An evaluation of laboratory tests for the detection and differential diagnosis of Cushing's syndrome

Adipose Tissue Compartments, Inflammation, and Cardiovascular Risk in the Context of Depression

The neurobiological and behavioral underpinnings linking mental disorders, in particular, major depressive disorder (MDD), with cardiovascular disorders are a matter of debate. Recent research focuses on visceral (intra-abdominal and epicardial) adipose tissue and inflammation and their impact on the development of cardiometabolic disorders. Intra-abdominal adipose tissue is defined as an endocrine active fat compartment surrounding inner organs and is associated with type 2 diabetes mellitus, a risk factor for the later development of cardiovascular disorders. Epicardial (pericardial) adipose tissue is a fat compartment surrounding the heart with close proximity to the arteries supporting the heart. Visceral adipose tissue (VAT) is an important source of inflammatory mediators that, in concert with other risk factors, plays a leading role in cardiovascular diseases. In conjunction with the behavioral (physical inactivity, sedentary lifestyle), psychological (adherence problems), and hormonal (dysfunction of the hypothalamus-pituitary-adrenal axis with subsequent hypercortisolism) alterations frequently accompanying MDD, an enhanced risk for cardiovascular disorders results.

Erythropoietin negatively regulates pituitary ACTH secretion

Erythropoietin (Epo) and Epo-receptor (EpoR) signaling, in addition to its classical role in erythropoiesis, exhibit a protective response in non-hematopoietic tissues. Mice with EpoR expression restricted to only hematopoietic tissues (ΔEpoRE), become obese, have low energy expenditure, and are glucose intolerant and insulin resistant. In the arcuate nucleus of the mouse hypothalamus, EpoR expression co-localizes in proopiomelanocortin (POMC) neurons. In vivo high-dose Epo treatment increases hypothalamus POMC, reduces food intake and fat mass accumulation. Here we report that Epo treatment also decreases plasma concentration of the pituitary derived POMC peptide, adrenocorticotropic hormone (ACTH). Conversely, ΔEpoRE mice show reduced hypothalamus POMC and high plasma concentrations of ACTH. In the pituitary, POMC is synthesized in the corticotroph cells, and here we examine Epo effect on pituitary POMC expression using the AtT-20 mouse corticotroph pituitary cell line. In AtT-20 cells, enzyme immunoassay analysis showed that Epo inhibits ACTH secretion. This effect is post-translational, as Epo treatment did not affect POMC mRNA expression but increased intracellular levels of ACTH peptide. Moreover, Epo reduced the basal intracellular calcium (Ca(2+)) levels, suggesting an effect in the Ca(2+)-signaling pathway. In summary, our studies suggest a novel regulatory pathway of ACTH secretion in the pituitary via EpoR-signaling. The higher plasma ACTH level in ΔEpoRE mice also suggests a possible mechanism of deregulated pituitary function with loss of Epo-signaling.

Hormonal regulation of the hypothalamic melanocortin system

Regulation of energy homeostasis is fundamental for life. In animal species and humans, the Central Nervous System (CNS) plays a critical role in such regulation by integrating peripheral signals and modulating behavior and the activity of peripheral organs. A precise interplay between CNS and peripheral signals is necessary for the regulation of food intake and energy expenditure in the maintenance of energy balance. Within the CNS, the hypothalamus is a critical center for monitoring, processing and responding to peripheral signals, including hormones such as ghrelin, leptin, and insulin. Once in the brain, peripheral signals regulate neuronal systems involved in the modulation of energy homeostasis. The main hypothalamic neuronal circuit in the regulation of energy metabolism is the melanocortin system. This review will give a summary of the most recent discoveries on the hormonal regulation of the hypothalamic melanocortin system in the control of energy homeostasis.

Associations between anthropometrical measurements, body composition, single-nucleotide polymorphisms of the hypothalamus/pituitary/adrenal (HPA) axis and HPA axis functioning

BACKGROUND

The relationship between hypothalamus/pituitary/adrenal (HPA) axis functioning and (visceral) obesity may be explained by single-nucleotide polymorphisms (SNPs) of the HPA axis. Objective  To investigate the relationship between the HPA axis SNP's 'BclI' in the glucocorticoid receptor gene and C8246T in the POMC gene and anthropometric measurements, body composition, 5-h cortisol concentrations, HPA axis feedback sensitivity, as well as HPA axis feedback sensitivity under stress in men and women. DESIGN/SUBJECTS/MEASUREMENTS: We assessed in 92 men and 102 women (18-55 years, BMI 19-41 kg/m(2) ) anthropometry, body composition using hydrodensitometry and deuterium dilution method, cortisol variability by measuring 5-h cortisol concentrations, HPA axis feedback functioning using a dexamethasone suppression test and HPA axis functioning under a challenged condition consisting of a standardized high intensity test with ingestion of 4 mg dexamethasone.

RESULTS

In female participants, the 8246C allele carriers compared to the 8246T allele carries were associated with a higher 5-h cortisol exposure (1·52 × 10(5) ± 0·8 vs 1·18 × 10(5) ± 0·6 nm·min, P < 0·05) and higher baseline postdexamethasone cortisol concentrations (54·5 ± 35·6 vs 37·4 ± 18·5 nm, P < 0·05). In male participants regarding the C8246T allele carriers and in both male and female participants regarding the BclI genotypes, no significant differences in anthropometric measurements, body composition and HPA axis functioning were observed. Multiple regression analysis showed that only increased 5-h cortisol exposure significantly related to changes in anthropometric measurements and body composition; the BclI and C8246T genotypes were not associated.

CONCLUSION

Our preliminary data show that in both men and women (18-55 years, BMI 19-41 kg/m(2) ), the SNP's BclI and C8246T of the HPA axis were primarily related to altered HPA axis functioning, rather than to altered anthropometric measurements and body composition.

Hypothalamic-pituitary-adrenal (HPA) axis functioning in relation to body fat distribution

OBJECTIVE

To relate hypothalamic-pituitary-adrenal (HPA) axis functioning and HPA feedback functioning to body fat distribution in normal weight to obese subjects.

PATIENTS

91 men and 103 women [age 18-45 years, BMI 19-35 kg/m(2), waist-to-hip ratio (WHR) 0.6-1.1].

MEASUREMENTS

Anthropometry, body composition using hydrodensitometry and deuterium dilution method, cortisol variability by measuring 5-h cortisol concentrations, HPA axis feedback functioning using a dexamethasone suppression test, and HPA axis functioning under a challenged condition consisting of a standardized high-intensity test with ingestion of 4 mg dexamethasone.

RESULTS

In men, an inverse relationship was observed between 5-h cortisol exposure (nmol/ml) and fat mass index (FMI) (kg/m(2)) (r = -0.55, P < 0.001). In women, relationships were observed between 5-h cortisol exposure (nmol/ml.min) and WHR (r = -0.49, P < 0.001), maximal workload (r = 0.32, P < 0.001) as well as oral contraceptive use (r = 0.38, P < 0.001). Similarly, in men, an inverse relationship was observed between negative feedback expressed as baseline concentrations minus post dexamethasone cortisol concentrations (nmol/ml) and FMI (r = -0.53, P < 0.001). In women, relationships were observed between negative feedback expressed as baseline concentrations minus post dexamethasone cortisol concentrations (nmol/ml) and WHR (r = -0.43, P < 0.001), maximal workload (r = 0.30, P < 0.001) as well as oral contraceptive use (r = 0.43, P < 0.001) in women. Moreover, an inverse relationship was observed between HPA axis functioning in a challenged condition expressed as percentage increase of cortisol concentrations after standardized high-intensity test with ingestion of 4 mg dexamethasone (%) and waist circumference (r = -0.21, P < 0.10) in men and WHR (r = -0.21, P < 0.05) in women. In men, strong positive relationships were observed between FMI and waist circumference (r = 0.85, P < 0.001), as well as waist-to-hip ratio (r = 0.70, P < 0.001).

CONCLUSION

Disturbance of HPA axis functioning under basal and challenged conditions is related to visceral fat accumulation.

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.

Preoperative diagnostic evaluation of children with Cushing's syndrome

Recent advances in biochemical and imaging studies have improved the diagnostic accuracy of Cushing's syndrome. To better define roles for these studies in children, the authors reviewed their experience with this rare group of patients. Fifteen children, aged 11 weeks to 17 years, were treated for noniatrogenic Cushing's syndrome over a 33-year period. All children presented with signs of hypercortisolism. Nineteen different diagnostic tests were used, reflecting changes in how these patients are evaluated. Pathological diagnoses were adrenal cortical carcinoma (3), primary adrenocortical nodular dysplasia (PAND) (2), and pituitary adenoma (10). Children with adrenal cortical carcinoma presented with an adrenal mass and at a younger age (mean, 22.3 months). Key diagnostic features of patients with PAND were a low plasma adrenocorticotrophin hormone (ACTH) and no suppression with high-dose dexamethasone. Children with a pituitary cause of Cushing's syndrome presented at an older age (mean, 15.7 years) and were diagnosed using a combination of high-dose dexamethasone testing, simultaneous inferior petrosal sinus sampling, and/or ovine corticotrophin-releasing hormone stimulation test. A strategy for the diagnosis of Cushing's syndrome in children is presented.

Chemiluminescence high performance liquid chromatography of corticosteroids using lucigenin as post-column reagent

A chemiluminescence high performance liquid chromatographic method for the determination of corticosteroids and tetrahydrocorticosteroids has been developed. Corticosteroids and their metabolites extracted from urine samples were separated using an ODS column and a mixture of methanol + water + 0.01 M sodium acetate solution (70:30:5) as eluent. The eluent from the column was mixed with the chemiluminescent solution containing lucigenin and Triton X-100 and a 0.28 M KOH solution by pumps and monitored by a chemiluminescence detector. No interference was encountered and the method is both precise and reproducible.

Determination of 17-hydroxycorticosteroids in urine by fluorescence high-performance liquid chromatography using Dns-hydrazine as a pre-column labeling reagent

A method is described for the determination of urinary 17-hydroxycorticosteroids using fluorescence high-performance liquid chromatography. After enzymatic hydrolysis, 17-hydroxycorticosteroids were extracted using an Extrelut column and then labeled with Dns-hydrazine in hydrochloric acid-ethanol solution. The labeled steroids were chromatographed on a microparticulate silica gel column, the mobile phase was dichloromethane-ethanol-water (900:60:40). The eluate was monitored on a fluorophotometer at 365 nm (excitation) and 505 nm (emission). Linearity of the fluorescence intensities (peak heights) of various 17-hydroxycorticosteroids were obtained between 60 pg and 20 ng. The assay was sensitive, precise and accurate. Comparison with the results obtained by radioimmunoassay gave correlation coefficients of 0.932 for tetrahydrocortisol and 0.930 for tetrahydrocortisone. The proposed method is clinically useful for the routine analysis of urinary 17-hydroxycorticosteroids.

Pituitary ACTH dependency of nodular adrenal hyperplasia in Cushing's syndrome. Report of two cases and review of the literature

Cushing's syndrome due to nodular adrenal hyperplasia comprises a clinically and biochemically heterogeneous group of disorders whose pathogenesis is unclear. We describe two patients with atypical steroid dynamics and large unilateral adrenal nodules who had pituitary ACTH-dependent disease. In the differential diagnosis of Cushing's syndrome, we recommend repeated ACTH measurement and selective venous sampling-particularly in those patients with impaired dexamethasone suppressibility and abnormal findings on computerized tomography.

Cushing's disease: a review of pathogenesis, diagnostic methods, and treatment

Cushing's disease is a form of Cushing's syndrome that results from excessive ACTH secretion with consequent adrenal hyperplasia and increased cortisol secretion. Most patients have an ACTH-secreting tumor; in others, a hypothalamic defect may play an important role. Steroid determinations and the dexamethasone suppression test can confirm overproduction of cortisol. Measurement of basal plasma ACTH level is perhaps the most reliable way to determine the cause of overproduction. Transsphenoidal surgery seems to be the initial treatment of choice, if the necessary neurosurgical expertise is available. If it is not, bilateral adrenalectomy combined with conventional pituitary irradiation can be used. Other alternatives are cobalt 60 high-voltage or heavy-particle irradiation and drugs that interfere with cortisol biosynthesis.

17-Hydroxycorticosteroids in urine

A new method has been devised to extract 17-hydroxycorticosteroids (17OH-CS) from a hydrolyzed urine using an EXTUBE fiber column. This extraction was combined with a modified Porter-Silber color reaction to quantitate total urinary 17OH-CS. The new method takes only half the time required in older methods. Recovery of tetrahydrocortisone in the new method was improved to 85--95% compared with 70% in the previous method. Between-run precision (C.V.%) was concentration dependent in both methods and was improved to 5--7% compared with 10--18% in the previous method. Evidence was obtained to demonstrate that the new methodology would provide the same information and interpretation as the older, more cumbersome method.

Cushing's syndrome: a review of diagnostic tests

This review presents an analysis and interpretation of the published experimental data that form the basis for laboratory tests commonly used for screening, definitive diagnosis, and differential diagnosis in Cushing's syndrome. The single-dose overnight dexamethasone suppression test is excellent for screening outpatients since this test has a very low incidence of false-negative results (1.9% of 154 patients with Cushing's syndrome). The definitive diagnosis of Cushing's syndrome is best established by combining basal state measurements of the daily urine-free cortisol excretion and late evening plasma cortisol levels with the 2-mg low-dose dexamethasone suppression test. The etiology of Cushing's syndrome is best determined by combining measurements of basal state plasma adrenocorticotropin (ACTH) levels with the 8-mg high-dose dexamethasone suppression test. Under certain conditions, the basal state daily urine excretion of 17-hydroxycorticosteroids and 17-ketogenic steroids, the insulin tolerance test, and the metyrapone test may be useful in the definitive or differential diagnosis of Cushing's syndrome.