PEAK EXPIRATORY NITRIC-OXIDE DIFFERENCES IN MEN AND WOMEN - RELATION TO THE MENSTRUAL-CYCLE

Objective-To develop a method to measure end expiratory nitric oxide c oncentration and to use it to determine whether there are sex related differences between healthy men and women. Design-Modification of comm ercially available chemiluminescent analyser to allow endogenous nitri c oxide (endothelium derived relaxing factor) to be measured in a sing le slow forced vital capacity manoeuvre with evaluation of between and within subject variability. Serial measurements in women throughout t he menstrual cycle. Setting-Specialist referral hospital. Subjects-59 healthy volunteers (40 men and 19 women). Results-Mean (SD) peak expir atory concentrations of nitric oxide in men (75 (20) ppb (parts per bi llion)), and women (70 (37) ppb (first measurement)) were >5 times tho se previously recorded. In women concentrations at midcycle (150(39) p pb) were significantly higher (mean difference 94.9(41), P < 0.001) th an during menstruation (59(25) ppb). Conclusion-Nitric oxide productio n (endothelium derived relaxing factor activity) is influenced by cycl ical hormonal changes in women. There was an increase of more than 100 % at mid cycle. This may be pertinent to the lower risk of cardiovascu lar disease in premenopausal women.