CYP19A1 and endometriosis: Similarly, in younger patients with endometriosis (n = 176), homozygous mutant SNP of CYP19 (genotype TT, 264Cys/Cys) showed a significantly lower risk of endometriosis (P = 0.03; OR = 0.71) when compared to the controls (n = 337) (Table 3).