A clinical and pathophysiological approach to traumatic brain injury-induced pituitary dysfunction

Acute neuroendocrine changes after traumatic brain injury

Introduction

Post-traumatic hypopituitarism (PTHP) is a significant, but often neglected consequence of traumatic brain injury (TBI).

Research question

We aimed to provide a comprehensive overview of epidemiology, pathophysiology, clinical features and diagnostic approaches of PTHP.

Materials and methods

MEDLINE, EMBASE, Cochrane Library and Web of Science were searched. 45 articles of human studies evaluating acute endocrine changes following mild, moderate and severe TBI were selected.

Results

Severity of TBI seems to be the most important risk factor of PTHP. Adrenal insufficiency (AI) was present in 10% of TBI patients (prevalence can be as high as 50% after severe TBI), and hypocortisolemia is a predictor of mortality and long-term hypopituitarism. Suppression of the thyroid axis in 2-33% of TBI patients may be an independent predictor of adverse neurological outcome, as well. 9-36% of patients with severe TBI exhibit decreased function of the somatotrophic axis with a divergent effect on the central nervous system. Arginine-Vasopressin (AVP) deficiency is present in 15-51% of patients, associated with increased mortality and unfavorable outcome. Due to shear and injury of the stalk hyperprolactinemia is relatively common (2-50%), but it bears little clinical significance. Sex hormone levels remain within normal values.

Discussion and conclusion

PTHP occurs frequently after TBI, affecting various axis and determining patients' outcome. However, evidence is scarce regarding exact epidemiology, diagnosis, and effective clinical application of hormone substitution. Future studies are needed to identify patients at-risk, determine the optimal timing for endocrine testing, and refine diagnostic and treatment approaches to improve outcome.

Evaluation of pituitary function and metabolic parameters in patients with traumatic maxillofacial fractures

PURPOSE

This study was designed to assess the pituitary functions of patients with traumatic maxillofacial fractures and compare the results with healthy controls.

METHODS

Thirty patients (mean age, 38.14 ± 14.15 years; twenty-six male, four female) with a traumatic maxillofacial fracture at least 12 months ago (mean 27.5 ± 6.5 months) and thirty healthy controls (mean age, 42.77 ± 11.36 years; twenty-five male, five female) were included. None of the patients were unconscious following head trauma, and none required hospitalization in intensive care. Basal pituitary hormone levels of the patients were evaluated. All patients and controls had a glucagon stimulation test and an ACTH stimulation test to evaluate the hypothalamic-pituitary-adrenal axis and the GH-IGF-1 axis.

RESULTS

Five of thirty patients (16.6%) had isolated growth hormone (GH) deficiency based on a glucagon stimulation test (GST). The mean peak GH level after GST in patients with hypopituitarism (0.54 ng/ml) was significantly lower than those without hypopituitarism (7.01 ng/ml) and healthy controls (11.70 ng/ml) (P < 0.001). No anterior pituitary hormone deficiency was found in the patients, except for GH.

CONCLUSION

Our study is the first to evaluate the presence of hypopituitarism in patients with traumatic maxillofacial fractures. Preliminary findings suggest that hypopituitarism and GH deficiency pose significant risks to these patients, particularly during the chronic phase of their trauma. However, these findings need to be validated in larger scale prospective studies with more patients.

Traumatic brain injury, abnormal growth hormone secretion, and gut dysbiosis

The gut microbiome has been implicated in a variety of neuropathologies with recent data suggesting direct effects of the microbiome on host metabolism, hormonal regulation, and pathophysiology. Studies have shown that gut bacteria impact host growth, partially mediated through the growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis. However, no study to date has examined the specific role of GH on the fecal microbiome (FMB) or the changes in this relationship following a traumatic brain injury (TBI). Current literature has demonstrated that TBI can lead to either temporary or sustained abnormal GH secretion (aGHS). More recent literature has suggested that gut dysbiosis may contribute to aGHS leading to long-term sequelae now known as brain injury associated fatigue and cognition (BIAFAC). The aGHS observed in some TBI patients presents with a symptom complex including profound fatigue and cognitive dysfunction that improves significantly with exogenous recombinant human GH treatment. Notably, GH treatment is not curative as fatigue and cognitive decline typically recur upon treatment cessation, indicating the need for additional studies to address the underlying mechanistic cause.

Optimal vitamin D level ameliorates neurological outcome and quality of life after traumatic brain injury: a clinical perspective

BACKGROUND

Deficiency of vitamin D along with traumatic brain injury (TBI) augments the risk of injury severity. This possibly affects the therapeutic regimen prescribed for TBI which may pessimistically affects its outcome.

METHODS

Studies literature search was conducted in Google Scholar and PubMed. The inclusions were studies performed clinically on both male and female. All included studies' references were also reviewed to find any additional relevance related to this review. Studies published in English were considered for this review. This review focuses upon the incidence of vitamin D deficiency in TBI and how it affects the Quality of life of the sufferer.

RESULTS

A total of 176 studies were reviewed and 58 were thoroughly focussed for review as they met inclusion criteria. These studies demonstrate that levels of vitamin D influence the recovery outcome after TBI. Vitamin D deficiency has been found to cause more deterioration in severe TBI than in patients with mild TBI.

CONCLUSION

Paucity of vitamin D significantly affects the outcome after brain injury. This clearly validates the necessity for screening of vitamin D levels in neurological deficit in order to reduce the risk of morbidity in terms of neurocognitive disorder.

The association between blast exposure and transdiagnostic health symptoms on systemic inflammation

Chronic elevation of systemic inflammation is observed in a wide range of disorders including PTSD, depression, and traumatic brain injury. Although previous work has demonstrated a link between inflammation and various diagnoses separately, few studies have examined transdiagnostic symptoms and inflammation within the same model. The objective of this study was to examine relationships between psychiatric and health variables and systemic inflammation and to determine whether mild traumatic brain injury (mTBI) and/or exposure to blast munitions moderate these relationships. Confirmatory factor analysis in a large sample (N = 357) of post-9/11 Veterans demonstrated a good fit to a four-factor model reflecting traumatic stress, affective, somatic, and metabolic latent variables. Hierarchical regression models revealed that each of the latent variables were associated with higher levels of systemic inflammation. However, the strongest relationship with inflammation emerged among those who had both war-zone blast exposures and metabolic dysregulation, even after adjusting for mental health latent variables. Exploratory analyses showed that blast exposure was associated with metabolic dysregulation in a dose-response manner, with self-reported closer blast proximity associated with the greatest metabolic dysregulation. Together, these results provide a greater understanding of the types of symptoms most strongly associated with inflammation and underscore the importance of maintaining a healthy lifestyle to reduce the impact of obesity and other metabolic symptoms on future chronic disease in younger to middle-aged Veterans.

CRHR1 mediates the transcriptional expression of pituitary hormones and their receptors under hypoxia

Hypothalamus-pituitary-adrenal (HPA) axis plays critical roles in stress responses under challenging conditions such as hypoxia, via regulating gene expression and integrating activities of hypothalamus-pituitary-targets cells. However, the transcriptional regulatory mechanisms and signaling pathways of hypoxic stress in the pituitary remain to be defined. Here, we report that hypoxia induced dynamic changes in the transcription factors, hormones, and their receptors in the adult rat pituitary. Hypoxia-inducible factors (HIFs), oxidative phosphorylation, and cAMP signaling pathways were all differentially enriched in genes induced by hypoxic stress. In the pituitary gene network, hypoxia activated c-Fos and HIFs with specific pituitary transcription factors (Prop1), targeting the promoters of hormones and their receptors. HIF and its related signaling pathways can be a promising biomarker during acute or constant hypoxia. Hypoxia stimulated the transcription of marker genes for microglia, chemokines, and cytokine receptors of the inflammatory response. Corticotropin-releasing hormone receptor 1 (CRHR1) mediated the transcription of Pomc, Sstr2, and Hif2a, and regulated the function of HPA axis. Together with HIF, c-Fos initiated and modulated dynamic changes in the transcription of hormones and their receptors. The receptors were also implicated in the regulation of functions of target cells in the pituitary network under hypoxic stress. CRHR1 played an integrative role in the hypothalamus-pituitary-target axes. This study provides new evidence for CRHR1 involved changes of hormones, receptors, signaling molecules and pathways in the pituitary induced by hypoxia.

Antibodies against the pituitary and hypothalamus in boxers

Traumatic brain injury (TBI), a growing public health problem worldwide, has recently been recognized as one of the leading causes of hypopituitarism. The main causes of TBI-induced pituitary dysfunction are car accidents, falls, violence, sports-related brain injury, and war accidents, including blast-related brain injuries. Car accidents and falls are the most common causes of TBI and pituitary dysfunction among the younger generation and elderly population, respectively. The prevalence of hypopituitarism after TBI is about 30%. GH is the most common hormone lost. The mechanisms underlying hypopituitarism are still unclear; however, recent studies have demonstrated that hypoxic insult, increased intracranial pressure, axonal injury, genetic predisposition, neuroinflammation, and autoimmunity may be responsible for the development of pituitary dysfunction. Neuroendocrine abnormalities are recently described in athletes dealing with contact sports, including boxing and kickboxing, which are characterized by chronic repetitive head trauma. Mild TBI and concussion are accepted in boxing and kickboxing. The positivity of antipituitary and antihypothalamic antibodies is also a significant risk factor in the development of neuroendocrine abnormalities. Autoimmune reaction may also be responsible for the reduction in pituitary volume in boxers with hypopituitarism. In this chapter, the role of autoimmunity in the occurrence of pituitary dysfunction among boxers is discussed.

Traumatic brain injuries induced pituitary dysfunction: a call for algorithms

Traumatic brain injury affects many people each year, resulting in a serious burden of devastating health consequences. Motor-vehicle and work-related accidents, falls, assaults, as well as sport activities are the most common causes of traumatic brain injuries. Consequently, they may lead to permanent or transient pituitary insufficiency that causes adverse changes in body composition, worrisome metabolic function, reduced bone density, and a significant decrease in one's quality of life. The prevalence of post-traumatic hypopituitarism is difficult to determine, and the exact mechanisms lying behind it remain unclear. Several probable hypotheses have been suggested. The diagnosis of pituitary dysfunction is very challenging both due to the common occurrence of brain injuries, the subtle character of clinical manifestations, the variable course of the disease, as well as the lack of proper diagnostic algorithms. Insufficiency of somatotropic axis is the most common abnormality, followed by presence of hypogonadism, hypothyroidism, hypocortisolism, and diabetes insipidus. The purpose of this review is to summarize the current state of knowledge about post-traumatic hypopituitarism. Moreover, based on available data and on our own clinical experience, we suggest an algorithm for the evaluation of post-traumatic hypopituitarism. In addition, well-designed studies are needed to further investigate the pathophysiology, epidemiology, and timing of pituitary dysfunction after a traumatic brain injury with the purpose of establishing appropriate standards of care.