Serum cortisol concentrations during low dose dexamethasone suppression test to screen for Cushing's syndrome

The addition of corticotropin-releasing hormone to 2-day low dose dexamethasone suppression test provides additional case detection

ABSTARCT

PURPOSE: The diagnostic value of adding a Corticotropin-Releasing Hormone (CRH) Stimulation Test to the 2-day Low Dose Dexamethasone Suppression Test (Dex-CRH Test) has been debated in the literature.

METHODS

We identified 65 patients with Cushing disease (CD) and 42 patients in whom a diagnosis of Cushing disease could not be confirmed (NCD) after a minimum follow-up of 14 months who underwent the Dex-CRH test.

RESULTS

The female sex ratio, median (range) age, and BMI were similar between the two groups. The follow-up for patients with CD and NCD was 74 (4-233) and 52 (14-146) months, respectively. Among 65 patients with CD, 5 (7.7%) had a cortisol level ≤1.4 µg/dl after LDDST but were appropriately classified as CD with a cortisol level >1.4 µg/dL at 15-min post CRH stimulation. In contrast, 3/42 patients (7.1%) in NCD had an abnormal Dex-CRH test. In only one of three patients, the LDDST was marginally normal (cortisol was 1.4 µg/dL and increased to 3.1 µg/dL 15-min post CRH). A cortisol cutoff value of >1.4 µg/dL during the Dex-CRH test provided a sensitivity of 100%, specificity of 93%, and diagnostic accuracy of 97% to diagnose CD. When patients without a Dex level were excluded (n = 74), the sensitivity did not change, but the specificity and accuracy of the Dex-CRH test increased to 97 and 99%, respectively.

CONCLUSION

The Dex-CRH Test provided additional case detection in 5/65 (7.7%) patients with CD. It resulted in one false-positive case compared to LDDST. Measurement of dexamethasone improved diagnostic accuracy of the test.

Dynamic Tests in Pituitary Endocrinology: Pitfalls in Interpretation during Aging

Aging and age-related diseases represent hot topics of current research. Progressive damage in morphology and function of cells and tissue characterizes the normal process of aging that is influenced by both genetic and environmental factors. The ability of each individual to adapt to these stressors defines the type of aging and the onset of age-related diseases (i.e., metabolic syndrome, inflammatory disorders, cancer, and neurodegenerative diseases). The endocrine system plays a critical role in this process because of its complex relationships with brain, immune system, and skeletal muscle; thus, alterations in hormonal networks occur during aging to maintain homeostasis, with consequent under- or overactivity of specific hypothalamic-pituitary-peripheral hormone axes. On the other hand, the increase in life expectancy has led to increasing incidence of age-related diseases, including endocrine disorders, which may prompt assessment of endocrine function in aging individuals. In this context, there is growing awareness that natural changes of endocrine physiology and physiopathology occurring with increasing age may necessitate age-driven diagnostic cutoffs requiring validation in the elderly. This review aims to analyze the available literature on the hormone response to the most important dynamic tests currently used in the clinical practice for the screening of anterior pituitary-related diseases to underline pitfalls in interpretation during aging.

HPA axis regulation and epigenetic programming of immune-related genes in chronically stressed and non-stressed mid-life women

Hypothalamic-pituitary-adrenal (HPA) axis dysregulation has been associated with altered immune function, but the underlying molecular mechanisms are unclear. Epigenetic processes, including DNA methylation, respond to the glucocorticoid end-products of the HPA axis (cortisol in humans) and could be involved in this neuroendocrine-immune crosstalk. Here we examined the extent to which variations in HPA axis regulation are associated with peripheral blood DNA (CpG) methylation changes in 57 chronically stressed caregivers and 67 control women. DNA methylation was determined with the Illumina 450k array for a panel of genes involved in HPA axis and immune function. HPA axis feedback was assessed with the low-dose dexamethasone suppression test (DST), measuring the extent to which cortisol secretion is suppressed by the synthetic glucocorticoid dexamethasone. After multiple testing correction in the entire cohort, higher post-DST cortisol, reflecting blunted HPA axis negative feedback, but not baseline waking cortisol, was associated with lower DNA methylation at eight TNF and two FKBP5 CpG sites. Caregiver group status was associated with lower methylation at two IL6 CpG sites. Since associations were most robust with TNF methylation (32% of the 450k-covered sites), we further examined functionality of this epigenetic signature in cultured peripheral blood mononuclear cells in 33 participants; intriguingly, lower TNF methylation resulted in higher ex vivo TNF mRNA following immune stimulation. Taken together, our findings link chronic stress and HPA axis regulation with epigenetic signatures at immune-related genes, thereby providing novel insights into how aberrant HPA axis function may contribute to heightened inflammation and disease risk.

The population genomics of within-host Mycobacterium tuberculosis

Recent progress in genomic sequencing from patient samples has allowed for the first detailed insight into the within-host genetic diversity of Mycobacterium tuberculosis (M.TB), revealing remarkably low levels of variation. While this has often been attributed to low mutation rates, other factors have been described, including resistance evolution (i.e., selective sweeps), widespread purifying and background selection, and, more recently, progeny skew. Here we review recent findings pertaining to the processes governing the evolutionary dynamics of M.TB, discuss their implications for improving our understanding of this important human pathogen, and make recommendations for future work. Significantly, this emerging evolutionary framework involving the joint estimation of demographic, selective, and reproductive processes is forming a new paradigm for the study of within-host pathogen evolution that will be widely applicable across organisms.

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.

How useful is urinary-free cortisol in the clinic?

Measurement of 24-h urine-free cortisol is frequently employed as a first-line screening and disease-monitoring test in Cushing's syndrome (CS). The quest for ‘cortisol specificity’ has seen the emergence of mass spectrometry (MS) based assays, particularly liquid chromatography/tandem mass spectrometry. In contrast to traditional immunoassays, liquid chromatography/tandem mass spectrometry ‘free cortisol’ measurement is less susceptible to ‘interference’ from cortisol precursors and metabolites. However, detection of these conjugates is important in mild CS and therefore, missed by MS if cortisol alone is measured. MS assays nevertheless are capable of measuring broad steroid profiles, including the potential to distinguish benign from malignant adrenal-based CS and detection of exogenous glucocorticoids. Until this is routine practice, we recommend against abandoning immunoassays measurement of urine-free cortisol.

Pitfalls in the diagnosis and management of Cushing's syndrome

Despite many recent advances, the management of patients with Cushing's disease continues to be challenging. Cushing's syndrome is a complex metabolic disorder that is a result of excess glucocorticoids. Excluding the exogenous causes, adrenocorticotropic hormone-secreting pituitary adenomas account for nearly 70% of all cases of Cushing's syndrome. The suspicion, diagnosis, and differential diagnosis require a logical systematic approach with attention paid to key details at each investigational step. A diagnosis of endogenous Cushing's syndrome is usually suspected in patients with clinical symptoms and confirmed by using multiple biochemical tests. Each of the biochemical tests used to establish the diagnosis has limitations that need to be considered for proper interpretation. Although some tests determine the total daily urinary excretion of cortisol, many others rely on measurements of serum cortisol at baseline and after stimulation (e.g., after corticotropin-releasing hormone) or suppression (e.g., dexamethasone) with agents that influence the hypothalamic-pituitary-adrenal axis. Other tests (e.g., measurements of late-night salivary cortisol concentration) rely on alterations in the diurnal rhythm of cortisol secretion. Because more than 90% of the cortisol in the circulation is protein bound, any alteration in the binding proteins (transcortin and albumin) will automatically influence the measured level and confound the interpretation of stimulation and suppression data, which are the basis for establishing the diagnosis of Cushing's syndrome. Although measuring late-night salivary cortisol seems to be an excellent initial test for hypercortisolism, it may be confounded by poor sampling methods and contamination. Measurements of 24-hour urinary free-cortisol excretion could be misleading in the presence of some pathological and physiological conditions. Dexamethasone suppression tests can be affected by illnesses that alter the absorption of the drug (e.g., malabsorption, celiac disease) and by the concurrent use of medications that interfere with its metabolism (e.g., inducers and inhibitors of the P450 enzyme system). In this review, the authors aim to review the pitfalls commonly encountered in the workup of patients suspected to have hypercortisolism. The optimal diagnosis and therapy for patients with Cushing's disease require the thorough and close coordination and involvement of all members of the management team.

Cushing's syndrome in type 2 diabetes patients with poor glycemic control

Cushing's syndrome may be more frequent in some specific patient groups such as type 2 diabetes and obesity. The aim of this study was to investigate the prevalence of Cushing's syndrome in outpatients with type 2 diabetes with poor glycemic control despite at least 3-months insulin therapy. Outpatients with type 2 diabetes whose glycemic control is poor (Hb Alc value >7 %) despite receiving at least 3-months long insulin treatment (insulin alone or insulin with oral antidiabetics) were included. Patients with classic features of Cushing's syndrome were excluded. Overnight 1 mg dexamethasone suppression test (DST) was performed as a screening test. A total of 277 patients with type 2 diabetes whose glycemic control is poor (Hb Alc value >7 %) despite insulin therapy were included. Two of the 277 patients with type 2 diabetes were diagnosed with Cushing's syndrome (0.72 %). Hypertension was statistically more frequent in the patients with cortisol levels ≥1.8 μg/dL than the patients with cortisol levels <1.8 μg/dL after overnight 1 mg DST (p = 0.041). Statistically significant correlation was determined between cortisol levels after 1 mg DST and age, daily insulin dose (r = 0.266 and p < 0.001, r = 0.163 and p = 0.008, respectively). According to our findings, the prevalence of Cushing's syndrome among patients with type 2 diabetes with poor glycemic control despite insulin therapy is much higher than in the general population. The patients with type 2 diabetes with poor glycemic control despite at least three months of insulin therapy should be additionally tested for Cushing's syndrome if they have high dose insülin requirements.

Cushing's disease, pseudo-Cushing states and the dexamethasone test: a historical and critical review

The dexamethasone (DXM) test has been widely used for diagnosing Cushing's disease (CD). The purpose of this paper is to review its diagnostic merit based on calculation of data extracted from earlier publications. Studies presenting individual values for patients with CD and normal subjects were identified through PubMed searches and references in pertinent studies. Calculation of the retrieved data demonstrated huge variation in the relative suppressibility, negative suppression being common. Furthermore, in almost each study retrieved, the pre and post DXM values were closely correlated. Finally, the generally accepted view that DXM causes less suppression in Cushing's disease than in euadrenal controls appears unfounded. A central issue in the definition of so-called "pseudo-Cushing's states" is failure to suppress cortisol secretion with DXM. From analysis of the literature it appears quite possible that this does not reflect a specific endocrine deficit, but a physiological "stress" reaction. The above issues question the diagnostic value of the test, in particular in clinically and biochemically borderline cases.

Is there value in routine screening for Cushing's syndrome in patients with diabetes?

CONTEXT

Subclinical Cushing's syndrome has been described among diabetic populations in recent years, but no consensus has emerged about the value of screening.

METHODS

We enrolled 201 consecutive patients attending our diabetes clinic and 79 controls. Patients with at least two of the following three criteria were offered screening using a 2300 h salivary cortisol test: glycosylated hemoglobin of at least 7%, body mass index of at least 25 kg/m(2), and a history of hypertension or blood pressure of at least 140/90 mm Hg. Results are expressed as mean +/- sem.

RESULTS

Mean nighttime salivary cortisol levels were similar in the two groups (8.5 +/- 1.0 nmol/liter for diabetic patients vs. 5.8 +/- 1.0 nmol/liter for controls). Forty-seven patients (23%) had a value of at least 10 nmol/liter, which was set as a conservative threshold above which further investigation would be performed. Thirty-five (75%) agreed to further testing with a 1-mg overnight dexamethasone test. Of the remaining 12 patients, 10 were followed up clinically for at least 1 yr, and no evidence was found of the syndrome evolving. In 28 patients, serum cortisol suppressed to 60 nmol/liter or less. Of the seven patients who failed this test, four agreed to a 2 mg/d 48-h dexamethasone test, with serum cortisol suppressing to 60 nmol/liter or less in all four. Three declined this test but had normal 24-h urinary free cortisol levels. No patient had clinical features of hypercortisolism.

CONCLUSIONS

The 1-3% detection rates of three recently published series have not been realized at our center where we studied a group using criteria making patients more likely to have hypercortisolism. Our results do not support the validity of screening patients without clinical features of Cushing's syndrome in the diabetes clinic.

Subclinical hypercortisolism among polycythemia vera patients

BACKGROUND

JAK2V617F, a somatic gain-of-function mutation involving the JAK2 tyrosine kinase gene, occurs in nearly all patients with polycythemia vera (PV). JAK2 is also essential in hypothalamo-pituitary-adrenal (HPA) axis system which is known to play a role in subsequent steroid secretion. The purpose of this study was to determine whether or not PV induces subclinical hypercortisolism (SH).

DESIGN

Cross-sectional study. In order to compare the prevalence of SH in PV and matched control individuals, we performed a case-controlled study, enrolling 31 PV and 20 age- and body mass index-matched patients.

METHODS AND RESULTS

Adrenal endocrine function was assessed in a cohort of 31 patients with PV. Baseline serum cortisol levels and 2-day 2 mg DST (dexamethasone suppression test, 0.5 mg dexamethasone orally every 6 hours for two days) showed a trend for higher serum cortisol levels in PV patients than in control subjects. Among the 31 patients, 6 had biological abnormality of the hypothalamic-pituitary-adrenal axis and were diagnosed as subclinical hypercortisolism. None of the subjects in the control group exhibited cortisol responses to DST higher than 50 nmol/L.

DISCUSSION

In conclusion, a relatively high prevalence of hypercortisolism was found in PV patients. As these observations were in a small cohort of PV, further studies are needed to evaluate HPA axis in PV patients.

The diagnosis of Cushing's syndrome: an Endocrine Society Clinical Practice Guideline

OBJECTIVE

The objective of the study was to develop clinical practice guidelines for the diagnosis of Cushing's syndrome.

PARTICIPANTS

The Task Force included a chair, selected by the Clinical Guidelines Subcommittee (CGS) of The Endocrine Society, five additional experts, a methodologist, and a medical writer. The Task Force received no corporate funding or remuneration.

CONSENSUS PROCESS

Consensus was guided by systematic reviews of evidence and discussions. The guidelines were reviewed and approved sequentially by The Endocrine Society's CGS and Clinical Affairs Core Committee, members responding to a web posting, and The Endocrine Society Council. At each stage the Task Force incorporated needed changes in response to written comments.

CONCLUSIONS

After excluding exogenous glucocorticoid use, we recommend testing for Cushing's syndrome in patients with multiple and progressive features compatible with the syndrome, particularly those with a high discriminatory value, and patients with adrenal incidentaloma. We recommend initial use of one test with high diagnostic accuracy (urine cortisol, late night salivary cortisol, 1 mg overnight or 2 mg 48-h dexamethasone suppression test). We recommend that patients with an abnormal result see an endocrinologist and undergo a second test, either one of the above or, in some cases, a serum midnight cortisol or dexamethasone-CRH test. Patients with concordant abnormal results should undergo testing for the cause of Cushing's syndrome. Patients with concordant normal results should not undergo further evaluation. We recommend additional testing in patients with discordant results, normal responses suspected of cyclic hypercortisolism, or initially normal responses who accumulate additional features over time.

Dynamic testing in Cushing's syndrome

Endogenous Cushing's syndrome (CS) results from chronic exposure to excess glucocorticoids. CS can be ACTH-dependent, caused by ACTH-secreting pituitary or ectopic tumours, or ACTH-independent, caused by cortisol-secreting adrenal tumours. CS can be an extremely difficult diagnosis to make, and assessment will include clinical, biochemical and radiological evaluation. Several screening tests are used for the confirmation of hyper-cortisolaemia and its differentiation from other, more frequent, clinical abnormalities, such as simple obesity, hypertension, depression etc. Other dynamic tests are useful for establishing the aetiology. We have reviewed the current literature on the diagnosis of CS, and based on these data and our own experience, suggest the most useful tests and diagnostic criteria to be used. We conclude that even though laboratory testing is a fundamental part of the investigation of patients with CS, the interpretation of the tests should always be performed with extreme care, as none of the tests has proven fully capable of distinguishing all cases of CS. The biochemical results should be interpreted jointly with the clinical aspects and the radiology findings in a probabilistic matrix, and not as part of a uniform algorithm.

The dexamethasone-suppressed corticotropin-releasing hormone stimulation test and the desmopressin test to distinguish Cushing's syndrome from pseudo-Cushing's states

OBJECTIVE

Cushing's syndrome (CS), when fully expressed, is easily diagnosed. Mild cases, however, may require careful distinction from pseudo-Cushing's states as may occur in depression, alcoholism, polycystic ovary disease and visceral obesity. The aim of the present study is a reappraisal of the diagnostic accuracy of the two tests most commonly used to differentiate CS from pseudo-Cushing's: corticotropin-releasing hormone (CRH) stimulation after low dose dexamethasone administration and desmopressin stimulation.

DESIGN

The study population comprised 32 patients with CS and 23 with pseudo-Cushing's evaluated retrospectively.

METHODS

Urinary free cortisol (UFC), serum cortisol at midnight and after low dose dexamethasone (1 mg overnight and 2 mg over two days) were measured. Further, patients were tested with dexamethasone + CRH and desmopressin and the diagnostic performances of the two tests were compared in the entire series as well as in patients with mild hypercortisolism only (i.e. UFC < 690 nmol/24 h).

RESULTS

As expected, measurement of UFC, assessment of cortisol rhythmicity and inhibition after 1 mg/2 mg dexamethasone failed to clearly classify patients with pseudo-Cushing's. Administration of CRH following 2-mg dexamethasone achieved 100% sensitivity but 62.5% specificity. Conversely, desmopressin testing correctly classified all but two patients with pseudo-Cushing's (90% specificity) with 81.5% sensitivity. Diagnostic accuracy was comparable in the subgroup with mild hypercortisolism (21 CS, all 23 pseudo-Cushing's patients). Desmopressin offered an incremental diagnostic effectiveness of 35.8/million inhabitants compared with dexamethasone + CRH as a second-line test.

CONCLUSIONS

Neither of the two tests guarantees absolute diagnostic accuracy. The specificity of dexamethasone + CRH is less brilliant than previously reported and appears to be inferior to desmopressin stimulation. The greatest diagnostic effectiveness results from the low-dose dexamethasone test combined with the desmopressin test. Skilful use of dynamic testing and balanced clinical judgement are necessary to distinguish between Cushing's syndrome and pseudo-Cushing's.

Long-term remission rates after pituitary surgery for Cushing's disease: the need for long-term surveillance

OBJECTIVE

There have been a few reports on long-term remission rates after apparent early remission following pituitary surgery in the management of Cushing's disease. An undetectable postoperative serum cortisol has been regarded as the result most likely to predict long-term remission. Our objective was to assess the relapse rates in patients who underwent transsphenoidal surgery in order to determine whether undetectable cortisol following surgery was predictive of long-term remission and whether it was possible to have long-term remission when early morning cortisol was measurable but not grossly elevated. Endocrinological factors associated with late relapse were also studied.

PATIENTS

We reviewed the long-term outcome in 63 patients who had pituitary surgery for the treatment of Cushing's disease between 1979 and 2000.

MEASUREMENTS

Case notes were reviewed and the current clinical and biochemical status assessed. Our usual practice was that early after the operation, an 08:00 h serum cortisol was measured 24 h after the last dose of hydrocortisone. This was followed by a formal low-dose dexamethasone suppression test. Current clinical status and recent 24-h urinary free cortisol values were used as an index of activity of the Cushing's disease. If there was evidence suggesting relapse, a low-dose dexamethasone suppression test was performed. In many patients, sequential collections of early morning urine specimens for urinary cortisol to creatinine ratio were also performed in an attempt to diagnose cyclical and intermittent forms of recurrent hypercortisolism. We did this if there was conflicting endocrine data, or if patients were slow to lose abnormal clinical features.

RESULTS

Mean age at diagnosis was 40.3 years (range 14-70 years). Mean follow-up up time was 9.6 years (range 1-21 years). Forty-five patients (9 males/36 females) achieved apparent remission immediately after surgery and were subsequently studied long term. Of these 45 patients, four have subsequently died while in remission from hypercortisolism. Ten of the remaining 41 patients have relapsed. Of those 10, six demonstrated definite cyclical cortisol secretion. Two of the 10 had undetectable basal serum cortisol levels in the immediate postoperative period. Thirty-one patients are still alive and in remission. Fourteen (45%) of the 31 who remained in remission had detectable serum cortisol levels (> 50 nmol/l) immediately postoperatively, and remain in remission after a mean of 8.8 years. Our relapse rate was therefore 10/45 (22%), after a mean follow-up time of 9.6 years, with mean time to relapse 5.3 years.

CONCLUSIONS

The overall remission rate of 56% (35/63) at 9.6 years follow-up is disappointing and merits some re-appraisal of the widely accepted principle that pituitary surgery must be the initial treatment of choice in pituitary-dependent Cushing's syndrome. Following pituitary surgery, careful ongoing expert endocrine assessment is mandatory as the incidence of relapse increases with time and also with increasing rigour of the endocrine evaluation. A significant number of our patients were shown to have relapsed with a cyclical form of hypercortisolism.

Discriminatory value of the low-dose dexamethasone suppression test in establishing the diagnosis and differential diagnosis of Cushing's syndrome

Cushing's syndrome requires a screening test of high sensitivity, followed by biochemical evaluation of the source of the tumor when the cause is ACTH dependent. The high-dose dexamethasone suppression test is still in common use as an aid in differential diagnosis, although its value has been queried. We have routinely used the low-dose dexamethasone suppression test for many years in the diagnosis of Cushing's syndrome but noticed that patients with pituitary-dependent Cushing's syndrome or Cushing's disease, usually showed some degree of suppression of their serum cortisol, compared to those with the ectopic ACTH syndrome. We therefore analyzed retrospectively the serum cortisol responses during the low-dose dexamethasone suppression test and the high-dose dexamethasone suppression test in 245 patients with ACTH-dependent Cushing's syndrome and compared the diagnostic utility of each test either alone or in combination with a standard test using CRH. Evaluation of the serum cortisol response at 24 and 48 h during the low-dose dexamethasone suppression test correctly identified 98% of patients with ACTH-dependent Cushing's syndrome and distinguished between pituitary and ectopic causes with a sensitivity of 82% and a specificity of 79%. In the same patients, the serum cortisol response to the high-dose dexamethasone suppression test had a slightly higher sensitivity (91%) and specificity (80%). However, the combined criteria of a more than 30% suppression of serum cortisol during the low-dose dexamethasone suppression test and/or a more than 20% increase in the CRH test had a significantly higher sensitivity (97%) and specificity (94%) than either the high-dose dexamethasone or the CRH tests alone in the differential diagnosis of ACTH-dependent Cushing's syndrome. It produced equivalent information to that when high-dose and CRH test results were combined. We therefore conclude that in our patient series, the serum cortisol response during the low-dose dexamethasone suppression test is highly sensitive in diagnosing Cushing's syndrome and, combined with the results of the serum cortisol response to the CRH test, offered a safe and cost-effective test in the differential diagnosis of ACTH-dependent Cushing's syndrome. There does not appear to be any necessity for retaining the high-dose dexamethasone suppression test in this diagnostic work-up.

Screening for Cushing's syndrome in obese women with and without polycystic ovary syndrome

Obesity and insulin resistance, menstrual abnormalities and clinical and biochemical signs of hyperandrogenism are common features in women with polycystic ovary syndrome (PCOS) and Cushing's syndrome (CS). Further, an overdrive of the pituitary-adrenal axis has been documented in PCOS and this condition is often present in women with CS. For this reason, screening for hypercortisolism is often needed in obese women with polycystic ovaries. The aim of this study was to compare the diagnostic value of different screening tests for CS in a population of obese premenopausal women with PCOS and without PCOS (OB) and in a group of patients with CS. We reviewed retrospectively the case records of 117 obese women of reproductive age (60 PCOS and 57 OB, BMI 25.1-70.1, 13-45 yr) who were screened for CS at our Institution in the years 1995-2001 and turned out to be free of the disease. Data were compared with those of 58 premenopausal obese women with active CS (BMI 25.1-50.2 kg/m2, 18-45 yr). Screening for CS was performed by urinary free cortisol (UFC) (three consecutive 24-h urine collections), cortisol circadian rhythm (blood samples taken at 08:00-17:00-24:00 h), and 1 mg overnight dexamethasone suppression test (DST). A 24:00 h plasma cortisol (MNC) of 207 nmol/l, a UFC of 221 nmol/day and plasma cortisol after DST of 50 nmol/l and 138 nmol/l were taken as cut-off values for the diagnosis of CS. As expected, patients with CS showed elevated basal and post-dexamethasone plasma cortisol and UFC levels (p < 0.001 vs OB and PCOS). PCOS had higher UFC (p < 0.005) but not MNC and post-DST plasma cortisol levels compared to OB. DST showed the greatest specificity and diagnostic accuracy in differentiating CS from PCOS and OB (both p < 0.05 vs MNC and UFC, according to the 138 nmol/l criterion) while MNC and UFC displayed a similar discriminatory value. However, by using a lower threshold (50 nmol/l) as response criterion, there were no diagnostic differences between DST and the other tests. Specificity and diagnostic accuracy of UFC measurement was lower in PCOS than in OB (both p < 0.05) whilst there were no differences between groups for DST and MNC. Similarly, the area under the ROC curve relative to DST, giving an estimate of the inherent diagnostic accuracy of the test, was slightly greater than those of MNC and UFC (z = 0.694 and z = 0.833 for DST vs MNC and UFC, respectively, both p = NS). These results indicate that the 1-mg DST and MNC are unaffected by the presence of PCOS and can be safely used to screen for CS premenopausal obese women with PCOS, while caution should be exercised in interpreting mildly elevated UFC levels in these patients.

Ectopic pro-opiomelanocortin syndrome

Ectopic POMC syndrome remains one of the most challenging differential diagnoses in endocrinology. Recent progress in the understanding of the tissue specific regulation of POMC gene expression and new insights into the processing of the POMC peptide in nonpituitary tissues has helped elucidate some of the molecular events leading to ectopic expression and secretion of POMC peptides. Corticotropin and other POMC-derived peptides have diverse effects on adrenal steroidogenesis, growth, and extra-adrenal tissues. Differences in POMC gene regulation in the corticotrope versus ectopic POMC-producing tumors provides a scientific framework for the clinical distinction between eutopic and ectopic Cushing's syndrome. In an attempt to revisit recent basic and clinical advances in the diagnosis of ectopic POMC syndrome the authors undertook an extensive literature review of 530 cases in 197 published papers and provided a molecular biologic, demographic and diagnostic update. According to this review, the four most common causes of ectopic POMC syndrome are the small cell carcinoma of the lung (27%), bronchial carcinoids (21%), islet cell tumor of the pancreas (16%), and thymic carcinoids (10%). Although the clinical features of patients with ectopic POMC syndrome are similar to those with Cushing's disease, subgroup analysis reveals a broad spectrum of severity and progression of signs and symptoms of hypercortisolism. The endocrine workup of a patient with suspected ectopic POMC syndrome includes the establishment of pathologic hypercortisolism, diagnosis of corticotropin dependency, and the differential diagnosis of corticotropin-dependent Cushing's syndrome. The use of a variety of baseline endocrine values, dynamic endocrine testing, and invasive procedures leads to the correct diagnosis in the majority of patients with ectopic POMC syndrome. Diagnostic imaging, including conventional radiological techniques and somatostatin receptor scintigraphy, aids in the correct localization and eventual treatment of ectopic POMC production.

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.

Bilateral inferior petrosal sinus sampling in the differential diagnosis of adrenocorticotropin-dependent Cushing's syndrome: a comparison with other diagnostic tests

To compare bilateral inferior petrosal sinus sampling (IPSS) with high dose dexamethasone (HDD) and CRH testing (using recently proposed stringent response criteria) in the differential diagnosis of ACTH-dependent Cushing's syndrome, we reviewed 53 consecutive cases. The main analysis was limited to 45 cases with confirmed diagnosis: 44 with pituitary dependency, proven by confirmatory histology and/or significant biochemical improvement after pituitary surgery, and 1 with ectopic ACTH syndrome. After HDD (2 mg every 6 h for 48 h), 21 of the 44 pituitary cases met the stringent more than 90% suppression criterion. Twenty-three of the 44 pituitary cases also underwent CRH testing; 16 of 23 met a stringent response criterion of a more than 50% serum cortisol rise. For HDD and CRH testing combined, 8 of 23 fulfilled both stringent criteria, 10 of 23 had discordant results, and 5 of 23 failed to fulfil either of the stringent criteria for pituitary dependency. IPSS was performed in all 44 of the proven pituitary cases; 36 had petrosal/peripheral ACTH ratios of 2.0 or more without CRH stimulation. Thus, in patients with proven pituitary disease, stringent response criteria to HDD and CRH testing were fulfilled by only 48% and 70%, respectively. IPSS, which gave direct evidence of pituitary ACTH secretion in 82% of the cases, is therefore considered necessary in a significant proportion of cases.

The low-dose dexamethasone suppression test in patients with adrenal incidentalomas: comparisons with clinically euadrenal subjects and patients with Cushing's syndrome

OBJECTIVE

Increasing evidence favours subtle glucocorticoid excess in many patients with adrenal incidentalomas. However, existing evidence is based mainly on the overnight dexamethasone suppression test, a test that is commonly abnormal even among clinically euadrenal subjects. The aim of the present study was to evaluate patients with adrenal incidentalomas for subtle glucocorticoid excess by the more specific low-dose dexamethasone test (LDDST). Moreover, since the criteria of what constitutes an abnormal cortisol response following this test have been largely anecdotal, we report our results in comparison with those obtained in clinically euadrenal subjects, and patients with Cushing's syndrome.

DESIGN

A prospective study of 57 patients with adrenal incidentalomas with CT characteristics highly suggestive of benign adrenocortical adenomas and 85 clinically euadrenal subjects consisting of 54 obese women with BMI > 30 kg/m2 (range 30-54.7), 13 women with BMI < 30 kg/m2 (range 20.3-29.6) and 18 healthy volunteers (10 women and eight men) over 40 years of age (mean age 51.7 +/- 9.9, range 40-74; mean BMI 30 +/- 6.6, range 20.3-47.5 kg/m2). A retrospective analysis was performed on 60 patients with a confirmed diagnosis of Cushing's syndrome.

MEASUREMENTS

All subjects were admitted to the endocrine ward and underwent a standard LDDST, as follows: after a 48-h stabilization period, a 24-h urine collection for basal urinary free cortisol was performed. Basal serum cortisol and plasma ACTH were measured at 0800 h the following day, and subjects were started on dexamethasone 0.5 mg 6-hourly for 2 days. Post-dexamethasone cortisol and ACTH levels were measured at 0800 h, 6 h after the last dose of dexamethasone.

RESULTS

Following dexamethasone suppression serum cortisol concentrations became undetectable (< 28 nmol/l) in all clinically euadrenal subjects. In patients with incidentally discovered adrenal masses, post-LDDST cortisol concentrations were undetectable in 12 (21%), between 28-140 nmol/l in 38 (67%), and 140-216 nmol/l in seven (12%) patients; post-LDDST cortisol values correlated positively with the size of the adenoma (r = +0.482, P < 0.001). Post-LDDST cortisol concentrations in patients with Cushing's syndrome ranged from 85 to 1786 nmol/l; in 3/42 (7%) patients with ACTH-dependent Cushing's syndrome cortisol concentrations were < 140 nmol/l.

CONCLUSIONS

On the basis of our data in a large group of clinically euadrenal subjects, we suggest that following LDDST cortisol concentrations should become undetectable with the currently used radioimmunoassays. In patients with adrenal incidentalomas, application of the LDDST confirmed the presence of incomplete suppression of cortisol in the majority of patients. We suggest that the LDDST is a sensitive index of autonomous cortisol production in patients with adrenal incidentalomas; following this test a grading of subtle glucocorticoid excess may be obtained but future studies correlating biochemical, clinical and epidemiological data are required, in order to develop widely agreed cut-off levels of clinically significant glucocorticoid excess in these patients.

Cushing's syndrome in childhood and adolescence

OBJECTIVE

To review the diagnosis, management and outcome of Cushing's syndrome in children and adolescents.

METHODS

We conducted a retrospective review of nine cases treated between 1976 and 1996 at the Royal Children's Hospital, Melbourne, Australia.

RESULTS

Six children with Cushing's disease and three with primary adrenal disease were identified. Mean age at diagnosis in the Cushing's disease patients was 11.3 years and in the children with primary adrenal disease 9.5 years. The most common presenting symptoms were weight gain and delayed growth. Two children had the unusual presenting symptoms of an eating disorder and hemihypertrophy, respectively. Laboratory diagnosis of Cushing's syndrome was established by demonstration of elevated urine free cortisol, loss of normal diurnal variation of serum cortisol, and loss of suppressibility of cortisol secretion by low dose dexamethasone. Investigations used to determine the aetiology of hypercortisolism included serum adrenocorticotropic hormone (ACTH) levels, high dose dexamethasone suppression tests, imaging studies, and inferior petrosal sinus sampling. Four patients with Cushing's disease had successful transphenoidal adenomectomies. Two patients with bilateral primary pigmented nodular adrenocortical dysplasia underwent bilateral adrenalectomies. One child with an adrenal adenoma was treated by left adrenalectomy.

CONCLUSIONS

Cushing's syndrome in children and adolescents remains a diagnostic challenge. Successful treatment often requires the use of multiple tests to achieve the correct diagnosis, appropriate surgery and a good long-term outcome.

A single sleeping midnight cortisol has 100% sensitivity for the diagnosis of Cushing's syndrome

OBJECTIVE

The diagnosis of Cushing's syndrome remains a major challenge in clinical endocrinology. Various screening tests are commonly used to support a biochemical diagnosis in the context of clinical suspicion. The aim of this study was to compare the sensitivity in the diagnosis of Cushing's syndrome of a single in-patient sleeping midnight cortisol to a standard 48-hour in-patient low-dose dexamethasone suppression test (LDDST) during the same admission.

DESIGN

A retrospective analysis was performed on 150 patients investigated in our department between the years 1970 and 1994 with a confirmed diagnosis of Cushing's syndrome.

PATIENTS

One hundred and fifty patients with a diagnosis of Cushing's syndrome were analysed: 110 with Cushing's disease; 12 with tumours with ectopic ACTH secretion; 8 with ACTH dependent Cushing's syndrome of so far undetermined origin; 17 with cortisol secreting adrenal tumours; 3 with adrenocortical nodular hyperplasia. Twenty normal volunteers and nine patients with non-endocrine conditions were also investigated as controls.

MEASUREMENTS

Plasma cortisol was measured by radioimmunoassay (RIA) in the 122 patients presenting after 1980, and by fluorimetry prior to this date.

RESULTS

In all the control subjects the sleeping midnight cortisol was < 50 nmol/l, below the lowest standard of the routine in-house RIA. In every patient with Cushing's syndrome the sleeping midnight cortisol was detectable with a value greater than 50 nmol/l, with a range of 70-2000 nmol/l. In contrast, in three cases, all of whom had proven Cushing's disease on histology, there was uncharacteristic complete suppression of plasma cortisol to < 50 nmol/l following the LDDST.

CONCLUSION

In this series of 150 cases, a single in-patient sleeping midnight cortisol above 50 nmol/l had a 100% sensitivity for the diagnosis of Cushing's syndrome, clearly different from normal subjects. In contrast, the low-dose dexamethasone suppression test had a sensitivity of 98% even when the drug was administered as an in-patient. We recommend that a low-dose dexamethasone suppression test should not be used alone for confirmation of Cushing's syndrome since it may miss 2% of cases.

Bilateral adrenalectomy: low mortality and morbidity in Cushing's disease

OBJECTIVE

We assessed the current role of bilateral adrenalectomy in the overall management strategy of hypercortisolism.

DESIGN

Retrospective review of case notes.

PATIENTS

Twenty-six patients (20F/6M); mean age 46 years (range 15-70 years), median duration of follow-up 5.25 years (0.6-19.1 years) who had undergone bilateral adrenalectomy at the Royal Victoria Hospital since 1972. Eighteen had had prior transsphenoidal surgery which did not control the hypercortisolism.

MEASUREMENTS

Morbidity, mortality, incidence of Nelson's syndrome.

RESULTS

Surgery was performed through bilateral postero-lateral incisions (20 patients) or a long epigastric incision (six patients). The mean combined weight of the adrenals at surgery was 11.2 g. Twenty patients received subcutaneous heparin and 18 antibiotic prophylaxis peri and post-operatively. There was no operative mortality. Minor complications included one post-operative wound infection and a small pneumothorax requiring drainage. Major complications occurred in two other patients, both with pre-existing invasive pituitary tumours and considered at high risk because of age and general debility. One patient had a massive pulmonary embolus and the other a subphrenic abscess post-operatively. This latter patient, the only mortality, died from an unrelated cause three years post-operatively. Six patients have subsequently undergone pituitary surgery and three have received external pituitary irradiation therapy for expanding tumours.

CONCLUSIONS

Bilateral adrenalectomy, in experienced hands, is a relatively safe and useful management option in patients with hypercortisolism. Growth of a pituitary adenoma post-operatively is now the most worrying complication.

Assessment of endocrine function after transsphenoidal surgery for Cushing's disease

OBJECTIVE

We assessed the endocrine outcome after transsphenoidal surgery for Cushing's disease.

DESIGN

Five-year (mean) follow-up (range 1 month-12 years) of patients undergoing transsphenoidal surgery for Cushing's disease between 1977 and 1990; review of case notes, current clinical and biochemical assessment including 24-hour urinary free cortisol.

SETTING

Northern Ireland.

SUBJECTS

Forty-one patients (33F: 8M); mean age at diagnosis 39.1 years (9-72 years).

MAIN OUTCOME MEASURES

Measurements of early post-operative 0800 h serum cortisol and 24-hour urinary free cortisol at least 24 hours after withdrawal of oral hydrocortisone therapy. This was followed by low dose dexamethasone testing. Current 24-hour urinary free cortisol measurements. Retrospective definition of cure.

RESULTS

Twenty-seven patients were either cured or improved by surgery, 14 were considered definite failures. Of 19 patients cured, eight had unmeasurable early post-operative 0800 h serum cortisol levels while of 15 tested, 13 had complete suppression with dexamethasone and two suppressed normally but to still measurable levels (39 and 60 nmol/l respectively). Seventeen patients in total have subsequently had bilateral adrenalectomy of whom two have developed Nelson's syndrome. Seven of the 41 patients were shown to have definite cyclical cortisol secretion first diagnosed post-operatively in three patients. Hormone deficiency included TSH (5), LH/FSH (1), cortisol (1) and ADH (temporary in 7, permanent in 1). In all, seven patients had some type of permanent hormonal deficiency post-operatively.

CONCLUSIONS

Transsphenoidal surgery offers a worthwhile cure rate without the necessity of life-long endocrine therapy. Post-operative endocrine assessment must be rigorous so that early further management can be planned in the significant percentage of patients in whom cure is not achieved. Early complete suppression on low dose dexamethasone testing is very suggestive of cure but repeated and long-term monitoring of 24-hour urinary free cortisol is advisable.

Cyclical Cushing's syndrome first diagnosed after pituitary surgery: a trap for the unwary

Three patients were studied after transsphenoidal microsurgery for Cushing's disease because their symptoms and signs were slow to settle and/or because they had variable endocrine results. All were established as having cyclical Cushing's syndrome, first diagnosed post-operatively. This may be a much more common finding than previously realized and emphasizes the need for detailed and ongoing endocrinological investigation after transsphenoidal surgery for Cushing's disease.

Endocrine function in patients with Cushing's disease before and after treatment

OBJECTIVE

To estimate the value of some commonly used tests in diagnosing Cushing's disease and to assess the outcome after treatment.

DESIGN

Follow-up of a consecutive group of patients for 4.1 to 109.6 months, median 34.4.

PATIENTS

Forty-six patients assumed to have ACTH dependent hypercorticism (of 50 patients with Cushing's syndrome) were included. Forty-five underwent transsphenoidal neurosurgery. Ten were treated preoperatively with radiotherapy.

MEASUREMENTS

Pituitary, adrenal, thyroid and gonadal function, radiology and pituitary histology were evaluated.

RESULTS

One main finding was a significant correlation between the urinary excretion of cortisol before and during administration of dexamethasone. Thus patients with modestly elevated urinary cortisol excretion had an apparently normal suppression. The urinary cortisol values during the dexamethasone test were significantly related to the peak plasma cortisol concentrations at the 30-minute ACTH tests. Computed tomography failed to identify an adenoma in 10 of the 19 patients who were histologically proved to harbour a corticotroph adenoma. At 6 months after radiotherapy, clinical and biochemical improvement was noted in none. Cure was achieved in 36 after neurosurgery. Eventually, adrenalectomy was needed in eight patients. Sixteen patients developed persisting adrenal insufficiency after neurosurgery so that the total number of patients on permanent steroid substitution was 24. Post-operative thyroid and gonadal insufficiency (in men and women of fertile age) was found in 36 and 49%, respectively.

CONCLUSIONS

The diagnostic value of measuring the cortisol excretion during dexamethasone administration appears doubtful. The outcome after neurosurgical treatment for Cushing's disease is not entirely satisfactory. Further studies are needed to decide whether adrenalectomy as the first line of therapy should be considered relevant in some patients with Cushing's disease.

The overnight dexamethasone test is a worthwhile screening procedure

The overnight low-dose dexamethasone test is a convenient screening procedure for Cushing's syndrome. Claims that the test is associated with a high incidence of 'false positives', rendering it of little value particularly in obese and hospital in-patients, have been investigated in the present study. The data from 100 consecutive subjects undergoing overnight low-dose dexamethasone tests to examine for the possibility of Cushing's syndrome, were reviewed. Cushing's syndrome was identified in four patients, normal suppression of cortisol values occurred in 84 patients and 12 patients exhibited false positive results. Differences in body weights, body mass indices or in-patient status did not distinguish between those subjects with normal suppression of plasma cortisol and those subjects who yielded false positive results. These data indicate that the simple overnight dexamethasone test substituted for the more cumbersome traditional 48-h dexamethasone test in 84 of 96 patients who did not have Cushing's syndrome. Thus the overnight test provides a useful screening procedure but a small percentage of patients, approximately 12.5%, will require additional procedures to exclude Cushing's syndrome.

Cushing's syndrome

Cushing's syndrome remains one of the most challenging problems in clinical endocrinology. Cushing's disease is caused in the majority of cases by basophil pituitary microadenomas which may be successfully treated by trans-sphenoidal hypophysectomy. Treatment with metyrapone or o,p'-DDD can always induce a clinical remission but not a cure, and neurotransmitter therapy may be effective in a minority of cases. Pituitary irradiation cures about half of cases in the long-term and may be used for surgical failures. Tumours producing ectopic ACTH are frequently benign, small and occult and may produce a syndrome clinically indistinguishable from Cushing's disease. Biochemical investigations cannot absolutely distinguish pituitary from ectopic sources of ACTH and therefore body CT scanning and percatheter venous sampling are essential diagnostic investigations. Tumour localization may result in resection and complete cure, although even small tumours may have a malignant potential. Adrenal tumours are readily diagnosed by plasma ACTH measurement and adrenal CT scanning. Adrenal adenomas are cured by adrenalectomy. Carcinomas may be treated by a combination of adrenalectomy, radiotherapy and o,p'-DDD, but long-term prognosis is poor.