The effect of the menstrual cycle on exhaled nitric oxide and urinary nitrate concentration.

Exhaled nitric oxide (NO), early morning urinary nitrites/nitrates and urinary female sex steroid conjugates were measured daily to investigate whether there was a variation in NO generation during the menstrual cycle. Exhaled NO concentrations and early morning urine samples were taken for 30 consecutive days in five healthy normotensive women with proven ovulation. The urine samples were analysed for nitrite-nitrate creatinine ratios, oestrone-3-glucuronide (EG) and pregnanediol-3-alpha glucuronide (PG). The mean (95% CI) exhaled NO concentration was 52 ng g-1 in the 150 readings and the mean molar urinary nitrate-creatinine ratio was 0.18. There was no temporal relationship between the measurement of NO production and urinary sex steroid conjugates within the menstrual cycle. These findings suggest that oestrogens do not modulate exhaled NO concentration and appear not to increase the production of the early morning urinary nitrates in healthy premenopausal women. There was also no sex difference in exhaled NO generation.