Plasma dexamethasone concentrations and the dexamethasone suppression test

Altered bioavailability or altered pharmacokinetics of dexamethasone (dex) may contribute to a positive Dexamethasone Suppression Test (DST) in psychiatric patients. We measured plasma dex and plasma cortisol concentrations in 32 patients with primary major depressive disorder (MDD), 14 patients with other psychiatric disorders, and 16 normal controls. Cortisol was measured by the competitive protein binding (CPB) assay and dex by RIA (IgG Corp.). Additionally, cortisol was measured by a fluorescent polarization immunoassay (FPIA) available on the Abbott TDx analyzer in an attempt to validate this method for use in the DST. The agreement between FPIA and CPB cortisol results was excellent. Depressed nonsuppressors, by definition, had significantly higher mean plasma cortisol concentrations than depressed suppressors, psychiatric controls, and normal volunteers at 8:00 AM, 3:00 PM, and 10:00 PM postdex. When DST nonsuppressors and suppressors were compared regardless of diagnostic group, plasma dex concentrations were significantly lower (p less than 0.01) in the DST nonsuppressors. There was a significant negative correlation between plasma cortisol levels and plasma dex levels across all subjects at 8:00 AM (r = -0.365, n = 44, p less than 0.05). When the subjects were sorted by diagnostic category, there was a strong, but not statistically significant, trend toward lower plasma dex concentrations in the melancholic nonsuppressors versus the melancholic suppressors and between the psychiatric control non-suppressors and the corresponding suppressor group. These relationships disappeared when we restricted our analyses to an empirically derived middle range of plasma dex concentrations within which the DST results were considered to be valid. We conclude that bioavailability or pharmacokinetics of dex may significantly contribute to DST results. Further investigation is needed to determine whether or not the quantification of dex and its metabolites and their determination at which specific timepoints during the DST will enhance the predictive or interpretive value of the DST in psychiatric patients.

Differential diagnosis and pathophysiology of Cushing's syndrome and primary affective disorder

Most patients with major depression have increased 24-hour urinary free cortisol and cortisol nonsuppression after dexamethasone administration, which are cornerstones of a diagnosis of Cushing's syndrome. Similarly, Cushing's syndrome patients often suffer from major psychiatric syndromes, most often depression. These similarities between the two conditions sometimes make it difficult to differentiate them and have led some investigators to suggest they are two points on a spectrum of endocrinologic dysfunction. This article reviews the literature comparing Cushing's syndrome and primary affective disorder and presents two cases that illustrate just how closely these diseases may resemble one another.

Pharmacokinetics of growth hormone secretion in humans induced by growth hormone releasing hormone

This investigation compares the age- and sex-related changes in growth hormone (GH) response to growth hormone releasing hormone (GHRH) in normal subjects using an appropriate pharmacokinetic model. Twenty-five subjects (14 males and 11 females) aged 23-89 yr received a single intravenous bolus dose (1 microgram/kg) of GHRH-40 solution. Plasma GH concentration-time profiles are best characterized by a biexponential equation (or one-compartment model) with first-order release and disappearance rates and an equilibration lag time. The harmonic mean release rate half-life is similar for both sexes (males: 12.6 min vs. females; 11.4 min) but significantly different across age groups (23-35 yr: 7.2 min vs. 50-89 yr: 16.8 min). The mean disappearance rate half-life and GHRH-equilibration time lag for females (33.6 and 20.4 min, respectively) and the higher age group subjects (32.4 and 21.6 min, respectively) are significantly longer than those of males (22.8 and 9 min, respectively) and the lower age-group subjects (21.6 and 8.4 min, respectively). The mean metabolic clearance rate of GH is significantly lower (p less than 0.02) for females than for males (3.1 vs. 4.83 ml/hr.m2). However, the production rate and the amount of GH released by the pituitary for our subjects appear to be very similar for both males (8.7 micrograms/hr.m2 and 4.65 micrograms/m2) and females (9.33 micrograms/hr.m2 and 5.11 micrograms/m2).

Growth hormone response to growth hormone releasing factor in Alzheimer's disease

Because of the well-established reduction in the concentration of somatostatin in several brain areas of patients with histologically verified Alzheimer's disease, we sought to determine if growth hormone (GH) secretion is altered in Alzheimer's disease. In order to study this, we assessed the GH response to growth hormone releasing factor (GRF) in 8 patients with Alzheimer's disease and 8 age-matched controls. Although there was no difference between the magnitude of the GRF-induced GH response (delta max GH response or area under the curve) between the Alzheimer's disease patients and the controls, the Alzheimer's patients exhibited a delayed GH response to GRF.

The corticotropin-releasing hormone test in patients with posttraumatic stress disorder

To evaluate the hypothalamic-pituitary-adrenal (HPA) axis in patients with posttraumatic stress disorder (PTSD), we measured adrenocorticotropin hormone (ACTH) and cortisol responses following administration of corticotropin-releasing hormone (CRH) in 8 combat veterans with chronic PTSD. The PTSD patients had a significantly lower ACTH response to CRH compared to a control group of normal volunteers. Blunted ACTH responses occurred in patients with PTSD alone, as well as those PTSD patients who also had major depression. The cortisol response, although reduced, was not significantly different from normal. The blunted ACTH response to CRH in PTSD patients is similar to that seen in other psychiatric disorders, such as depression, panic disorder, and anorexia nervosa.

Intracerebroventricular infusion of interleukin 1 rapidly decreases peripheral cellular immune responses

Low doses (50-200 pg or 3.1-12.4 fmol) of interleukin 1 (IL-1) infused into the brain of rats produced rapid suppression of various cellular immune responses in peripheral lymphocytes of rats. Fifteen minutes after infusion of purified IL-1 beta into the lateral ventricle, natural killer cell activity, response to phytohemagglutinin stimulation, and interleukin 2 production were markedly suppressed in lymphocytes isolated from blood and spleen. These effects were due to infusion of IL-1 into brain since they did not occur when IL-1 was infused into the cisterna magna (essentially posterior to brain) or was injected intraperitoneally. Effects of IL-1 in brain could be blocked by simultaneous infusion of alpha-melanocyte-stimulating hormone, which is known to block the biological actions of IL-1. To stimulate release of endogenous IL-1 in brain, lipopolysaccharide was infused; this produced similar effects as IL-1, and these effects also were blocked by alpha-melanocyte-stimulating hormone. At longer intervals after infusion of IL-1 and lipopolysaccharide (3, 6, and 24 hr), immune responses returned to baseline or remained suppressed; i.e., "rebound" immunopotentiation did not occur. Finally, IL-1 infusion suppressed cellular immune responses in adrenalectomized animals, thereby showing that the effects of central IL-1 on peripheral cellular immune responses were, at least in part, independent of the stimulatory effect of IL-1 on secretion of adrenal hormones. These results indicate a link from brain to peripheral immune responses by means of action of a cytokine acting in the brain.

Circadian rhythm of adrenergic regulation of adrenocorticotropin and cortisol secretion in man

The effects of the alpha-adrenergic agonist methoxamine on the human hypothalamic-pituitary-adrenal axis was assessed by a placebo-controlled study in the morning and one in the evening. A 5-mg iv bolus dose of methoxamine in normal subjects caused a significant rise in plasma ACTH and cortisol concentrations in the morning study. However, no significant change in plasma cortisol or ACTH concentrations was noted during the evening study. These studies suggest the existence of a diurnal variation in alpha 1-adrenergic regulation of the hypothalamic-pituitary-adrenal axis.

One stressful event blocks multiple actions of diazepam for up to at least a month

Based on recent findings of this laboratory, the hypothesis was tested that a single stressful encounter might have a persistent antidiazepam influence. Our results indicate that one exposure to a brief stressful event up to at least one month earlier prevented completely the effect of diazepam on pentylenetetrazole-induced changes in dopamine in the rat frontal cortex, elevations of plasma corticosterone levels and seizures.

Growth hormone-releasing factor stimulation test in depression

The authors administered the growth hormone-releasing factor (GRF) stimulation test to 19 patients with major depression and 19 age- and sex-matched control subjects to test the hypothesis that a blunted growth hormone (GH) response to clonidine reflects a central alpha 2-adrenergic receptor subsensitivity in depression. GH response to GRF was significantly higher in patients with depression than in control subjects. This group difference was mainly attributable to three of the 19 depressed patients who exhibited markedly high GH responses to GRF. These results suggest that the blunted GH response to clonidine seen in patients with depression is not due to a pituitary defect in GH secretion.

Growth hormone response to growth hormone-releasing factor in depression

A blunted growth hormone (GH) response to clonidine and other pharmacologic stimuli has been reported in patients with depression. This blunted growth hormone response to clonidine has led to the speculation that there is a central alpha-2 adrenergic receptor subsensitivity in depression. This hypothesis is based on the assumption that the pituitary somatotroph response to growth hormone-releasing factor (GHRF) is not altered in depression. In the present preliminary study, the somatotroph response to GHRF in depressed patients and normal controls has been evaluated in four depressed patients and four age- and sex-matched controls. The GH response to GRF is highly variable both in normal individuals and in the depressed patients studied. Larger numbers of patients and controls must be studied before any definitive conclusions can be drawn about GH responses to GRF in depressed patients.

Modern pollen spectra from lakes in arctic western Canada

Fifty-four samples of modern sediment from Banks Island and the Melville–Horton region of the Northwest Territories illustrate the major features of pollen deposition from the high to low arctic. Modern pollen deposition in the high arctic of Banks Island is characterized by up to 14% windblown tree pollen. Indicator taxa of the high and mid arctic include Oxyria (<5–23%), Saxifragaceae, Saxifraga oppositifolia, and Cruciferae (all up to 8%) and Dryas (up to 3%). Arboreal pollen increases to 60% in low-arctic and subarctic samples. Pollen concentration decreases from between 3 500 and 20 000 in the low arctic to less than 5 000 grains/cm3 in the high and mid arctic. Pollen spectra from the Late Glacial of northwestern Canada differ from those of the modern high and mid arctic not only by the absence of trees and shrubs but also in the relative proportions of Artemisia and of such indicator taxa as Oxyria and Saxifragaceae.

The metabolism of debrisoquine in man: (1) regioselectivity of hydroxylation and (2) aberrant oxidative metabolism in two sibling patients with carbimazole-induced agranulocytosis

The regioselectivity of the metabolic hydroxylation of debrisoquine has been determined in 43 healthy British white volunteers and the priority was found to be in the order 4 greater than 7 greater than 6 greater than 5 greater than 8. The order of preference for hydroxylation position was independent of debrisoquine 4-hydroxylation phenotype. The extent of total aromatic hydroxylation varied widely between individuals and was largely independent of the extent of 4-hydroxylation, and thus of the influence of the DH/DL locus. Two sisters and their blood relations all excreted comparatively large amounts of the phenolic metabolites in their urine, indicating some genetic basis for the control of aromatic oxidation of debrisoquine in man. These same two sisters had previously developed agranulocytosis in association with carbimazole therapy.

Sulphoxidation of S-carboxymethyl-L-cysteine in the rhesus monkey (Macaca mulatta), cynomologus monkey (Macaca fascicularis), African green monkey (Cercopithecus aethiops) and the marmoset (Callithrix jacchus)

The metabolic pathways giving rise to the urinary metabolites of S-carboxymethyl-L-cysteine have been identified for the rhesus, cynomologus, African green and marmoset species of monkey. The formation of a sulphoxide metabolite from the sulphide precursor is a reaction important in these species. The metabolic profile displayed by the marmoset was distinct from the three Old World species, with the rhesus and cynomologus being similar to man.

Plasma cortisol determination for the dexamethasone suppression test. Comparison of competitive protein-binding and commercial radioimmunoassay methods

Quality control serum samples and postdexamethasone plasma pools were used to compare 16 commercial cortisol radioimmunoassay kits with the competitive protein-binding assay for plasma glucocorticoids that we used to standardize the dexamethasone suppression test (DST). Thirteen radioimmunoassays gave higher criterion values for the DST than those established using the competitive protein-binding assay. The range of radioimmunoassay criterion values was 4.34 to 8.70 mu mg/dL. Possible explanations are given for these findings, and their importance to the clinical utility of the DST are emphasized. Each laboratory should validate its own criterion cortisol value for depression based on local data, including appropriate control groups.

Metabolic oxidation phenotypes as markers for susceptibility to lung cancer

That bronchial carcinoma is not an inevitable consequence of cigarette smoking has stimulated the search for host factors that might influence the susceptibility of the individual smoker. One plausible host factor would be a polymorphic gene controlling the metabolic oxidative activation of chemical carcinogens, giving rise to wide inter-subject variation in the generation of cancer-inducing and/or promoting species. Recently, three genetic polymorphisms of human metabolic oxidation have been demonstrated (as characterized by debrisoquine, mephenytoin and carbocysteine), with the metabolism of several substrates exhibiting the phenomenon. Debrisoquine 4-hydroxylation segregates into two human phenotypes, each comprising characteristic metabolic capability. We report here the frequency of debrisoquine 4-hydroxylation phenotypes in age-, sex- and smoking history-matched bronchial carcinoma and control patients. Cancer patients showed a preponderance of probable homozygous dominant extensive metabolizers (78.8%) with few recessive poor metabolizers (1.6%) compared with smoking controls (27.8% and 9.0% respectively). We conclude that the gene controlling debrisoquine 4-hydroxylation may be a host genetic determinant of susceptibility to lung cancer in smokers and that it represents a marker to assist in assessing individual risk.

A Holocene pollen record of boreal forest history from the Travaillant Lake area, Lower Mackenzie River Basin

A 396-cm sediment sequence from SW Lake in the boreal woodland zone near Travaillant Lake, Northwest Territories, Canada, provides a Holocene record of pollen percentages and species interactions. Three local pollen assemblage zones are described: a Betula–Populus–Juniperus zone from 10 500 to 9000 years BP, a Picea–Betula zone from 9000 to 5100 years BP, and a Picea–Betula–Alnus zone from 5100 years BP to the present. The earliest vegetation recorded at this site is a mosaic of poplar groves, juniper and Shepherdia shrub, and fragmentary patches of tundra, replaced rapidly by spruce woodland at roughly 8500 years BP, dominated initially by Picea glauca. Picea mariana spread extensively between 8500 and 5000 years BP, probably as a function of increasing paludification. The present spruce-dominated vegetation was in place by 5000 years BP. Some changes in the pollen record can be explained by the Milankovitch early Holocene period of warmer summers followed by a cooling to modern conditions by 5000 years BP. Others require explanations in terms of edaphic factors or biological interactions among the main taxa.

Comparison of plasma cortisol and corticosterone in the dexamethasone suppression test for melancholia

The suppression of plasma corticosterone (B), measured by radioimmunoassay (RIA), was compared to simultaneous suppression of plasma cortisol (F), measured as total corticoids by a competitive protein binding (CPB) assay, in the overnight dexamethasone suppression test (DST). Baseline plasma B concentrations in 10 control subjects were 4.04 +/- 1.07 ng/ml (X +/- S.D.) at 0800 hr and 1.51 +/- 0.68 ng/ml at 1600 hr. Post-dexamethasone 1600 hr B levels in the controls were 0.46 +/- 0.29 ng/ml. An early escape of plasma B (greater than 1.2 ng/ml), like that of F (greater than 5 micrograms/dl), during the overnight 24 hr 1.0 mg dose DST was noted in patients with melancholia (endogenous depression). Half-hourly catheter samples in a normal subject stimulated to escape from dexamethasone suppression showed that in general, plasma B concentrations parallel plasma F concentrations over a 12 hr period. Repeated weekly DSTs on two patients with different psychiatric diagnoses resulted in B : F correlations of 0.74 and 0.60. Overall agreement between B- and F-DST outcomes in all categories tested at 1600 and 2300 hr was 93%; the agreement in the melancholic and non-endogenous depressed groups was 100%. Post-dexamethasone, both B and F were suppressed 55-60% below the criterion level in controls. In those patients who escaped from dexamethasone suppression, the percentage increase in plasma B above the criterion level was significantly greater (+55%) than the corresponding percentage change in plasma F. Most patients with borderline abnormal F-DSTs (3.5 - 4.9 micrograms/dl) exhibited clearly abnormal B-DSTs (greater than 1.2 ng/ml). We conclude that the use of dexamethasone suppression of plasma B (using 1.2 ng/ml as the abnormal criterion value) is an additional indicator of an abnormal DST in depressed patients.

Spectral binding studies of the polymorphically metabolized drugs debrisoquine, sparteine and phenformin by cytochrome P-450 of normal and hydroxylation deficient rat strains

The mechanisms of polymorphic drug hydroxylation of debrisoquine, sparteine and related drugs in vivo have been investigated using Cyt P-450 preparations of inbred rat strains as an in vitro model of the poor and extensive metabolizer phenotypes found in various rat strains and in man. Optical difference spectroscopy with debrisoquine, sparteine, phenformin and three other drugs (selected test compounds with proven or suspected hydroxylation polymorphisms in man) exhibited Type 1 binding in normal Sprague-Dawley, Fischer and Lewis Cyt P-450, whereas no Type I drug binding was found in the hydroxylation deficient DA rat liver Cyt P-450. Cyt P-450 content and Type II drug binding of metiamide was the same in normal and hydroxylation deficient rat liver microsomes. The pronounced Type I drug binding in extensive hydroxylation Cyt P-450 and the defective Type I binding in DA Cyt P-450 in vitro, therefore, closely parallels the polymorphic hydroxylation pattern of these test drugs found in the four rat strains studied in vivo. Consequently, missing binding properties of Cyt P-450 or of its micro-environment might represent the enzymatic defect underlying the genetically determined hydroxylation deficiency of polymorphically metabolized drugs in the poor metabolizer phenotype in the DA rat and, by inference, in man.