Cortisol Dynamics Following Acute Traumatic Brain Injury

ObjectiveTo investigate the serum status and dynamics of total cortisol(COR), adrenocorticotropin (ACTH), corticosteroid-binding-globulin (CBG), free cortisol (FC) and free cortisol index (FCI) in different stages after acute traumatic brain injury(TBI), and to find out the neuroendocrine alterations represented by changes of these hormones, then help to guide clinical administration of glucocorticoids(GCs). MethodsThe research was carried out in Neurosurgical centers of General Hospital, Tianjin Medical University and Huanhu Hospital in Tianjin. From July to September in 2005, 55 TBI patients with an admitting post-trauma period within 24h were included in this study as test group. Patients were classified into three subgroups: mildly, moderately and severely injured groups. Thirteen non-stress individuals were studied as contrast.ACTH and total COR were measured by a solid-phase, two-side sequential chemiluminescent immunometric assay, and CBG was measured by a competitive radioimmunoassay, FC was calculated by Coolens equation. Data were analyzed with SPSS11.0, a two-tailed P value was considered significant. COR, ACTH, CBG, FC and FCI were compared among non-stress contrast and mild, moderate and severe TBI group, to elucidate the acute stressful reactions, diurnal rhythm alterations and dynamic changes of the hormones, meanwhile, adrenal cortex function was evaluated in these patients. Results1. In 55 patients of this group, with 24h following acute TBI, COR, ACTH, FC and FCI were higher than non-stress contrast(P < 0.05), while hormones in severelyinjured group were higher than moderately-mildly injured group(P < 0.05)and herniation group higher than non-herniation group(P < 0.05). CBG was rather constant between groups.2. Following acute TBI, emergency craniotomy group showed higher COR and ACTH levels than conservative group before operation (P < 0.05). The first day after operation or trauma, no difference was observed (P > 0.05).In craniotomy group, COR> ACTH and CBG decreased(P < 0.05).3. Following acute TBI, diurnal rhythm of COR, ACTH, FC and FC lost in moderately-severely injured group, while preserved in mildly injured group. CBG was relatively constant and no diurnal rhythm character was observed.4. In the 7 days post-trauma, COR, ACTH, FC and FCI experienced rapid elevation then decreased quickly, ACTH returned to normal level within the first day due to a short plasma half-life;COR, FC and FCI dropped slower, returned to normal level between day 3 and day5.5. COR> ACTH levels of favorable outcome group and poor outcome group experienced gradual decrease in the post-trauma period. But COR recovered to normal range on day 2 in favorable outcome group, quicker than poor outcome group on day 5.6. No COR> ACTH> CBG> FC and FCI difference was observed between skull base fracture group and no fracture group. After traumatic brain injury, adrenal insufficiency could be observed in some patients, but mostly transient. Outcome of patients with transient low cortisol levels was not significantly different from "normal" patients (P > 0.05), but 3 patients with persistent low COR were with poor outcome.Conclusions1. Traumatic brain injury acts as an intensive stress factor, can bring about prompt activation of hypothalamic-pituitary-adrenal (HPA) axis, represented by rapidlyincreased serum COR, FC and FCI, the increase is mostly evident in severely injured group. ACTH level is correlated with intensity of injury, increasing with enhanced injury severity.2. Emergency craniotomy may function as another stressful factor when the body is in peak of stress, but shows no obvious augment effect on hormones reaction, on the contrary, may relieve the body from stress.3. Early post-trauma, inherent diurnal rhythms of COR, ACTH, FC and FCI are preserved in mildly injured group while disturbed in moderately-severely injured patients.4. Following acute TBI, COR, ACTH, FC and FCI elevate rapidly then decrease quickly, ACTH decrease rapidly to normal within the first day due to a short plasma half-life. COR, FC and FCI draw back slower, return to normal between day 3 and 5.5. COR levels of favorable outcome group recover to normal range quickly on day 2, while in poor outcome group, COR return to normal range more slowly on day5.6. COR and ACTH are not sufficient to predict short-term outcome of TBI. Posttraumatic adrenal insufficiency may present in different stages of TBI, but not correlated with short-term outcome, patients with persistent low COR are of poor outcome.