Neuroendocrine Responses to Traumatic Brain Injury

Traumatic brain injury (TBI) which is a growing public health problem worldwide has recently been recognized as one of the most common causes of pituitary dysfunction. The causes of TBI-induced pituitary dysfunction are car accidents, falls, sports-related brain injuries, violence and war accidents including blast-related brain injuries. Traffic road accidents and falls are more common in young people and older people, respectively. Recent data revealed that neuroendocrine abnormalities may also occur in athletes dealing with contact sports including boxing and kickboxing. On the other hand, pituitary volume in boxers with hypopituitarism is smaller when to compared to the boxers with normal pituitary function and healthy subjects. Boxing and kickboxing are characterized by chronic repetitive head trauma and they are accepted as mild traumatic braininjury (Concussion). The prevalence of hypopituitarism after TBI is about 30% and GH is the most common hormone lost. Posterior pituitary involvement is rare and 5% of the patients develops diabetes insipidus. The mechanisms underlying the hypopituitarism after TBI are still unclear; however, recent studies have demonstrated that hypoxic insult, axonal injury, vascular injury, genetic predisposition, neuroinflammation and autoimmunity may be responsible for the development pituitary dysfunctiom. The frequency of hypopituitarism is significantly lower in TBI victims with APO E3/E3 than in those without APO E3/E3 genotype. The positivity of antipituitary and anti-hypothalamic antibodies is also a significant risk factor. Altered expression of miR-126-3p and miR-3610 may play a role in the occurrence of hypopituitarism after TBI.Treatment of hypopituitarism with appropriate replacement of deficient hormones is beneficial in the improvement of symptoms and quality of life.