HIF1A and altitude sickness: We determined FMD values, NO, ET-1, asymmetric dimethylarginine (ADMA), vascular endothelial growth factor (VEGF), and hypoxia-inducible factor 1 (HIF-1) levels in healthy individuals who entered a plateau area from the plain area by gradients of elevation to assess the mechanism of the occurrence and development of AMS, identify predictive markers for the early diagnosis and prognosis of acute altitude sickness, and determine an optimal entry mode for healthy individuals into plateau areas from the plain areas.