Steroid 5α-reductase 1 polymorphisms and testosterone/ dihydrotestosterone ratio in male patients with hypospadias

Background/Aim: Defects in the steroid 5α-reductase type 2 (SRD5A2) activity cause decreased formation of dihydrotestosterone (DHT) from testosterone (T), resulting in defective masculinization of external genitalia; the T/DHT ratio is increased. We investigated 10 patients with elevated T/DHT ratios in whom mutations in the SRD5A2 and AR genes had been excluded to find out whether structural alterations of the SRD5A1 gene could contribute to their genital malformations. Methods: Single-strand conformation polymorphism analysis and direct sequencing were used to detect variations in the SRD5A1 gene of the patients and of 49 adult fertile men who served as controls. Results: The sequence analysis of exon 3 of the SRD5A1 gene indicated an adenine-toguanine change (ACA vs. ACG), both triplets encoding the amino acid residue threonine. The ACG sequence was detected in 57% of all subjects and was equally distributed in patients and controls. The T/DHT ratio was significantly higher in controls with the ACG variant as compared with those having the ACA variant. However, no particular sequence aberration was found in the SRD5A1 genes of either group. Conclusion: Mutant SRD5A1 isoenzyme does not seem to play a crucial role in the development of hypospadias.