Pirina P, et al. - Researchers sought to establish the levels of circulating serotonin in chronic obstructive pulmonary disease (COPD). They also investigated the eventual relations between serotonin and oxidative stress markers. They assessed the whole blood serotonin in 43 consecutive patients with stable COPD and in 43 age and sex-matched healthy controls. In COPD, higher levels of circulating serotonin were demonstrated in the findings and it was inversely correlated with the worsening of airway obstruction. Compared to the controls, serotonin blood levels were significantly higher in COPD patients.