S100A6 and Infertility: In summary, the eutopic endometrium of infertile patients with OE exhibited markedly higher (P < 0.01) 17β-HSD1 levels, higher (P < 0.05) tissue E2 levels, and a lower (P < 0.01) PRB:PRA ratio than the control, infertile, secretory phase endometrium during the secretory phase.