Circulating levels of nitric oxide in fertile women in relation to the menstrual cycle

Objective: To investigate nitric oxide (NO) production in the two phases of normal menstrual cycle. Design: Prospective clinical study. Setting: Normal human volunteers in an academic research environment. Patient(s): Fifteen normally cycling women. Intervention(s): Follicle growth monitoring by ultrasound, serum, and plasma sampling in the midfollicular phase, at ovulation, and in the midsecretory phase. Main Outcome Measure(s): Plasma concentration of NO stable oxidation products and serum concentrations of E(2) and P. Result(s): Plasma concentration of NO metabolites resulted higher in the follicular phase with respect to the secretory phase and peaked at midcycle. Conclusion(s): The results strongly support the existence of an E(2) control of NO production and release. The significant reduction in NO metabolites observed in the secretory phase suggests a possible opposing action of P on either NO production or release.