FGF19 and polycystic ovary syndrome: Although no significant correlations were observed between FGF19 and individual PCOS-related indices (e.g., FSH, LH, and testosterone), a positive correlation with AMH (a marker of ovarian reserve) and E2 and a negative correlation with LH (a driver of androgen excess) suggest the potential involvement of FGF19 in follicular development and hormonal regulation.