Folliculogenesis is negatively impacted by the hyperandrogenic and insulin-resistant environment typical of PCOS, which is common across all phenotypes but commonly worsened in instances of obesity, by disrupting intra-ovarian signalling pathways, including as PI3K/AKT, ERK1/2, and TGF-β/SMAD pathways [24]. Here, TGFB1 is linked to polycystic ovary syndrome.