 Lifetime prevalence of post-traumatic stress disorder PTSD is estimated at 8. Exposure to traumatic events increases the risk of poor physical health, and chronic PTSD often leads to disability. The pathophysiology of PTSD is continually being explored in order to help find better treatment modalities for this debilitating disorder. Proposed mechanisms for the altered stress axis in PTSD include changes at the level of the pituitary. Though the pituitary stress hormone axis has been explored, no work has been done to evaluate for changes in the pituitary volume in response to these changes in the stress axis in PTSD. We have designed a study which will assess for differences in pituitary volumes. We will compare volumes in patients with PTSD, non-PTSD subjects who have had a history of trauma, and healthy controls. We will test the HPA axis through the dexamethasoneCRH test, a standardized diagnostic test, and correlate the findings with changes in the pituitary volume. Moreover, we will assess for changes in other endocrine axes and proteins. 