Dopamine receptor D2 genotype (3438) is associated with moderate/severe endometriosis in infertile women in Brazil

OBJECTIVE: To compare the prevalence of dopamine receptor D2 polymorphisms in patients with peritoneal endometriosis and in healthy control subjects. DESIGN: Case-control study. SETTING: University hospital. PATIENT(S): One hundred seven women aged ≥18 years who were enrolled when seeking care for infertility caused by peritoneal endometriosis or for tubal ligation. INTERVENTION(S): We performed DNA extraction of peripheral blood, followed by polymerase chain reaction to confirm single-strand polymorphisms and to sequence two polymorphisms. MAIN OUTCOME MEASURE(S): We sequenced two polymorphisms in exon 7 of the dopamine receptor D2 (DRD2) gene. Polymorphism 1 occurs in nucleotide 3420 (cytosine to thymine, 313 histidine), and polymorphism 2 occurs in nucleotide 3438 (cytosine to thymine, 319 proline). RESULT(S): The frequency of the DRD2 polymorphism 2 was increased in subjects with peritoneal moderate/severe endometriosis. Analysis of the DRD2 genotypes demonstrates an odds ratio of 2.98 (95% confidence interval 1.47-6.04) for polymorphism 2 in peritoneal moderate/severe endometriosis. CONCLUSION(S): Our results revealed that an excess of DRD2 polymorphism 2 was found in exon 7 in women with peritoneal moderate/severe endometriosis. The presence of polymorphism 2 could cause a defect in a post-receptor signaling mechanism, resulting in a mild increase in serum prolactin levels. Thus, the potential angiogenic role of prolactin may play a role in the implantation of ectopic endometriosis tissue.