A pilot study of a neuroendocrine test battery in posttraumatic stress disorder

Hypothalamus and Post-Traumatic Stress Disorder: A Review

Humans have lived in a dynamic environment fraught with potential dangers for thousands of years. While fear and stress were crucial for the survival of our ancestors, today, they are mostly considered harmful factors, threatening both our physical and mental health. Trauma is a highly stressful, often life-threatening event or a series of events, such as sexual assault, war, natural disasters, burns, and car accidents. Trauma can cause pathological metaplasticity, leading to long-lasting behavioral changes and impairing an individual's ability to cope with future challenges. If an individual is vulnerable, a tremendously traumatic event may result in post-traumatic stress disorder (PTSD). The hypothalamus is critical in initiating hormonal responses to stressful stimuli via the hypothalamic-pituitary-adrenal (HPA) axis. Linked to the prefrontal cortex and limbic structures, especially the amygdala and hippocampus, the hypothalamus acts as a central hub, integrating physiological aspects of the stress response. Consequently, the hypothalamic functions have been attributed to the pathophysiology of PTSD. However, apart from the well-known role of the HPA axis, the hypothalamus may also play different roles in the development of PTSD through other pathways, including the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-gonadal (HPG) axes, as well as by secreting growth hormone, prolactin, dopamine, and oxytocin. This review aims to summarize the current evidence regarding the neuroendocrine functions of the hypothalamus, which are correlated with the development of PTSD. A better understanding of the role of the hypothalamus in PTSD could help develop better treatments for this debilitating condition.

The Involvement of Prolactin in Stress-Related Disorders

The most important and widely studied role of prolactin (PRL) is its modulation of stress responses during pregnancy and lactation. PRL acts as a neuropeptide to support physiological reproductive responses. The effects of PRL on the nervous system contribute to a wide range of changes in the female brain during pregnancy and the inhibition of the hypothalamic-pituitary axis. All these changes contribute to the behavioral and physiological adaptations of a young mother to enable reproductive success. PRL-driven brain adaptations are also crucial for regulating maternal emotionality and well-being. Hyperprolactinemia (elevated PRL levels) is a natural and beneficial phenomenon during pregnancy and lactation. However, in other situations, it is often associated with serious endocrine disorders, such as ovulation suppression, which results in a lack of offspring. This introductory example shows how complex this hormone is. In this review, we focus on the different roles of PRL in the body and emphasize the results obtained from animal models of neuropsychiatric disorders.

Post traumatic stress disorder and the adrenal gland

Low serum and urinary Cortisol has been a consistent finding in post traumatic stress disorder (PTSD). Glucocorticoid receptor numbers are increased. PTSD patients have a significantly lower adrenocorticotropic hormone (ACTH) in response to corticotrophin releasing hormone (CRH) when compared to a control group of normal volunteers. The dexamethasone suppression test exhibits an exaggerated suppression response of Cortisol to dexamethasone, when the dose utilised is lower than that utilised to test patients with depression. Increased urine levels of noradrenaline and dopamine has been noted in patients with PTSD. This is believed to be related to the hyperarousal state of PTSD.

Status of glucocorticoid alterations in post-traumatic stress disorder

The current status of glucocorticoid alterations in post-traumatic stress disorder (PTSD) will be described in this chapter. Emphasis will be placed on data that suggest that at least some glucocorticoid-related observations in PTSD reflect pretraumatic glucocorticoid status. Recent observations have provided some evidence that pretraumatic glucocorticoid alterations may arise from genetic, epigenetic, and possibly other environmental influences that serve to increase the likelihood of developing PTSD following trauma exposure, as well as modulate attendant biological alterations associated with its pathophysiology. Current studies in the field of PTSD employ glucocorticoid challenge strategies to delineate effects of exogenously administered glucocorticoids on neuroendocrine, cognitive, and brain function. Results of these studies have provided an important rationale for using glucocorticoid strategies in the treatment of PTSD.

Advances in Understanding Neuroendocrine Alterations in PTSD and Their Therapeutic Implications

The findings from investigations of the neuroendocrinology of posttraumatic stress disorder (PTSD) have highlighted alterations that have not historically been associated with pathologic processes, and have, accordingly, raised several questions about the nature of the findings and their relationship to PTSD. The most infamous of these observations--low cortisol levels--has been the subject of much discussion and scrutiny because the finding has been both counterintuitive, and not uniformly reproducible. This fact notwithstanding, novel therapeutic approaches to the treatment of PTSD are in large part predicated on the assumption that glucocorticoid levels may be lower in PTSD. This article summarizes important neuroendocrine observations in cortisol and provides strategies for understanding what has emerged over the past two decades, to be a complex and sometimes contradictory literature.

Hypothalamic-pituitary-adrenal axis activity and sleep in posttraumatic stress disorder

Alterations of the hypothalamic-pituitary-adrenal (HPA) axis and sleep disturbances have been described separately in post-traumatic stress disorder (PTSD). It is not known if HPA alterations and sleep disturbances are associated in PTSD. This study examined sleep and HPA activity in 20 male medication-free subjects with PTSD and 16 matched healthy controls. Two nights of polysomnography were obtained and 24-h urinary cortisol was collected during day 2. Subjects self-administered a low-dose (0.5 mg) salivary dexamethasone test at home. Compared with controls, PTSD subjects had higher 24-h urinary microg cortisol/g creatinine (mean+/-SD 40+/-17 vs 28+/-12, p=0.03) but not significantly higher 24-h urinary cortisol (mean+/-SD 52+/-15 microg/day vs 43+/-23, p=0.19). PTSD subjects showed a trend towards less cortisol suppression after dexamethasone (73%+/-18 vs 83%+/-10, p=0.06). In the combined sample, delta sleep was significantly and negatively correlated with 24-h urinary cortisol (r=-0.36, p=0.04), and with 24-h urinary cortisol/g creatinine on a trend level (r=-0.34, p=0.06). Our results suggest that increased cortisol is negatively associated with delta sleep. This may contribute to sleep abnormalities in conditions associated with elevated cortisol, possibly including PTSD. Future studies should explore the temporal relationship between HPA activity, sleep disturbances, and psychopathology after a traumatic event.

Neuroendocrine aspects of PTSD

This chapter discussed how neuroendocrine findings in posttraumatic stress disorder (PTSD) potentially inform hypothalamic-pituitary-adrenal (HPA) alterations in PTSD and highlight alterations relevant to the identification of targets for drug development. Most studies demonstrate alterations consistent with an enhanced negative feedback inhibition of cortisol on the pituitary, an overall hyperreactivity of other target tissues (adrenal gland, hypothalamus), or both in PTSD. However, findings of low cortisol and increased reactivity of the pituitary in PTSD are also consistent with reduced adrenal output. The observations in PTSD are part of a growing body of neuroendocrine data providing evidence of insufficient glucocorticoid signaling in stress-related neuropsychiatric disorders.

Lower cortisol levels in depressed patients with comorbid post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is often comorbid with major depressive episodes (MDEs) and both conditions carry a higher rate of suicidal behavior. Hypothalamic-pituitary-adrenal (HPA) axis and serotonin abnormalities are associated with both conditions and suicidal behavior, but their inter-relation is not known. We determined cortisol response to placebo or fenfluramine in MDE, MDE and PTSD (MDE+PTSD), and healthy volunteers (HVs) and examined the relation of cortisol responses to suicidal behavior. A total of 58 medication-free patients with MDE (13 had MDE+PTSD) and 24 HVs were studied. They received placebo on the first day and fenfluramine on the second day. Cortisol levels were drawn before challenge and for 5 h thereafter. The MDE+PTSD group had the lowest plasma cortisol, the MDE group had the highest, and HVs had intermediate levels. There were no group differences in cortisol response to fenfluramine. Suicidal behavior, sex, and childhood history of abuse were not predictors of baseline or postchallenge plasma cortisol. Cortisol levels increased with age. This study finds elevated cortisol levels in MDE and is the first report of lower cortisol levels in MDE+PTSD. The findings underscore the impact of comorbidity of PTSD with MDE and highlight the importance of considering comorbidity in psychobiology.

Hypothalamic-pituitary-adrenal alterations in PTSD: are they relevant to understanding cortisol alterations in cancer?

Recent studies of hypothalamic-pituitary-adrenal axis alterations in PTSD have demonstrated a specific type of hyperresponsivity of this stress hormonal system characterized by a greater negative feedback inhibition of cortisol, which may paradoxically serve to lower cortisol levels. The occurrence of cancer has been recently described by many investigators as an event that fulfills the DSM-IV criteria for a "traumatic event" that has been demonstrated in some cases to be linked with the subsequent development of PTSD. This review considers the extent to which neuroendocrine alterations observed in PTSD may be useful in understanding cortisol alterations involved in cancer.

Circuits and systems in stress. II. Applications to neurobiology and treatment in posttraumatic stress disorder

This paper follows the preclinical work on the effects of stress on neurobiological and neuroendocrine systems and provides a comprehensive working model for understanding the pathophysiology of posttraumatic stress disorder (PTSD). Studies of the neurobiology of PTSD in clinical populations are reviewed. Specific brain areas that play an important role in a variety of types of memory are also preferentially affected by stress, including hippocampus, amygdala, medial prefrontal cortex, and cingulate. This review indicates the involvement of these brain systems in the stress response, and in learning and memory. Affected systems in the neural circuitry of PTSD are reviewed (hypothalamic-pituitary-adrenal axis (HPA-axis), catecholaminergic and serotonergic systems, endogenous benzodiazepines, neuropeptides, hypothalamic-pituitary-thyroid axis (HPT-axis), and neuro-immunological alterations) as well as changes found with structural and functional neuroimaging methods. Converging evidence has emphasized the role of early-life trauma in the development of PTSD and other trauma-related disorders. Current and new targets for systems that play a role in the neural circuitry of PTSD are discussed. This material provides a basis for understanding the psychopathology of stress-related disorders, in particular PTSD.

Current status of cortisol findings in post-traumatic stress disorder

This article summarizes findings of hypothalamic-pituitary-adrenal axis alterations in post-traumatic stress disorder (PTSD) and evaluates likely reasons for the lack of agreement among published studies. Sources of variance caused by methodologic and interpretative differences are highlighted, but the disparate findings are explained as illustrating a more complex neuroendocrinology of PTSD than has previously been described.

Biological markers and diagnostic accuracy in the genetics of posttraumatic stress disorder

Family and twin studies suggest a substantial genetic contribution to the etiology of posttraumatic stress disorder (PTSD). Identification of the nature of this genetic contribution should enhance understanding of the pathophysiology of PTSD and suggest improved therapeutic strategies for its treatment. However, a broadly defined phenotype, specific requirement for an environmental exposure and high frequency of comorbid psychiatric illness all complicate genetic studies of PTSD. It is likely that genetic heterogeneity, incomplete penetrance, pleiotropy and the involvement of more than one gene all constitute formidable obstacles to the genetic analysis of PTSD. One way to circumvent these problems is to perform genetic analysis of traits associated with PTSD, rather than PTSD itself, an approach that has been fruitful for other diseases with complex modes of inheritance. Hypothalamic-pituitary-adrenal axis hypofunction, physiologic markers of increased arousal, and increased acoustic startle response are all potential PTSD-associated traits that might be susceptible to genetic analysis. However, the capacity of these traits to distinguish PTSD from non-PTSD patients and their familial pattern must be better defined before they can be employed in genetic studies.

Role of norepinephrine in the pathophysiology and treatment of posttraumatic stress disorder

This review focuses on the role of norepinephrine (NE) in traumatic stress. The review is divided into three sections. The first section, "Norepinephrine and Arousal," describes preclinical studies related to norepinephrine's role in arousal, orienting to novel stimuli, selective attention and vigilance. It also contains a brief discussion of NE and its relationship to fear-provoking stimuli followed by preclinical and clinical studies that demonstrate heightened noradrenergic neuronal reactivity, increased alpha 2 receptor sensitivity and exaggerated arousal in organisms that have been exposed to chronic uncontrollable stress. The second section, "Norepinephrine and Memory," describes preclinical and clinical studies related to norepinephrine's role in enhanced encoding of memory for arousing and aversive events and in subsequent re-experiencing symptoms such as, intrusive memories and nightmares. The third section, "Norepinephrine and Pharmacologic Treatment," briefly discusses the use of adrenergic blockers, clonidine and propranol, as well as tricyclic and MAO inhibitors, for the treatment of PTSD. Finally, we attempt to synthesize trauma-related preclinical and clinical studies of norepinephrine. We do this, in part, by focusing on a series of yohimbine studies in subjects with PTSD because data from these studies allow for a discussion that brings together preclinical and clinical findings relevant to trauma-related alterations in arousal and memory.

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.

Assessment of noradrenergic functioning in patients with non-combat-related posttraumatic stress disorder: a study with desmethylimipramine and orthostatic challenges

The functioning of the noradrenergic system was assessed in 16 patients with non-combat-related posttraumatic stress disorder (PTSD) and the same number of age- and sex-matched healthy subjects by measuring (1) plasma norepinephrine (NE) levels in supine and upright postures, and (2) growth hormone (GH) responses to challenge with desmethylimipramine (DMI), a NE reuptake inhibitor. Subjects were cannulated at 08:30 h after an overnight fast. Blood samples were drawn for NE levels with subjects in a supine position and after 5 min of standing. After subjects were allowed to rest for 30 min in a supine position, a blood sample was drawn for basal GH (T-15) levels. The second baseline sample was drawn 15 min later (T0), at which time DMI (1 mg/kg) was given orally, and further blood samples were drawn at 90, 120, and 180 min. PTSD patients had significantly higher baseline NE levels and blunted NE responsivity to postural challenge compared with normal subjects. Basal and DMI-induced GH levels, on the other hand, did not differ in PTSD versus normal subjects. Overall, these findings suggest that non-combat-related PTSD patients have peripheral noradrenergic dysregulation, but central postsynaptic alpha 2-adrenergic receptor sensitivity is not altered in this patient population.

Prolactin response to buspirone challenge in the presence of dopaminergic blockade

Buspirone-stimulated prolactin release has been employed as an indirect measure of central serotonin activity; however, it is not clear whether serotonergic or dopaminergic systems are responsible for this response. In an attempt to further elucidate the mechanism, we studied the prolactin response to buspirone in eight subjects in the presence of maximal dopaminergic receptor blockade with metoclopramide under placebo-controlled, double-blind conditions. The prolactin response to buspirone in the presence of metoclopramide was not statistically different from that to placebo under the same conditions. The demonstration of further prolactin release by a bolus of thyrotropin-releasing hormone under maximal dopaminergic receptor blockade provided evidence against potential pituitary prolactin depletion by metoclopramide. These results lend further support to a dopaminergic mechanism in buspirone-induced prolactin secretion; therefore, further caution is warranted in interpreting the results of this challenge test as a measure of serotonergic activity in the brain.

Buspirone induced prolactin release in mania

Prolactin responses to buspirone challenge were examined in 11 manic patients and 11 healthy controls. Of the 11 manic patients, six were treated with lithium alone for 3 weeks, and the buspirone challenge test was repeated. The results showed (1) that there was no difference in prolactin response to buspirone challenge between manic patients and healthy controls, and (2) that there was no correlation between delta (delta) prolactin levels and severity of manic symptoms. Lithium treatment led to a large reduction in delta (delta) prolactin levels, which did not correlate with changes in symptom severity. These results support the possibility that 5HT1A receptors are probably not involved in the pathophysiology of mania.

Hypersensitivity of the hypothalamic-pituitary-adrenal axis to naloxone in post-traumatic stress disorder

Naloxone, which increases endogenous corticotropin-releasing hormone (CRH) release by blocking an inhibitory opioidergic tone on the hypothalamic-pituitary-adrenal (HPA) axis, was administered in a dose-response protocol to seven healthy volunteers and 13 patients with treated posttraumatic stress disorder (PTSD). Six of the PTSD patients showed an increased hormonal response to the lowest naloxone dose (6 micrograms/kg) compared to both the control subjects and the other PTSD patients. This difference persisted on detailed subgroup analysis, although it was less marked at the highest naloxone dose (125 micrograms/kg). The responses of the other seven PTSD patients were indistinguishable from those of the control group. The greater responses of the six PTSD patients could not be explained on the basis of associated psychiatric illnesses or psychotropic drug therapy, and did not correlate with standard psychological testing or severity of PTSD. The results of this preliminary study therefore suggest that a hypersensitivity of the HPA axis to endogenous CRH stimulation may occur in PTSD.

Neuroendocrine probes of serotonergic function: a critical review

Neuroendocrine probes of serotonergic function are based on the premise that serotonin (5-HT) exhibits an excitory influence on the release of certain anterior pituitary hormones and that the extent of release of these hormones following a challenge with a 5-HT agonist would provide an index of central 5-HT activity. This paper critically reviews studies published to date on healthy volunteers to assess the validity of tests of serotonergic function. Using standardized criteria, it is concluded that although extensive data is available on 5-HT-neuroendocrine probes, there is no test that is currently available that would fulfil all the proposed requirements for a test to be acceptable, although ipsapirone, m-chlorophenylpiperazine (m-CPP), and possibly fenfluramine challenge tests come very close. The rapid development and availability of more specific and stereo-selective 5-HT agonists/antagonists seem to indicate that it will not be too long before a valid neuroendocrine test for the assessment of serotonergic function emerges.

Effect of fluoxetine on noradrenergic mediated growth hormone release: a double blind, placebo-controlled study

Twelve patients with DSM-III-R major depressive illness were tested for growth hormone (GH) response to desipramine (DMI), a noradrenergic (NA) reuptake inhibitor. The response is mediated by NA alpha 2 receptors. They were then randomly assigned to treatment under double-blind conditions with either fluoxetine, the highly selective serotonin reuptake inhibitor or placebo. After 4 weeks they were retested. Fluoxetine but not placebo was effective in promoting recovery in four of the six patients treated. Patients treated with fluoxetine showed a significant decrease in DMI-mediated GH release irrespective of therapeutic outcome. This is consistent with marked alteration of NA function and raises questions as to the selectivity of fluoxetine.