DPP4 and polycystic ovary syndrome: Western blotting analysis showed that, compared to the control group, DPP4, ACSL4 and TFR1 expression (Fig. 7I and Supplementary Fig. 7, p < 0.0001) was increased and GPX4 expression (Fig. 7H, MD of PCOS and ERA = 0.5684, 0.7660, p < 0.0001, p < 0.0001) decreased in both the HD DHEA and ERA groups.