Figure 4.

Microbial dynamics during the menstrual cycle. The diversity of bacteria during the menstrual cycle depends on variations in the sex hormone cycle (estrogen and progesterone) and endometrial fluctuations. In particular, during the stages with higher estradiol levels, species such as L. crispatus, L. kitasatonis, L. amylovorus, L. jensenni, and P. acnes increase their density in the genitourinary tract. Conversely, a decrease in estradiol and progesterone creates an environment rich in species such as G. vaginalis, L. iners, and Streptococcus spp., which can lead to infections and pro-inflammatory states. These changes depend on variations in the sex hormone cycle (estrogen and progesterone) and endometrial fluctuations during the different stages of the menstrual cycle.