Overnight urinary free cortisol determination: a screening test for the diagnosis of Cushing's syndrome

The EFLM European Urinalysis Guideline 2023

BACKGROUND

The EFLM Task and Finish Group Urinalysis has updated the ECLM European Urinalysis Guidelines (2000) on urinalysis and urine bacterial culture, to improve accuracy of these examinations in European clinical laboratories, and to support diagnostic industry to develop new technologies.

RECOMMENDATIONS

Graded recommendations were built in the following areas.

MEDICAL NEEDS AND TEST REQUISITION

Strategies of urine testing are described to patients with complicated or uncomplicated urinary tract infection (UTI), and high or low-risk to kidney disease.

SPECIMEN COLLECTION

Patient preparation, and urine collection are supported with two quality indicators: contamination rate (cultures), and density of urine (chemistry, particles).

CHEMISTRY

Measurements of both urine albumin and α1-microglobulin are recommended for sensitive detection of kidney disease in high-risk patients. Performance specifications are given for urine protein measurements and quality control of multiproperty strip tests.

PARTICLES

Procedures for microscopy are reviewed for diagnostic urine particles, including urine bacteria. Technologies in automated particle counting and visual microscopy are updated with advice how to verify new instruments with the reference microscopy.

BACTERIOLOGY

Chromogenic agar is recommended as primary medium in urine cultures. Limits of significant growth are reviewed, with an optimised workflow for routine specimens, using leukocyturia to reduce less important antimicrobial susceptibility testing. Automation in bacteriology is encouraged to shorten turn-around times. Matrix assisted laser desorption ionization time-of-flight mass spectrometry is applicable for rapid identification of uropathogens. Aerococcus urinae, A. sanguinicola and Actinotignum schaalii are taken into the list of uropathogens. A reference examination procedure was developed for urine bacterial cultures.

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.

Accuracy of Laboratory Tests for the Diagnosis of Cushing Syndrome

CONTEXT

The diagnosis of Cushing syndrome (CS) can be challenging. It remains to be determined which diagnostic tests are the most accurate.

OBJECTIVE

To summarize the accuracy of diagnostic tests for CS using contemporary meta-analytic techniques (hierarchical models).

DATA SOURCES

PubMed, Embase, Scopus, Web of Science, and the Cochrane Database of Systemic Reviews (inception until August 3, 2018).

STUDY SELECTION

Studies performed in adults that determined the accuracy of one or more diagnostic tests: overnight 1-mg dexamethasone suppression test (DST), 2-day low-dose DST (2d DST), 24-hour urinary free cortisol (UFC), late-night salivary cortisol (LNSC), midnight serum cortisol (MSC), and the dexamethasone-suppressed CRH (dex-CRH) and desmopressin (dex-DDAVP) tests.

DATA EXTRACTION

Two authors independently extracted data and performed methodological assessments.

DATA SYNTHESIS

One hundred thirty-nine studies (14 140 participants) were included in the analysis. The respective sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio (95% confidence interval [CI]) estimates include the following: DST 98.6% (96.9%-99.4%), 90.6% (86.4%-93.6%), 10.5 (7.2-15.3), and 0.016 (0.007-0.035); 2d DST 95.3% (91.3%-97.5%), 92.8% (85.7%-96.5%), 13.2 (6.47-27.1), and 0.051 (0.027-0.095); UFC 94.0% (91.6%-95.7%), 93.0% (89.0%-95.5%), 13.3 (8.47-21.0), and 0.065 (0.046-0.092); LNSC 95.8% (93.%-97.2%), 93.4% (90.7%-95.4%), 14.6 (10.3-20.7), and 0.045 (0.030-0.066); MSC 96.1% (93.5%-97.6%), 93.2% (88.1%-96.3%), 14.2 (7.96-25.2), and 0.042 (0.026-0.069); and dex-CRH 98.6% (90.4%-99.8%), 85.9% (67.6%-94.7%), 7.0 (2.80-17.6), and 0.016 (0.002-0.118). A single study evaluated dex-DDAVP. Meta-regression and a novel network meta-analytic approach suggest that DST is the most sensitive while UFC is the least sensitive.

CONCLUSIONS

All of the included diagnostic tests for CS are highly sensitive and specific. It appears that the DST is the most sensitive while the UFC is less sensitive. The specificity of all first-line tests appears comparable.

Obesity and the hypothalamic-pituitary-adrenal axis in adolescent girls

Stress and stress-related concomitants, including hypothalamic-pituitary-adrenal (HPA) axis activation, are implicated in obesity and its attendant comorbidities. Little is known about this relationship in adolescents. To begin to address this important knowledge gap, we studied HPA axis activity in 262 healthy adolescent girls aged 11, 13, 15, and 17 years. We hypothesized that obesity would be correlated with increased HPA axis activity and reactivity. Measures of HPA axis activity included 3 blood samples obtained midday (between 1:00 and 2:00 pm) over the course of 40 minutes; overnight urine free cortisol; and cortisol levels 0, 20, and 40 minutes after venipuncture (cortisol reactivity). Measures of adiposity included body mass index (BMI), BMI z score (BMI-Z), percentage body fat, and fat distribution (central adiposity) assessed by dual-energy x-ray absorptiometry. Daytime levels of serum cortisol were inversely associated with BMI-Z and central adiposity (P < .05). The urine free cortisol excretion rate was positively correlated with BMI, BMI-Z, and central adiposity. There was blunting of cortisol response to venipuncture with increasing adiposity. Our results suggest that there may be reduced cortisol levels during the day and increased levels at night with increasing degree of adiposity. This study provides preliminary findings indicating an alteration of the circadian rhythm of cortisol with obesity. We conclude that obesity is associated with altered HPA activity in adolescent girls. The clinical implications of our findings require further investigation.

Dysfunctional pancreatic beta-cells of critical stress play a more prominent role in the development of stress diabetes in critically burned Korean subjects

The purposes of this study are to identify the predictive parameters for the development of stress-induced hyperglycemia and to investigate the glucose metabolic homeostasis in critically burned Korean subjects. We conducted a prospective cross-sectional study of adult patients with glucose management targeting fasting and postprandial blood glucose levels less than 140 and 200 mg/dL, respectively, in patients with unrecognized diabetes. Clinical and laboratory stress parameters and insulin secretory and sensitivity parameters were assessed. Stimulated C-peptide and 24-hour urinary free cortisol predicted new-onset stress diabetes requiring insulin therapy. The subjects requiring insulin therapy were leaner and more insulin sensitive than insulin-free subjects, without significance. Glycated hemoglobin, stimulated C-peptide, homeostasis model assessment of insulin resistance, and age had a significant influence on the mean daily dose of insulin. Our present data showed that Korean subjects with dysfunctional pancreatic beta-cells of critical stress are prone to become stress diabetic and require more insulin to control the hyperglycemia.

Diagnostic value of salivary cortisol in Cushing's syndrome (CS)

OBJECTIVE

The diagnosis of Cushing's syndrome (CS) remains a challenge in clinical endocrinology. The aim of this study was to determine the reproducibility and diagnostic value of late-night salivary cortisol (SAF(23)) for CS and its utility along the follow-up of treated patients. In addition, using the same radioimmunoassay reactives, the cut-off values for saliva and serum cortisol, assessed synchronically after the overnight 1 mg dexamethasone suppression test (DST), were defined.

DESIGN

Twenty-one patients with confirmed CS and 121 volunteers were studied. All the subjects collected 24-h urine for cortisol (UFC). On the same day whole saliva was obtained from the subjects at 23 h for SAF(23). The intraclass coefficient of correlation (ICC) of SAF(23) was estimated in 47 subjects (21 CS and 26 C). At 8 h, after DST, simultaneous saliva and serum samples for cortisol (SAF(dex) and F(dex), respectively) were obtained in 51 subjects (17 CS and 34 C). After specific therapy, 18 patients with CS were followed with SAF(23) measurements. SAF and F were expressed as nM.

RESULTS

The intraclass coefficient of correlation of SAF(23) was 0.89 in CS and 0.83 in C. SAF(23) > 3.8 nM showed a sensitivity and specificity of 100% and 97.5%, respectively, for diagnosing CS. SAF(23) correlated positively with UFC (r = 0.685; P = 0.0001). After DST, SAF(dex) significantly correlated with F(dex) (r = 0.61, P < 0.0001). A cut-off value of SAF(dex) > 2.0 nM and F(dex) > 50.0 nM detected CS with 100% sensitivity and specificity. After successful surgical therapy, 13 patients with CS had SAF(23) levels < 3.8 nM (1.4 +/- 0.8 nM).

CONCLUSIONS

SAF(23) and SAF(dex) seem to be good screening tools based on their noninvasive nature, remarkable reproducibility and diagnostic performances.

Management of Cushing's disease: outcome in patients with microadenoma detected on pituitary magnetic resonance imaging

OBJECT

Outcomes of therapy for Cushing's disease (CD) vary depending on different aspects of presentation and diagnostic studies. The authors designed this study to verify the remission rate and outcomes after transsphenoidal surgery (TSS) for patients with CD who had positive findings on MR imaging.

METHODS

Patients who had presented with CD at the University of Virginia for initial treatment between July 1992 and December 2005 were retrospectively reviewed. The patients included in the study were considered to be optimal surgical candidates, defined as an adult (>18 years of age) with classic clinical features of CD, laboratory studies confirming a central (pituitary/hypothalamic) adrenocorticotropic hormone-dependent source of disease, and an MR imaging study revealing a microadenoma in the sella turcica.

RESULTS

A total of 167 patients fulfilled the criteria. Thirty were men (18%) and 137 were women (82%). The mean age was 42.3 years (range 18.2-77 years). All patients underwent TSS. Surgical remission was achieved in 148 patients (88.6%), which was correlated with the surgeon's intraoperative identification of an adenoma (p=0.03). Histopathological confirmation of an adrenocorticotropic hormone-secreting adenoma strongly correlated with remission (p=0.0001). Three patients (1.8%) had postoperative cerebrospinal fluid leaks, and 1 patient had meningitis. Transient diabetes insipidus was diagnosed and treated in 10 patients (6%), whereas permanent diabetes insipidus occurred in 8 patients (4.8%). Panhypopituitarism followed the surgery in 14 patients (8.3%), 13 of whom underwent total hypophysectomy (9 initially and 4 with early reoperations), and in 1 of 10 patients who underwent subtotal hypophysectomy. Nineteen patients (12.8%) who were initially in remission developed recurrent CD after an average of 50 months. The mean follow-up for the 167 patients was 39 months (range 6-157 months). Gamma Knife surgery was the most common modality of radiotherapy used to treat 31 patients (18.5%) who did not achieve remission or later presented with recurrent disease. Bilateral adrenalectomies were performed in 10 patients in the series (6%), 2 of whom developed Nelson's syndrome. The overall posttreatment remission rate was 95.8%.

CONCLUSIONS

Even in patients with ideal diagnostic criteria of CD, there remain a significant number of cases in which TSS alone is not adequate to assure long-lasting remission. A multidisciplinary approach is essential to the achievement of satisfactory overall remission rates.

Diagnostic approach to Cushing disease

✓ In Cushing disease, a pituitary corticotroph neoplasm causes secondary adrenal hypercortisolism. This condition has known morbidity and mortality, underscoring the need for an efficient and accurate diagnostic approach. An 11 p.m. salivary cortisol level is a modern, simple initial screening tool for the diagnosis of Cushing syndrome. Confirmation with a 24-hour urinary free cortisol test and/or a low-dose dexamethasone suppression test may subsequently be performed. Patients with repeatedly equivocal results should be reevaluated after several months or undergo a corticotropin-releasing hormone (CRH) stimulation test following low-dose dexamethasone suppression to help rule out pseudo-Cushing states. The presence of low morning serum adrenocorticotropic hormone (ACTH) levels then distinguishes primary adrenal hypercortisolism from Cushing disease and the ectopic ACTH syndrome. Patients with moderate ACTH levels can undergo CRH stimulation testing to clarify the underlying disease because those with an ACTH-independent disorder have blunted subsequent ACTH levels. Once ACTH-dependent hypercortisolemia is detected, magnetic resonance (MR) imaging of the pituitary gland can be performed to detect a pituitary neoplasm. Normal or equivocal MR imaging results revealing small pituitary lesions should be followed up with inferior petrosal sinus sampling, a highly specific measure for the diagnosis of Cushing disease in experienced hands. If necessary, body imaging may be used in turn to detect sources of ectopic ACTH.

Evaluation and treatment of Cushing's syndrome

Cushing's syndrome results from sustained pathologic hypercortisolism caused by excessive corticotropin (ACTH) secretion by tumors in the pituitary gland (Cushing's disease, 70%) or elsewhere (15%), or by ACTH-independent cortisol secretion from adrenal tumors (15%). The clinical features are variable, and no single pattern is seen in all patients. Those features most specific for Cushing's syndrome include abnormal fat distribution, particularly in the supraclavicular and temporal fossae, proximal muscle weakness, wide purple striae, and decreased linear growth with continued weight gain in a child. Patients with characteristics of glucocorticoid excess should be screened with measurements of saliva or urine cortisol or dexamethasone suppression testing. The diagnosis of Cushing's syndrome should be followed by the measurement of plasma ACTH concentration to determine whether the hypercortisolism is ACTH-independent. In ACTH-dependent patients, bilateral inferior petrosal sinus sampling with measurement of ACTH before and after administration of ACTH-releasing hormone most accurately distinguishes pituitary from ectopic ACTH secretion. Surgical resection of tumor is the optimal treatment for all forms of Cushing's syndrome; bilateral adrenalectomy, medical treatment, or radiotherapy are sought in inoperable or recurrent cases. The medical treatment of choice is ketoconazole. The prognosis is better for Cushing's disease and benign adrenal causes of Cushing's syndrome than adrenocortical cancer and malignant ACTH-producing tumors.

Screening and diagnosis of Cushing's syndrome

Screening studies in high-risk populations have suggested that Cushing's syndrome is more common than previously appreciated. Patients who have specific signs and symptoms or clinical diagnoses known to be associated with hypercortisolism should be considered for screening. The measurement of late-night salivary cortisol provides the most sensitive method for screening, and urine-free cortisol and low-dose dexamethasone suppression testing may be used for confirmation of the diagnosis of endogenous hypercortisolism

Dexamethasone infusion testing in the diagnosis of Cushing's syndrome

Cushing's syndrome and its various aetiologies is a markedly difficult diagnosis to make given its subtle signs, sometime cyclical nature, and the lack of a single definitive diagnostic test. Although a great variety of diagnostic tests have been developed to assist in the diagnosis, even with the best clinical acumen, biochemistry and medical imaging the diagnosis can remain elusive. The long low and high dose oral dexamethasone suppression test is cumbersome, costly and often requiring an extended inpatient stay. The utility of the dexamethasone suppression test would be greatly enhanced if it could be performed as a short outpatient procedure. In this study we sought to confirm and refine the clinical utility of the high dose 4 mg intravenous dexamethasone suppression test as an alternative diagnostic test for Cushing's syndrome. There were a total of 31 subjects: 8 patients with proven pituitary Cushing's disease, 3 with primary adrenal tumors, 10 with pseudo-Cushing's syndrome and 10 healthy controls. All subjects with pseudo-Cushing's syndrome suppress serum cortisol at +5 and at +24 hours. In subjects with pituitary Cushing's disease, 7 out of 8 (88%) had serum cortisol suppressed at +5 hours but rebounded at +24 hours to at least 70% of the original serum level. Primary adrenal tumors showed a pattern of non-suppression throughout. The 4 mg intravenous dexamethasone suppression test is excellent in ruling out pseudo-Cushing's syndrome. This test is much simpler and more convenient than the oral dexamethasone suppression test in confirming clinical suspicion of pituitary Cushing's disease.

The midnight-to-morning urinary cortisol increment method is not reliable for the assessment of hypothalamic-pituitary-adrenal insufficiency in patients with end-stage kidney disease

A previous study reported that the midnight-to-morning urinary cortisol increment method could be used to reliably assess the insufficiency of the hypothalamic-pituitary-adrenal (HPA) axis. The principal aim of the present study is to verify whether the midnight-to-morning urinary cortisol increment is a reliable method for the assessment of the HPA axis in patients with various degrees of impaired kidney function. Fifty-six clinically stable patients with chronic kidney disease (CKD) and 14 healthy subjects were enrolled in the present study. Patients with CKD were divided on the basis of glomerular filtration rate (GFR) into the following arbitrary groups: mild (GFR: 60-89 ml/min/1.73 m2, no.=15), moderate (GFR: 30-59 ml/min/1.73 m2, no.=12) and severe kidney insufficiency (GFR: 15-29 ml/min/1.73 m2, no.=13), and hemodialysis patients. Plasma cortisol and ACTH levels were measured. The HPA axis was assessed by short Synacthen test and overnight dexamethasone suppression test. Double voided urine samples were collected at midnight and waking in the patients and the controls. Urinary free cortisol (UFC) and creatinine levels were measured and the UFC/creatinine ratio (Cort/Cr) was calculated. Then, the Cort/Cr increment was calculated as the morning Cort/Cr minus the midnight Cort/Cr. Baseline plasma cortisol levels were not significantly different between two groups. However, we found that CKD patients had significantly greater plasma ACTH levels than controls. The patients with CKD had also significantly lower morning UFC levels than controls and there was a progressive fall in morning UFC levels with decreasing GFR. The assessment of the HPA axis in patients with GFR lower than 29 ml/min was hampered by falsely abnormal responses to the midnight-to-morning urinary cortisol increment method. Plasma cortisol responded normally to exogenously administered ACTH, while plasma cortisol was suppressed by overnight dexamethasone administration in all patients with CKD. In conclusion, this method is not a reliable test for assessment of the HPA insufficiency in patients with GFR lower than 29 ml/min.

[Cortisol in night-urine: Introduction of a research method in psychoneuroendocrinology]

Cortisol is one of the major parameters investigated in psychoneuroendocrinological research, but the methods employed for sample collecting are often unsatisfactory. A suitable method of sample collection should allow for the integrative assessment of long-term changes of the HPA-system, should be non-invasive, and should not exceed the subject's compliance. The assessment of cortisol in night-urine fulfils these demands; although this method has been occasionally employed, it has not yet been described systematically. For the first time a detailed description is given here that allows for a standardized replication. In ten previous studies and three investigations of our own this method has been successfully applied to detect changes in the cortisol excretion of patients with endocrinological and psychiatric disorders as well as in subjects under conditions of psychosocial stress. The determination of cortisol in night-urine represents an ideal method for the assessment of changes in the basal HPA-activity in numerous areas of psychoneuroendocrinological research, e.g. field and screening studies in natural environment, clinical studies in psychiatry and especially follow-up studies in psychotherapy research.

Fat distribution in obese women is associated with subtle alterations of the hypothalamic-pituitary-adrenal axis activity and sensitivity to glucocorticoids

OBJECTIVES

Obesity with abdominal body fat distribution (A-BFD) and hypothalamic-pituitary-adrenal (HPA) axis activity are somehow linked, but the exact interactions still need clarification. Obese subjects display normal circulating plasma cortisol concentrations with normal circadian rhythms. However, when the HPA axis is pharmacologically challenged, body fat distribution matters and then A-BFD obese women differ from those with subcutaneous body fat distribution (P-BFD). We hypothesized that lower dose provocative and suppressive tests than those used to diagnose hypercortisolism of tumour origin or adrenal insufficiency would shed some light on the characteristics of the HPA axis activity in relation with body fat distribution.

PATIENTS AND METHODS

Fifty premenopausal obese women were grouped according to their body fat mass distribution. Their plasma cortisol responses to (i) two low doses of dexamethasone (0.25 and 0.5 mg) with (ii) low dose of the ACTH analogue tetracosactrin (1 microg) were assessed. Salivary cortisol was also determined during the ACTH test.

RESULTS

A-BFD differed from P-BFD women in terms of HPA axis responsiveness. They had comparatively: (i) increased nocturnal cortisol excretion (9.38 +/- 2.2 vs. 6.82 +/- 0.91 nmol/micromol creatinine, A-BFD vs. P-BFD, respectively, P = 0.03); (ii) increased salivary cortisol response to ACTH stimulation (1 microg) [salivary cortisol peak: 33.4 (14.1-129) vs. 28.5 (13.2-42.8) nmol/l; salivary AUC: 825 (235-44738) vs. 537 (69-1420) nmol/min/l; A-BFD vs. P-BFD, P = 0.04 for both]; and (iii) increased pituitary sensitivity to dexamethasone testing [postdexamethasone (0.25 mg) plasma cortisol levels: 163 (26-472) vs. 318 (26-652) nmol/l and postdexamethasone (0.5 mg) plasma cortisol levels: 26 (26-79) vs. 33 (26-402) nmol/l; A-BFD vs. P-BFD, P = 0.01 for both).

CONCLUSIONS

These data demonstrate differences in the HPA axis activity and sensitivity to glucocorticoids between obese women differing in their body fat distribution, with both enhanced negative and positive feedback in those with abdominal obesity. Several mechanisms may explain these differences: central vs. peripheral hypotheses. Thus, abdominal obesity does not appear to be linked solely to one pathophysiological hypothesis.

The desmopressin test in the differential diagnosis between Cushing's disease and pseudo-Cushing states

Differentiating Cushing's disease (CD) from pseudo-Cushing (PC) states may still be difficult in current practice. Because desmopressin (1-deamino-8D-arginine vasopressin, DDAVP), a vasopressin analogue, stimulates ACTH release in patients with CD but not in the majority of normal, obese, and depressed subjects, we investigated its ability to discriminate CD from PC states. One hundred seventy-three subjects (76 with active CD, 30 with PC, 36 with simple obesity, and 31 healthy volunteers) were tested with an iv bolus of 10 microg DDAVP. Sixty-one of these subjects also underwent a control study with saline. DDAVP induced marked ACTH and cortisol rises in CD (P < 0.005 vs. saline, for both ACTH and cortisol) but not in PC. A significant ACTH elevation occurred upon DDAVP administration also in normal and obese subjects, but it was much smaller than that observed in patients with CD (P < 0.0001). A peak absolute ACTH increase (> or =6 pmol/L), after DDAVP, allowed us to recognize 66 of 76 patients with CD and 88 of 97 subjects of the other groups. The same criterion correctly identified 18 of 20 patients with mild CD (24-h urinary free cortisol < or = 690 nmol/day) and 29 of 30 PC, resulting in a diagnostic accuracy of 94%, which was definitely higher than that displayed by urinary free cortisol, overnight 1-mg dexamethasone suppression test, and midnight plasma cortisol. In conclusion, the DDAVP test seems to be a useful adjunctive tool for the evaluation of hypercortisolemic patients chiefly because of its ability to differentiate mild CD from PC states.

Urinary protein and albumin excretion corrected by creatinine and specific gravity

Timed urine collections are difficult to use in clinical practice owing to inaccurate collections making calculations of the 24-h albumin or protein excretion questionable. One of our goals was to assess the 'correction' of urinary albumin and (or) protein excretion by dividing these by either the creatinine concentration or the term, (specific gravity-1)x100(1). The 24-h creatinine excretion can be estimated based on the patients' gender, age and weight. We studied the influence of physiological extremes of hydration and exercise, and protein and creatinine excretion in patients with or suspected kidney disorders. Specimens were collected from healthy volunteers every 4 h during one 24-h period. We assayed the collections individually to give us an assessment of the variability of the analytes with time, and then reassayed them after combining them to give a 24-h urine. For all volunteers, the mean intra-individual CVs based on the 4-h collections expressed in mg/24 h were 80.0% for albumin and 96.5% for total protein (P0.2). The CVs were reduced by dividing the albumin or protein concentration by the creatinine concentration or by the term, (SG-1)x100. This gave a CV for mg albumin/g creatinine of 52% (P<0.1 vs. albumin mg/g creatinine); mg protein/g creatinine of 39% (P<0.05 vs. mg protein/g creatinine); mg albumin/[(SG-1)x100] of 49% (P<0.1 vs. albumin)/[(SG-1)x100]; and mg protein/[(SG-1)x100] of 37% (P<0. 05 vs. mg protein)/[(SG-1)x100]. For the 68 subjects in the study, the strongest correlation was between the creatinine concentrations and the 24-h urine volume: r=0.786, P<0.001. The correlation of (SG-1)x100 vs. the 24-h urine volume was: r=0.606, P<0.001; for (SG-1)x100 and the creatinine concentration, the correlation was: r=0.666, P<0.001. Compared to the volunteers, the albumin and protein excretion in mg/24 h were more variable in the patients. The same was true if the albumin or protein concentrations were divided by the creatinine concentration or by (SG-1)x100. Protein and albumin concentrations were lower in dilute urines. Dividing the albumin or protein concentrations by the creatinine concentration reduced the number of false negative protein and albumin results. Dividing the albumin or protein values in mg/24 h by (SG-1)x100 eliminated fewer false negatives. Albumin concentrations increased significantly after vigorous exercise. The increase was almost eliminated when the albumin result was divided by the creatinine concentration suggesting that a decreased urine flow and not increased glomerular permeability causes an increase of post-exercise albuminuria. The same was true for proteinuria. A dipstick test plus an optical strip reader that can measure urine protein, albumin, and creatinine and calculate the appropriate ratios provides a better screening test for albuminuria or proteinuria than one measuring only albumin or protein.

The dexamethasone-suppressed corticotrophin-releasing hormone stimulation test in anorexia nervosa

OBJECTIVE

The dexamethasone-CRH test (combination of dexamethasone-induced suppression of HPA axis function and subsequent stimulation with oCRH) (Dex-CRH test) has been proposed to fully distinguish ACTH-dependent Cushing's disease (CD) from pseudo-Cushing's states (PCS), i.e. tumoural vs. functional hypercortisolism. A plasma cortisol concentration greater than 38 nmol/l 15 min after CRH injection has been demonstrated to identify all cases of CD and to exclude all cases of PCS. Although obviously not a PCS from a clinical point of view, anorexia nervosa (AN) is associated with CRH-driven hyperactivity of the HPA axis. This study reports the response of AN patients, a model of functional biological hypercortisolism, to the Dex-CRH test.

PATIENTS AND METHODS

Nineteen women affected with anorexia nervosa and 6 healthy sex-matched controls were studied.

RESULTS

Three of 19 AN patients had an abnormal 24-h urinary free cortisol excretion (UFC), whereas 1 of 19 AN had increased overnight UFC. AN subjects had inadequately suppressed plasma cortisol after low-dose dexamethasone suppression test (LDDST) (cortisol 192.8 +/- 63.4 vs. < 27 nmol/l, AN vs. controls, respectively). Seven of 19 AN patients had plasma cortisol levels above 50 nmol/l after LDDST. None of the AN patients had CRH-induced increases in plasma ACTH or cortisol (basal cortisol 192. 8 +/- 63.4 and peak cortisol 181.7 +/- 59.9 nmol/l). Despite unresponsivenessto CRH and because of the lack of suppression after dexamethasone, using the single plasma cortisol threshold value of 38 nmol/l obtained at 15 min during the Dex-CRH test would have been misclassified in half of our AN population (9 of 19).

CONCLUSION

Since anorexia nervosa represents a model of functional hypercortisolism that shares similar pathophysiological mechanisms to the other causes of pseudo-Cushing's states, we suggest testing all causes of pseudo-Cushing's states using the dexamethasone-CRH approach to (i) describe the actual responses of clinically relevant pseudo-Cushing's states and (ii) to improve our knowledge of the pathophysiological discrepancies between the various causes of pseudo-Cushing's states. Lastly, the evaluation of dexamethasone metabolism (absorption, volume of distribution, clearance) may help to gain more insight into the diagnostic value of the dexamethasone-CRH test.

Abdominal obesity increases overnight cortisol excretion

Although plasma and 24 h urinary free cortisol (UFC) levels are normal in obese subjects, pharmacological investigations have identified minor hypothalamo-pituitary-adrenal axis differences in patients with abdominal body fat distribution (A-BFD) vs peripheral BFD (P-BFD). Using recent tools such as saliva cortisol or overnight urinary free cortisol upon creatinine ratio (UFC/UC) determinations, we have investigated a population of obese females according to their body fat distribution. In-patients subjects (no.=82) were subjected to routine biochemical testing, 24 h and overnight UFC/UC, basal and post-1 mg overnight dexamethasone-suppressing test plasma and saliva cortisol determinations. Central obesity defined by a waist-to-hip ratio (WHR) >0.85 was found in 64% of the subjects vs 87% when defined by waist girth (WG) corrected for age. Despite identical body mass index, A-BFD subjects were more prone to hypertension using both classifications and had higher triglycerides (WHR classification) or higher triglycerides, cholesterol and glycemia (WG classification). Plasma cortisol levels were similar but saliva cortisol levels were lower in the A-BFD group using the WG classification. The 24 h UFC/UC were similar but the overnight UFC/UC were higher in the A-BFD group using the WHR classification. These mild differences in cortisol nocturnal secretion and free cortisol indexes in subjects with different body fat mass distribution suggest that their hypothalamo-pituitary-adrenal axis has a spontaneously subtly different regulation.

Newer diagnostic techniques and problems in Cushing's disease

The best diagnostic approach to patients with suspected Cushing's disease continues to evolve. The introduction of transsphenoidal pituitary surgery as the treatment of choice for Cushing's disease as well as the absence of any pituitary imaging abnormalities in many patients with Cushing's disease has made accurate diagnosis and differential diagnosis essential. In the authors' opinion, two or three late night (11 PM) salivary cortisol determinations and the measurement of 24-hour UFC are the best and simplest means to evaluate patients with suspected hypercortisolism. L-DST can no longer be recommended to exclude the diagnosis of Cushing's disease, particularly if the hypercortisolism is mild. The combination of L-DST and CRH stimulation is a new and apparently sensitive means to establish the presence or absence of pathologic hypercortisolism in equivocal cases. In the absence of an overt pituitary tumor on MR imaging, inferior petrosal sinus sampling with CRH stimulation should be performed to secure the diagnosis of Cushing's disease as well as identify the probable location of the corticotroph adenoma.