Dexamethasone suppressibility of plasma pregnenolone or dehydroepiandrosterone in gonadectomized patients.

The 9 AM dexamethasone suppression test was carried out in gonadectomized patients, and plasma pregnenolone or dehydroepiandrosterone (DHA) was radioimmunoassayed following various amounts of dexamethasone administration. Pregnenolone, as well as the plasma ACTH level, was completely suppressed with 1 mg dexamethasone, whereas 4 mg or 8 mg of dexamethasone was needed to induce a complete DHA suppression. These findings suggest that the gonads alone contribute to the poor dexamethasone suppressibility of pregnenolone in normal subjects, and that adrenal DHA secretion might be also regulated by an unidentified factor other than ACTH, which would be suppressed with large doses of dexamethasone.     

Single-dose four hour dexamethasone suppression test in normal men and its application for the diagnosis of cushing's syndrome

As a four hour morning test, plasma cortisol levels were radioimmunoassayed before and at two and four hours after dexamethasone (0, 0.5 mg, 1.0 mg or 2.0 mg) was administered at 8–9 a.m. in 20 normal subjects. The 1.0 mg four hour test was most effective in suppression of cortisol and it showed the same suppressibility as the widely used single-dose overnight test. With the 1.0 mg four hour test, 2 patients with Cushing's syndrome due to adrenal hyperplasia could be differentiated from normal and obese subjects.The four hour morning test would be more useful than the widely used overnight test from the reasons; i) it shows the same suppressibility as the overnight test, ii) it obviates the need for bothersome midnight administration of dexamethasone, iii) because it takes only one morning to perform, it can save a day, iv) and it might be applicable for the differential diagnosis of Cushing's syndrome because 4.0 mg morning test resulted in complete suppression of plasma cortisol in a tested Cushing's syndrome, whereas with even 8.0 mg, plasma cortisol was not suppressed in the overnight test in 2 such patients examined.     

Overnight (1 mg) dexamethasone suppression testing reliably distinguishes non-cushingoid obesity from Cushing's syndrome.

To determine the sensitivity of the overnight 1-mg dexamethasone suppression test in diagnosing Cushing's syndrome, we evaluated the cortisol responses of 55 subjects (25 non-obese individuals with body mass index less than 25 kg/m2, 20 obese individuals with body mass index greater than 30 kg/m2, and 10 patients with surgically proven Cushing's syndrome) following ingestion of 1 mg dexamethasone at midnight. The basal 8 AM plasma cortisol levels among non-obese and obese individuals and patients with Cushing's syndrome were 310 +/- 85, 377 +/- 91, and 813 +/- 270 nmol/L, respectively. Following 1 mg of dexamethasone, Cushing's syndrome patients showed minimal suppression of cortisol to 609 +/- 180 nmol/L (P = 0.79). Non-obese and obese individuals suppressed to 18.7 +/- 6.0 nmol/L (P less than 0.001) and 22 +/- 7.1 nmol/L (P = 0.003), respectively. The results demonstrated similar cortisol responses to overnight dexamethasone suppression in obese and non-obese groups, and clearly distinguished these subjects from those with Cushing's syndrome. Obesity is not a confounding factor in the 1-mg dexamethasone suppression test.     

Combined administration of human corticotropin-releasing factor and lysine vasopressin induces cortisol escape from dexamethasone suppression in healthy subjects

Inadequate suppression of plasma cortisol after 1-2 mg dexamethasone is frequently observed in depressive patients. To further investigate the pathophysiology underlying cortisol nonsuppression after dexamethasone we compared cortisol and corticotropin (ACTH) response to human corticotropin-releasing factor (h-CRF), lysine vasopressin (LVP), and a concurrent administration of both peptides after pretreatment with 1.5 mg dexamethasone in six male controls. Neither h-CRF nor LVP were able to produce a marked elevation of dexamethasone suppressed plasma cortisol and ACTH. If both peptides were administered in combination, a substantial escape of plasma cortisol from dexamethasone suppression was observed. ACTH responses changed in concordance with those of cortisol indicating that the LVP-CRF interaction takes place at the pituitary level. Our finding is consistent with a multihormonal control of pituitary-adrenal activity and bears several implications for interpretation of dexamethasone suppression test results in depressive illness.     

The changes in plasma cortisol and urinary free cortisol by an overnight dexamethasone suppression test in patients with Cushing's disease

We studied the suppressibility of cortisol secretion in 15 patients with Cushing's disease by measuring morning plasma cortisol level as well as the 24-hour urinary free corisol (UFC) excretion following single doses of increasing amounts of dexamethasone (ranging from 0.5 to 32 mg) given at 11 p.m. The mean plasma cortisol level in patients with Cushing's disease was twice as high as in normal subjects, whereas the mean UFC in these patients was 6 times as high. Plasma cortisol in seven patients were suppressed by less than 4 mg of dexamethasone (in 2 cases, less than 0.5 mg; in 3 cases, less than 2 mg; and in 2 cases less than 4 mg). In these cases, basal plasma cortisol and UFC were less than 25 micrograms/dl and 350 micrograms/day, respectively. Among the other eight patients, plasma cortisol was partially suppressed in 5 cases and not suppressed in 3 cases by high doses of dexamethasone (16-32 mg). In these cases the basal plasma cortisol and UFC were more than 25 micrograms/dl and 350 micrograms/day, respectively. There was a significant correlation between the basal plasma cortisol and UFC (r = 0.687, p less than 0.01). These data suggest that the suppression by increasing amounts of dexamethasone in most cases with Cushing's disease was related to the severity of hypercortisolism.     

Influence of D-thyroxine on plasma thyroid hormone levels and TSH secretion.

Triiodothyronine (T3), thyroxine (T4), basal TSH and TSH after stimulation with TRH were determined in healthy subjects and patients treated with D-thyroxine (DT4). After a dosage of 6 mg DT4 the D/L T4 plasma concentration rose about 4-fold 4 hours after application and was only moderately elevated 14 hours later. To achieve constantly elevated T4 levels 3 mg DT4 were applied in the further experiment every 12 hours. The D/L T4 plasma concentration rose 2.5-4-fold and there was a small but significant increase of the D/L T3 plasma concentration. 74 hours after onset of treatment basal TSH was below detectable limits and the increase of TSH 30 min after injection of 200 mug TRH (TRH test) was only about 15% compared to zero time. The time course of TSH suppression was investigated after treatment with DT4 and LT4 (single dosage of 3 mg). TRH-tests were performed before, 10, 26, 50 and 74 hours after the first dosage of D or LT4. There was no difference in the time course of basal TSH and TSH stimulated by TRH. In 10 patients on DT4 long-term therapy, basal and stimulated TSH were found to be below the detectable limits of 0.4 mug/ml. Our results show that (1) plasma half-life of DT4 is less than 1 day, (2) TSH suppression after D and LT4 treatment is very similar, and (3) in patients on long-term DT4 treatment, TSH plasma concentration is below detectable limits even after stimulation with TRH.     

Assessment of the Utility of the High-Dose Dexamethasone Suppression Test in Confirming the Diagnosis of Cushing Disease

ObjectiveTo determine the utility of high-dose dexamethasone suppression (HDDS) tests to confirm the diagnosis of Cushing disease (CD).MethodsIn this retrospective study, we reviewed medical records of patients who underwent either the overnight 8-mg HDDS test or the 2-day 2-mg HDDS test every 6 hours. The percentage suppression of morning serum cortisol and the percentage suppression of 24-hour urine free cortisol (UFC) were calculated.ResultsOf 141 patients with proven CD who underwent HDDS tests, 77 (55%) underwent the overnight 8-mg HDDS test and 64 (45%) underwent the 2-day 2-mg HDDS test every 6 hours. With the overnight 8-mg HDDS test, 73 of 77 patients (95%) had greater than 50% suppression and 48 of 77 patients (62%) had greater than 80% suppression of the morning serum cortisol in comparison with the baseline value. With the 2-day 2-mg HDDS test, only 41 of 64 patients (64%) had greater than 90% suppression of 24-hour UFC.ConclusionWe conclude that the overnight 8-mg HDDS test accurately confirmed the diagnosis of CD with a high sensitivity of 95% with use of a criterion of greater than 50% suppression; in contrast, the sensitivity was only 62% with use of a more precise cutoff of greater than 80% suppression. The 2-day 2-mg HDDS test with a criterion of greater than 90% suppression of 24-hour UFC had a sensitivity of 64%. These results confirm the limited precision of the HDDS tests. (Endocr Pract. 2012;18:152-157)     

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

Forty four subjects (23 obese controls, 11 patients with possible Cushing''s syndrome, and 10 patients with definite Cushing''s syndrome) underwent low dose (0 X 5 mg every six hours for two days) dexamethasone suppression tests during which serum cortisol concentration at 0800 and excretion of urinary free cortisol over 24 hours were measured. Serum cortisol concentration fell to below 60 nmol/1 (2 X 2 micrograms/100 ml) in 31 subjects and remained above 250 nmol/1 (9 X 1 micrograms/100 ml) in the 13 others. Excretion of urinary free cortisol showed a similar response, falling to below 110 nmol (40 micrograms)/24 h in 31 and remaining above 180 nmol (65 micrograms)/24 h in the 13 others. There was complete concordance between the two variables in terms of the pattern of response. Serum cortisol concentration fell to below 60 nmol/1 (2 X 2 micrograms/100 ml) in at least 97% (31 of a possible 32) of subjects without Cushing''s syndrome. On the other hand, a serum cortisol concentration of above 250 nmol/1 (9 X 1 micrograms/100 ml) after low dose dexamethasone gave a false positive diagnosis of Cushing''s syndrome in at most only one of 13 patients (7 X 7%). Measurement of serum cortisol concentration during the low dose dexamethasone test is simpler than, and as accurate and reliable as, measurements of urinary steroids.     

Mild adrenal 3 beta-hydroxysteroid dehydrogenase deficiency with hyperaldosteronism

The patient was admitted to our hospital at 19 and again at 22-yr of age for hirsutism and hypertension. Her baseline and ACTH-stimulated plasma 17-hydroxy pregnenolone, dehydroepiandrosterone and dehydroepiandrosterone sulfate were increased whereas plasma 17-hydroxy progesterone and androstenedione were normal and responded poorly to ACTH. Plasma deoxycorticosterone, corticosterone and cortisol baseline levels were normal, and they responded normally to ACTH. The plasma aldosterone concentration (PAC) was always high and responded well to ACTH, angiotensin III and furosemide-upright stimulation. However, plasma renin activity (PRA) was normal or slightly high, and responded normally to furosemide-upright stimulation and fluorohydrocortisone suppression. Dexamethasone (2 mg/day) for 1-2 weeks suppressed the androgens, cortisol and corticosterone levels. PRA and PAC were suppressed temporally, but PRA returned to normal and PAC to be a high level after 2 weeks of dexamethasone administration. Blood pressure was also reduced temporally but returned to a high level after 2 weeks of dexamethasone. These results indicate that primary aldosteronism and dexamethasone-suppressible hyperaldosteronism were not likely to be present, and unknown aldosterone stimulating factors which potentiated the action of endogenous angiotensin II or ACTH might be responsible for the hyperaldosteronism in this patient. We conclude that this patient had a mild and non-salt losing 3 beta-HSD deficiency in the zona reticularis with normal fasciculata and high glomerulosa function.     

Effect of Dexamethasone on Oral Glucose Tolerance in Healthy Adults

ObjectiveTo determine the dose-response and time course of action of a single dose of dexamethasone on plasma glucose and insulin dynamics in healthy adults.MethodsParticipants included healthy adults who met the following inclusion criteria: 18 to 65 years of age, body mass index of 18 to 25 kg/m2, no family history of diabetes mellitus, not taking any medication known to affect glucose tolerance, and nonpregnant state for female participants. Each participant underwent 3 sequential blocks of 75-g oral glucose tolerance tests (OGTTs) on days 1, 2, and 3; this sequence was repeated on 3 different occasions separated by more than 2 weeks. On the first day of each block, participants reported to the research center after a 10- to 12-hour overnight fast, and fasting baseline blood samples for glucose, insulin, and C-peptide were obtained. Baseline (0 mg) OGTT was then performed with a 75-g glucose load, and blood samples were collected at 30, 60, 90, and 120 minutes for measurements of glucose, insulin, and C-peptide. After the baseline OGTT on day 1, a single dose of either 2-, 4- or 8-mg of dexamethasone was administered orally. Twenty-four and 48 hours later, participants returned for additional OGTTs.ResultsTen healthy volunteers (4 male and 6 female) were enrolled. The effect of dexamethasone was maximal 24 hours after 8-mg dexamethasone compared with the effect observed after no dexamethasone administration. At 60 minutes during the OGTT (following 8-mg dexamethasone), blood glucose increased from 127 ± 7.1 mg/dL (6.35 ± 0.36 mmol/L) to 176 ± 19 mg/dL (8.8 ± 0.95 mmol/L), insulin increased from 49.3 ± 3.2 μIU/mL (342 ± 22 pmol/L) to 119.7 ± 10.1 μIU/mL (831 ± 70 pmol/L), and C-peptide increased from 6376 ± 510 pg/L (1913 ± 153 pmol/L) to 10 143 ± 1016 pg/L (3043 ± 305 pmol/L); the 60-minute levels returned towards baseline at 48 hours. Smaller changes were observed with 2- and 4-mg dexamethasone. Twenty-four hours after 8-mg dexamethasone, there was a 2.2- and 1.5-fold increase in homeostasis model assessment of insulin resistance and homeostasis model assessment of β cell, respectively, and a 2.5-fold decrease in the Matsuda sensitivity index.ConclusionsA single oral dose of 8-mg dexamethasone increases blood glucose, insulin, and C-peptide levels maximally at 24 hours, 1 hour following 75-g OGTT. A dexamethasone stress test might identify persons at increased risk for type 2 diabetes. (Endocr Pract. 2010:16:770-777)     

Plasma and Urinary 11-Hydroxycorticosteroids in Differential Diagnosis of Cushing's Syndrome

Morning plasma 11-hydroxycorticoids, urinary 11-hydroxycorticoids, and urinary 17-oxogenic steroids were measured before and during a dexamethasone suppression test. This consisted in the administration by mouth of 2 mg of dexamethasone daily for 48 hours, followed by 8 mg daily for 48 hours. In addition midnight plasma 11-hydroxycorticoids were measured before the start of the test. The subjects investigated were 21 patients with Cushing''s syndrome, 27 obese female patients, 10 female patients with the Stein-Leventhal syndrome, and 8 female patients with idiopathic hirsutism.The results showed that the clearest distinction between the groups was made by measurement of the basal urinary 11-hydroxycorticoid excretion, where, in the group of patients with Cushing''s syndrome, all the levels were well above the upper limit of normal. In addition raised midnight plasma 11-hydroxycorticoid levels were of great diagnostic value. By using these results together with those of the dexamethasone suppression tests it was possible to make a firm preoperative diagnosis of pituitary-dependent Cushing''s syndrome in 90% of patients in this series.     

Plasma acth and cortisol levels in depressed patients: Relation to dexamethasone suppression test

Blood samples collected from normal subjects and newly hospitalized depressed patients at 8 AM on the day before and at 8 AM and 4 PM the day after receiving dexamethasone, 1 mg orally at 11 PM, were analyzed for ACTH and cortisol. The mean plasma ACTH values of these two groups were not significantly different at any of the times, while the cortisol levels of the depressed patients were significantly higher than those of the normal subjects at 8 AM pre-dexamethasone (P<0.001). There was no correlation between plasma ACTH and cortisol values in either group. The cortisol responses to dexamethasone in depressed patients revealed two subgroups. In one subgroup, the cortisol was suppressed as much as in normal subjects, but in the other, cortisol levels were not suppressed. The post-dexamethasone ACTH rebounded at 4 PM in the latter subgroup to higher values than in the subgroup with suppressed cortisol levels and in the normal subjects. After dexamethasone, the ACTH values were negatively correlated with plasma cortisol only in the normal subjects (P<0.01), not in the depressed patients. These results indicate that ACTH levels do not account for the elevated cortisol and the failure of dexamethasone to suppress cortisol levels in some depressed patients.     

A plasma dexamethasone radioimmunoassay

A double antibody radioimmunoassay for estimation of plasma dexamethasone is reported. Dexamethasone antiserum was produced by immunization of rabbits with dexamethasone-3-carboxymethyloxime-bovine serum albumin conjugate. All the endogenous steroids tested cross reacted less than 1%. Cortisol with a cross reaction of 0.4% gave significant interference in some plasma samples. This Interference could be removed by chromatography. The recoveries of dexamethasone added to plasma and corrected for procedural losses were 99 ± 9% after dichloromethane extraction and 98 ± 10% after paper chromatography. After dichloromethane extraction and after paper chromatography, the intraassay and inter-assay coefficients of variation were less than 11%. The peak dexamethasone levels were observed between 30 and 60 minutes after a single 1 mg oral dose in two normal subjects. The half-times of disappearance from plasma were 4 and 4.5 hours. During a constant infusion (50 μg/70 kg BW/hr) of dexamethasone phosphate, the plasma dexamethasone level reached a level of 250 ng/dl at 8 hours. It is concluded that plasma dexamethasone levels after either oral or intravenous administration may be measured specifically by radioimmunoassay.     

Studies on the "low dose" suppressible Cushing's disease.

Diagnosis of Cushing's disease in most cases can be established by the standard dexamethasone suppression test without difficulty. However, some cases were known to be normally suppressed by the standard low dose of dexamethasone (2 mg daily). The case we encountered recently was also normally suppressed by either the rapid (Nugent) or the standard (Liddle) method. This fact prompted us to study the usefulness of a single dose of 0.5 mg of dexamethasone to suppress the plasma cortisol in the normal. It was concluded that the single oral dose of 0.5 mg of dexamethasone given at 11 p.m. on the previous night suppressed the plasma cortisol efficiently the following morning in the normal, thus making the differentiation of particular cases of Cushing's disease from the normal possible. The disappearance of plasma dexamethasone did not differ significantly between the normal and the Cushing's disease.     

Activated hypothalamic pituitary adrenal axis in patients with metabolic syndrome

Metabolic syndrome (MetS) is correlated with the activity of hypothalamic-pituitary-adrenal axis (HPA), but the underlying mechanism still remains elusive. The aim of this study was to investigate the HPA axis function in patients with MetS. This case-control study included 159 people. They were divided into 2 groups. The first group included 73 healthy volunteers (control group: 19 males, 54 females, mean±SD: 49.9±7.5 years old, with BMI: 27.9±4.42?kg/m2) and the second group included 86 patients with MetS (case group: 48 males, 38 females, mean±SD: 52.2±7.6 years old, with BMI: 30.5±5.35?kg/m2). An oral glucose tolerance test (OGTT) was performed for all subjects after a 12-h overnight fast, and blood samples were obtained for determination of ACTH, cortisol, insulin, C-peptide, and glucose levels. Serum cortisol after an overnight dexamethasone suppression test was determined in both groups. Patients with MetS had serum cortisol levels after an overnight dexamethasone suppression test significantly higher than controls. During OGTT plasma ACTH levels were higher at all time points in patients with MetS compared to controls, whereas serum cortisol levels were comparable between the 2 groups. Plasma ACTH during OGTT was also correlated with most of the components of MetS. The HPA axis in patients with MetS seems to be more active as evidenced by the higher cortisol levels after the overnight dexamethasone suppression test and by the higher ACTH levels during OGTT. This functional hypercortisolism might be involved in the pathogenesis of the metabolic syndrome.     

Overnight Dexamethasone Suppression Test: A Reliable Screen for Cushing's Syndrome in the Obese

Objective: Reevaluation of the validity of the 1-mg overnight dexamethasone suppression test (ODST) as a screening test for Cushing's syndrome in obese patients. Research Methods and Procedures: Eighty-six obese patients (body mass index, 30 to 53 kg/m²) that were referred to a general endocrine outpatient clinic for evaluation of simple obesity, diabetes mellitus, hypertension, polycystic ovary disease, or pituitary tumor. One milligram dexamethasone was administered orally at 11:00 pm , and serum cortisol levels were measured the following morning between 8:00 am and 9:00 am . Suppression of serum cortisol to <80 nM (3 μg/dL) was chosen as the cut-off point for normal suppression. Patients with serum cortisol levels ≥80 nM were evaluated for Cushing's syndrome. Results: Suppression of morning cortisol levels to <80 nM occurred in 79 of the 86 obese patients. Seven patients had serum cortisol levels higher than 80 nM; five were eventually diagnosed with Cushing's syndrome and two were considered false positive results in view of normal 24-hour free urinary cortisol and normal suppression on a low dose dexamethasone suppression test (0.5 mg of dexamethasone every 6 hours for 2 days). We found a false positive rate of 2.3% for the ODST using a cut-off serum cortisol of 80 nM. Discussion: The ODST is a valid screening test for Cushing's syndrome in the obese population. The false positive rate was 2.3%, even when using a strict cut-off serum cortisol of 80 nM. Abnormal cortisol suppression in obese patients should be investigated and not be considered false positive results.     

The measurement of 18-hydroxy-11-deoxycorticosterone in human plasma by radioimmunoassay

A radioimmunoassay method for the measurement of plasma levels of 18-hydroxy-11-deoxycorticosterone (18-OH-DOC) has been developed. The antiserum against 18-OH-DOC was produced in rabbits immunized against 18-OH-DOC-3-oxime-bovine serum albumin. Plasma (1–2 ml) was extracted with dichloromethane and chromatographed on paper. The purified extracts were incubated with antiserum at a $\text{1}\text{22,000}$ dilution for $\text{1}\text{2}$ hour at 37°C and for 2 hours at 4°C. Saturated ammonium sulfate was used to separate free from bound 18-OH-DOC. 1, 2-³H-18-OH-DOC was added to all samples to correct for losses and to determine the percent free. Pyridine (0.1%) was added to solvents to maintain the stability of 18-OH-DOC. Recovery after extraction was 58 ± 8 (S.D.)%. The accuracy and precision of the method were acceptable, and a sensitivity of 2 pg per sample enabled the measurement of very low levels of 18-OH-DOC. High specificity was demonstrated by a low blank value (0 ± 0.2 pg) and by demonstrating that alternative paper chromatography separation systems gave results not differing significantly from those obtained by the present method. The mean 8AM plasma 18-OH-DOC level was 8.5 ± 1.2 ng per 100 ml in 18 normotensive control subjects. There was a marked response of plasma 18-OH-DOC to ACTH stimulation and dexamethasone suppression and a significant increase after 3 hours upright posture.     

Dexamethasone increases neutral sphingomyelinase activity and sphingosine levels in 3T3-L1 fibroblasts

The activity of neutral sphingomyelinase (EC 3.1.4.12) in a plasma membrane enriched fraction was found to be increased in dexamethasone treated cells. The elevation of sphingomyelinase activity was blocked by cycloheximide indicating that protein synthesis was required for the steroid action. Ceramidase (EC3.5.1.23) activity was unaffected by the dexamethasone treatment. Levels of sphingosine in 3T3-L1 Cells were also increased after treatment with 10(-7) M dexamethasone for 2 and 4 hours.     

Cortisol-suppressible dexamethasone-nonsuppressible cyclic Cushing's disease with evidence of clinical and biochemical remission with bromocriptine.

We report a rare case of a 57-year-old female patient with Cushing's disease who had clinically and biochemically proven cyclicity. There were periodic increases in plasma ACTH and cortisol and urinary free cortisol and 17-OHCS. Plasma CRH was undetectable and plasma ACTH responded to exogenous CRH when basal plasma cortisol was relatively low. Neither plasma ACTH nor cortisol responded to dexamethasone (oral and intravenous) but plasma ACTH was clearly suppressed by cortisol infusion. With 40 mg/day bromocriptine, the periodic hypercortisolemia disappeared and the patient was maintained on remission. The response of plasma cortisol to dexamethasone suppression test was also normalized.     

Detection of glucocorticoid receptors in leukemia cells by dexamethasone-induced cytolysis and [3H]-dexamethasone binding

The presence of glucocorticoid receptors on the leukemic cells of 33 patients affected with acute lymphatic leukemia (ALL) and 6 patients affected with acute myeloic leukemia (AML) was investigated by dexamethasone-induced cytolysis and [3H] dexamethasone binding. The tests undertaken proved that after 20 hours of incubation 9 of 26 non-T-non-B-ALL (c-ALL and unclassified ALL) and 2 of AML were lysed with dexamethasone; blood lymphocytes and bone marrow leukocytes of healthy donors, however, were not affected. Non-T-non-B-ALL and AML were able to bind essentially more [3H] dexamethasone than T-ALL. There existed no correlation between dexamethasone binding and dexamethasone-induced cytolysis.