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) results in defective virilization in karyotypic males. Different mutations in the 5 alpha-reductase type 2 gene cause the phenotypic variability of the disease. In this report we describe four prepubertal patients with a predominantly male phenotype who carry homozygous point mutations in the 5 alpha-reductase type 2 gene and address the specific T and DHT response to different human chorionic gonadotropin (hCG) stimulation tests. For molecular genetic analysis, DNA from peripheral blood leucocytes was studied. The coding region of the 5 alpha-reductase type 2 gene was characterized by exon-specific polymerase chain reaction amplification, non-radioactive single strand polymorphism analysis, and direct sequencing. Three different homozygous point mutations (Gly196-Ser, Arg227-Gln and Ala228-Thr) were identified in the patients. In contrast, in the DNA from 100 phenotypically normal males only two heterozygous abnormalities (Ile196-Ile, delta Met157) were characterized. For hormonal studies, T and DHT were measured in serum before and after hCG stimulation employing different protocols. HCG stimulation with 5000 IU/m2 once and prolonged stimulation with seven injections of 1500 IU hCG per single dose every other day were used.


CONCLUSIONS
While abnormal T/DHT ratios were identified with both hCG protocols in the patients, prolonged stimulation lead to higher T values and to higher T/DHT rations, and hence to a better discrimination of pathologic results.
Hiort
O
O
Department of Paediatrics, Medical University of Lübeck, Germany.
Willenbring
H
H
Albers
N
N
Hecker
W
W
Engert
J
J
Dibbelt
L
L
Sinnecker
G H
GH
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000172:deficiency* / Q000235:genetics; D000595:Amino Acid Sequence / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D006063:Chorionic Gonadotropin; D003241:Consanguinity; D013196:Dihydrotestosterone / Q000097:blood*; D012734:Disorders of Sex Development / Q000201:enzymology / Q000235:genetics*; D005091:Exons / Q000235:genetics; D006720:Homozygote; D006801:Humans; D007021:Hypospadias / Q000201:enzymology / Q000235:genetics; D007223:Infant; D007231:Infant, Newborn; D007527:Isoenzymes / Q000172:deficiency / Q000235:genetics; D007621:Karyotyping; D008297:Male; D008969:Molecular Sequence Data; D010641:Phenotype; D017354:Point Mutation / Q000235:genetics*; D012016:Reference Values; D013739:Testosterone / Q000097:blood*
D006063:Chorionic Gonadotropin; D007527:Isoenzymes; D013196:Dihydrotestosterone; D013739:Testosterone; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase