Glycogen levels in undiluted genital fluid and their relationship to vaginal pH, estrogen, and progesterone

Background: Colonization of the female lower genital tract with Lactobacillus provides protection against STIs and adverse pregnancy outcomes. Growth of genital Lactobacillus is postulated to depend on epithelial cell-produced glycogen. However, the amount of cell-free glycogen in genital fluid available for utilization by Lactobacillus is not known. Methods: Eighty-five genital fluid samples from 7 pre-menopausal women taken over 4-6 weeks were obtained using the Instead SoftCup¹ (EvoFem, Inc., San Diego, CA, USA) by consented donors. Cell-free glycogen and glucose in genital fluids and estrogen and progesterone in blood were quantified. Findings: Glycogen ranged from 0.1-32 μg/μl. There were significant differences between women in glycogen over the observation period. There was a strong negative correlation between glycogen and vaginal pH (r = -0.542, p<0.0001). In multivariable analysis, free glycogen levels were significantly negatively associated with both vaginal pH and progesterone (p< 0.001 and p = 0.004, respectively). Estrogen, glucose, age, sexual intercourse 24 hours prior to visit, and days after the initial visit were not significantly associated with free glycogen levels. Conclusion: Cell-free glycogen concentrations can be very high, up to 3% of genital fluid, and are strongly associated with acidic vaginal pH. However, the fluctuations in glycogen levels in individuals and differences between individuals do not appear to be associated with estrogen.