FNDC5 and polycystic ovary syndrome: As one of the reproductive endocrinal and metabolism disorders, some clinical studies have found changes in serum irisin levels in PCOS patients compared with healthy women, but the results were controversial (Bacopoulou et al., 2018; Wang et al., 2018; Chang et al., 2019; Luo et al., 2021; Onat et al., 2022).