Clinical studies have demonstrated that traumatic brain injury (TBI) and aneurysmal subarachnoid hemorrhage (SAH) are frequent causes of long-term disturbances of hypothalamo-pituitary function. This study aimed to assess the prevalence and associated factors of post-traumatic hypopituitarism in a large national registry of patients with TBI and SAH. Data were collected from 14 centers in Germany and Austria treating patients for TBI or SAH and performing endocrine assessments. Data were collected using a structured, internet-based study sheet, obtaining information on clinical, radiological, and hormonal parameters. A total of 1242 patients (825 TBI, age 43.5±19.7 years; 417 SAH, age 49.7±11.8 years) were included. We studied the prevalence of hypopituitarism reported based on different definitions of laboratory values and stimulation tests. Stimulation tests for the corticotropic and somatotropic axes were performed in 26% and 22% of the patients, respectively. The prevalence of hypopituitarism in the chronic phase (at least 5 months after the event) by laboratory values, physician diagnoses, and stimulation tests, was 35%, 36%, and 70%, respectively. Hypopituitarism was less common in the acute phase. According to the frequency of endocrine dysfunction, pituitary hormone secretion was impaired in the following sequence: ACTH, LH/FSH, GH, and TSH. TBI patients with abnormal stimulation tests had suffered from more severe TBI than patients with normal stimulation tests. In conclusion, our data confirm that hypopituitarism is a common complication of TBI and SAH. It is possible that patients with a higher likelihood of hypopituitarism were selected for endocrine stimulation tests.