PTGDS and polycystic ovary syndrome: Taking all this into account, it is not surprising that many of the proteins that were differentially expressed between pregnant PCOS cases and controls in the dataset have also been linked to pre-eclampsia, e.g. properdin, insulin-like growth factor 2 (IGF2), PF4, coagulation factor XII (F12), FBL1, apolipoprotein C3 (APOC3), hemopexin (HPX), apolipoprotein E (APOE), PLG, vitronectin (VTN), ZAG1, prostaglandin-H2 D-isomerase (PTGDS) and the complement component C8 alpha chain (C8A)18.