Androgen receptor gene CAG and GGC repeat lengths in cryptorchidism

Cryptorchidism is the most common congenital birth defect in male children, and accumulating evidence suggests that genetic abnormalities may be associated with it. The androgen receptor has two polymorphic sites in exon 1, with different numbers of CAG and GGC repeats, resulting in variable lengths of polyglutamine and polyglycine stretches. Longer CAG repeats result in a reduced androgen receptor transcriptional activity, but the role of the GGC triplets is less clear. In this study we analysed CAG and GGC repeat lengths in men with a history of cryptorchidism, associated or not with impairment of sperm production, in comparison with normal fertile subjects.

We analysed CAG and GGC repeat lengths in a group of 105 ex-cryptorchid men in comparison with 115 fertile non-cryptorchid men.

No difference was found between patients and controls in the mean and median values, and in distribution of CAG and GGC, when considered separately. However, the analysis of the joint distribution of CAG and GGC showed that some combinations are significantly more frequent in men with bilateral cryptorchidism (who frequently presented severe testiculopathies), in a manner similar to that found in idiopathic infertile subjects.

Although further studies are needed to elucidate the possible role of specific CAG/GGC combinations as a causative factor, these data suggest a possible association between androgen receptor gene polymorphisms and cryptorchidism.