Context: Hypospadias is a common inborn error of the male genitalia of complex, and still elusive, etiology. The presence of active estrogen receptors (ESR) in the developing male urethra, predominantly the ESR2, has suggested a role of estrogens in the otherwise androgen dependent male genital differentiation. Moreover imbalances between these two steroid hormones have been suggested to disturb the external genital development. This has been supported by the association between longer (CA)n variants in the ESR2 gene with lower androgen levels as well as with hypospadias.

Objectives: The aim of this study was to analyze the effect of ESR2 gene variants on the risk to hypospadias.

Design, participants and methods: Four haplotype-tagging SNPs (rs2987983, rs1887994, rs1256040, and rs1256062), the (CA)n polymorphism and two additional promoter SNPs (rs10483774 and rs1271572), mapping to a transcription factor binding region, were typed and analyzed in a Swedish cohort of 354 boys with non-syndromic hypospadias and 380 healthy controls.

Results: Association was identified with longer variants of the (CA)n polymorphism in intron 6 and with a region of intense transcription factor binding, in the putative promoter region, mapping to rs2987983 and rs10483774. The two regions are in low linkage disequilibrium, meaning that they are not necessarily inherited together as a haplotype; logistic regression analysis, however, indicates that these two risk effects are not independent.

Conclusions: The present study evidences two non independent risk factors for hypospadias in the ESR2 gene. We discuss possible mechanisms by which these variants may affect male urethral development.