Parathyroid hormone-related protein (PTHrP) is an autocrine growth and differentiation factor for alveolar type II epithelial cells. Type II cells secrete pulmonary surfactant and are pluripotent cells with a role in alveolar epithelial repair after lung injury. The goals of this study were to investigate whether the levels of PTHrP in bronchoalveolar lavage liquid (BAL) varied between patients who did and did not develop lung injury after pulmonary thromboendarterectomy (PTE). BAL was performed in 48 patients undergoing PTE for unresolved pulmonary emboli. Samples were obtained following induction of anesthesia, following separation from cardiopulmonary bypass, and 48 h postoperatively. PTHrP was measured by radioimmunoassay. Lung injury was diagnosed in 23 patients on the basis of hypoxemia (PaO(2)/FIO(2) < 300) and the presence of lung infiltrates in the absence of infection or atelectasis. Patients with lung injury had significantly lower preoperative BAL levels of PTHrP, 21 (21-30) pg/ml (median, interquartile gap), compared to patients without lung injury, 34 (21-41) pg/ml (P < 0.05). Preoperative BAL PTHrP levels < 32 pg/ml predicted lung injury with a positive predictive value of 60% and negative predictive value of 82%. The odds of developing lung injury for patients with preoperative PTHrP levels below this cutpoint were 6 times the odds for patients with higher levels.