Corticotropin-releasing-factor induced pituitary-adrenal response in depression

How to measure glucocorticoid receptor's sensitivity in patients with stress-related psychiatric disorders

Stress is a state of derailed homeostasis and a main environmental risk factor for psychiatric diseases. Chronic or uncontrollable stress may lead to a dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, which is a common feature of stress-related psychiatric disorders. One of the key mechanisms underlying a disturbed HPA axis is an impaired function of the glucocorticoid receptor (GR) with an enhanced or reduced feedback sensitivity for glucocorticoids and subsequently altered concentrations of peripheral cortisol. GR function is regulated by a multiprotein complex including the different expression of the hsp90 co-chaperone FK 506 binding protein 51 (FKBP5) that may be genetically determined or acquired in response to stressful stimuli. Specific patterns of a dysregulation of the HPA axis and GR function are found in different stress-related psychiatric entities e.g. major depression, job-related exhaustion or posttraumatic stress disorder. GR challenge tests like the dexamethasone-suppression test (DST), the dexamethasone-corticotropin-releasing hormone (dex-CRH) test or most recently the analysis of the dexamethasone-induced gene expression are employed to sensitively measure HPA axis activity in these disorders. They provide information for a stratification of phenotypic similar but neurobiological diverse psychiatric disorders. In this review we present a synopsis of GR challenge tests with a focus on the application of the DST, the CRH test and the dex-CRH test as well as the dexamethasone-induced gene expression in stress-related psychiatric entities.

Stress hormone response to the DEX-CRH test and its relation to psychotherapy outcome in panic disorder patients with and without agoraphobia

This study tested whether the hormonal stress response to the DEX-CRH test may be predictive of the psychotherapy success for panic disorder (PD). Thirty-four patients diagnosed either with agoraphobia with PD or PD without agoraphobia were subjected to cognitive behavioural therapy (CBT). Patients (pre-therapy) and healthy volunteers were exposed to the DEX-CRH test. Blood samples were taken for cortisol and adrenocorticotropic hormone (ACTH) assessment. Established panic-specific questionnaires were handed out for the pre-therapy and post-therapy evaluation of disease severity (with reference to panic beliefs and agoraphobic cognitions, fear of bodily sensations, agoraphobic avoidance behaviour). Repeated measures ANCOVA were conducted for the analysis of the pre-therapy hormonal response, and Pearson's correlation analysis to test for associations with the psychotherapy outcome. Data analyses revealed large effect sizes for CBT in the clinical measures (η² ≥ 0.321), main effects of time for cortisol and ACTH with no differences between both groups, and significant associations between cortisol release and agoraphobic cognitions for the patients. PD diagnosis had no impact on the hormonal response. However, those patients with higher cortisol release showed less improvement after CBT (significantly for agoraphobic cognitions). Clinical implications of these findings are the prediction of the therapy success from a potential endocrine correlate whose persistency (if assessed repeatedly) during the treatment may predict (non-)response to the current treatment, possibly representing a decision support for a change in treatment to avoid the continuation of an inefficient treatment.

Cortisol stress response in post-traumatic stress disorder, panic disorder, and major depressive disorder patients

BACKGROUND

Previous research has focussed extensively on the distinction of HPA-axis functioning between patient groups and healthy volunteers, with relatively little emphasis on a direct comparison of patient groups. The current study's aim was to analyse differences in the cortisol stress response as a function of primary diagnosis of panic disorder (PD), post-traumatic stress disorder (PTSD), and major depressive disorder (MDD).

METHODS

A total of n=30 PD (mean age±SD: 36.07±12.56), n=23 PTSD (41.22±10.17), n=18 MDD patients (39.00±14.93) and n=47 healthy control (HC) individuals (35.51±13.15) participated in this study. All the study participants were female. The Trier Social Stress Test (TSST) was used for reliable laboratory stress induction. Blood sampling accompanied the TSST for cortisol and ACTH assessment. Panic-related, PTSD-specific questionnaires and the Beck Depression Inventory II were handed out for the characterisation of the study groups. Repeated measure ANCOVAs were conducted to test for main effects of time or group and for interaction effects. Regression analyses were conducted to take comorbid depression into account.

RESULTS

26.7% of the PD patients, 43.5% of the PTSD patients, 72.2% of the MDD patients and 80.6% of the HC participants showed a cortisol stress response upon the TSST. ANCOVA revealed a cortisol hypo-responsiveness both in PD and PTSD patients, while no significant group differences were seen in the ACTH concentrations. Additional analyses showed no impact of comorbid depressiveness on the cortisol stress response. MDD patients did not differ in the hormonal stress response neither compared to the HC participants nor to the PD and PTSD patients.

CONCLUSION

Our main findings provide evidence of a dissociation between the cortisol and ACTH concentrations in response to the TSST in PTSD and in PD patients, independent of comorbid depression. Our results further support overall research findings of a cortisol hypo-responsiveness in PD patients. A hypo-response pattern was also seen in the PTSD patients agreeing with previous finding on the cortisol stress reactivity following TSST stress induction in these patients. Patients with a primary MDD diagnosis showed descriptively higher cortisol concentrations compared to the anxiety patients, and lower cortisol concentrations as the healthy individuals. The limitations of the study and implications for future studies will be discussed.

Interaction of stress, corticotropin-releasing factor, arginine vasopressin and behaviour

Stress mediates the activation of a variety of systems ranging from inflammatory to behavioral responses. In this review we focus on two neuropeptide systems, corticotropin-releasing factor (CRF) and arginine vasopressin (AVP), and their roles in regulating stress responses. Both peptides have been demonstrated to be involved in anxiogenic and depressive effects, actions mediated in part through their regulation of the hypothalamic-pituitary-adrenal axis and the release of adrenocorticotropic hormone. Because of the depressive effects of CRF and AVP, drugs modifying the stress-associated detrimental actions of CRF and AVP are under development, particularly drugs antagonizing CRF and AVP receptors for therapy in depression.

Urocortins: CRF's siblings and their potential role in anxiety, depression and alcohol drinking behavior

It is widely accepted that stress, anxiety, depression and alcohol abuse-related disorders are in large part controlled by corticotropin-releasing factor (CRF) receptors. However, evidence is accumulating that some of the actions on these receptors are mediated not by CRF, but by a family of related Urocortin (Ucn) peptides Ucn1, Ucn2 and Ucn3. The initial narrow focus on CRF as the potential main player acting on CRF receptors appears outdated. Instead it is suggested that CRF and the individual Ucns act in a complementary and brain region-specific fashion to regulate anxiety-related behaviors and alcohol consumption. This review, based on a symposium held in 2011 at the research meeting on "Alcoholism and Stress" in Volterra, Italy, highlights recent evidence for regulation of these behaviors by Ucns. In studies on stress and anxiety, the roles of Ucns, and in particular Ucn1, appear more visible in experiments analyzing adaptation to stressors rather than testing basal anxiety states. Based on these studies, we propose that the contribution of Ucn1 to regulating mood follows a U-like pattern with both high and low activity of Ucn1 contributing to high anxiety states. In studies on alcohol use disorders, the CRF system appears to regulate not only dependence-induced drinking, but also binge drinking and even basal consumption of alcohol. While dependence-induced and binge drinking rely on the actions of CRF on CRFR1 receptors, alcohol consumption in models of these behaviors is inhibited by actions of Ucns on CRFR2. In contrast, alcohol preference is positively influenced by actions of Ucn1, which is capable of acting on both CRFR1 and CRFR2. Because of complex distribution of Ucns in the nervous system, advances in this field will critically depend on development of new tools allowing site-specific analyses of the roles of Ucns and CRF.

Does midbrain urocortin 1 matter? A 15-year journey from stress (mal)adaptation to energy metabolism

This review summarizes some of the milestones of the research on the biological functions(s) of midbrain urocortin 1 (Ucn1) since its discovery 15 years ago. Detailed characterization of Ucn1 in the midbrain revealed its overall significance in food intake and regulation of homeostatic equilibrium and mood under stress. In addition, we have recently found a conspicuous alteration in midbrain Ucn1 levels in brains of depressed suicide victims. Furthermore, from the results from the genetically modified animals, a picture is emerging where corticotrophin-releasing factor promotes the initial reactions to stress, whereas Ucn1 seems to be crucial for management of the later adaptive phase. In the case of imbalance in action of these principle stress mediators, vulnerability to stress-related brain diseases is enhanced.

Centrally administered urocortin 3 inhibits food intake and gastric emptying in mice

Urocortin 3 (Ucn3) is recognized as a member of the corticotropin-releasing factor (CRF) family, which plays an important role in regulating food intake. We investigated the effects of centrally administered Ucn3 on food intake and gastric emptying in mice. Intracerebroventricular (ICV)administration of Ucn3 (0.1–1 nmol per mouse) decreased food intake in a dose-dependent manner. The inhibitory effect of Ucn3 on food intake was less potent than that of centrally administered CRF and Urocortin 1. ICV administration of Ucn3 (0.1–1 nmol per mouse) decreased the gastric emptying rate in a dose-dependent manner. Ucn3 decreased food intake in high-fat diet-fed obese mice as well as in lean mice. These results indicated that Ucn3 influences feeding behavior and gut motility, and may be a promising therapeutic target in the treatment of eating and functional gastrointestinal disorders.

A pharmacological tool to assess vasopressinergic co-activation of the hypothalamus-pituitary-adrenal axis more integrally in healthy volunteers

Pharmacological function tests consisting of 100 µg hCRH (corticorelin) and 10 µg dDAVP (desmopressin) mimic endogenous hypothalamus-pituitary-adrenal (HPA) axis activation. However, physiological CRH concentrations preclude informative vasopressinergic co-activation (using dDAVP) and independent quantification of both corticotrophinergic (using hCRH) and vasopressinergic (using dDAVP) activation is limited due to administration on separate occasions. This randomized, double-blind, placebo-controlled, partial five-way crossover study in healthy males and females (six : six) examined whether (1) concomitant administration of dDAVP and hCRH provides more informative vasopressinergic co-activation than dDAVP alone; and (2) whether the administration of dDAVP followed two hours later by hCRH can quantify both vasopressinergic and corticotrophinergic activation on a single test day. Combining 10 µg dDAVP with 10 µg and 30 µg hCRH caused dose-related ACTH and cortisol release which was larger than with 10 µg dDAVP alone and respectively comparable to and greater than that induced by 100 µg hCRH. Using 10 µg dDAVP alone demonstrated limited ACTH release while the effects of 100 µg hCRH two hours later were three times as large. ACTH and cortisol released by 10 µg dDAVP returned to baseline prior to 100 µg hCRH administration and dDAVP did not influence the response to subsequent hCRH administration. Dose-related vasopressinergic co-activation of the HPA axis was induced by combining 10 µg dDAVP with 10 µg and 30 µg hCRH. Combining 10 µg dDAVP with 10 µg hCRH induced the potentially most informative vasopressinergic co-activation since it is not restricted by ceiling or flooring effects. The hCRH response was not affected by prior dDAVP, allowing for a practical function test examining both HPA activation routes on the same day.

Metoclopramide as pharmacological tool to assess vasopressinergic co-activation of the hypothalamus-pituitary-adrenal (HPA) axis: a study in healthy volunteers

The synthetic vasopressin (AVP) analogue desmopressin (dDAVP) has been used as pharmacological function test to quantify vasopressinergic co-activation of the hypothalamus-pituitary-adrenal (HPA) axis in the past. Such exogenous vasopressinergic stimulation may induce confounding cardiovascular, pro-coagulatory and anti-diuretic effects and low endogenous corticotrophin-releasing-hormone (CRH) levels may limit its potential to reliably assess co-activation. Alternatively, the dopamine-2-(D2)-antagonist metoclopramide is believed to induce co-activation indirectly by releasing endogenous AVP. We investigated this indirect co-activation with metoclopramide under conditions of low and enhanced endogenous CRH release in healthy volunteers. A randomized, double-blind, placebo-controlled, four-way crossover study was performed in 12 healthy males. CRH release was induced by administering an oral 5-hydroxytryptophan (5-HTP) 200 mg function test. Co-activation was investigated by administering metoclopramide 10mg intravenously around the expected maximal effect of 5-HTP. The neuroendocrine effects were compared to those of metoclopramide alone, the 5-HTP test alone and matching placebo. Metoclopramide safely induced HPA-axis activation by itself, and potently synergized 5-HTP-induced corticotrophinergic activation of the HPA axis. These findings are indicative of vasopressinergic co-activation and suggest a role for metoclopramide as a practical function test for co-activation of the HPA axis. However, its application will be hampered pending clarification of the exact pharmacological mechanism by which metoclopramide induces co-activation of the HPA axis.

Chronic psychosocial stress affects corticotropin-releasing factor in the paraventricular nucleus and central extended amygdala as well as urocortin 1 in the non-preganglionic Edinger-Westphal nucleus of the tree shrew

Stressful stimuli evoke neuronal and neuroendocrine responses helping an organism to adapt to changed environmental conditions. Chronic stressors may induce maladaptive responses leading to psychiatric diseases, such as anxiety and major depression. A suitable animal model to unravel mechanisms involved in the control of adaptation to chronic stress is the psychological subordination stress in the male tree shrew. Subordinate male tree shrews exhibit chronic hypothalamo-pituitary-adrenal (HPA) activation as reflected in continuously elevated cortisol secretion, and structural changes in the hippocampal formation. Corticotropin-releasing factor (CRF) is the major peptide released upon activation of the HPA axis in response to stress. Recent evidence suggests that besides CRF, urocortin 1 (Ucn1) also plays a role in stress adaptation. We have tested the significance of CRF and Ucn1 in adaptation to chronic psychosocial stress in male tree shrews exposed for 35 days to daily psychosocial conflict, by performing semi-quantitative immunocytochemistry for CRF in the parvocellular hypothalamic paraventricular nucleus (pPVN), extended amygdala, viz. central extended amygdala (CeA) and dorsolateral nucleus of the bed nucleus of the stria terminalis (BNSTdl) as well as that for Ucn1 in the non-preganglionic Edinger-Westphal nucleus (npEW). Compared to unstressed animals, psychosocial stress resulted in an immediate and sustained activation of the HPA axis and sympathetic tone as well as reduced testosterone concentration and decreased body and testis weights vs. non-stressed tree shrews. In the pPVN, the number of CRF-immunoreactive neurons and the specific signal density of CRF-immunoreactive fiber terminals in the CeA were strongly reduced (-300 and -40%, respectively; P<0.05), whereas no significant difference in CRF fiber density was found in BNSTdl. The npEW revealed 4 times less Ucn1-immunoreactive neurons (P<0.05). These clear effects on both Ucn1- and CRF-neuropeptide contents may reflect a crucial mechanism enabling the animal to adapt successfully to the stressors, and point to the significance of the pPVN, CeA and npEW in stress-induced brain diseases.

Antidepressant-like effects of the CRF family peptides, urocortin 1, urocortin 2 and urocortin 3 in a modified forced swimming test in mice

Most of the evidence suggests that corticotropin-releasing hormone (CRH) is involved in mood disorders. The CRF receptors type 1 (CRF(1) receptors) elicit a stress response, and their natural and synthetic antagonists have been studied as possible drugs against depression, whereas CRF receptors type 2 (CRF(2) receptors) appear to alleviate the stress response and mediate anxiolytic action. Other CRF family peptides are urocortin 1 (Ucn 1), urocortin 2 (Ucn 2) and urocortin 3 (Ucn 3). Little is known about the action of Ucn 1, Ucn 2 and Ucn 3 on depressive disorders. Antidepressant-like effects of Ucn 1, Ucn 2 and Ucn 3 (0.13, 0.25 and 0.5 microg/2 microl, i.c.v.) were assayed in mice in a modified forced swimming test (FST). This modified FST predicts the clinical efficacy of an antidepressant drug through the scoring of immobility, climbing and swimming behavior. The study demonstrated that Ucn 1 had no action on any of parameters studied in the modified FST. Ucn 2 elicited antidepressive-like action by shortening the immobility time. Additionally Ucn 2 significantly increased the climbing and swimming times. Ucn 3 likewise displayed an antidepressive-like effect by shortening the immobility time, and increasing the climbing and swimming times. The results suggest that CRF(2) receptor stimulation by Ucn 2 or Ucn 3 leads to antidepressant-like action, but dual stimulation of the CRF(1) and CRF(2) receptors by Ucn 1 does not trigger antidepressant-like action in the modified mouse FST.

Mice with mutations in the HPA-system as models for symptoms of depression

Genetically engineered mice hold promise to help us understand the effects of enhanced or reduced gene activity upon behavior and metabolism. Because many basic and clinical studies suggest that alterations of the hypothalamic pituitary adrenocortical (HPA) system are involved in the development and course of depression, mouse mutants with genetic modifications of genes regulating the HPA system were generated. This review summarizes these effects and concludes that advanced technologies allowing for regional overexpression or inactivation of genes or introduction of polymorphisms into the mouse genome are well suited to explain individual symptoms or symptom patterns prevalent among depressives. However, as depression is a complex disorder in which minor changes of many genes as well as environmental factors (including epigenetic programming) play a causal role and determine the phenotype, the use of mice with single gene mutations needs to be critically discussed when attempting to create a genetic animal model of depression.

Desmopressin augments pituitary-adrenal responsivity to corticotropin-releasing hormone in subjects with chronic fatigue syndrome and in healthy volunteers

BACKGROUND

Corticotropin-releasing hormone (CRH) and vasopressin (VP) are the two principal neuropeptide regulators of the hypothalamic-pituitary-adrenal axis in man, with VP serving to augment CRH-induced adrenocorticotropic hormone (ACTH) release. Unlike VP, desmopressin (DDAVP), which is a synthetic analogue of VP, when administered alone, has not been shown in healthy subjects to have consistent ACTH-releasing properties. It has been suggested that chronic fatigue syndrome (CFS), characterized by profound fatigue and a constellation of other symptoms, may be caused by a central deficiency of CRH.

METHODS

We administered 100 micrograms ovine CRH (oCRH) and 10 micrograms DDAVP, both alone and in combination, to a group of subjects with CFS, and to a group of healthy volunteers. Our aim was to establish the effect of DDAVP on CRH-induced ACTH release in these two groups.

RESULTS

The delta-ACTH responses to oCRH were attenuated in the CFS (21.0 +/- 4.5 ng/L) compared to the control subjects (57.8 +/- 11.0 ng/L; t = 3.2, df = 21, p < .005). The delta-cortisol responses were also reduced in the CFS (157.6 +/- 40.7 nmol/L) compared to the healthy subjects (303.5 +/- 20.9 nmol/L; t = 3.1, df = 21, p < .01). The delta-ACTH and delta-cortisol responses to DDAVP alone did not differ between the two groups. On administration of both CRH and DDAVP no response differences between the two groups for either ACTH (p = .3) or cortisol output (p = .87) were established. Comparing the ACTH and cortisol responses to CRH and CRH/DDAVP in only those individuals from each group who had both tests, the cortisol output to the combination was significantly greater in the CFS compared to the healthy group. The ACTH output was also increased in the former group, though this was not significant.

CONCLUSIONS

DDAVP augments CRH-mediated pituitary-adrenal responsivity in healthy subjects and in patients with CFS. That DDAVP was capable of normalizing the pituitary-adrenal response to oCRH in the CFS group suggests there may be increased vasopressinergic responsivity of the anterior pituitary in CFS and/or that DDAVP may be exerting an effect at an adrenal level.

Vasopressin and the regulation of hypothalamic-pituitary-adrenal axis function: implications for the pathophysiology of depression

The role of arginine vasopressin (AVPNP) in the control of adrenocorticotropic hormone (ACTH) secretion is explored, and in particular, its involvement in various stress response paradigms which may be of relevance in our understanding of the pathophysiology of depression. VP is released from two sites in the hypothalamus; the parvicellular division of the paraventricular nucleus (PVN), where corticotropin releasing hormone (CRH) is also formed, and from the magnocellular neurons of the supraoptic nucleus (SON) and the PVN. The intricate interaction with CRH, the other main ACTH secretagogue, and with glucocorticoids, the inhibitory feedback component of hypothalamic-pituitary-adrenal-axis (HPA) activity, is outlined. That VP plays an important role in the stress response is now beyond doubt. Examination of the impact of psychological stressors on the differential expression of VP and CRH at a hypothalamic and pituitary level has been facilitated by advances in molecular biological techniques. Of importance has been the cloning of the V1b receptor gene, the receptor at which AVP is active in the anterior pituitary. Chronic stress paradigms, associated with HPA hyperresponsiveness, and ACTH release following a novel superimposed stress, have been found with relative consistency to show a shift in the CRH:AVP ratio. This may relate to differing feedback sensitivity of AVP to glucocorticoid feedback restraint and the greater responsivity of AVP over CRH to chronic stimulatory stress input. Evidence for functionally distinct pools of ACTH releasing corticotropes, and the finding that AVP levels more closely correlate with ACTH levels than do CRH levels, suggest a more dynamic role for AVP in activity of the stress axis, and a primarily permissive function for CRH. The renewed interest in the role of VP in HPA axis activity may have important implications for furthering our understanding of psychiatric conditions such as depression, where significant dysregulation of this axis is seen. Elevated baseline cortisol, dexamethasone non-suppression and blunted CRH/ACTH release have been consistently documented. The possible contribution of VP to this hyperactivity, despite its known synergy with CRH, has been largely neglected. In animal models there is clear evidence that chronic psychological stressors increase the ratio of AVP to CRH production. Psychosocial stressors are intrinsically linked with depressive illness. The finding of elevated levels of AVP in postmortem studies of depressives and the lowering of CSF AVP levels by antidepressants, raises the question of the precise role of AVP in the overactivity of the HPA in depression, a finding that is currently attributed to overdrive of its HPA regulatory companion, CRH.

Blunted ACTH response to hypoglycemic stress in depressed patients but not in patients with schizophrenia

In this study, 7 hospitalized patients with major depression (MD), 5 hospitalized patients with schizophrenia (S), and 13 control subjects (C) were administered 0.15 units/kg of regular insulin at 1600 h by intravenous bolus infusion. ACTH, cortisol, and glucose levels were measured intermittently for 2h following infusion. Baseline ACTH, cortisol and glucose levels were similar in Cs, MDs, and Ss. The mean glucose nadir was equivalent for Cs, patients with MD, and patients with S. Patients with MD had a blunted ACTH response (F = 3.28; df = 12,126; p = .0004) and cortisol response (F = 4.20; df = 12,132; p = .0001) to hypoglycemia when compared to Cs and patients with S. Carroll Depression Rating Scale scores in patients with S (23 +/- 10) were similar to patients with MD (30 +/- 8) and significantly higher than in controls (1 +/- 2) (F = 55.2; df = 2.22; p = .0001). These findings suggest that patients with MD show different ACTH and cortisol responses to hypoglycemic stress which are not explained by negative feedback of baseline ACTH or cortisol, glucose nadir, or the number of depressive symptoms per se.

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.

Implications of altered limbic-hypothalamic-pituitary-adrenocortical (LHPA)-function for neurobiology of depression

The current article suggests that the neuroendocrine system constitutes a bidirectional link between the brain and humoral homeostasis in the periphery. Any change of neuronal activity in the brain--regardless whether induced by external stimuli or endogenous errors of metabolism--may result in altered composition of gene products. Among these are peptides which directly or indirectly alter endocrine activity and may concomitantly induce a variety of behavioral effects. This has been experimentally demonstrated by neuropeptidergic manipulation of sleep-electroencephalographic (EEG) measures and behavioral studies in animals. An integral part of the neuroendocrine communication are effects of peripheral hormones upon brain structures and their interactions with the immune system. Within this framework all hormones of the limbic-hypothalamic- pituitary-adrenocortical (LHPA)-axis play a dominant role, because: (1) corticotropin-releasing hormone (CRH) was shown to integrate centrally behavioral and metabolic responses to stress; and (2) corticosteroids exert a host of neurochemical changes within the CNS which by far exceed their primary endocrine feedback action. As a corollary, hyperexposure to corticosteroids induces widespread changes of neuronal cell biology which are of clinical significance for depression research (e.g. neuronal cell loss in the hippocampus, down-regulation of glucocorticoid receptors within monoaminergic neurons). Clinical neuroendocrine research over the past years focussed upon evaluation of pathophysiology underlying dexamethasone resistant cortisol levels or hypercortisolism linked to depression and utilized advanced methods for multihormonal analysis and newly synthesized neuropeptides (e.g. CRH) for challenge studies in combination with neurophysiological assessments.(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction of outcome in depressed patients by weekly monitoring with the dexamethasone suppression test

Forty-three depressed patients in hospital were studied with weekly dexamethasone suppression tests (DSTs) and were followed as out-patients for at least three months after discharge. The detection rate of patients with LHPA axis dysfunction increased from 41% with a single DST to 59% with serial DSTs. There was a poor correlation between weekly post-dexamethasone cortisol levels and Hamilton depression rating scores. In patients with evidence of LHPA axis dysfunction, a DST at discharge discriminated effectively between a good and a poor outcome group; persistent non-suppression was strongly linked with a relapse of depression in the first three months after discharge. In general, our results support previous claims that the DST is a state marker for depressive illness.

Function of the adrenal cortex in patients with major depression

Failure to suppress cortisol secretion after administration of dexamethasone occurs in up to 50% of depressed patients. To test whether this hypothalamic-pituitary-adrenal (HPA) overactivity is associated with adrenocortical hyperresponsiveness, we performed dexamethasone suppression tests (DSTs) and adrenocorticotropic hormone (ACTH) stimulation tests in depressed subjects and subjects with other psychiatric disorders. Three groups were defined: depressed nonsuppressors, depressed suppressors, and other suppressors. While predexamethasone and postdexamethasone cortisol concentrations were greater in the depressed nonsuppressor group, ACTH concentrations did not differ among groups. After receiving alpha-ACTH[1-24] (4.2 micrograms/kg), depressed nonsuppressors had greater increases in stimulated cortisol secretion than the other groups. These results demonstrate that in a subgroup of depressed patients, HPA overactivity is associated with adrenocortical hyperresponsiveness.

Multiple depressive episodes and plasma postdexamethasone cortisol levels

The hypothalamic-pituitary-adrenal (HPA) axis is dysregulated in many patients with major depressive disorder (MDD). To determine whether or not a past history of depressive episodes is associated with this dysregulation, we studied the relationships among number of past depressive episodes, number of previous hospitalizations for depression, and number of years since first depressive episode and biological markers of depression (postdexamethasone plasma cortisol levels and dexamethasone suppressor/nonsuppressor status). No significant relationships were detected.

The HPA axis response to insulin hypoglycemia in depression

Dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis, demonstrated by failure to suppress cortisol secretion after dexamethasone, is found in approximately 50% of patients with major depression (MD). In this study, we examined the response of adrenocorticotrophic hormone (ACTH) and cortisol to insulin-induced hypoglycemia in 20 healthy controls and 18 inpatients with MD [12 dexamethasone suppressors (S) and 5 dexamethasone nonsuppressors (NS)]. After the administration of 0.15 U/kg of regular insulin, both controls and patients with MD showed an increase in plasma ACTH and cortisol levels. Controls had a significantly higher ACTH peak (p less than 0.01) and ACTH increment (p less than 0.01) than MD patients. There were no statistically significant differences between patients who were S and NS. Although baseline plasma cortisol levels were significantly higher in MD patients, there were no significant differences in the peak cortisol or increment in plasma cortisol after hypoglycemia between patients with MD and controls or between patients who were S and those who were NS. These findings suggest that a defect exists in the regulation of the HPA axis at the pituitary level in MD and that this defect is not necessarily reflected in the dexamethasone suppression status of the patient.

Responses to corticotropin-releasing hormone in the hypercortisolism of depression and Cushing's disease. Pathophysiologic and diagnostic implications

Primary depression can be associated with substantial hypercortisolism, thus prompting some researchers to suggest that depression shares pathophysiologic features with Cushing's disease. Clinically, depression can be difficult or impossible to distinguish from mild or early Cushing's disease that is associated with depressive features. The purpose of this study was to evaluate whether the pituitary-adrenal responses to ovine corticotropin-releasing hormone could help to clarify the mechanism of hypercortisolism in depression and in Cushing's disease and to assist in the differential diagnosis of these disorders. As compared with controls (n = 34), depressed patients (n = 30) had basal hypercortisolism (P less than 0.001) that was associated with attenuated plasma ACTH responses to ovine corticotropin-releasing hormone (P less than 0.001). This indicates that in patients with depression, the corticotroph cell in the pituitary responds appropriately to the negative feedback of high cortisol levels. In contrast, patients with Cushing's disease (n = 29) had plasma ACTH hyperresponsiveness to ovine corticotropin-releasing hormone (P less than 0.001), despite basal hypercortisolism (P less than 0.001), which indicates a gross impairment of the mechanism by which cortisol exerts negative feedback on the pituitary. Less than 25 percent of the patients with depression or Cushing's disease had peak ACTH responses that overlapped. We conclude that the pathophysiologic features of hypercortisolism in depression and Cushing's disease are distinct in each of the disorders and that the ovine corticotropin-releasing hormone stimulation test can be helpful in their differential diagnosis.

Abnormal ACTH and cortisol responses to ovine corticotropin releasing factor in patients with primary affective disorder

To further explore hypothalamic pituitary adrenal regulation in patients with affective illness, we administered 1 microgram/kg of synthetic ovine corticotropin releasing factor at 2000h to 26 drug-free patients with this disorder and to 15 healthy controls. Compared to controls, depressed patients (N = 12) showed a significant elevation in baseline cortisol and significant reductions in the net ACTH and cortisol responses to corticotropin releasing factor. These findings were normal in manic (N = 6) and improved (N = 8) subjects. An additional finding was that baseline cortisol and net ACTH and cortisol responses to CRF were negatively correlated in the entire group of patients and controls as well as in the patients alone. These data indicate that the reduced ACTH and cortisol responses to CRF in depression reflect normal functioning of the pituitary corticotroph cell (i.e., that the negative feedback effect of cortisol on ACTH secretion in depression is physiologically intact, effectively serving as a brake on the ACTH response to exogenous CRF. Thus, the hypercortisolism of depression may be due to a hypothalamic defect, possibly involving hypersecretion of endogenous CRF. This possibility may be of particular interest in light of clinical observations that depression can often be precipitated by stress and by data in experimental animals that CRF may influence several processes known to be altered in the overall symptom complex of depression.

Corticotropin-releasing factor (CRF): stimulation in normal controls and in patients with Cushing's syndrome

Synthetic ovine and human CRF were given as an i.v. bolus to six healthy volunteers in four and two different dosages, respectively (oCRF: 25, 50, 100 and 200 micrograms; hCRF: 50 and 100 micrograms). There was a significant increase of ACTH and cortisol after the injection of all dosages though the dose-response relationship was only significant between the 50 and 100 micrograms dose of oCRF. No significant differences between ACTH and cortisol secretion after oCRF and hCRF were observed. Repetitive stimulation by hCRF led to repetitive release of identical amounts of ACTH. The CRF test with the 100 micrograms dosage was used in patients with proven Cushing's syndrome (n = 30). Results showed that the CRF test is useful in making the differential diagnosis of established Cushing's syndrome. In patients with ACTH-dependent Cushing's disease (n = 21), normal or elevated basal ACTH levels were significantly higher after stimulation by CRF compared to normal controls, with one exception. The pattern of cortisol secretion after CRF administration corresponded to the pattern of ACTH secretion in these patients. In two patients with ectopic ACTH syndrome, extremely elevated ACTH and cortisol levels did not change or showed only a small increase after CRF administration. In patients with unilateral adrenal adenoma or carcinoma (n = 7), suppressed ACTH levels did not rise after CRF administration. In addition, no significant change in cortisol secretion could be observed. After surgical removal of cortisol-producing adrenal tumors, the ACTH response to CRF can be demonstrated when cortisol levels are still undetectable. Pulsatile administration of CRF in one patient after unilateral adrenalectomy revealed that ACTH responses to CRF normalize rapidly but cannot be sustained if CRF administration is withdrawn, suggesting that the cause of adrenal failure after unilateral adrenalectomy for Cushing's syndrome or with long-term corticoid therapy is due to hypothalamic CRF deficiency. The suppression of ACTH responses to CRF in glucocorticoid-treated patients correlated with the daily corticoid dosage. Since the ACTH hyper-response to CRF in six patients with Cushing's disease was suppressed by short-term dexamethasone treatment, the pituitary as a target site for feedback inhibition also was demonstrated.

Cortisol and corticosterone response after syn-corticotropin in relationship to dexamethasone suppressibility of cortisol

The current study was designed to investigate whether glucocorticoid output after syn-ACTH stimulation is different in depression associated with dexamethasone suppression test (DST) nonsuppression from the euthymic state and DST suppression. We gave 28 depressives a DST and an adrenocortical challenge with synthetic ACTH. Fourteen patients were nonsuppressors on the DST. After successful drug treatment, the subjects were reinvestigated by both tests; all DSTs revealed plasma cortisol concentrations below the criterion value of 50 ng/ml. Cortisol and corticosterone responses after syn-ACTH tended to be higher during depression. After clinical remission, higher cortisol and corticosterone responses occurred in those patients who were DST nonsuppressors during depression. This finding suggests that patients who suffer from a depression which is linked to an abnormal pituitary--adrenocortical regulation develop an enhanced sensitivity of the adrenal cortex to ACTH.

Corticotropin-releasing factor (CRF)--a review

Corticotropin-releasing factor (CRF), a 41 amino acid polypeptide, has been isolated from ovine hypothalamic extracts, sequenced, and synthesized. It has a high potency for stimulating the secretion of corticotropin-like and beta-endorphin-like immunoactive substances in vitro and in vivo in laboratory animals and humans. The high concentration of CRF-like immunoactivity in hypophyseal portal plasma supports the hypothesis that CRF is the physiological hypothalamic factor. Human and rat CRF (rCRF) also have been purified and synthesized. They have an 83% sequence homology with ovine CRF (oCRF). oCRF-like activity has been found in human hypothalamus, pituitary stalk, posterior pituitary, thalamus, cerebral cortex, cerebellum, pons, medulla oblongata, spinal cord and in the adrenal, lung, liver, stomach, duodenum and pancreas. oCRF-like activity also has been found in the human placenta and in tissues producing ectopic ACTH. The action of CRF can be potentiated by vasopressin, oxytocin, epinephrine, norepinephrine, VIP, and angiotensin II. Intracerebroventricular administration of CRF in the rat produces prolonged elevations of plasma epinephrine, norepinephrine, glucose and glucagon; elevates mean arterial pressure and heart rate; increases motor activity and exploration in familiar surroundings and oxygen consumption; and decreases feeding and sexual behavior. Testing with CRF has enabled the separation of patients with hypothalamic and pituitary adrenal insufficiency. The CRF stimulation test has been useful in distinguishing pituitary from ectopic causes of Cushing's disease. The distribution of CRF within and beyond the hypothalamus provides an anatomical context for the observation that CRF can simultaneously activate and coordinate metabolic, circulatory and behavioral responses that are adaptative in 'stressful' situations. CRF not only stimulates the pituitary-adrenal axis in man, but it also influences several aspects of CNS function which may be of relevance to psychiatric illnesses.

Neuroendocrine changes in depression

Biological research in depression has concentrated on 'endogenous' depressions and over the past 30 years has been guided by the amine theory. Neuroendocrine abnormalities in depression have been reported for over 20 years and include changes in the hypothalamic-pituitary-adrenal and thyroid axes, in growth hormone and prolactin secretion. As neurotransmitters regulate neuroendocrine secretion, inter-relationships between neurochemical and neuroendocrine abnormalities may provide a window for understanding the pathophysiology of depression. The availability of these biological markers for depression opens new possibilities for research in psychiatric diagnosis and for management.

ACTH, cortisol, and corticosterone output after ovine corticotropin-releasing factor challenge during depression and after recovery

Synthetic ovine corticotropin releasing factor (o-CRF) was administered as an intravenous bolus (100 micrograms) to eight patients suffering from a major depressive disorder, endogenous subtype. All patients showed inadequately suppressed cortisol levels after 1 mg dexamethasone. After clinical remission and normalized dexamethasone responses, these patients were reinvestigated with o-CRF stimulation. The mean adrenocorticotropic hormone (ACTH) release from the pituitary corticotroph cells was indiscriminate at both test sessions. Cortisol and corticosterone output after o-CRF tended to be higher during depression than after recovery. The o-CRF-induced increments observed with corticosterone were more marked in comparison with cortisol. Within the limitations of the current protocol, our preliminary data lend support to the view that an increased pituitary ACTH reserve or adrenocortical steroid reserve is not likely to be responsible for the defective pituitary-adrenal regulation in some dexamethasone-resistant depressives.

Persistent elevation of urinary free cortisol and loss of circannual periodicity in recovered depressive patients. A trait finding

By comparing a group of 8 normal subjects with 7 recovered depressive patients who had been dexamethasone suppression test (DST) nonsuppressors while depressed, the following differences were identified: (1) mean urinary free cortisol (UFC) levels were significantly higher for recovered depressive patients than for controls in the summer and fall as well as for the year; (2) patients who had recovered from depression lost their circannual pattern of cortisol excretion; and (3) there was a positive correlation between depressive symptoms as reflected on the Beck Depression Inventory and UFC levels in recovered patients but not controls. The elevated UFC levels in depressed patients with DST nonsuppression represents the first trait marker which persists over time. The implications of the close association between UFC levels and depressive symptoms is discussed.

Clinical studies with corticotropin releasing factor: implications for the diagnosis and pathophysiology of depression, Cushing's disease, and adrenal insufficiency

Corticotropin releasing factor (CRF) is a 41 amino acid peptide first isolated from sheep hypothalami and thought to be a principal modulator of the hypothalamic-pituitary-adrenal cortical (HPA) axis. We report herein a series of clinical studies with CRF in healthy volunteers and in patients with abnormalities in HPA function, including depression, Cushing's disease, Cushing's syndrome, and Addison's disease. Our data indicate that CRF can be a diagnostic aid in distinguishing various disorders of the HPA axis from one another, including Cushing's disease from depression and secondary from tertiary adrenal insufficiency. Moreover, the hormone responses to CRF help clarify the pathophysiology of the HPA abnormalities in several disorders. For instance, our data indicate that hypercortisolism in Cushing's disease results principally from a defect at the level of the pituitary; in contrast, in depression the defect seems to be hypothalamic, possibly involving hypersecretion of endogenous CRF. This latter possibility is of particular interest in light of clinical observations that depression often can be precipitated by stress. Moreover, data from experimental animals show that CRF may influence several processes known to be altered in the overall symptom complex of depression, including not only pituitary-adrenal function, but also motor activity, appetite regulation and sexual behavior.