In contrast, the PCOS + MS group showed significant increases in the endometrial decidualization markers ER, PR, and PRL when compared to the PCOS group (Fig. 4C and D, MD of ER, PR, and PRL = − 400.1, − 339.3, − 474.3, p = 0.0043, p = 0.0024, p = 0.0063; Fig. 4E and Supplementary Fig. 5, MD of ER, PR, and PRL = − 0.5009, − 0.4169, − 0.4156, p < 0.0001, p = 0.0039, p = 0.0009;). Here, PRL is linked to polycystic ovary syndrome.