Background: Steroid 5α-reductase catalyzes the conversion of testosterone into the more active androgen, dihydrotestosterone (DHT). In 46, XY patients with recessive mutations in steroid 5α-reductase type 2 enzyme (SRD5A2) gene, the degree of ambiguity ranges from isolated hypospadias to severe undermasculinization. SRD5A2 gene is located on chromosome 2 (p23 region) and is comprised of five exons and four introns.
Objective and hypotheses: Multiple mutations distributed throughout the coding region of the SRD5A2 gene have been identified in patients with steroid 5α-reductase type 2 enzyme deficiency. We studied the SRD5A2 gene mutation in 23 patients with undescended testis.
Method: Patients were evaluated by HCG stimulated T:DHT ratio (>10). Peripheral blood samples were collected from the subjects and genomic DNA was isolated. SRD5A2 gene was amplified by polymerase chain reaction using different sets of primers and reaction conditions specific for the 5 exon of SRD5A2 gene. DNA sequencing was carried out using a ABI-Prism automated DNA sequencer. DNA sequencing of the SRD5A2 gene reautomated DNA sequencer.
Results: Exons 25 of the SRD5A2 gene were normal in 23 cases. DNA sequencing of the SRD5A2 gene revealed that the rare allele (leucine) of the V89L polymorphism in exon 1 was over represented in seven patients.
Conclusion: We detected three boys being homozygous for the leucine allele, four were heterozygous. This corresponds to an allele frequency of 0.78 for the valine allele and 0.22 for the leucine allele.
20 - 22 Sep 2014
European Society for Paediatric Endocrinology