EDN1 and obstructive sleep apnea syndrome: Recent studies have established a relationship between OSA and the following key biomarkers: a) endothelin-1 (ET-1), a marker of endothelial dysfunction; b) high sensitivity troponin T (hs Trop-T), a marker of myocardial injury; c) high-sensitivity C-reactive protein (hs-CRP), a marker of inflammation; d) cardiac neurohormone N-terminal pro-brain natriuretic peptide (NT-proBNP), a marker of ventricular strain, and e) fibrinogen, a marker of hypercoagulation [5].