GREB1 and endometriosis: SNP rs13394619 is intronic to the growth regulation by estrogen in breast cancer 1 gene (GREB1) where it disrupts a splice site, and the effect allele A is also associated with decreased risk (OR = 0.92; 95% CI = 0.88–0.96; P = 5.8 × 10−5; Phet = 0.61) of endometriosis (Table 2), with similar results (OR = 0.92; 95% CI = 0.88–0.96; P = 4.6 × 10−4; Phet = 0.69) in Grade B analysis (Supplementary Table S2).