Traumatic brain injury (TBI) is the most common cause of death and disability in young adults living in industrialised countries, in which 180-250 persons per 100 000 per year die or are hospitalised as a result. Neuroendocrine derangements after TBI have received increasing recognition in recent years because of their potential contribution to morbidity, and possibly mortality, after trauma. Marked changes of the hypothalamo-pituitary axis have been documented in the acute phase of TBI, with as many as 80% of patients showing evidence of gonadotropin deficiency, 18% of growth hormone deficiency, 16% of corticotrophin deficiency and 40% of patients demonstrating vasopressin abnormalities leading to diabetes insipidus or the syndrome of inappropriate anti-diuresis. Longitudinal prospective studies have shown that some of the early abnormalities are transient, whereas new endocrine dysfunctions become apparent in the post-acute phase. There remains a high frequency of hypothalamic-pituitary hormone deficiencies among long-term survivors of TBI, with approximately 25% patients showing one or more pituitary hormone deficiencies. This is a higher frequency than previously thought and suggests that most cases of post-traumatic hypopituitarism (PTHP) remain undiagnosed and untreated. PTHP has been associated with adverse outcome both in the acute and chronic phases after injury. These data underscore the need for the identification and appropriate timely management of hormone deficiencies, in order to optimise patient recovery from head trauma, improve quality of life and avoid the long-term adverse consequences of untreated hypopituitarism.