Circadian changes in hormone levels in asthma

Mean changes in peak expiratory flow rate (PEFR) and the plasma concentrations of cortisol, epinephrine, cyclic AMP, and histamine over a 24-hour period in patients with nocturnal asthma. The nadir in PEFR, which occurs at 4 AM, is associated with low levels of cortisol and epinephrine and high levels of the bronchoconstrictor mediator, histamine.