However, it is notable that in the subgroup of women with PCOS, plasma GDF-15 levels were negatively correlated with circulating osteocalcin and positively correlated with urine deoxypyridinoline (107), in keeping with the evidence discussed earlier relating to the positive regulation of osteoclastic differentiation by GDF-15 in osteocytic cells (106). Here, GDF15 is linked to polycystic ovary syndrome.