PTGS2 and endometriosis: We along with others have shown that an isoform of cyclooxygenase-2 (COX-2) is overexpressed in ectopic endometrial cells [17–20] and that PGE2, PGF2α, and other specific prostaglandins are present at abnormally high levels in uterine tissues of women suffering from menorrhagia, dysmenorrhoea, or endometriosis [21–23].