GDF15 and polycystic ovary syndrome: Additionally, GDF-15 levels were higher (1.89 ng/mL, IQR 2.73 ng/mL) among women previously treated with metformin compared to those who were never treated with metformin (1.18 ng/mL, IQR 2.73 ng/mL; p = 0.007) in the PCOS group (Figure 1B).