There are two main HPA axis reactivity phenotypes that we previously detected in a population of female PTSD patients subjected to a social stress test: HPA axis responders showed a rapid increase in blood cortisol and ACTH levels in response to stress while the HPA axis non-responder group showed a blunted endocrine HPA axis response despite a marked psychological stress reaction (72). The gene discussed is POMC; the disease is post-traumatic stress disorder.