In this review, we summarize several key signaling pathways closely involved in the pathogenesis of PCOS: the PI3K/Akt, TLR4/NF-κB, Nrf2/HO-1, AMPK, MAPK, JAK/STAT, Wnt/β-catenin, Notch, Hippo/YAP, TGF-β/Smads, and hedgehog pathways. The gene discussed is HMOX1; the disease is polycystic ovary syndrome.