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 SoftCup® (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.