酮康唑治疗, 胸部CT显示右肺内一个直径约5 mm小结节在9个月内无明显变化。生长抑素受体显像和氟脱氧葡萄糖-正电子发射断层显像(fluorodeoxyglucose-positron emission tomography, FDG-PET)不能确定肺内结节为分泌ACTH的肿瘤。岩下窦静脉取血结果表明病因为异位ACTH综合征。胸腔镜下右肺中叶切除术后, 血ACTH、皮质醇和24 h尿游离皮质醇均降至正常。组织学证实该结节为典型支气管类癌, 免疫组织化学染色示ACTH阳性。  结论  岩下窦静脉取血对于异位分泌ACTH肿瘤的定位诊断非常重要, 对于疑诊异位ACTH综合征的患者应进行岩下窦静脉取血联合不同的影像学诊断技术来定位病灶, 必要时可行探查手术。     

Estimation of urinary unconjugated androstenedione, dehydroepiandrosterone, testosterone, cortisol, aldosterone and 18-hydroxycorticosterone as a potential tool for assessing adrenal status

A method is described for the simultaneous assay of non-conjugated androstenedione, dehydroepiandrosterone, testosterone, cortisol, aldosterone and 18-hydroxycorticosterone in urine. The method involves solid-phase extraction, automatic high performance liquid chromatography and subsequent radioimmunological quantitation of the individual steroids. Excretion rates of these urinary free steroids were determined in normal males and females. There were no significant sex differences in excretion rates, although both urinary free testosterone and dehydroepiandrosterone were distinctly lower in females than in males. Representative measurements of the excretion rates of patients with Cushing's disease, Addison's disease, ectopic corticotropin syndrome and hirsutism were made. The present method has been shown to be well suited for routine purposes. Its final diagnostic significance for monitoring alterations in glucocorticoid, mineralocorticoid and androgenic activity of the adrenal cortex has yet to be explored.     

Cushing's disease: clinical manifestations and diagnostic evaluation

The most common endogenous cause of Cushing's syndrome is Cushing's disease. Frequent clinical findings include weight gain, truncal obesity, striae, hypertension, glucose intolerance and infections. Cranial nerve II may be affected by enlarging pituitary adenomas in Cushing's disease; cranial nerves III, IV and VI may also be affected. The evaluation of patients with suspected Cushing's disease and syndrome requires an understanding of the proper use and limitations of the tests commonly included in the diagnostic work-up. The best screening test for Cushing's syndrome is a 24-hour urine collection with analysis for urinary free cortisol excretion. Low-dose and high-dose dexamethasone suppression tests, corticotropin assays, a corticotropin-releasing hormone stimulation test and inferior petrosal sinus catheterization may be required for a definitive diagnosis. Magnetic resonance imaging is useful in localizing the lesion. Surgical removal of the lesion by a transphenoidal approach is usually successful, but long-term follow-up is required. Some patients require lifetime glucocorticoid replacement therapy.     

Determination of urinary free cortisol by liquid chromatography-tandem mass spectrometry

Measurement of urinary free cortisol is clinically important in the diagnosis of Cushing's syndrome. While liquid chromatography (LC) with UV detection provides much better specificity than immunologic methods, certain drugs cause interference. Detection by mass spectrometry (MS) is a potentially superior method. Our analysis utilizes 1 mL urine spiked with 6-alpha-methylprednisolone as internal standard. The samples were extracted with dichlormethane and the extract was washed, evaporated to dryness and analyzed by LC-MS/MS operating in the negative mode after separation on a reversed-phase C18 column. The calibration curves for analysis of urinary cortisol exhibited consistent linearity and reproducibility in the range of 10-400 nmol/L. Inter-assay CVs were 4.0-7.6%, at mean concentrations of 21-153 nmol/L. The detection limit was 1 nmol/L (signal-to-noise ratio=3). The mean recovery of cortisol added to urine ranged from 67% to 87% and that of the internal standard from 71% to 76%. The regression equation for the LC-MS/MS (x) and HPLC (y) methods was: y=1.095x+8.0 (r=0.996; n=111). Drugs known to interfere with UV detection did not cause problems here. The sensitivity and specificity of the MS/MS method for urinary free cortisol offer advantages over HPLC with UV detection by eliminating drug interference. The higher equipment costs in comparison with HPLC methods using UV detection are balanced by higher throughput, thanks to shorter chromatographic run times.     

Midnight serum cortisol: comparison of healthy volunteers and hospitalized patients with Cushing's syndrome

Diurnal variation in serum cortisol is nearly always absent in patients with Cushing's syndrome (CS), as shown by elevated levels of midnight serum cortisol (MSC). The sensitivity of MSC in the diagnosis of CS has been shown to be 96-100% measured on an inpatient basis. The purpose of this study was to state reference values for MSC measured on an outpatient basis in healthy non-sleeping controls, and to calculate the sensitivity and specificity of the test in patients with verified CS based on these data. Thirty-six healthy volunteers (11 males, 25 females) with a median age of 40.5 (range 22-60) years and a mean body mass index (BMI) of 27.0+/-5.9kg/m2 were included in the study. Serum cortisol was measured at 24.00h. In 35 CS patients (5 males, 30 females) with a median age of 44.5 (range 23-79) years and mean BMI of 28.5+/-6.9 kg/m2, MSC was measured on the first night after admission to hospital, in a non-sleeping state. All controls, with the exception of one, had MSC values below 200nmol/L. One CS patient showed an MSC level below 200nmol/L. Based on these observations, the sensitivity and specificity of the test were 97.1% and 97.2%, respectively, when 200nmol/L was used as the cut-off limit. Non-sleeping state does not seem to compromise the sensitivity or the specificity of the test.