Phenotypic classification of male pseudohermaphroditism due to steroid 5α-reductase 2 deficiency

Abstract

Conversion of testosterone (T) to dihydrotestosterone (DHT) in genital tissue is catalysed by the enzyme 5α‐reductase 2, which is encoded by the SRD5A2 gene. The potent androgen DHT is required for full masculinization of the external genitalia. Mutations of the SRD5A2 gene inhibit enzyme activity, diminish DHT formation, and hence cause masculinization defects of varying degree. The classical syndrome, formerly described as pseudovaginal perineoscrotal hypospadias, is characterized by a predominantly female phenotype at birth and significant virtilization without gynecomastia at puberty. We investigated nine patients with steroid 5α‐reductase 2 deficiency (SRD). Phenotypes, which were classified according to the severity of the masculinization defect, varied between completely female (SRD type 5), predominantly female (SRD type 4), ambiguous (SRD type 3), predominantly male with micropenis and hypospadias (SRD type 2), and completely male without overt signs of undermasculinization (SRD type 1). T/DHT‐ratios were highly increased (>50) in the classical syndrome (SRD type 5), but variable in the less severe affected patients (SRD types 1–4) (14–35). Mutations in the SRD5A2 gene had been characterized using PCR‐SSCP analysis and direct DNA sequencing. A small deletion was encountered in two patients, while all other patients had single base mutations which result in amino acid substitutions. We conclude that phenotypes may vary widely in patients with SRD5A2 gene mutations spanning the whole range from completely female to normal male without distinctive clinical signs of the disease. Hence, steroid 5α‐reductase deficiency should be considered not only in sex reversed patients with female or ambiguous phenotypes, but also in those with mild symptoms of undermasculinization as encountered in patients with hypospadias and/or micropenis. A classification based on the severity of the masculinization defect may be used for correlation of phenotypes with enzyme activities and genotypes, and for comparisons of phenotypes between different patients as the basis for clinical decisions to be made in patients with pseudohermaphroditism due to steroid 5α‐reductase 2 deficiency. © 1996 Wiley‐Liss, Inc.

Pesticides Exposure and Risk of Hypospadias

“…Excretion of 5 /5 steroid metabolites, and enzyme activity in cultured fibroblasts from genital skin have also been examined (Peterson R et al, 1985). These parameters are highly variable and difficult to interpret in prepubertal children, and T/DHT ratios are increased only in the most severely affected patients Sinnecker GH et al, 1996). More recently, direct evaluation of allelic variants in the SRD5A2 gene has been used to diagnose SRD5A2 deficiency .…”

The 5α-Reductase Type II A49T and V89L High-Activity Allelic Variants are More Common in Men with Prostate Cancer Compared with the General Population

“…The A49T mutation seemed to have the highest impact on the enzymatic activity 5 increasing the conversion of testosterone to DHT 6-fold in vitro 6 , whereas the V89L L-allele was associated with approximately 30% lower SRD5A2 activity 7 and lower prevalence in African Americans 8 . The R227Q mutation was first reported in boys with hypospadias and micropenis 9 . Recently a study from China, a low risk country for CaP, taking all three variants into consideration, could not confirm a significant association of these SRD5A2 polymorphisms with CaP risk 10 .…”

Systematization of ambiguous genitalia

“…This raises the intriguing possibility that basal levels of androgen in females can lead to masculinization of the genital tubercle, and estrogen is required to counter the influence of androgen. 5,6,26,27 Mutations in the androgen receptor (as in the testicular feminization or Tfm mutation), by contrast, cause feminization of the external genitalia, such that Tfm mutant male genitalia are indistinguishable from female genitalia. 26 Mutations in the gene that encodes 5a-reductase 2, which converts testosterone to dihydrotestosterone, also disrupt masculinization of the genital tubercle and cause defects ranging from hypospadias and micropenis to complete feminization of the external genitalia.…”