Objective To investigate the relationship between antipituitary antibodies (APAs) and hypopituiarism following traumatic brain injury (TBI),as well as the severity of brain injury.Methods The study included 73 patients who suffered TBI 9 to 12 months ago and were diagnosed with hypopituitarism during the follow-up.Based on their Glasgow Coma Scale (GCS) on admission they were categorized into three groups:A (3-8),B (9-12) and C (13-15).Levels of plasma pituitary hormones (GH,TT,FT3 and FSH/LH) and APAs were measured in all patients with chemiluminescence assays and ELISA,respectively.Results Patients in group A had higher levels of APAs and lower levels of hormones compared with those in group B(P＜0.001) or group C(P＜0.001),while no significant difference was found between group B and group C for levels of either APAs (P＞0.05) or hormones (P＞0.05).Levels of APAs were negatively correlated with both GH (r=-0.64071,P＜0.001) and GCS (r=-0.50132,P＜0.001).Conclusion The present investigation provides preliminary evidence that APAs may be associated with the development of TBI-induced hypopituiarism.It suggests that the severity of hypopituiarism following TBI could be predicted by measuring the level of APAs.