Endothelial nitric oxide synthase G894T polymorphism increases the risk of infertility in women with endometriosis

Endometriosis is a chronic disease with adverse implications for fertility. We investigated the G894T polymorphism in the endothelial nitric oxide synthase gene in fertile and infertile women with endometriosis. This prospective study included a group of 52 women with a laparoscopic diagnosis of endometriosis. DNA was extracted from blood obtained from 47 patients and analyzed by PCR. The overall cohort was divided into infertile (n = 24) and fertile (n = 23) subgroups and compared in terms of genotypic and allelic frequencies. The genotypic distribution followed Hardy-Weinberg equilibrium (c² = 2.21, P = 0.137) and included the GG genotype in 28/47 GT in 14/47, and TT in 5/47 of the samples. Genotypic and allelic frequencies between fertile and infertile women with endometriosis showed that absence of the TT genotype was associated with fertility in endometriosis patients (P = 0.0623). The T allele was present in 17 patients of the infertile group and 7 patients of the fertile group (P = 0.025). This allele was significantly associated with infertility (relative risk = 2.21, 95% confidence interval 1.56 - 3.08) for the recessive model of inheritance. Our findings suggest that women with endometriosis and the G894T polymorphism in the endothelial nitric oxide synthase gene are at increased risk of infertility.