Hypopituitarism after moderate or severe traumatic brain injury (TBI) is usually underdiagnosed and therefore undertreated. Its course can be divided in an acute phase during the first 14 days after TBI with 50 to 80% risk of hypopituitarism, and a chronic phase, beginning three months after the event, with a prevalence of hypopituitarism that ranges from 2 to 70%. Its pathophysiology has been addressed in several studies, suggesting that a vascular injury to the pituitary tissue is the most important mechanism during the acute phase, and an autoimmune one during chronic stages. In the acute phase, there are difficulties to correctly interpret pituitary axes. Hence, we propose a simple and cost-effective algorithm to detect and treat a potential hypothalamic-pituitary-adrenal axis impairment and alterations of sodium homeostasis, both of which can be life-threatening. In the chronic phase, post-concussion syndrome is the most important differential diagnosis. Given the high prevalence of hypopituitarism, we suggest that all pituitary axes should be assessed in all patients with moderate to severe TBI, between 3 to 6 months after the event, and then repeated at 12 months after trauma by a specialized team in pituitary disease.