5α-Reductase-2 Deficiency: Clinical Findings, Endocrine Pitfalls, and Genetic Features in a Large Italian Cohort

[Value of the human chorionic gonadotropin stimulation test in the diagnosis of disorder of sexual development in children]

OBJECTIVES

To investigate the value of the human chorionic gonadotropin (hCG) stimulation test in the diagnosis of disorder of sexual development (DSD) in children.

METHODS

A retrospective analysis was conducted on 132 children with DSD. According to the karyotype, they were divided into three groups: 46,XX group (n=10), 46,XY group (n=87), and sex chromosome abnormality group (n=35). The above groups were compared in terms of sex hormone levels before and after hCG stimulation test, and the morphological manifestation of the impact of testicular tissue on the results of the hCG stimulation test was analyzed.

RESULTS

There was no significant difference in the multiple increase of testosterone after stimulation among the three groups (P>0.05). In the 46,XY group, the children with 5α-reductase type 2 deficiency had a testosterone-to-dihydrotestosterone ratio higher than that of the 46,XY DSD children with other causes. Morphological analysis showed that DSD children with testicular tissue demonstrated a significantly higher multiple increase in testosterone after stimulation compared to children without testicular tissue (P<0.05).

CONCLUSIONS

The hCG stimulation test has an important value in assessing the presence and function of testicular interstitial cells in children with different types of DSD, and it is recommended to perform the hCG stimulation test for DSD children with unclear gonadal type.

Genetic control of typical and atypical sex development

Sex development relies on the sex-specific action of gene networks to differentiate the bipotential gonads of the growing fetus into testis or ovaries, followed by the differentiation of internal and external genitalia depending on the presence or absence of hormones. Differences in sex development (DSD) arise from congenital alterations during any of these processes, and are classified depending on sex chromosomal constitution as sex chromosome DSD, 46,XY DSD or 46,XX DSD. Understanding the genetics and embryology of typical and atypical sex development is essential for diagnosing, treating and managing DSD. Advances have been made in understanding the genetic causes of DSD over the past 10 years, especially for 46,XY DSD. Additional information is required to better understand ovarian and female development and to identify further genetic causes of 46,XX DSD, besides congenital adrenal hyperplasia. Ongoing research is focused on the discovery of further genes related to typical and atypical sex development and, therefore, on improving diagnosis of DSD.

The Genotype-Phenotype Correlation in Human 5α-Reductase Type 2 Deficiency: Classified and Analyzed from a SRD5A2 Structural Perspective

The phenotype of the 5α-reductase type 2 deficiency (5αRD2) by the SRD5A2 gene mutation varies, and although there have been many attempts, the genotype-phenotype correlation still has not yet been adequately evaluated. Recently, the crystal structure of the 5α-reductase type 2 isozyme (SRD5A2) has been determined. Therefore, the present study retrospectively evaluated the genotype-phenotype correlation from a structural perspective in 19 Korean patients with 5αRD2. Additionally, variants were classified according to structural categories, and phenotypic severity was compared with previously published data. The p.R227Q variant, which belongs to the NADPH-binding residue mutation category, exhibited a more masculine phenotype (higher external masculinization score) than other variants. Furthermore, compound heterozygous mutations with p.R227Q mitigated phenotypic severity. Similarly, other mutations in this category showed mild to moderate phenotypes. Conversely, the variants categorized as structure-destabilizing and small to bulky residue mutations showed moderate to severe phenotypes, and those categorized as catalytic site and helix-breaking mutations exhibited severe phenotypes. Therefore, the SRD5A2 structural approach suggested that a genotype-phenotype correlation does exist in 5αRD2. Furthermore, the categorization of SRD5A2 gene variants according to the SRD5A2 structure facilitates the prediction of the severity of 5αRD2 and the management and genetic counseling of patients affected by it.

Mutational analysis of compound heterozygous mutation p.Q6X/p.H232R in SRD5A2 causing 46,XY disorder of sex development

Background

Over 100 mutations in the SRD5A2 gene have been identified in subjects with 46,XY disorder of sex development (DSD). Exploration of SRD5A2 mutations and elucidation of the molecular mechanisms behind their effects should reveal the functions of the domains of the 5α-reductase 2 enzyme and identify the cause of 46,XY DSD. Previously, we reported a novel compound heterozygous p.Q6X/p.H232R mutation of the SRD5A2 gene in a case with 46,XY DSD. Whether the compound heterozygous p.Q6X/p.H232R mutation in this gene causes 46,XY DSD requires further exploration.

Methods

The two 46,XY DSD cases were identified and sequenced. In order to identify the source of the compound heterozygous p.Q6X/p.H232R mutation, the parents, maternal grandparents, and maternal uncle were sequenced. Since p.Q6X mutation is a nonsense mutation, p.H232R mutation was transfected into HEK293 cells and dihydrotestosterone (DHT) production were analyzed by liquid chromatography–mass spectrometry (LC–MS) for 5α-reductase 2 enzyme activities test. Apparent michaelis constant (Km) were measured of p.H232R mutation to analyze the binding ability change of 5α-reductase 2 enzyme with testosterone (T) or NADPH.

Results

The sequence results showed that the two 46,XY DSD cases were the compound heterozygous p.Q6X/p.H232R mutation, of which the heterozygous p.Q6X mutation originating from maternal family and heterozygous p.H232R mutation originating from the paternal family. The function analysis confirmed that p.H232R variant decreased the DHT production by LC–MS test. The Km analysis demonstrated that p.H232R mutation affected the binding of SRD5A2 with T or NADPH.

Conclusions

Our findings confirmed that the compound heterozygous p.Q6X/p.H232R mutation in the SRD5A2 gene is the cause of 46,XY DSD. p.H232R mutation reduced DHT production while attenuating the catalytic efficiency of the 5α-reductase 2 enzyme.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13052-022-01243-4.

Individualized care for patients with intersex (disorders/differences of sex development): Part 3

The focus of this article is to review the complex determinants of gender assignment in a child with a disorder of sex development using four different clinical cases. While the care of patients with DSD may be shared across several specialties and opinions regarding their management may vary, this may be further complicated by psychosocial, cultural and economic factors. In this regard, access to behavioral health specialists with experience and specialization in the treatment of patients with DSD should be a foundational component of the standard of care and can greatly assist in the complex decision-making regarding gender assignment. We recommend an individualized approach by a multidisciplinary team utilizing a range of evolving strategies, including outcome data (or lack thereof) to support families during the decision-making process.

5α-Reductase-2 deficiency: is gender assignment recommended in infancy? Two case-reports and review of the literature

PURPOSE

Gender assignment represents one of the most controversial aspects of the clinical management of individuals with Differences of Sex Development, including 5α-Reductase-2 deficiency (SRD5A2). Given the predominant female appearance of external genitalia in individuals with SRD5A2 deficiency, most of them were assigned to the female sex at birth. However, in the last years the high rate of gender role shift from female to male led to recommend a male gender assignment.

METHODS

We here describe two cases of subjects with SRD5A2 deficiency assigned as females at birth, reporting their clinical histories and psychometric evaluations (Body Uneasiness Test, Utrecht Gender Dysphoria Scale, Bem Sex-Role Inventory, Female Sexual Distress Scale Revised, visual analogue scale for gender identity and sexual orientation) performed at the time of referral at the Florence Gender Clinic.

RESULTS

Both patients underwent early surgical interventions without being included in the decision-making process. They had to conform to a binary feminine gender role because of social/familiar pressure, with a significant impact on their psychological well-being. Psychometric evaluations identified clinically significant body uneasiness and gender incongruence in both subjects. No sexually related distress and undifferentiated gender role resulted in the first subject and sexually related distress and androgynous gender role resulted in the second subject.

CONCLUSIONS

The reported cases suggest the possibility to consider a new approach for gender assignment in these individuals, involving them directly in the decision-making process and allowing them to explore their gender identity, also with the help of GnRH analogues to delay pubertal modifications.

Clinical characteristics and genotype-phenotype correlations of 130 Chinese children in a high-homogeneity single-center cohort with 5α-reductase 2 deficiency

Background

Patients with steroid 5α‐reductase 2 deficiency (5α‐RD) caused by SRD5A2 (OMIM #607306) variants present variable genotypes and phenotypes. The genotype‐phenotype correlations remain unclear.

Methods

We investigated genotype‐phenotype correlations of SRD5A2 variants in a large Chinese single‐center cohort. Phenotypes were categorized using the external masculinization score (EMS), urethral meatus and gonad position, and penile length‐standard deviation score.

Results

Of the 130 included patients, 113 had hypospadias, and 17 had a normal urethral meatus position. Testosterone/dihydrotestosterone (T/DHT) values were not significantly associated with phenotypic severity (p = 0.539–0.989). Of the 31 SRD5A2 variants, including 10 novel variants, p.R227Q was the most prevalent (39.62%), followed by p.Q6* (16.92%), p.R246Q (13.46%), and p.G203S (10.38%). Compared to biallelic missense mutations, biallelic nonsense mutations were associated with a lower EMS and urethral meatus score (p = 0.009 and p = 0.024, respectively). Patients homozygous for p.R227Q exhibited mild and variable phenotypes, while those homozygous for p.Q6*, p.R246Q, or p.G203S showed consistently severe phenotypes. The phenotypes were variable and milder in patients with compound heterozygosity for p.R227Q and these mutations.

Conclusion

T/DHT does not predict phenotype severity. The most prevalent SRD5A2 variant in Han Chinese is p.R227Q, which is associated with milder phenotypes and greater phenotypic variability. SRD5A2 variants may significantly influence phenotypic variation.

Mutational analysis of SRD5A2: From gene to functional kinetics in individuals with steroid 5α-reductase 2 deficiency

Human steroid 5α-reductase 2 (SRD5A2) plays a determinative role in the masculinization of external genitalia. To date, approximately 114 different mutations of the SRD5A2 gene have been reported; however, little information is available about their impact on catalytic function or their three-dimensional (3D) structures. We determined the effect of point mutations on the testosterone-depend kinetic constants (K_m,app and V_max,app) and structural characteristics of SRD5A2 from Mexican patients with 46,XY-steroid 5α-reductase 2 deficiency. PCR-SSCP assays identified ten distinct gene variants and sequencing analysis identified missense mutations [p.V3I, p.S14R, p.A52T, p.F118L, p.R145W, p.R171S, p.L226P, p.F229S, p.S245Y, and p.A248V]. Mutations were re-created by site-directed mutagenesis and expressed in HEK293 cells. Functional studies demonstrated that 8 variants led to partial (K_m,app = 0.16-2.6 μM; V_max,app = 224-2640 pmol/mg P/min) or complete losses of activity compared to the wild-type enzyme (K_m,app = 0.7 μM; V_max,app = 4044 pmol/mg P/min). All the mutations were assessed using multiple software tools and the results predicted that all of the mutations were associated with disease or damage. Mapping mutations on the model of a 3D structure of SRD5A2 demonstrated alterations in contact sites with their proximal amino acids. Our data show that mutations affect the catalytic efficiency (V_max/K_m) or result in residual enzymatic activity, which could be due to erroneous interactions between amino acid residues, the substrate testosterone, or NADPH.

Serum Anti-Müllerian Hormone in the Prediction of Response to hCG Stimulation in Children With DSD

INTRODUCTION

The relationship between serum anti-Müllerian hormone (AMH) and the testosterone response to human chorionic gonadotropin (hCG) stimulation test is unclear.

METHODS

Children who had hCG stimulation tests in one tertiary centre from 2001 to 2018 were included (n = 138). Serum testosterone was measured before (day 1 [D1]) and after 3 days (D4) of hCG stimulation. Sixty-one of these children also had prolonged hCG stimulation for 2 more weeks and serum testosterone measured after 21 days (D22). All children had a serum AMH measured on D1.

RESULTS

Of the 138 children, D4 testosterone was normal in 104 (75%). AMH was low in 24/138 (17%) children, and 16 (67%) of these had a low D4 testosterone. Median AMH in those who had a normal vs low D4 testosterone was 850 pmol/L (24, 2280) and 54 pmol/L (0.4, 1664), respectively (P < 0.0001). An AMH > 5th centile was associated with a low D4 testosterone in 18/118 (13%; P < 0.0001). Of the 61 children who had prolonged hCG stimulation, D22 testosterone was normal in 39 (64%). AMH was low in 10/61(16%) children and 9 (90%) of these had a low D22 testosterone. Median AMH in children who responded and did not respond by D22 was 639 pmol/L (107, 2280) and 261 pmol/L (15, 1034) (P < 0.0001).

CONCLUSION

A normal AMH may provide valuable information on overall testicular function. However, a low AMH does not necessarily predict a suboptimal testosterone response to hCG stimulation.

Integrative and Analytical Review of the 5-Alpha-Reductase Type 2 Deficiency Worldwide

Introduction

The conversion of testosterone into dihydrotestosterone is catalyzed by the 5α-reductase type 2 enzyme which plays a crucial role in the external genitalia virilization. It is encoded by the SRD5A2 gene. Allelic variants in this gene cause a 46,XY DSD with no genotype-phenotype relationship. It was firstly reported in the early 70s from isolated clusters. Since then, several cases have been reported. Putting together, it will expand the knowledge on the molecular bases of androgen milieu.

Methods

We searched for SRD5A2 allelic variants (AV) in the literature (PubMed, Embase, MEDLINE) and websites (ensembl, HGMD, ClinVar). Only cases with AV in both alleles, either in homozygous or compound heterozygous were included. The included cases were analyzed according to ethnicity, exon, domain, aminoacid (aa) conservation, age at diagnosis, sex assignment, gender reassignment, external genitalia virilization and functional studies. External genitalia virilization was scored using Sinnecker scale. Conservation analysis was carried out using the CONSURF platform. For categorical variables, we used X2 test and Cramer's V. Continuous variables were analyzed by t test or ANOVA. Concordance was estimated by Kappa.

Results

We identified 434 cases of 5ARD2 deficiencies from 44 countries. Most came from Turkey (23%), China (17%), Italy (9%), and Brazil (7%). Sixty-nine percent were assigned as female. There were 70% of homozygous allelic variants and 30% compound heterozygous. Most were missense variants (76%). However, small indels (11%), splicing (5%) and large deletions (4%) were all reported. They were distributed along with all exons with exon 1 (33%) and exon 4 (25%) predominance. Allelic variants in the exon 4 (NADPH-binding domain) resulted in lower virilization (p<0.0001). The codons 55, 65, 196, 235 and 246 are hotspots making up 25% of all allelic variants. Most of them (76%) were located at conserved aa. However, allelic variants at non-conserved aa were more frequently indels (28% vs 6%; p<0.01). The overall rate of gender change from female to male ranged from 16% to 70%. The lowest rate of gender change from female to male occurred in Turkey and the highest in Brazil. External genitalia virilization was similar between those who changed and those who kept their assigned gender. The gender change rate was significantly different across the countries (V=0.44; p<0.001) even with similar virilization scores.

Conclusion

5ARD2 deficiency has a worldwide distribution. Allelic variants at the NADPH-ligand region cause lower virilization. Genitalia virilization influenced sex assignment but not gender change which was influenced by cultural aspects across the countries. Molecular diagnosis influenced on sex assignment, favoring male sex assignment in newborns with 5α-reductase type 2 deficiency.

In silico and functional studies reveal novel loss-of-function variants of SRD5A2, but no variants explaining excess 5α-reductase activity

Androgens are steroid hormones essential for human male and female development. Steroid reductases 5α (SRD5As) are key enzymes in androgen biosynthesis. Mutations in the human SRD5A2 are known to cause loss-of-function and severe 46,XY undervirilization. Gain-of-function variants have been suggested in androgen excess syndromes, but have not been found so far. Therefore we searched for gain-of-function mutations in the human SRD5A2 gene which might explain hyperandrogenic disorders such as the polycystic ovary syndrome, premature adrenarche and prostate cancer. We screened databases for candidate variants and characterised them in silico with the help of a novel SRD5A2 model. We selected 9 coding SNPs (A49T, R50A, P106L, P106A, N122A, L167S, R168C, P173S, R227Q) that have not been described in manifesting individuals, and assessed their enzyme kinetic properties in HEK293 cells. SRD5A2 activity was assessed by conversion of testosterone (T), progesterone (Prog) and androstenedione (Δ4A) to their 5α-reduced metabolites. Variants R50A and P173S showed partial activity with substrates T (34% and 28%) and Δ4A (37% and 22%). With substrate Prog variants P106L, P106A, L167S and R168C in addition showed partial activity (15% to 64%). Functional testing of all other variants showed loss-of-function. As predicted in our in silico analysis, all coding SNPs affected enzyme activity, however none of them showed gain-of-function. Thus excess 5α-reductase activity might be rather regulated at the (post)-transcriptional and/or post-translational level. However through this work seven new coding SNPs were characterised which might be of clinical relevance. It is possible that individuals carrying these SNPs show a minor phenotype that is not yet identified.

Genotype-phenotype correlation, gonadal malignancy risk, gender preference, and testosterone/dihydrotestosterone ratio in steroid 5-alpha-reductase type 2 deficiency: a multicenter study from Turkey

BACKGROUND

Studies regarding genetic and clinical characteristics, gender preference, and gonadal malignancy rates for steroid 5-alpha-reductase type 2 deficiency (5α-RD2) are limited and they were conducted on small number of patients.

OBJECTIVE

To present genotype-phenotype correlation, gonadal malignancy risk, gender preference, and diagnostic sensitivity of serum testosterone/dihydrotestosterone (T/DHT) ratio in patients with 5α-RD2.

MATERIALS AND METHODS

Patients with variations in the SRD5A2 gene were included in the study. Demographic characteristics, phenotype, gender assignment, hormonal tests, molecular genetic data, and presence of gonadal malignancy were evaluated.

RESULTS

A total of 85 patients were included in the study. Abnormality of the external genitalia was the most dominant phenotype (92.9%). Gender assignment was male in 58.8% and female in 29.4% of the patients, while it was uncertain for 11.8%. Fourteen patients underwent bilateral gonadectomy, and no gonadal malignancy was detected. The most frequent pathogenic variants were p.Ala65Pro (30.6%), p.Leu55Gln (16.5%), and p.Gly196Ser (15.3%). The p.Ala65Pro and p.Leu55Gln showed more undervirilization than the p.Gly196Ser. The diagnostic sensitivity of stimulated T/DHT ratio was higher than baseline serum T/DHT ratio, even in pubertal patients. The cut-off values yielding the best sensitivity for stimulated T/DHT ratio were ≥ 8.5 for minipuberty, ≥ 10 for prepuberty, and ≥ 17 for puberty.

CONCLUSION

There is no significant genotype-phenotype correlation in 5α-RD2. Gonadal malignancy risk seems to be low. If genetic analysis is not available at the time of diagnosis, stimulated T/DHT ratio can be useful, especially if different cut-off values are utilized in accordance with the pubertal status.

Translating genomics to the clinical diagnosis of disorders/differences of sex development

The medical and psychosocial challenges faced by patients living with Disorders/Differences of Sex Development (DSD) and their families can be alleviated by a rapid and accurate diagnostic process. Clinical diagnosis of DSD is limited by a lack of standardization of anatomical and endocrine phenotyping and genetic testing, as well as poor genotype/phenotype correlation. Historically, DSD genes have been identified through positional cloning of disease-associated variants segregating in families and validation of candidates in animal and in vitro modeling of variant pathogenicity. Owing to the complexity of conditions grouped under DSD, genome-wide scanning methods are better suited for identifying disease causing gene variant(s) and providing a clinical diagnosis. Here, we review a number of established genomic tools (karyotyping, chromosomal microarrays and exome sequencing) used in clinic for DSD diagnosis, as well as emerging genomic technologies such as whole-genome (short-read) sequencing, long-read sequencing, and optical mapping used for novel DSD gene discovery. These, together with gene expression and epigenetic studies can potentiate the clinical diagnosis of DSD diagnostic rates and enhance the outcomes for patients and families.

Growth Pattern in Chinese Children With 5α-Reductase Type 2 Deficiency: A Retrospective Multicenter Study

BACKGROUND

5α-reductase type 2 deficiency (5αRD) is an autosomal recessive hereditary disease of the group of 46, XY disorders of sex development (DSD).

OBJECTIVE

To study the growth pattern in Chinese pediatric patients with 5αRD.

SUBJECTS

Data were obtained from 141 patients with 5αRD (age: 0-16 years old) who visited eight pediatric endocrine centers from January 2010 to December 2017.

METHODS

In this retrospective cohort study, height, weight, and other relevant data were collected from the multicenter hospital registration database. Baseline luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T), and dihydrotestosterone (DHT) after human chorionic gonadotropin (HCG) stimulation test were measured by enzyme enhanced chemiluminescence assay. Bone age (BA) was assessed using the Greulich-Pyle (G-P) atlas. Growth curve was constructed based on λ-median-coefficient of variation method (LMS).

RESULTS

The height standard deviation scores (HtSDS) and weight standard deviation scores (WtSDS) in 5αRD children were in the normal range as compared to normal boys. Significantly higher HtSDS was observed in patients with 5αRD who were <1 year old (t = 3.658, 2.103, P = 0.002, 0.048, respectively), and higher WtSDS in those <6 months old (t = 2.756, P = 0.012). Then HtSDS and WtSDS decreased gradually and fluctuated near the median of the same age until 13 years. WtSDS in 5αRD children from northern China were significantly higher than those from the south (Z = -2.670, P = 0.008). The variation tendency of HtSDS in Chinese 5αRDs was consistent with the trend of stimulating T. HtSDS and stimulating T in the external masculinization score (EMS) <7 group were slightly higher than those in EMS ≥ 7 group without significant difference. Additionally, the ratio of BA over chronological age (BA/CA) was significantly <1 in children with 5αRD.

CONCLUSION

Children with 5αRD had a special growth pattern that was affected by high levels of T, while DHT played a very small role in it. Their growth accelerated at age <1 year, followed by slowing growth and fluctuating height near normal median boys' height. The BA was delayed in 5αRD children. Androgen treatment, which may be considered anyway for male 5αRD patients with a micropenis, may also be beneficial for growth.

Association of SRD5A2 gene mutations with risk of hypospadias in the Iranian population

BACKGROUND

Hypospadias is one of the most common forms of congenital malformation of the male external genitalia worldwide. The ratio in the Iranian population is one in 250 live male births. The conversion of testosterone to dihydrotestosterone (DHT) in the presence of steroid 5α-reductase 2, which is encoded by SRD5A2 gene, plays an important role in the normal development of the male reproductive system.

METHODS

We examined whether SRD5A2 gene mutations (V89L and A49T polymorphisms) are associated with the risk of hypospadias in the Iranian population. We performed exons sequencing for SRD5A2 gene in 109 hypospadias patients.

RESULTS

We identified two new mutations in the subgroups of affected cases: including a substitution of the nucleotide T > A in the codon 73 [c.219T > A (p.Leu73_Ser74insHisPro)] and an insertion of an extra A nucleotide in the codon 77 [c.229insA* (p.Gly77*)]. Additionally, we performed PCR-RFLP for the two identified polymorphisms and revealed that V89L [OR = 5.8, 95% CI (3.8-8.8), p value < 0.001] and A49T [OR = 10.16, 95% CI (3.94-26.25), p value < 0.001] are significantly associated with hypospadias occurrence in patients. Our haplotype analysis further indicated that the Leu-Ala haplotype increases risk of hypospadias; conversely, the Val-Ala haplotype decreases the risk of hypospadias in the studied patients.

CONCLUSIONS

This study demonstrates that polymorphisms in the SRD5A2 gene could be considered as a risk factor for hypospadias disease emergence.