HDAC9 and polycystic ovary syndrome: These microbial shifts activate a coordinated molecular response through key receptors (FXR, GPR43, TGR5, AhR) and inhibit critical pathogenic pathways (TLR4/NF-κB, NLRP3, HDAC), culminating in a multi-organ reversal of PCOS features: improved insulin sensitivity and metabolic homeostasis, suppressed hyperandrogenism, restored ovulatory function, and resolved chronic inflammation.