A GWAS in Idiopathic/Unexplained Infertile Men Detects a Genomic Region Determining Follicle-Stimulating Hormone Levels

Abstract

Context: Approximately 70% of infertile men are diagnosed with idiopathic (abnormal semen parameters) or unexplained (normozoospermia) infertility, with the common feature of lacking etiologic factors. Follicle-stimulating hormone (FSH) is essential for initiation and maintenance of spermatogenesis. Certain single-nucleotide variations (SNVs; formerly single-nucleotide polymorphisms [SNPs]) (ie, FSHB c.-211G > T, FSHR c.2039A > G) are associated with FSH, testicular volume, and spermatogenesis. It is unknown to what extent other variants are associated with FSH levels and therewith resemble causative factors for infertility.

Objective: We aimed to identify further genetic determinants modulating FSH levels in a cohort of men presenting with idiopathic or unexplained infertility.

Methods: We retrospectively (2010-2018) selected 1900 men with idiopathic/unexplained infertility. In the discovery study (n = 760), a genome-wide association study (GWAS) was performed (Infinium PsychArrays) in association with FSH values (Illumina GenomeStudio, v2.0). Minor allele frequencies (MAFs) were analyzed for the discovery and an independent normozoospermic cohort. In the validation study (n = 1140), TaqMan SNV polymerase chain reaction was conducted for rs11031005 and rs10835638 in association with andrological parameters.

Results: Imputation revealed 9 SNVs in high linkage disequilibrium, with genome-wide significance (P < 4.28e-07) at the FSHB locus 11p.14.1 being associated with FSH. The 9 SNVs accounted for up to a 4.65% variance in FSH level. In the oligozoospermic subgroup, this was increased up to 6.95% and the MAF was enhanced compared to an independent cohort of normozoospermic men. By validation, a significant association for rs11031005/rs10835638 with FSH (P = 4.71e-06/5.55e-07) and FSH/luteinizing hormone ratio (P = 2.08e-12/6.4e-12) was evident.

Conclusions: This GWAS delineates the polymorphic FSHB genomic region as the main determinant of FSH levels in men with unexplained or idiopathic infertility. Given the essential role of FSH, molecular detection of one of the identified SNVs that causes lowered FSH and therewith decreases spermatogenesis could resolve the idiopathic/unexplained origin by this etiologic factor.

Keywords: follicle-stimulating hormone (FSH); genome-wide association study (GWAS); idiopathic male infertility; single-nucleotide variation (SNV).

Figure 1.

Selection of study population. In a retrospective query of our database with an 8-year time range, approximately 7678 patients infertile men were selected. After applying strict selection criteria, a study population of 1900 men with idiopathic or unexplained male infertility were identified. The discovery cohort, to perform the genome-wide association (GWA) analysis, comprised 760 men according to our power analysis. The validation cohort, to perform the TaqMan single-nucleotide variation polymerase chain reaction, comprised 1140 men. The supplemental cohort for minor allele frequency comparison consists of men with normozoospermia.

Figure 2.

Discovery cohort: association of imputed single-nucleotide variations (SNVs) with follicle-stimulating hormone (FSH) levels. Manhattan plot of imputed genome-wide association study data depicts SNVs associated with FSH. X axis: genomic coordinates of tested SNVs on respective chromosomes. Y axis: significance level on a –log₁₀ scale. The suggestive significance threshold is indicated by the gray horizontal line (P = 8.56e-6). The genome-significance threshold is indicated by the black horizontal line (P = 4.28e-7).

Figure 3.

Genomic region of chromosome 11p14.1. Regional association plot of 11p14.1 visualized by LocusZoom. Dots present individual single-nucleotide variations (SNVs). Colors indicate pair-wise r² values between each SNV and rs11031005, describing patterns of linkage disequilibrium around FSHB (for color figure refer online version).

Figure 4.

Association between single-nucleotide variations (SNVs) rs11031005 and rs10835638 and follicle-stimulating hormone (FSH) serum levels using an additive model. Box plot depicting FSH serum levels for genotypes in the validation cohort (n = 1140). Medians are drawn as straight lines. Upper and lower hinges correspond to the 25th and 75th percentiles, respectively. Upper and lower whiskers extend to 1.5 interquartile ranges. Data beyond the end of the whiskers are not shown.