Exhaled nitric oxide is associated with cyclic changes in sexual hormones

BACKGROUND: We hypothesized that changes in the levels of sexual hormones during the menstrual cycle influence the concentration of nitric oxide in the exhaled air (FeNO) and alveolar exhaled nitric oxide (CANO). METHODS: Twelve healthy, non allergic women in their reproductive age (age range 25-37 years) were recruited. Subjects were studied, on alternate days, over the course of their menstrual cycle. At each visit, measurements of FeNO and CANO were performed. Progesterone and 17-β-estradiol concentrations were measured in salivary samples. RESULTS: Eight subjects completed the study. The levels of FeNO and CANO were 13 ± 4.7 pbb and 3.5 ± 1.9 pbb, respectively (mean ± SD). The mean salivary concentration of progesterone was 65.1 ± 16.2 pg/ml (mean ± SD), with a range of 32.4-107.7 pg/ml, and the concentration of 17 β-estradiol was 6.0 ± 1.6 pg/ml, with a range of 3.1-12.9 pg/ml. The Generalized Estimating Equations procedure demonstrated that levels of progesterone influenced both FeNO and CANO (Wald χ2 = 11.60, p = 0.001; and Wald χ2 = 87.55, p = 0.001, respectively). On the contrary, the salivary levels of 17 β-estradiol were not significantly associated with FeNO (Wald χ2 = 0.087, p = 0.768) or CANO (Wald χ2 = 0.58, p = 0.448). CONCLUSION: In healthy women, the menstrual cycle-associated hormonal fluctuations selectively influence the levels of bronchial and alveolar NO. The current findings may have important clinical implications for the interpretation of eNO levels, by identifying a patient-related factor that influences the eNO measurements.