Brain injury and neuroendocrine function

Physical injury constitutes a major form of stress to the human body. The neuroendocrine response to trauma, an essential component of the adaptive process to this type of stress, has been an area of interest for endocrinologists for decades. In head-injured patients, structural as well as functional changes may be evident at the hypothalamic and pituitary level. Studies have shown considerable variation in the neuroendocrine response to brain injury. Generally, during the acute phase, the pituitary gland responds to trauma with two secretory patterns. Adrenocorticotropic hormone, prolactin, and growth hormone levels increase. On the other hand, thyroid-stimulating hormone, luteinizing hormone, and follicle-stimulating hormone levels either remain normal or decrease. These functional changes can vary depending on the time of assessment after the injury. Other factors such as severity of brain injury and associated injuries, hemodynamic status, timing of hormone sampling, the pulsatile nature of some hormones, assays used, and the effects of drugs can influence serum hormone determinations. Permanent neuroendocrine damage, specifically variable degrees of pituitary insufficiency, can occur at different times after head injury. This can have potential adverse effects during the recovery period and on the rehabilitation process. This article reviews neuroendocrine changes and their consequences after traumatic brain injury with remarks on the underlying pathophysiologic mechanisms and clinical outcomes.