Genetics of endometriosis:: a role for the progesterone receptor gene polymorphism PROGINS?

OBJECTIVE Endometriosis is a steroid-dependent disease with a particular genetic background, but the locations of possible genomic aberrations are still poorly clarified. We have investigated the potential association between endometriosis and the PROGINS 306 base pair insertion polymorphism in intron G of the progesterone receptor (PR) gene, which has been reported previously to segregate with this disease. DESIGN In a case-control study, we examined the PROGINS polymorphism of the progesterone receptor gene in 131 Italian women affected by endometriosis diagnosed according to published criteria for the definition of the definite disease. Control subjects were represented by 127 Italian women without laparoscopic evidence of the disease. MEASUREMENTS Peripheral blood samples, DNA extraction and polymerase chain reaction (PCR) were used to genotype women for the presence of the PROGINS polymorphism. RESULTS We found a statistically significant difference in the distribution of PROGINS genotypes between patients with and without endometriosis. The frequency of the PROGINS allele T2 was 17.2% and 11%, respectively, in affected women and in controls [odds ratio (OR) = 1.7, 95% confidence interval (CI) 1.0-2.8]. This association was stronger in patients with more severe forms of endometriosis, such as an infiltrating disease or a disease characterized by severe pelvic adhesions (OR 2.4, 95% CI 1.2-4.8; and OR 2.7, 95% CI 1.4-5.3, respectively). Combination of the results from an earlier study and the current data indicates that carrying the allele variant T2 is associated with a twofold increase in the risk of developing endometriosis (OR 2.0, 95% CI 1.3-2.9). CONCLUSIONS Our results further support the idea that the PROGINS polymorphism of the progesterone receptor may be associated with an increased risk of endometriosis.