Objective To investigate the expression and role of adrenomedullin (ADM) and adrenomedullin receptor (ADMR) in patients with chronic obstructive pulmonary disease (COPD).Methods Small pulmonary artery remodeling was observed using morphometric analysis. Theexpression of ADM and ADMR mRNA in lung tissue was calculated by in situ hybridization in 9 COPD cases. Cardiac catheterization was performed in 22 COPD cases to monitor changes of hemodynamic parameters and patients were divided into two groups based on mean pulmonary artery pressure (mPAP). The cases without pulmonary hypertension (PH) were placed in Group A (n=12) and those with PH were placed in Group B (n=10). The levels of pulmonary arterial plasma ADM were measured by radioimmunoassay. Blood gas analysis was also conducted.Results The ratio of vascular wall thickness to external diameter (MT%) and the ratio osed in the pulmonary artery walls of control subjects . The expression levels were 01). Statistically positive relationships were visible between ADM and ADMR, and the plasma ADM level of Group B was significantly higher than that of Groupon to mPAP and pulmonary vascular resistance (PVR), while being negatively correlated to levels of PaO2.Conclusion ADM may play an extremely protective role as a local autocrine/paracrine factor in COPD.