Shorter androgen receptor CAG repeat lengths associated with cryptorchidism risk among Hispanic white boys.

Abstract

Cryptorchidism is the most frequent congenital malformation among males, the major established risk factor for testicular germ cell tumors, and a presumed infertility risk factor. Androgens are essential for testicular descent, and functional genetic polymorphisms in the androgen receptor gene (AR) are postulated to influence cryptorchidism risk. The aim of the study was to investigate whether the CAG repeat length polymorphism in exon 1 of the AR is associated with cryptorchidism risk. We conducted a family-based genotype-risk association study employing the transmission disequilibrium test for genotypic variants transmitted on the X-chromosome at a university-affiliated regional children's hospital. We studied 127 Hispanic boys with persistent cryptorchidism and comorbidities described in detail and their biological mothers. Genotypes defined by number of CAG repeats were measured for each member of participating son-mother pairs. Associations between CAG tract length genotype and cryptorchidism risk were estimated using matched-pairs logistic regression. Cryptorchidism risk was significantly associated with shorter CAG repeats [CAG≤19 vs. CAG≥20, odds ratio (OR)=0.44; 95% confidence interval (CI), 0.23-0.88]. This association was restricted to cryptorchidism with accompanying comorbidities, which was primarily hernia [CAG≤19 vs. CAG≥20, OR=0.35 (95% CI, 0.16-0.78)], and was strongest for bilateral cryptorchidism [CAG≤19 vs. CAG≥20, OR=0.09 (95% CI, 0.010-0.78)]. Androgen receptor genotypes encoding moderate functional variation may influence cryptorchidism risk, particularly among boys with bilateral nondescent or congenital hernia, and may explain in part the elevated risk of testicular seminoma experienced by ex-cryptorchid boys. Mechanistic research is warranted to examine both classical and nonclassical mechanisms through which androgens may influence risk of cryptorchidism and related conditions.