Male pseudohermaphroditism due to 5 alpha-reductase-2 deficiency in an Arab kindred

The Molecular Basis of 5α-Reductase Type 2 Deficiency

The 5α-reductase type 2 enzyme catalyzes the conversion of testosterone into dihydrotestosterone, playing a crucial role in male development. This enzyme is encoded by the SRD5A2 gene, which maps to chromosome 2 (2p23), consists of 5 exons and 4 introns, and encodes a 254 amino acid protein. Disruptions in this gene are the molecular etiology of a subgroup of differences of sex development (DSD) in 46,XY patients. Affected individuals present a large range of external genitalia undervirilization, ranging from almost typically female external genitalia to predominantly typically male external genitalia with minimal undervirilization, including isolated micropenis. This is an updated review of the implication of the SRD5A2 gene in 5α-reductase type 2 enzyme deficiency. For that, we identified 451 cases from 48 countries of this particular 46,XY DSD from the literature with reported variants in the SRD5A2 gene. Herein, we present the SRD5A2 mutational profile, the SRD5A2 polymorphisms, and the functional studies related to SRD5A2 variants to detail the molecular etiology of this condition.

Effects of chromosomal sex and hormonal influences on shaping sex differences in brain and behavior: Lessons from cases of disorders of sex development

Sex differences in brain development and postnatal behavior are determined largely by genetic sex and in utero gonadal hormone secretions. In humans however, determining the weight that each of these factors contributes remains a challenge because social influences should also be considered. Cases of disorders of sex development (DSD) provide unique insight into how mutations in genes responsible for gonadal formation can perturb the subsequent developmental hormonal milieu and elicit changes in normal human brain maturation. Specific forms of DSDs such as complete androgen insensitivity syndrome (CAIS), congenital adrenal hyperplasia (CAH), and 5α-reductase deficiency syndrome have variable effects between males and females, and the developmental outcomes of such conditions are largely dependent on sex chromosome composition. Medical and psychological works focused on CAH, CAIS, and 5α-reductase deficiency have helped form the foundation for understanding the roles of genetic and hormonal factors necessary for guiding human brain development. Here we highlight how the three aforementioned DSDs contribute to brain and behavioral phenotypes that can uniquely affect 46,XY and 46,XX individuals in dramatically different fashions. © 2016 Wiley Periodicals, Inc.

Clinical biochemistry of dihydrotestosterone

Dihydrotestosterone (DHT) is the most potent natural androgen in humans. There has been an increasing interest in this androgen and its role in the development of primary and secondary sexual characteristics as well as its potential roles in diseases ranging from prostate and breast cancer to Alzheimer's disease. Despite the range of pathologies shown to involve DHT there is little evidence for measurement of serum DHT in the management of these diseases. In this review we describe the physiology of DHT production and action, summarize current concepts in the role of DHT in the pathogenesis of various disorders of sexual development, compare current methods for the measurement of DHT and conclude on the clinical utility of DHT measurement. The clinical indications for the measurement of DHT in serum are: investigation of 5α reductase deficiency in infants with ambiguous genitalia and palpable gonads; men with delayed puberty and/or undescended testes; and to confirm the presence of active testicular tissue. Investigation is aided by the use of human chorionic gonadotrophin stimulation. Due to paucity of published data on this procedure, it is important to follow guidelines prescribed by the laboratory performing the analysis to ensure accurate interpretation.

Isoenzyme type 1 of 5alpha-reductase is abundantly transcribed in normal human genital skin fibroblasts and may play an important role in masculinization of 5alpha-reductase type 2 deficient males

OBJECTIVE

5alpha-reductase enzymes reduce testosterone (T) to the most potent androgen dihydrotestosterone (DHT). Two isoenzymes are known to day. While the type 2-enzyme (5RII) is predominantly expressed in male genital tissues and mutations are known to cause a severe virilization disorder in genetic males, the role of the type 1-enzyme (5RI) in normal male androgen physiology is unclear. We investigated whether 5RI is transcribed in normal male genital skin fibroblasts (GSFs) and if the transcription is regulated by age or by androgens themselves.

METHODS

GSF from 14 normally virilized males of different ages, ranging from 8 months to 72 years, obtained at circumcision were cultured. Total RNA was isolated after incubation for 48 h with 100 nM T or without androgens. Each sample was amplified in triplicate by real-time PCR with porphobilinogen desaminase as a housekeeping gene used for semiquantification. Selected cultures were analyzed after incubation with 10 and 100 nM T and 1 and 100 nM DHT for 24, 48 and 120 h.

RESULTS

5RI was transcribed in all investigated samples with a 4.5-fold variability in the mRNA concentration of different individuals. However, neither age-related regulation nor significant influence of T or DHT on the transcription rate was discovered.

CONCLUSION

Since 5RI is abundantly transcribed in GSFs, we hypothesize that this isoenzyme may play important roles in the androgen physiology of normally virilized males and may contribute to masculinization in 5RII-deficient males at the time of puberty.

Choice of gender in 5alpha-reductase deficiency: a moving target

Steroid 5alpha-reductase deficiency is a rare, male-limited autosomal recessive disorder caused by mutation in the SRD5A2 gene resulting in a deficiency of dihydrotestosterone (DHT) during fetal development. Here we report an affected 46,XY adolescent who was born with incompletely virilized genitalia and was raised in the female gender. At 12 years of age, the patient requested feminizing genital surgery. Surgery was withheld and psychiatric counseling was instituted. At 14 years of age, the patient's gender identity and role appeared to be in transition from a female to an increasingly male gender. This case demonstrates that in patients with disorders such as 5alpha-reductase deficiency, in which significant prenatal androgen exposures are combined with postnatal virilization, adult gender identity and gender role may be a dynamic process that is not complete until well after adolescence.