Common genetic variants in the sex hormone-binding globulin (SHBG) gene in idiopathic recurrent pregnancy loss: a case control study

Abstract

Background A role for sex hormone-binding globulin (SHBG) in determining the pregnancy outcome was evidenced by the rise in SHBG levels during pregnancy linked with favorable pregnancy, while reduction in SHBG levels and hyperandrogenemia were linked with poor pregnancy outcome. Since SHBG production is genetically determined, this study investigated the association of SHBG polymorphisms with the susceptibility to recurrent pregnancy loss (RPL).

Methods Retrospective case-control study, involving 308 women with RPL, and 310 control women RPL, defined as ≥3 consecutive miscarriages, and with the same partner, was the main outcome measure. SHBG genotyping was done by allelic exclusion method (real-time PCR).

Results Of the seven tested SHBG SNP, lower MAF of rs6257 was seen in RPL cases than in control women, which was linked with lower risk of RPL, after controlling for key covariates. At the genotype level, significantly higher frequencies of heterozygous rs858521 and rs6259, and homozygous rs858521 genotype carriers, and reduced frequency of heterozygous rs6257 and homozygous rs6257 and rs6259 genotype carriers were seen in RPL cases vs. control women, respectively. Univariate regression analysis confirmed the positive association of rs858521 and rs6259 with RPL. Multivariate regression analysis confirmed the positive association of rs858521 heterozygote and homozygote genotypes with RPL; only heterozygous rs6259 remained associated with RPL. Haploview analysis demonstrated marked linkage disequilibrium among 6 of the 7 tested SHBG SNP. Of the possible 6-locus haplotypes, 12 were common, and were included in subsequent analysis. Within these haplotypes, only increased frequency of CCGTGA haplotypes was seen in RPL cases, thus conferring RPL susceptibility.

Conclusions Specific SHBG variants, and SHBG haplotypes are associated with altered risk of RPL, suggesting role for SHBG as RPL candidate gene.