Laboratory differentiation of Cushing's syndrome

Whom Should We Screen for Cushing Syndrome? The Endocrine Society Practice Guideline Recommendations 2008 Revisited

CONTEXT

Cushing syndrome (CS) is a rare and serious disease with high mortality. Patients are often diagnosed late in the course of the disease.

OBJECTIVE

This work investigated whether defined patient populations should be screened outside the at-risk populations defined in current guidelines.

METHODS

As part of the prospective German Cushing registry, we studied 377 patients with suspected CS. The chief complaint for CS referral was documented. Using urinary free cortisol, late-night salivary cortisol, and the 1-mg dexamethasone suppression test as well as long-term clinical observation, CS was confirmed in 93 patients and ruled out for the remaining 284.

RESULTS

Patients were referred for 18 key symptoms, of which 5 were more common in patients with CS than in those in whom CS was ruled out: osteoporosis (8% vs 2%; P = .02), adrenal incidentaloma (17% vs 8%, P = 0.01), metabolic syndrome (11% vs 4%; P = .02), myopathy (10% vs 2%; P < .001), and presence of multiple symptoms (16% vs 1%; P < .001). Obesity was more common in patients in whom CS was ruled out (30% vs 4%, P < .001), but recent weight gain was prominent in those with CS. A total of 68 of 93 patients with CS (73%) had typical chief complaints, as did 106 of 284 of patients with ruled-out CS status (37%) according to the Endocrine Society practice guideline 2008.

CONCLUSION

The 2008 Endocrine Society Practice guideline for screening and diagnosis of CS defined at-risk populations that should undergo testing. These recommendations are still valid in 2022.

Indication to dynamic and invasive testing in Cushing's disease according to different neuroradiological findings

PURPOSE

Dynamic testing represents the mainstay in the differential diagnosis of ACTH-dependent Cushing's syndrome. However, in case of undetectable or detectable lesion < 6 mm on MRI, bilateral inferior petrosal sinus sampling (BIPSS) is suggested by current guidelines. Aim of this study was to analyze the performance of CRH, desmopressin and high-dose dexamethasone suppression test (HDDST) in the differential diagnosis of ACTH-dependent Cushing's syndrome as well as the impact of invasive and noninvasive tests on surgical outcome in patients affected by Cushing's disease (CD).

METHODS

Retrospective analysis on 148 patients with CD and 26 patients with ectopic ACTH syndrome.

RESULTS

Among CD patients, negative MRI/lesion < 6 mm was detected in 97 patients (Group A); 29 had a 6-10 mm lesion (Group B) and 22 a macroadenoma (Group C). A positive response to CRH test, HDSST and desmopressin test was recorded in 89.4%, 91·4% and 70.1% of cases, respectively. Concordant positive response to both CRH/HDDST and CRH/desmopressin tests showed a positive predictive value of 100% for the diagnosis of CD. Among Group A patients with concordant CRH test and HDDST, no difference in surgical outcome was found between patients who performed BIPSS and those who did not (66.6% vs 70.4%, p = 0.78).

CONCLUSIONS

CRH, desmopressin test and HDDST have high accuracy in the differential diagnosis of ACTH-dependent CS. In patients with microadenoma < 6 mm or non-visible lesion, a concordant positive response to noninvasive tests seems sufficient to diagnose CD, irrespective of MRI finding. In these patients, BIPSS should be reserved to discordant tests.

Diurnal Salivary Cortisol Profiles in Patients with Cushing's Syndrome

BACKGROUND

Quantification of salivary cortisol is one of the highly sensitive and specific screening parameters for Cushing's syndrome (CS). However, only late-night salivary cortisol is part of the standard screening procedure. In this study, we aimed to analyze salivary cortisol day profiles in patients with different types of CS to test whether specific patterns might be relevant for diagnosis and subtyping.

MATERIAL AND METHODS

Among 428 patients including those with confirmed Cushing's syndrome (N=111, of those 75 with Cushing's disease, 27 patients with adrenal CS and nine patients with ectopic CS), autonomous cortisol secretion (N=39) or exclusion of CS (control group, N=278) salivary cortisol was measured five times a day.

RESULTS

At each of the five time points, salivary cortisol was significantly higher in patients with CS compared to the control group (p≤0.001). Using the entire profile instead of one single salivary cortisol at 11 p.m. improved diagnostic accuracy (85 vs. 91%) slightly. Patients with ACTH-dependent CS had higher salivary cortisol levels than patients with adrenal CS. Also, morning cortisol was significantly higher in patients with ectopic CS than in patients with Cushing's disease (p=0.04). Nevertheless, there was a strong overlap between diurnal profiles, and the diagnostic yield for subtyping was low.

DISCUSSION

The study results show that using diurnal salivary cortisol profiles for CS diagnosis results in a limited increase in diagnostic accuracy. With significant differences between Cushing subtypes, cortisol profiles are not useful in everyday clinical practice for subtyping of CS.

Pituitary magnetic resonance imaging vs. bilateral inferior petrosal sinus sampling: comparison between non-invasive and invasive diagnostic techniques for Cushing's disease-a narrative review

Cushing's syndrome is a pathological clinical condition caused by an exposure of elevated cortisol levels over a long period of time. It is therefore essential to establish what the cause of hypercortisolism is. In most cases (about 80%) the pathological process is due to adrenocorticotropic hormone (ACTH), while in a minor part of the cases (about 20%) the cause is represented by a pathology of the adrenal glands and therefore not related to ACTH. Most patients with ACTH dependent Cushing's syndrome have a pituitary microadenoma; in the remaining cases (30%), the high level of cortisol is linked to an ectopic secretion of ACTH. Surgical removal of the pituitary adenoma represents the treatment of choice in Cushing's disease (CD) patients; it is therefore necessary to identify and precisely locate the pituitary tumour responsible for the secretion of ACTH. Adequate diagnostic information is very often, even with magnetic resonance imaging (MRI), and in these cases we rely on bilateral inferior petrosal sinuses sampling (BIPSS). This procedure is considered the gold standard method for the diagnosis, but like any other diagnostic method it is not free from erroneous results such as false positives or false negatives.

Simultaneous Determination of Total Cortisol and Cortisone in Human Plasma by Liquid Chromatography-Tandem Mass Spectrometry: Method Development, Validation and Preliminary Clinical Application

Background:

Cortisol as a major glucocorticosteroid product of the adrenal cortex which has been recognized as a stress biomarker in evaluating stress related disorders for a long time. Plasma concentration of cortisol and its metabolite cortisone are usually changed in physiological and psychological tension, anxiety and depression. In order to study these changes properly, we need a sensitive, accurate and reproducible assay for plasma cortisol and cortisone determination. </P><P> Objective: The aim of this study was to develop a sensitive and robust method for the determination of total cortisol and cortisone in human plasma using mass spectrometry.

Methods:

A fast, sensitive and selective liquid chromatography-tandem mass spectrometry (LCMS/ MS) method was developed, validated, and then the levels of cortisol and cortisone were determined. Plasma samples cleanup procedure was composed of two steps: the first was a protein precipitation with 1 % formic acid in acetonitrile, and the second was an on-line solid phase extraction (SPE). Afterwards, cortisol and cortisone were separated using a C18 ACQUITY UPLC BEHTM column with a gradient elution. The mobile phase A was 0.1 % formic acid in water, the mobile phase B was 0.1 % methanol. For the detection we used a XEVO TQ-S mass spectrometer operating in the ESI positive mode.

Results:

The time of analysis was 6.5 minutes and the quantification range was 5-600 ng/mL for cortisol and cortisone, with > 94% recovery for all analytes (cortisol, cortisone and internal standards). The method was validated according to the EMA guideline for bioanalytical method validation.

Conclusion:

A simple and sensitive LC-MS/MS method was developed and validated for measurement of cortisol and cortisone in human plasma. Our findings indicate that the proposed analytical method is suitable for routine analysis.

Toward a Diagnostic Score in Cushing's Syndrome

Cushing's syndrome (CS) is a classical rare disease: it is often suspected in patients who do not have the disease; at the same time, it takes a mean of 3 years to diagnose CS in affected individuals. The main reason is the extreme rarity (1-3/million/year) in combination with the lack of a single lead symptom. CS has to be suspected when a combination of signs and symptoms is present, which together make up the characteristic phenotype of cortisol excess. Unusual fat distribution affecting the face, neck, and trunk; skin changes including plethora, acne, hirsutism, livid striae, and easy bruising; and signs of protein catabolism such as thinned and vulnerable skin, osteoporotic fractures, and proximal myopathy indicate the need for biochemical screening for CS. In contrast, common symptoms like hypertension, weight gain, or diabetes also occur quite frequently in the general population and per se do not justify biochemical testing. First-line screening tests include urinary free cortisol excretion, dexamethasone suppression testing, and late-night salivary cortisol measurements. All three tests have overall reasonable sensitivity and specificity, and first-line testing should be selected on the basis of the physiologic conditions of the patient, drug intake, and available laboratory quality control measures. Two normal test results usually exclude the presence of CS. Other tests and laboratory parameters like the high-dose dexamethasone suppression test, plasma ACTH, the CRH test, and the bilateral inferior petrosal sinus sampling are not part of the initial biochemical screening. As a general rule, biochemical screening should only be performed if the pre-test probability for CS is reasonably high. This article provides an overview about the current standard in the diagnosis of CS starting with clinical scores and screenings, the clinical signs, relevant differential diagnoses, the first-line biochemical screening, and ending with a few exceptional cases.

The role of inferior petrosal sinus sampling in ACTH-dependent Cushing's syndrome: review and joint opinion statement by members of the Italian Society for Endocrinology, Italian Society for Neurosurgery, and Italian Society for Neuroradiology

In the management of adrenocorticotropic hormone (ACTH)–dependent Cushing's syndrome, inferior petrosal sinus sampling (IPSS) provides information for the endocrinologist, the neurosurgeon, and the neuroradiologist. To the endocrinologist who performs the etiological diagnosis, results of IPSS confirm or exclude the diagnosis of Cushing's disease with 80%–100% sensitivity and over 95% specificity. Baseline central-peripheral gradients have suboptimal accuracy, and stimulation with corticotropin-releasing hormone (CRH), possibly desmopressin, has to be performed. The rationale for the use of IPSS in this context depends on other diagnostic means, taking availability of CRH and reliability of dynamic testing and pituitary imaging into account. As regards the other specialists, the neuroradiologist may collate results of IPSS with findings at imaging, while IPSS may prove useful to the neurosurgeon to chart a surgical course. The present review illustrates the current standpoint of these 3 specialists on the role of IPSS.

Surgical remission of Cushing's syndrome reduces cardiovascular risk

OBJECTIVE

Recent studies have questioned the reversibility of complications of Cushing's syndrome (CS) after successful surgical treatment. The aim of this study was to assess the outcome of patients with CS who achieved disease remission compared with those patients with persistent hypercortisolism and matched controls.

DESIGN

A retrospective study of 75 patients with CS followed at an academic center.

METHODS

Cardiovascular risk profile was evaluated in 51 patients with CS in remission (group 1) and 24 patients with persistent disease (group 2) and compared with 60 controls. Mortality of patients with CS was compared with the background population.

RESULTS

In group 1, the frequency of cardiovascular risk factors dropped after disease remission even if it remained higher at the last follow-up than in the control group. In group 2, the frequency of cardiovascular risk factors remained unchanged during follow-up. The rate of cardiovascular and thromboembolic events was higher in group 2 than in group 1, as was the mortality rate (two deaths in group 1 and nine in group 2; ratio of two SMRs, 0.11; 95% CI, 0.011-0.512). Survival was significantly longer in group 1 than in group 2 (87 months, 80-98 vs 48 months, 38-62; P<0.0001).

CONCLUSIONS

Successful surgical treatment of hypercortisolism significantly improves cardiovascular risk and may reduce the mortality rate. Patients with persistent disease have increased morbidity and mortality when compared with patients in remission.

Determination of cortisol in serum, saliva and urine

Cortisol is quantitatively the major glucocorticoid product of the adrenal cortex. The main reason to measure cortisol is to diagnose human diseases characterised by deficiency of adrenal steroid excretion in Addison's disease or overproduction in Cushing's syndrome (CS). In both cases a sensitive, accurate and reproducible assay of cortisol is required. Several methods have been described for the quantitative measurement of cortisol in both serum and urine. The most widely used methods in routine clinical laboratories are immunoassays (IA) and enzyme immunoassays (EIA), luminescence and fluorescence assays, which are available in numerous commercial kits and on automated platforms. However, there remains a number of problems in the so-called direct immunoassays if extraction and prepurification are not carried out before the assay. Recently, more specific chromatographic methods have been introduced, such as high pressure liquid chromatographic (HPLC) or liquid chromatography tandem mass spectrometric assays (LC-MS/MS). The high specificity especially of LC-MS/MS facilitates reliable measurement of cortisol both in plasma, urine and saliva samples.

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.

Cortisol secretion, bone health, and bone loss: a cross-sectional and prospective study in normal non-osteoporotic women in the early postmenopausal period

OBJECTIVE

The aim of the study was to evaluate the relationship between cortisol secretion, bone health, and bone loss in a cohort of normal women in the early postmenopausal period.

METHODS

We measured lumbar and hip bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) and heel ultrasound parameters in 82 healthy, nonosteoporotic (lumbar T-score ≥-2.0) women (median age 52.5 years, range 42-61). These women were examined in two sessions, 1 year apart, in the early postmenopausal period (onset of menopause between 6 and 60 months). Parameters of the hypothalamic-pituitary-adrenal (HPA) axis function were morning serum cortisol, morning and midnight salivary cortisol, 24-h urinary free cortisol (UFC), serum cortisol after 0.5 and 1 mg overnight dexamethasone, and DHEA-S.

RESULTS

In multiple regression analyses, the following significant inverse correlations were found: i) lumbar BMD and either 24-h UFC (P<0.005) or morning serum cortisol (P<0.05), ii) total femur and femoral neck BMD with morning serum cortisol (P=0.05 and P<0.05), and iii) heel ultrasound stiffness index and midnight salivary cortisol (P<0.005). The annual rate of change in lumbar and femoral BMD did not correlate with any of the above-mentioned hormonal variables. No difference was found in the parameters of HPA axis function in slow (loss of BMD <1%) vs fast (loss of BMD ≥3%) bone losers.

CONCLUSIONS

HPA axis may contribute to postmenopausal bone health, but differences in cortisol secretion do not influence the differential rate of bone loss between slow and fast bone losers in the early postmenopausal period, at least in healthy women.

Subclinical Cushing's syndrome: definition and management

Subclinical Cushing's syndrome is an ill-defined endocrine disorder that may be observed in patients bearing an incidentally found adrenal adenoma. The concept of subclinical Cushing's syndrome stands on the presence of ACTH-independent cortisol secretion by an adrenal adenoma, that is not fully restrained by pituitary feed-back. A hypercortisolemic state of usually minimal intensity may ensue and eventually cause harm to the patients in terms of metabolic and vascular diseases, and bone fractures. However, the natural history of subclinical Cushing's syndrome remains largely unknown. The present review illustrates the currently used methods to ascertain the presence of subclinical Cushing's syndrome and the surrounding controversy. The management of subclinical Cushing's syndrome, that remains a highly debated issue, is also addressed and discussed. Most of the recommendations made in this chapter reflects the view and the clinical experience of the Authors and are not based on solid evidence.

Children with Cushing's syndrome: Primary Pigmented Nodular Adrenocortical Disease should always be suspected

Primary Pigmented Nodular Adrenocortical Disease (PPNAD) is a rare form of bilateral adrenocortical hyperplasia that is inherited in an autosomal dominant manner and leads to ACTH-independent Cushing's syndrome (CS). PPNAD may be isolated or associated with Carney Complex (CNC). For the diagnosis of PPNAD and CNC, in addition to the hormonal and imaging tests, searching for PRKAR1A mutations may be recommended. The aims of the present study are to discuss the clinical and molecular findings of two Brazilian patients with ACTH-independent CS due to PPNAD and to show the diagnostic challenge CS represents in childhood. Description of two patients with CS and the many sequential steps for the diagnosis of PPNAD is provided. Sequencing analysis of all coding exons of PRKAR1A in the blood, frozen adrenal nodules (patients 1 and 2) and testicular tumor (patient 1) is performed. After several clinical and laboratory drawbacks that misled the diagnostic investigation in both patients, the diagnosis of PPNAD was finally established and confirmed through pathology and molecular studies. In patient 1, sequencing of PRKAR1A gene revealed a novel heterozygous 10-bp deletion in exon 3, present in his blood, adrenal gland and testicular tumor. The etiologic diagnosis of endogenous CS in children is a challenge that requires expertise and a multidisciplinary collaboration for its prompt and correct management. Although rare, PPNAD should always be considered among the possible etiologies of CS, due to the high prevalence of this disease in this age group.

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.

Inhibitory effect of prepro-thyrotrophin-releasing hormone (178-199) on adrenocorticotrophic hormone secretion by human corticotroph tumours

Prepro-thyrotrophin-releasing hormone (TRH) (178-199), a 22-amino acid cleavage product of the TRH prohormone, has been postulated to act as an adrenocorticotrophin hormone (ACTH)-release inhibitor. Indeed, although in vitro evidence indicates that this peptide may inhibit basal and stimulated ACTH secretion in rodent anterior pituitary primary cultures and cell lines, not all studies concur and no study has as yet evaluated the effect of this peptide in Cushing's disease. The present study aimed to test the effect of preproTRH(178-199) in human tumoural corticotrophs. Twenty-four human ACTH-secreting pituitary tumours (13 macroadenomas, 11 microadenomas) were collected during surgery and incubated with 10 or 100 nm preproTRH(178-199). ACTH secretion was assessed after 4 and 24 h of incubation by immunometric assay and expressed relative to levels observed in control, unchallenged wells (= 100%). Parallel experiments were performed in rat anterior pituitary primary cultures. A clear inhibition of ACTH secretion at 4 and 24 h was observed in 12 specimens (for 10 nm ppTRH: 70 +/- 4% control at 4 h and 83 +/- 5% control at 24 h; for 100 nm ppTRH: 70 +/- 4% control at 4 h and 85 +/- 5% control at 24 h), whereas a mild and short-lasting stimulatory effect was observed in three tumours and no changes in ACTH secretion in the remaining nine tumoural specimens. The inhibitory effect of preproTRH(178-199) was more evident in macroadenomas and significantly correlated with sensitivity to dexamethasone inhibition. Significant inhibition of ACTH secretion by preproTRH(178-199) in rat pituitary cultures was observed after 24 h of incubation. The present study conducted in a large series of human corticotroph tumours shows that preproTRH(178-199) inhibits tumoural ACTH secretion in a sizable proportion of specimens, in close relation to the size of the tumour and its sensitivity to glucocorticoid negative feedback. This appears a promising avenue of research and further studies are warranted to explore the full scope of preproTRH(178-199) as a regulator of ACTH secretion.

Hair analysis provides a historical record of cortisol levels in Cushing's syndrome

The severity of Cushing's Syndrome (CS) depends on the duration and extent of the exposure to excess glucocorticoids. Current measurements of cortisol in serum, saliva and urine reflect systemic cortisol levels at the time of sample collection, but cannot assess past cortisol levels. Hair cortisol levels may be increased in patients with CS, and, as hair grows about 1 cm/month, measurement of hair cortisol may provide historical information on the development of hypercortisolism. We attempted to measure cortisol in hair in relation to clinical course in six female patients with CS and in 32 healthy volunteers in 1 cm hair sections. Hair cortisol content was measured using a commercially available salivary cortisol immune assay with a protocol modified for use with hair. Hair cortisol levels were higher in patients with CS than in controls, the medians (ranges) were 679 (279-2500) and 116 (26-204) ng/g respectively (P<0.001). Segmental hair analysis provided information for up to 18 months before time of sampling. Hair cortisol concentrations appeared to vary in accordance with the clinical course. Based on these data, we suggest that hair cortisol measurement is a novel method for assessing dynamic systemic cortisol exposure and provides unique historical information on variation in cortisol, and that more research is required to fully understand the utility and limits of this technique.

Improved liquid chromatography-tandem mass spectrometry method in clinical utility for the diagnosis of Cushing's syndrome

Determination of urinary free cortisol is one of the first lines in screening for the diagnosis of Cushing's syndrome where its measurement is mostly done by immunoassay. Although easy to perform, immunoassays suffer from the problem of assay interferences and are unable to measure cortisone levels. To enhance such techniques for clinical diagnosis, an improved liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed for the simultaneous determination of urinary free cortisol and cortisone. The leftover urine samples from immunoassay were collected and subjected to facile solid-phase extraction cleanup. In the analysis of 130 urine samples from patients, 65 (50%) were found to have elevated urinary free cortisol (UFC) by immunoassay; but only 13 (10.8%) were found to have elevated UFC by this improved LC-MS/MS method. Nine out of the 13 patients, which showed elevated UFC by LC-MS/MS, were surgically confirmed to have Cushing's syndrome/disease. By setting a two times upper limit as a cut-off, the immunoassay gave a positive predictive value of 43.5%, whilst by using the improved method, a positive predictive value of 90% was obtained. Although several tests have been used extensively in first line screening for the diagnosis of Cushing's syndrome, none has ever shown with full capability of distinguishing all cases of Cushing's syndrome from normal and/or obese individuals. This method has shown superior analytical advantages over existing immunoassay type in terms of sensitivity, specificity and capability to diagnose Cushing's syndrome. Comparison between existing spectrometric methods, the reported developed method shown here, provides a simpler sample preparation procedure and meets with the high throughput demand of clinical laboratories.

Cortisol assays and diagnostic laboratory procedures in human biological fluids

The overview of cortisol physiology, action and pathology is achieved in relation to the hypothalamic-pituitary-adrenal axis alteration by laboratory investigation. The measurements of cortisol and related compound levels in blood, urine and saliva used to study the physiological and pathological cortisol involvement, are critically reviewed. The immunoassay and chromatographic methods for cortisol measurement in the various biological fluids are examined in relation to their analytical performances, reference ranges and diagnostic specificity and sensitivity. Moreover, blood, urine and saliva cortisol level measurements are described taking into account the diagnostic implications. The deduction is that each method requires the definition of its own reference range and its related diagnostic cut-off levels. Thus, this review, stressing the analysis procedures, could help to understand and compare the results of the different assays.

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.

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.