Traumatic brain injury (TBI), a huge public health problem, has been shown to result in hypopituitarism in 20-50% of patients, but the mechanisms of hypothalamic-pituitary dysfunction are unclear. In studies on injured animals, the occurrence of antipituitary antibodies (APA) has been shown, but such studies in patients are currently lacking in the literature. In this clinical study by Tanriverdi et al, the presence of APA at the third year of TBI was investigated, along with the association between TBI-induced hypopituitarism and APA. Twenty-nine patients who had completed a three-year follow-up were included, of which 18 had mild, 6 had moderate and 5 had severe TBI. The patients, along with 60 age and sex matched controls were tested for APAs using an indirect immunofluorescence method. Basal hormone levels including free tri-iodothyronine, free thyroxine, thyrotrophin, prolactin, cortisol, adrenocoticotrophin, follicle-stimulating hormone, luteinizing hormone and insulin-like growth factor were measured. The study found that APAs were present in 13 of the 29 TBI patients, but in none of the controls. Pituitary dysfunction development was higher in APA positive patients (46.2%) compared to APA negative patients (12.5%). A significant association between APA positivity and hypopituitarism due to TBI was also observed. This study is the first time the presence of APAs has been reported in TBI patients 3 years after TBI, and provides evidence to suggest that autoimmunity may contribute in the development of TBI-induced hypopituitarism. The authors conclude that this association opens a new area of study for TBI induced pituitary dysfunction. Tanriverdi, F., De Bellis, A., Bizzarro, A., Sinisi, A., Bellastella, G., Pane, E., Bellastella, A., Unluhizarci, K., Selcuklu, A., Casanueva, F., Kelestimur, F. European Journal of Endocrinology 159: 7-13. DOI: 10.1530/EJE-08-0050