Abstract
Sex hormone binding globulin (SHBG) is involved in delivering sex hormones to target tissues. We investigated the association between the (TAAAA) n repeat polymorphism, and Asp327Asn polymorphism in the SHBG gene with semen quality and idiopathic male infertility. We studied 168 men with idiopathic infertility [oligoasthenoteratozoospermia (OAT)] and equal number of age-matched normal controls. The serum levels of SHBG, reproductive and thyroid hormones, and Inhibin B were measured. Semen parameters were also assessed. The genotype assays for the SHBG polymorphism were done using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Baseline SHBG levels tended to be lower in infertile men (21.1 ± 7.2 nmol/l) compared to normal fertile men (24.7 ± 7.9 nmol/l). SHBG levels tended to be higher among the subjects with the Asn/Asn (25.84 ± 3.6 nmol/l) and S/S (24.50 ± 5.4 nmol/l) genotypes compared to subjects with the Asp/Asn (24.38 ± 3.2 nmol/l) and L/L (18.44 ± 4.2 nmol/l) genotypes of the SHBG gene. The genotype frequencies of Asp/Asp were 80.9% in cases and 71.4% in controls ( P = 0.001). The variant Asp/Asn genotype was associated with a more than 50% reduced risk of infertility (OR: 0.46, 95% CI: 0.25–0.80, P = 0.001). Genotype analysis demonstrated six SHBG (TAAAA) n alleles with 6–11 repeats. Long SHBG (TAAAA) n alleles (>8 repeats) were at greater frequency in infertile men than fertile subjects ( P = 0.001), whereas short SHBG (TAAAA) n alleles (≤8 repeats) tended to be more frequent in fertile men than cases ( P = 0.001). Men with the 9/X TAAAA repeat genotype displayed a 2.82-fold increased risk of infertility (95% CI: 1.27–4.79, P = 0.01). There were strong and significant positive correlations between plasma SHBG and sperm count ( r = 0.672, P = 0.01), sperm motility ( r = 0.721, P = 0.01) and sperm morphology ( r = 0.574, P = 0.02). We concluded that the SHBG Asp237Asn and (TAAAA) n polymorphisms may influence SHBG levels and as a result, male infertility. Multicenter large scale studies are warranted to better elucidate the role of SHBG gene polymorphism in male infertility.
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More From: The Journal of Steroid Biochemistry and Molecular Biology
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