The Neuroendocrinology of Medically Unexplained Syndromes

Physical symptoms account for more than half of all outpatient visits in the United States each year, and yet one-third to half of all such presentations lack a clear physical explanation (1,2). Such conditions are labeled on the basis of excluding known disease and as a group they have been designated as functional somatic syndromes or medically unexplained syndromes (3,4). One such medically unexplained syndrome is chronic fatigue syndrome (CFS) (5,6), a relatively common condition of unclear origin that is estimated to affect as many as 400 per 100,000 adults with increased prevalence among minorities, women, and persons in lower-income brackets (7). CFS is associated with disability and poor health-related quality of life and is characterized by disabling fatigue of at least 6 mo in duration (5–8).