Reduction of Soluble Leptin Receptor Levels in Women with Unexplained Infertility and the Effect of Leptin Receptor Gln223Arg Polymorphism on its Serum Level

Background & Objective: Soluble leptin receptor (sOB-R) is the most important leptin-binding protein that can affect the level of active biological leptin. The Gln223Arg polymorphism in the leptin receptor (LEP-R) gene is associated with obesity, which can be a factor for infertility. The purpose of this study was to evaluate sOB-R levels in women with unexplained infertility and investigate the effect of LEP-R gene polymorphism on sOB-R serum levels . Materials & Methods: One hundred and two women with unexplained infertility and 112 fertile women were studied in this case-control study. Subjects in both groups had a normal hormonal profile with age below 40 years. The levels of sOB-R were measured using the enzyme-linked immunosorbent assay (ELISA) method. Results: There was a 2-fold decrease in sOB-R levels in the infertile group compared to the control group (P=0.001). Although sOB-R levels were lower in overweight and obese infertile subjects, this difference was not significant. However, this difference was significant compared to the control group. There was a direct correlation between body mass index (BMI), age, and infertility. Although sOB-R levels in Arg/Arg genotypes were higher than in Gln/Gln and Arg/Gln genotypes in the infertile group, they were not statistically significant. A significant decrease was observed in sOB-R levels of Gln/Gln and Arg/Gln genotypes in the infertile group compared to the control group. Conclusion: There was a reverse correlation between sOB-R levels and unexplained infertility. It seems that, by a decrease in serum sOB-R, the serum leptin levels increase, which can enhance leptin inhibitory effects in infertility.