effect of posttraumatic serum thyroid hormone levels on severity and mortality of patients with severe traumatic brain injury

traumatic brain injury (tbi) is an important cause of death and disability in young adults ,and may lead to physical disabilities and long-term cognitive, behavioral psychological and social defects. there is a lack of definite result about the effect of thyroid hormones after traumatic brain injury in the severity and no data about their effect on mortality of the injury. the aim of this study is to evaluate the effect of thyroid hormones after traumatic brain injury in the severity and mortality and gain a clue in brain injury prognosis. in a longitudinal prospective study from february 2010 until february 2011, we checked serum levels of t3, t4, tsh and tbg of severely brain injured patients and compared the relationship of them with primary glasgow coma scale (gcs) score and mortality of patients. statistical analysis used spss 11.5 software with using chi-square and fisher exact test. serum levels of t3 and t4 were decreased after brain trauma but not tsh and tbg. mortality rates were higher in patients with lower t4 serum levels. the head injury was more severe in whom with low t3 and t4. follow a severe brain injury a secondary hypothyroidism is happened due to pituitary dysfunction. also, serum level of t3 and t4 on the first day admission affect on primary gcs score of patients which is an indicator of severity of brain injury. in addition, mortality rates of severely brain injured patients have a high correlation with the serum level of t4 in the first day admission.