Escape from dexamethasone-induced ACTH and cortisol suppression by corticotrophin-releasing hormone: modulatory effect of basal dexamethasone levels

HPA axis and sleep: identifying subtypes of major depression

It is increasingly acknowledged that the diagnosis of major depression encompasses patients who do not necessarily share the same disease biology. Though the diagnostic criteria allow the specification of different subtypes, e.g. melancholic and atypical features, a consensus still has to be reached with regard to the clinical symptoms that clearly delineate these subtypes. Beside clinical characteristics, biological markers may help to further improve identification of biologically distinct endophenotypes and, ultimately, to devise more specific treatment strategies. Alterations of the hypothalamus-pituitary-adrenal (HPA) axis and sleep architecture are not only commonly observed in patients with major depression, but the nature and extent of these alterations can help to identify distinct subtypes. Thus, a HPA overdrive, due to enhanced secretion of corticotropin-releasing hormone (CRH) and an impaired negative feedback via glucocorticoid receptors, seems to be most consistently observed in patients with melancholic features. These patients also show the clearest sleep-electroencephalogram (EEG) alterations, including disrupted sleep, low amounts of slow wave sleep (SWS), a short rapid eye movement (REM) latency and a high REM density. In contrast, patients with atypical features are characterized by reduced activity of the HPA axis and ascending noradrenergic neurons in the locus coeruleus. Though sleep-EEG alterations have been less thoroughly examined in these patients, there are data to suggest that SWS is not reduced and that REM sleep parameters are not consistently altered. While the atypical and melancholic subtypes of major depression may represent the extremes of a spectrum, the distinct clinical features provide an opportunity to further explore biological markers, as well as environmental factors, contributing to these clinical phenotypes. Moreover, dysregulations of the HPA axis and sleep-EEG alterations can also be induced in rodents, thereby allowing alignment of critical biological aspects of a human disease subtype with an animal model. Such "Translational Research" efforts should help to develop targeted therapies for distinct patient populations.

High-dose naloxone (1.0 mg/kg): psychological and endocrine effects in normal male subjects pretreated with one milligram of dexamethasone

The possible participation of the endogenous opioid system (EOS) in the negative feedback of the hypothalamic-pituitary-adrenal axis (HPA-a) activated by low doses (1 mg) of dexamethasone (Dex) was investigated. Ten male healthy subjects (mean age 31.5 +/- 1.9 SEM) were studied on 2 separate days, in a double-blind, cross-over and placebo-controlled design. All subjects were pretreated with 1.0 mg Dex orally the night (2300 h) before both test days. On the study days, subjects were admitted at 0700 h for cannula insertion; the administration of an i.v. bolus of either naloxone (Nal) (1.0 mg/kg) or saline solution (Sal) i.v. was started at 0900 h. Before and following each infusion, mood was measured by a Visual Analogue Scales (VAS) and by the Affective Quality Scale (AQS) every 30 min and blood samples were taken at 15-min intervals. Blood pressure and heart rate were also monitored. Before Dex administration, plasma cortisol levels were within the normal range in all subjects (210.4 +/- 13 ng/ml), while after 9 h after Dex cortisol levels showed the expected significant (p < 0.01) decrease (11.5 +/- 1.9 and 15.04 +/- 0.7 ng/ml for Sal and Nal test days respectively). There were no detectable increases in plasma cortisol levels following either Nal nor Sal administration. However, there was a Nal-induced significant increase in LH (p < 0.01) thus indicating that an effective opioid blockade at the level of the hypothalamic-pituitary unit occurred. There were also a mild and selective Dex + Nal-induced dysphoric (mood factors related to subjects perception of their cognition) and bradycardic effects (p < 0.05). These results suggest that the EOS is not directly involved in the negative feedback triggered by low doses of Dex of the HPA-a, and that there might be a possible glucocorticoid-opioid interaction for the modulation of some aspects of mood.

Adrenocorticotropic hormone, beta-endorphin and cortisol responses to oCRH in unipolar depressed patients pretreated with dexamethasone

1. Corticotropin-releasing hormone (ovine CRH, 100 micrograms intravenous bolus) was given to 63 unipolar depressed inpatients following the 1 mg overnight dexamethasone suppression test (DST). The depressed patients included 18 minor, 24 simple major and 21 melancholic subtypes. 2. Baseline or postdexamethasone plasma levels of intact adrenocorticotropic hormone (ACTH), beta-endorphin/beta-lipotropin (beta END/beta LPH), cortisol, and dexamethasone were measured, as well as the post DST+CRH hormone responses. 3. CRH administration 9.5 hr after dexamethasone resulted in a significant enhancement of ACTH, beta END/beta LPH and cortisol secretion. The post DST+CRH ACTH and beta END/beta LPH- but not cortisol-values exceeded their baseline hormone levels. The post DST+CRH ACTH--but not beta END/beta LPH or cortisol-levels were significantly higher in major depressives compared to minor depressives. The post DST+CRH ACTH and beta END/beta LPH--but not cortisol-levels were significantly higher in DST nonsuppressors than suppressors. The post DST+CRH ACTH levels were significantly and positively related to severity of illness. 4. The results provide evidence that the pathophysiology underlying the abnormal DST+CRH and DST tests in melancholia is localized at the pituitary level and may consist of a CRH-driven breakthrough of corticotropic cell secretion synergized by central and peripheral agents, in conjunction with a decrease in glucocorticoid feedback suppressibility.

Indole-pyruvic acid, a tryptophan ketoanalogue, antagonizes the endocrine but not the behavioral effects of repeated stress in a model of depression

Increased glucocorticoid secretion is frequent in mood disorders and is normalized by long-term antidepressant therapy. Many antidepressants act by increasing central serotonin transmission. We investigated the effects of a serotonin precursor, indole-pyruvic acid (IPA), in an animal model of depression based on repeated exposure to unpredictable stress. Rats were divided in groups, and IPA (20 mg/kg), the tricyclic antidepressant imipramine (IMI) (5 mg/kg), or vehicle was administered daily during 3 weeks of repeated exposure to various stressors according to the procedure described by Katz et al [Katz RJ, Roth KA, Carroll BJ (1981): Neurosci Biobehav Rev 5:247-251]. After treatment, rats were evaluated for stress-induced exploratory behavior and killed 24 hr later. Serum corticosterone levels and glucocorticoid receptor (GR) immunoreactivity (IR) in the nuclei of neurons located in the hippocampal subregion CA1 were also measured. Rats exposed to repeated stress showed a lower exploratory behavior score (p < 0.01), higher basal corticosterone levels (p < 0.01), and stronger GR IR in the hippocampus (p < 0.05) than control rats. All of these effects were antagonized by IMI treatment. IPA administration did not affect the behavioral response induced by repeated stress (p < 0.01) but normalized serum corticosterone levels. In addition, IPA treatment produced a decrease in GR IR (p < 0.05 versus control group) that was not modified by exposure to repeated stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of age on the cortisol response to human corticotropin-releasing hormone in depressed patients pretreated with dexamethasone

A combined dexamethasone-human corticotropin-releasing hormone (hCRH) test was applied to 63 individuals--44 patients with major depressive episode (22 male, age 49.5 +/- 13.4 years, and 22 female, 44.6 +/- 11.9 years) and 19 normal male controls (age 42.0 +/- 16.8 years). In normal controls, premedication with 1.5 mg dexamethasone at 11:00 PM substantially inhibited the stimulated release (expressed as area under the time course curve) of cortisol on the day after 100 micrograms hCRH was administered at 3:00 PM. In contrast, depressives responded with significant rises in cortisol (normal controls, 4.1 +/- 4.0 x 10(3) ng/ml/min; depressives, 12.7 +/- 8.3 x 10(3) ng/ml/min; p less than 0.01). Multiple stepwise regression analysis disclosed significant effects of age (T = 3.55, p less than 0.01) and severity of depression (T = 5.42, p less than 0.01) on cortisol release in patients. Such an influence of age upon pituitary-adrenocortical regulation was absent among healthy controls. We postulate that the underlying mechanisms involve changes in corticosteroid receptors in the brain of depressives, impairing the sensitivity with which the brain-pituitary system can detect the dexamethasone feedback signal. Altered glucocorticoid neuroregulation in depression is apparently accelerated by the aging process.

Hypercortisolism and its possible neural bases

As is clear from the pages of this journal, biological psychiatrists remain fascinated by the phenomenon of dexamethasone (DEX) resistance and the hypercortisolism of various neuropsychiatric disorders. The mere existence of the endocrine abnormalities attests to the biological reality of these disorders. Furthermore, progress continues in using the occurrence of these endocrine defects as both diagnostic and prognostic markers of disease subtypes. Progress has also been made in understanding the mechanisms underlying the endocrine defects. The adrenocortical axis is vastly complex, involving multiple hypothalamic-releasing factors under CNS control, shifting pituitary and adrenal sensitivies to hormonal signals, and feedback regulation at all three levels. What defects within this system produce DEX resistance and hypercortisolism? In this paper, we review data suggesting that the endocrine problems is, at least in part, neural in nature. Drawing upon a rodent literature, we will also suggest some models by which this can occur. The hypercortisolism found in cases of affective disorders, anorexia nervosa, Alzheimer's disease, among the very aged or the chronically stressed, is not a uniform phenomenon. Basal cortisol concentrations can be elevated in all or part of the circadian cycle. Resistance to glucocorticoid (GC) feedback inhibition (as typically demonstrated by DEX resistance) can occur; the resistance can be complete, or occur as early escape from DEX suppression. Finally, elevated basal cortisol concentrations and DEX resistance can occur independently of each other. Until the end of this review, we will conveniently refer to these variants of adrenocortical hyperactivity as "hypercortisolism." In addition, rather than using the term "hypercortisolism" for the rat, we will use "hyperadrenocorticism" (as they secrete corticosterone, rather than cortisol).

Psychiatric implications of altered limbic-hypothalamic-pituitary-adrenocortical activity

Hormones of the limbic-hypothalamic-pituitary-adrenocortical (LHPA) system are much involved in central nervous system regulation. The major LHPA neuropeptides, corticotropin-releasing hormone (CRH), vasopressin (AVP) and corticotropin (ACTH) do not only coordinate the neuroendocrine response to stress, but also induce behavioral adaptation. Transcription and post-translational processing of these neuropeptides is regulated by corticosteroids secreted from the adrenal cortex after stimulation by ACTH and other proopiomelanocortin derived peptides. These steroids play a key role as regulators of cell development, homeostatic maintenance and adaptation to environmental challenges. They execute vitally important actions through genomic effects resulting in altered gene expression and nongenomic effects leading to altered neuronal excitability. Since excessive secretory activity of this particular neuroendocrine system is part of an acute stress response or depressive symptom pattern, there is good reason to suspect that central actions of these steroids and peptides are involved in pathophysiology determining the clinical phenotype, drug response and relapse liability. This overview summarizes the clinical neuroendocrine investigations of the author and his collaborators, while they worked at the Department of Psychiatry in Mainz. The major conclusions from this work were: (1) aberrant hormonal responses to challenges with dexamethasone, ACTH or CRH are reflecting altered brain physiology in affective illness and related disorders; (2) hormones of the LHPA axis influence also nonendocrine behavioral systems such as sleep EEG; (3) physiologically significant interactions exist between LHPA hormones, the thyroid, growth hormone, gonadal and other neuroendocrine systems; (4) hormones of the LHPA axis constitute a bidirectional link between immunoregulation and brain activity; and (5) future psychiatric research topics such as molecular genetics of affective disorders, familial risk studies, drug response analysis and neurobiology of aging will benefit from extended knowledge of neural corticosteroid effects at a clinical, cellular, and molecular level.

Corticotropin releasing hormone stimulation test: diagnostic aspects in Cushing's syndrome

The effect of exogenous ovine Corticotropin-Releasing Hormone (oCRH) on plasma ACTH and cortisol levels was investigated in 10 normal volunteers and in 37 patients with Cushing's syndrome (26 with pituitary-dependent disease, 5 with an adrenal adenoma, 2 with an adrenal carcinoma and 4 with bilateral nodular hyperplasia). In all normal subjects and in patients with Cushing's disease, oCRH 100 micrograms as a bolus produced an increase in both plasma ACTH and cortisol. The peak of ACTH occurred after 15-30 min, while plasma cortisol showed highest levels between 30 and 60 min after oCRH administration. The hormonal response in Cushing's disease showed great variability with a clear hyperresponsiveness at least in 6 out of 26 patients with Cushing's disease. A slight and delayed response occurred in 3 cases of bilateral nodular adrenal hyperplasia, while a fourth case showed hyperresponsiveness similar to that found in pituitary-dependent Cushing's disease. No response was observed in patients with an adrenal tumor. Eleven patients with Cushing's disease were tested before and 1 month after pituitary microadenomectomy. After surgery basal cortisol levels were reduced in 10 and became unresponsive or less responsive to oCRH. ACTH patterns were variable with a normal response only in few cases. Although this test seems of limited value in the diagnosis of hypercortisolism, it is a useful tool to differentiate some types of Cushing's syndrome (adrenal tumor from pituitary-dependent Cushing's disease). Variable patterns of response in cases with bilateral nodular adrenal hyperplasia limit the usefulness of this test in recognizing this rare form of hypercortisolism.