MOLECULAR-GENETIC ANALYSIS AND HUMAN CHORIONIC-GONADOTROPIN STIMULATION TESTS IN THE DIAGNOSIS OF PREPUBERTAL PATIENTS WITH PARTIAL 5-ALPHA-REDUCTASE DEFICIENCY

Reduced conversion of testosterone (T) to dihydrotestosterone (DHT) re sults in defective virilization in karyotypic males. Different mutatio ns in the 5 alpha-reductase type 2 gene cause the phenotypic variabili ty of the disease. In this report we describe four prepubertal patient s with a predominantly male phenotype who carry homozygous point mutat ions in the 5 alpha-reductase type 2 gene and address the specific T a nd DHT response to different human chorionic gonadotropin (hCG) stimul ation tests. For molecular genetic analysis, DNA from peripheral blood leucocytes was studied. The coding region of the 5 alpha-reductase ty pe 2 gene was characterized by exon-specific polymerase chain reaction amplification, non-radioactive single strand polymorphism analysis, a nd direct sequencing. Three different homozygous point mutations (Gly( 196)-Ser, Arg(227)-Gln and Ala(228)-Thr) were identified in the patien ts. In contrast, in the DNA from 100 phenotypically normal males only two heterozygous abnormalities (Ile(196)-Ile, Delta Met(157)) were cha racterized. For hormonal studies, T and DHT were measured in serum bef ore and after hCG stimulation employing different protocols, HCG stimu lation with 5000 IU/m(2) once and prolonged stimulation with seven inj ections of 1500 IU hCG per single dose every other day were used. Conc lusion While abnormal T/DHT ratios were identified with both hCG proto cols in the patients, prolonged stimulation lead to higher T values an d to higher T/DHT ratios, and hence to a better discrimination of path ologic results.