In this setting, both heterozygous mutant SNP (genotype AG, 289Ser/Gly) and homozygous mutant SNP (genotype AA, 289Ser/Ser) of HSD17B3 showed a significantly decreased risk of endometriosis (P = 0.005; OR = 0.57) and P = 0.02; OR = 0.69), respectively, as compared to the controls (n = 337). This evidence concerns the gene HSD17B3 and endometriosis.