Changes in Exhaled Carbon Dioxide during the Menstrual Cycle and Menopause.

Introduction: The menstrual cycle (MC) reflects multifaceted hormonal changes influencing women's metabolism, making it a key aspect of women's health. Changes in hormonal levels throughout the MC have been demonstrated to influence various physiological parameters, including exhaled carbon dioxide (CO₂). Lumen is a small handheld device that measures metabolic fuel usage via exhaled CO₂. This study leverages exhaled CO₂ patterns measured by the Lumen device to elucidate metabolic variations during the MC, which may hold significance for fertility management. Additionally, CO₂ changes are explored in menopausal women with and without hormonal replacement therapy (HRT).

Methods: This retrospective cohort study analyzed exhaled CO₂ data from 3,981 Lumen users, including eumenorrheal women and menopausal women with and without HRT. Linear mixed models assessed both CO₂ changes of eumenorrheal women during the MC phases and compared between menopausal women with or without HRT.

Results: Eumenorrheic women displayed cyclical CO₂ patterns during the MC, characterized by elevated levels during the menstrual, estrogenic and ovulation phases and decreased levels during post-ovulation and pre-menstrual phases. Notably, despite variations in cycle length affecting the timing of maximum and minimum CO₂ levels within a cycle, the overall pattern remained consistent. Furthermore, CO₂ levels in menopausal women without HRT differed significantly from those with HRT, which showed lower levels.

Conclusion: This study reveals distinct CO₂ patterns across MC phases, providing insights into hormonal influences on metabolic activity. Menopausal women exhibit altered CO₂ profiles in relation to the use or absence of HRT. CO₂ monitoring emerges as a potential tool for tracking the MC and understanding metabolic changes during menopause.