Effect of metyrapone on the pituitary-adrenal axis in depression: relation to dexamethasone suppressor status

Pathways Connecting Late-Life Depression and Dementia

Late-life depression is associated with significant cognitive impairment. Meta-analyses showed that depression is associated with an increased risk for Alzheimer’s disease (AD) and it might be an etiological factor for AD. Since late-life depression is often connected with cognitive impairment and dementia is usually associated with depressive symptoms, a simple diagnostic approach to distinguish between the disorders is challenging. Several overlapping pathophysiological substrates might explain the comorbidity of both syndromes. Firstly, a stress syndrome, i.e., elevated cortisol levels, has been observed in up to 70% of depressed patients and also in AD pathology. Stress conditions can cause hippocampal neuronal damage as well as cognitive impairment. Secondly, the development of a depression and dementia after the onset of vascular diseases, the profile of cerebrovascular risk factors in both disorders and the impairments depending on the location of cerebrovascular lesions, speak in favor of a vascular hypothesis as a common factor for both disorders. Thirdly, neuroinflammatory processes play a key role in the etiology of depression as well as in dementia. Increased activation of microglia, changes in Transforming-Growth-Factor beta1 (TGF-beta1) signaling, production of pro-inflammatory cytokines as well as reduction of anti-inflammatory molecules are examples of common pathways impaired in dementia and depression. Fourthly, the neurotrophin BDNF is highly expressed in the central nervous system, especially in the hippocampus, where it plays a key role in the proliferation, differentiation and the maintenance of neuronal integrity throughout lifespan. It has been associated not only with antidepressant properties but also a reduction of cognitive impairment and therefore could be involved also in AD. Another etiologic factor is amyloid accumulation, as plasma amyloid beta-42 independently predicts both late-onset depression and AD. Higher plasma amyloid beta-42 predicts the development of late onset depression and conversion to possible AD. However, clinical trials with antibodies against beta amyloid recently failed, i.e., Solanezumab, Aducanumab, and Crenezumab. An overproduction of amyloid-beta might simply reflect a form of synaptic plasticity to compensate for neuronal dysfunction in different kind of neurological and psychiatric diseases of multiple etiologies. The tau hypothesis, sex/gender specific differences, epigenetics and the gut microbiota-brain axis imply other potential common pathways connecting late-life depression and dementia. In conclusion, different potential pathophysiological links between dementia and depression highlight several specific synergistic and multifaceted treatment possibilities, depending on the individual risk profile of the patient.

Efficacy of off-label augmentation in unipolar depression: A systematic review of the evidence

Treatment of unipolar depression with currently available antidepressants is still unsatisfactory. Augmentation with lithium or second generation antipsychotics is an established practice in non-responders to antidepressant monotherapy, but is also associated with a substantial non-response rate and with non-tolerance. Based on a systematic review of the literature, including meta-analyses, randomized controlled trials (RCTs), non-randomized comparative studies and case studies, off-label augmentation agents (administered in addition to an antidepressant, without FDA approval for treatment of MDD) were identified and evaluated regarding their efficacy using levels of evidence. The agents had to be added to an existing antidepressant regime with the aim of achieving an improved clinical response to an ongoing antidepressant treatment (augmentation) or an earlier onset of effect when starting antidepressant and augmentation agent simultaneously (acceleration). Five substances, modafinil, ketamine, pindolol, testosterone and estrogen (the latter two in hormone-deficient patients) were shown to be clinically effective in high evidence studies. For the six drugs dexamethasone, mecamylamine, riluzole, amantadine, pramipexole and yohimbine clear proof of efficacy was not possible due to low levels of evidence, small sample sizes or discordant results. For the two agents methylphenidate and memantine only studies with negative outcomes could be found. Overall, the quality of study designs was low and results were often contradictory. However, the use of pindolol, ketamine, modafinil, estrogen and testosterone might be an option for depressed patients who are not responding to antidepressant monotherapy or established augmentation strategies. Further high quality studies are necessary and warranted.

Hypothalamic-Pituitary--Adrenal Axis-Feedback Control

The hypothalamo-pituitary-adrenal axis (HPA) is responsible for stimulation of adrenal corticosteroids in response to stress. Negative feedback control by corticosteroids limits pituitary secretion of corticotropin, ACTH, and hypothalamic secretion of corticotropin-releasing hormone, CRH, and vasopressin, AVP, resulting in regulation of both basal and stress-induced ACTH secretion. The negative feedback effect of corticosteroids occurs by action of corticosteroids at mineralocorticoid receptors (MR) and/or glucocorticoid receptors (GRs) located in multiple sites in the brain and in the pituitary. The mechanisms of negative feedback vary according to the receptor type and location within the brain-hypothalmo-pituitary axis. A very rapid nongenomic action has been demonstrated for GR action on CRH neurons in the hypothalamus, and somewhat slower nongenomic effects are observed in the pituitary or other brain sites mediated by GR and/or MR. Corticosteroids also have genomic actions, including repression of the pro-opiomelanocortin (POMC) gene in the pituitary and CRH and AVP genes in the hypothalamus. The rapid effect inhibits stimulated secretion, but requires a rapidly rising corticosteroid concentration. The more delayed inhibitory effect on stimulated secretion is dependent on the intensity of the stimulus and the magnitude of the corticosteroid feedback signal, but also the neuroanatomical pathways responsible for activating the HPA. The pathways for activation of some stressors may partially bypass hypothalamic feedback sites at the CRH neuron, whereas others may not involve forebrain sites; therefore, some physiological stressors may override or bypass negative feedback, and other psychological stressors may facilitate responses to subsequent stress.

A review of Atypical depression in relation to the course of depression and changes in HPA axis organization

Depression is a clinically heterogenous condition defined by sub-types that can have diametrically opposed features, such as sleep and appetite. Within the same individual these features may change over time, and different symptom clusters may respond selectively to different treatments. It has been hypothesized that different pathophysiological processes may be operating in the different sub-types of depression and specifically that Melancholic depression may be associated with relative overactivity, and Atypical depression with relative hypoactivity, of the hypothalamic drive of the HPA axis. A consistent finding that emerges from the literature is that the experience of depression alters over the course of the illness with the features of Atypical depression dominating a more chronic clinical picture. This suggests that different stress states characterize the different profiles of depression as the illness becomes more chronic. There is evidence that the corticotropin-releasing hormone (CRH) control of HPA axis output is reduced in Atypical, compared to Melancholic, sub-types, but there is no convincing evidence that overall HPA activity, i.e., cortisol output, reduces. We suggest that there is a "switch" in the regulation of the HPA system from CRH to arginine vasopressin (AVP) control as stress becomes more sustained or repeated; resulting in an altered homeostasis within the HPA system. Cortisol, and the neuropeptides CRH and AVP, have different neurobiological, behavioural and experiental effects. The "switch" process should result in different neuropeptide/cortisol combinations and ratios and may explain the changing profile of depression over time. The heuristic merit in making a distinction between the different clinical states of depression will be discussed.

Pathophysiology of hypercortisolism in depression: pituitary and adrenal responses to low glucocorticoid feedback

OBJECTIVE

To test three theories of hypercortisolemia in depression-hypothalamic overdrive, impaired glucocorticoid feedback, or autonomous cortisol production.

METHOD

We applied an overnight low-cortisol feedback strategy by administering metyrapone to hypercortisolemic depressed in-patients and control subjects.

RESULTS

Under metyrapone, the increases of plasma adrenocorticotropic hormone (ACTH) concentrations and of basal and pulsatile ACTH secretion were not exaggerated in hypercortisolemic depressed patients compared with control subjects. ACTH approximate entropy (ApEn) did not differ at baseline or under metyrapone. Thus, neither hypothalamic overdrive nor irregular ACTH secretion was seen. We did not detect impaired cortisol feedback: the ACTH response was not reduced, and ApEn measures that are sensitive to feedback changes were comparable in both groups. Metyrapone disrupted cortisol secretory regularity in depressed and control subjects. On the baseline day, basal cortisol secretion was significantly increased and was highly irregular (high ApEn), and ACTH-cortisol cross-ApEn was markedly elevated in high-cortisol patients.

CONCLUSION

Classical feed-forward overdrive and impaired feedback theories of hypercortisolemia in depression were not supported. Depressive hypercortisolemia may result from alternative pathophysiological mechanisms involving irregular basal hypersecretion of cortisol, associated with adrenal enlargement, possibly through splanchnic sympathetic activation of the adrenal cortex.

Synaptic regulation of the hypothalamic-pituitary-adrenal axis and its modulation by glucocorticoids and stress

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been implicated in a range of affective and stress-related disorders. The regulatory systems that control HPA activity are subject to modulation by environmental influences, and stressful life events or circumstances can promote subsequent HPA dysregulation. The brain is a major regulator of the HPA axis, and stress-induced plasticity of the neural circuitry involved in HPA regulation might constitute an etiological link between stress and the development of HPA dysregulation. This review focuses on the synaptic regulation of neuroendocrine corticotropin-releasing hormone (CRH) neurons of the hypothalamic paraventricular nucleus, which are the cells through which the brain predominantly exerts its influence on the HPA axis. CRH neuronal activity is largely orchestrated by three neurotransmitters: GABA, glutamate, and norepinephrine. We discuss our current understanding of the neural circuitry through which these neurotransmitters regulate CRH cell activity, as well as the plastic changes in this circuitry induced by acute and chronic stress and the resultant changes in HPA function.

Synaptic regulation of the hypothalamic-pituitary-adrenal axis and its modulation by glucocorticoids and stress

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been implicated in a range of affective and stress-related disorders. The regulatory systems that control HPA activity are subject to modulation by environmental influences, and stressful life events or circumstances can promote subsequent HPA dysregulation. The brain is a major regulator of the HPA axis, and stress-induced plasticity of the neural circuitry involved in HPA regulation might constitute an etiological link between stress and the development of HPA dysregulation. This review focuses on the synaptic regulation of neuroendocrine corticotropin-releasing hormone (CRH) neurons of the hypothalamic paraventricular nucleus, which are the cells through which the brain predominantly exerts its influence on the HPA axis. CRH neuronal activity is largely orchestrated by three neurotransmitters: GABA, glutamate, and norepinephrine. We discuss our current understanding of the neural circuitry through which these neurotransmitters regulate CRH cell activity, as well as the plastic changes in this circuitry induced by acute and chronic stress and the resultant changes in HPA function.

Oestrogen: an overlooked mediator in the neuropsychopharmacology of treatment response?

Major depression (MD) and anorexia nervosa (AN) often present comorbidly and both share some affective symptoms, despite obvious phenotypic differences. In the illness phase, pathophysiological evidence indicates similar abnormalities in both clinical groups including dysfunction in the serotonin (5-HT) system (of which some abnormalities persist following recovery) and between 60% and 80% of patients in both groups present with significant hyperactivity of the hypothalamo-pituitary-adrenal (HPA) axis. First-line approach to treatment for MD involves modulation of the 5-HT system using selective serotonin reuptake inhibitors (SSRIs). For AN, treatment with SSRIs has been shown to be considerably less effective compared to MD. Both illnesses show marked dysregulation in the HPA axis. A consequence of SSRI treatment is a reduction and/or normalization of indices of the HPA axis [i.e. cortisol, adrenocorticotropic hormone (ACTH)], which is consistent with recovery levels in both clinical groups. Oestrogen (in high doses) has been shown to exert antidepressant effects and positively impact on MD symptoms as a treatment in its own right, or in combination with antidepressants, in women of menopausal age. It is proposed that a combination of SSRIs and oestrogen therapy may facilitate physiological normalization in MD in women of non-menopausal age and in AN. Preliminary evidence suggests oestrogen treatment alone is of some benefit to patients and it is proposed that a combination of SSRI and oestrogen will precipitate and potentially accelerate symptomatic remission. Should this approach be successful, it offers the capacity for improvement over traditional antidepressant use in women diagnosed with MD and a novel strategy for the treatment of AN, a serious clinical illness associated with the highest mortality of any psychiatric condition.

Neuroendocrine aspects of hypercortisolism in major depression

A consistent finding in biological psychiatry is that hypothalamic-pituitary-adrenal (HPA) axis physiology is altered in humans with major depression. These findings include hypersecretion of cortisol at baseline and on the dexamethasone suppression test. In this review, we present a process-oriented model for HPA axis regulation in major depression. Specifically, we suggest that acute depressions are characterized by hypersecretion of hypothalamic corticotropin-releasing factor, pituitary adrenocorticotropic hormone (ACTH), and adrenal cortisol. In chronic depressions, however, enhanced adrenal responsiveness to ACTH and glucocorticoid negative feedback work in complementary fashion so that cortisol levels remain elevated while ACTH levels are reduced. In considering the evidence for hypercortisolism in humans, studies of nonhuman primates are presented and their utility and limitations as comparative models of human depression are discussed.

Anxious-retarded depression: relation with plasma vasopressin and cortisol

Dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis is related to melancholic or endogenous depression; however, the strength of this relationship depends on the definition of the specific depression subcategory. A two-dimensionally defined subcategory, anxious-retarded depression, is related to melancholic depression. Since arginine vasopressin (AVP) activates the HPA axis, and both major depression and the melancholic subcategory are associated with elevated plasma AVP levels, we investigated whether the plasma AVP level is also elevated in anxious-retarded depression, melancholic depression and anxious-retarded melancholic depression, and whether plasma AVP and cortisol levels are correlated in these subcategories. A total of 66 patients with major depression not using oral contraception were investigated. Patients with anxious-retarded depression had a highly significant AVP-cortisol correlation, while no such correlation was found in patients with nonanxious-retarded depression. Log-transformed mean plasma AVP values were higher in patients with anxious-retarded depression than in patients with nonanxious-retarded depression. Patients with anxious-retarded melancholic depression also had a significantly elevated level of plasma AVP and a highly significant correlation between plasma AVP and cortisol levels. The correlation was low in patients with melancholic depression. Anxious-retarded depression may be a useful refinement of the melancholic subcategory with regard to dysregulation of the HPA axis and plasma AVP release.

Novel approaches to the treatment of depression by modulating the hypothalamic - pituitary - adrenal axis

Many patients with major depression show evidence of over-activation of the hypothalamic - pituitary - adrenal axis (HPA), as evidenced by hypercortisolism and adrenal hyperplasia. Such over-activity is associated with increased corticotropin releasing factor (CRF) reactivity in the CSF and blunted release of ACTH in response to CRF infusion. Recent evidence suggests a switch from CRF to AVP regulation of the axis during depression, with depressed patients showing enhanced response to ddAVP infusion. The HPA provides multiple potential sites for antidepressant development. The use of glucocorticoid antagonists, cortisol synthesis inhibitors, CRF and AVP antagonists have been suggested. Copyright 2001 John Wiley & Sons, Ltd.

Separation induced changes in squirrel monkey hypothalamic-pituitary-adrenal physiology resemble aspects of hypercortisolism in humans

When separated from groups, squirrel monkeys respond with significant increases in plasma cortisol and adrenocorticotropic hormone (ACTH). While cortisol remains elevated above pre-separation levels, significant reductions occur in ACTH. Monkeys that respond with greater increases in cortisol subsequently exhibit greater reductions in ACTH, which suggests that reductions in ACTH are mediated by corticosteroid feedback. Monkeys that respond with greater increases in cortisol also tend to exhibit greater cerebrospinal fluid levels of the dopamine metabolite HVA, but not the norepinephrine metabolite MHPG, or corticotropin-releasing factor (CRF). Attenuation of corticosteroid feedback with metyrapone results in significant increases in circulating ACTH, and in older monkeys increases plasma HVA. Similar findings in humans have been reported in clinical studies of hypercortisolism and major depression.

Psychoneuroendocrinology of post-traumatic stress disorder

In 1980, the diagnosis of post-traumatic stress disorder (PTSD) was established to describe the long-lasting symptoms that can occur following exposure to extremely stressful life events. This article reviews the findings of neuroendocrinologic alterations in PTSD and summarizes the finding of hypothalamic-pituitary-adrenal (HPA), catecholamine, hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-gonadal (HPG) systems. These are the neuroendocrine systems that have been studied in PTSD. Also included is a review of the basic facts about PTSD and biologic data.

Dexamethasone augmentation in treatment-resistant depression

A total of 10 patients who fulfilled DSM-III-R criteria for major depression were recruited to the study, each of whom had failed to respond to a 6-week course of treatment with either sertraline or fluoxetine. Each subject had baseline serum cortisol measurements together with a Hamilton depression (HAMD) score. All patients were started on dexamethasone (3 mg daily) for 4 days, while remaining on their antidepressant treatment. Further Hamilton ratings were made on days 5 and 21. Six patients showed a significant improvement, whilst two showed a minimal response. A good clinical response was associated with a high baseline cortisol level.

Preservation of hypothalamic-pituitary-adrenal axis fast-feedback responses in depression

Depression is associated with overactivity of the hypothalamic-pituitary-adrenal (HPA) axis, which may be attributable to defective negative feedback. Fast feedback is the earliest phase of this, and has previously been suggested to be abnormal. A total of 30 physically healthy volunteers, 15 patients with DSM-III-R major depression and an age- and sex-matched control group received a standardized challenge of hydrocortisone (5 micrograms kg-1 min-1) or placebo over a period of 1 h. ACTH1-39 responses to hydrocortisone challenge did not differ significantly between healthy volunteers and patients with major depression. The fast-feedback response to hydrocortisone challenge is preserved in major depression when ACTH is measured directly.

Serotonin and the regulation of hypothalamic-pituitary-adrenal axis function

That serotonin (5HT) is involved in regulating hypothalamic-pituitary- adrenal axis (HPA) function has long been recognized. A variety of drugs including precursors of 5HT such as 5HTP, drugs which release 5HT such as fenfluramine and drugs which act directly on 5HT receptors such as ipsapirone increase cortisol and ACTH concentrations. There is a general assumption that such stimulation occurs at a hypothalamic level. However, our increasing understanding of the complex interplay between 5HT and the HPA raises questions as to the validity of this simple model. An increasing volume of experimental research indicates that 5HT can act directly on the adrenal gland and possibly on the anterior pituitary as well. These findings have major implications for the interpretation of neuroendocrine studies of 5HT conducted in psychiatric conditions, such as depression.

Treatment of major depression with metyrapone and hydrocortisone

Eight inpatients with Major Depression were treated with metyrapone and hydrocortisone in a balanced order placebo-controlled single-blind cross-over study. The hydrocortisone dose (30 mg daily) was a physiological replacement dose and the metyrapone dose was titrated against plasma cortisol in order to keep cortisol within physiological limits. The treatment resulted in a significant reduction in depressive symptoms. This placebo-controlled study replicates the results of several uncontrolled studies but leaves open for further study the mechanism by which the combined administration of metyrapone and hydrocortisone might exert its antidepressant effect.

Studies of the secretion of corticotropin-releasing factor and arginine vasopressin into the hypophysial-portal circulation of the conscious sheep. II. The central noradrenergic and neuropeptide Y pathways cause immediate and prolonged hypothalamic-pituitary-adrenal activation. Potential involvement in the pseudo-Cushing's syndrome of endogenous depression and anorexia nervosa

Studies were performed to determine the effects of intracerebroventricular norepinephrine (NE) or neuropeptide Y (NPY) on the ovine hypothalamic-pituitary-adrenal (HPA) axis. NE (50 micrograms) increased mean hypophysial-portal corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) levels (1 h, 1.3- and 2.9-fold; 4 h, 2.2- and 5.7-fold) and caused acute and sustained increases in mean plasma ACTH and cortisol. NPY (50 microgram) also increased mean CRF and AVP levels (1 h, 1.4- and 4.2-fold; 4 h, 1.1- and 1.9-fold), increased pituitary-adrenal activity at 1 h, and caused ACTH hypersecretion at 4 h. When added to cultured ovine anterior pituitary cells, NPY neither increased basal ACTH release nor augmented CRF- or AVP-induced ACTH release. We conclude that: (a) activation of either the central noradrenergic or NPY pathways causes an acute and sustained stimulation of the ovine HPA axis; (b) such activation increases the AVP/CRF ratio, suggesting a dominant role for AVP in the ovine stress response; and (c) the central noradrenergic or NPY systems may cause sustained HPA activation by attenuating or disrupting the glucocorticoid negative feedback on those brain areas concerned with regulation of the HPA axis. The possible roles of the central noradrenergic and NPY systems in the etiology of the hypercortisolemia of endogenous depression and anorexia nervosa are discussed.

Glucocorticoids and the genesis of depressive illness. A psychobiological model

Abnormalities in the hypothalamic-pituitary-adrenal axis (HPA) have been the most consistently demonstrated biological markers in depressive illness. Numerous other neuroendocrine disturbances have also been described, including blunted clonidine-induced growth hormone release and blunted fenfluramine-induced prolactin release. These disturbances are generally interpreted in terms of monoaminergic receptor dysfunction. The theory presented here suggests that chronic stress which activates the HPA will in certain susceptible people produce changes in central monoamines. The high level of glucocorticoid receptors on such central neurons is postulated as mediating the alterations. Thus monoamine abnormalities, rather than being a core aetiological feature of depression, are seen as secondary to HPA overdrive.

Hypothesis: cytokines may be activated to cause depressive illness and chronic fatigue syndrome

Abnormalities in the regulation of the hypothalamo-pituitary-adrenal (HPA) axis are a well recognised feature of endogenous depression. The mechanism underlying this phenomenon remains obscure although there is strong evidence suggesting excessive CRH activity at the level of the hypothalamus. We propose a novel hypothesis in which we suggest that the aetiological antecent to CRH hyperactivity is cytokine activation in the brain. It is now well established both that interleukins -1 and -6 are produced in a number of central loci and that cytokines are potent stimulators of the HPA axis. Hence, we suggest that activation of IL-1 and IL-6 by specific mechanisms (such as neurotropic viral infection) in combination with the consequent CRH-41 stimulation, may (via their known biological effects) underly many of the features found in major depression and other related disorders, particularly where chronic fatigue is a prominent part of the symptom complex. This theory has considerable heuristic value and suggests a number of experimental stratagems which may employed in order to confirm or reject it.