17beta-hydroxysteroid dehydrogenase-3 deficiency: a rare endocrine cause of male-to-female sex reversal

Lessons from 17β-HSD3 deficiency: Clinical spectrum and complex molecular basis in Chinese patients

17β-Hydroxysteroid dehydrogenase type 3 (17β-HSD3) deficiency is rarely reported in Chinese patients with 46, XY disorders of sexual development (DSD). Seven subjects with 17β-HSD3 deficiency were identified from 206 Chinese 46, XY DSD patients using targeted next-generation sequencing (NGS). Serum AD and T levels were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In silico and functional studies were performed to evaluate the enzymatic activity impairment of HSD17B3 variants. A minigene assay was performed in an exonic splicing variant. Our results showed that four novel and five reported HSD17B3 variants were identified in 7 unrelated patients. The patients showed cryptic presentation during childhood and classical virilization after puberty with T/AD ratio< 0.4. A heterozygous large deletion from the 5'UTR to exon 1 was identified in a patient with a monoallelic variant of p.N130S. Although predicted to be 'likely pathogenic', only p. S232P and p. S160F drastically reduced the enzymatic activity of 17β-HSD3. A previously reported 'missense' variant c 0.277 G>A (p. E93K) was revealed to have no impact on enzyme activity but resulted in aberrant splicing of exon 3 and was reclassified as an exonic splicing variant. In our study, one nonsense, one exonic splicing, one deletion, one large deletion and five missense variants were detected in patients with 17β-HSD3 deficiency, expanding the clinical and molecular profile of this disorder. In silico analysis should be cautiously interpreted when the heredity pattern and functional study are inconsistent.

Disorder of Sex Development Due to 17-Beta-Hydroxysteroid Dehydrogenase Type 3 Deficiency: A Case Report and Review of 70 Different HSD17B3 Mutations Reported in 239 Patients

The 17-beta-hydroxysteroid dehydrogenase type 3 (17-β-HSD3) enzyme converts androstenedione to testosterone and is encoded by the HSD17B3 gene. Homozygous or compound heterozygous HSD17B3 mutations block the synthesis of testosterone in the fetal testis, resulting in a Disorder of Sex Development (DSD). We describe a child raised as a female in whom the discovery of testes in the inguinal canals led to a genetic study by whole exome sequencing (WES) and to the identification of a compound heterozygous mutation of the HSD17B3 gene (c.608C>T, p.Ala203Val, and c.645A>T, p.Glu215Asp). Furthermore, we review all HSD17B3 mutations published so far in cases of 17-β-HSD3 deficiency. A total of 70 different HSD17B3 mutations have so far been reported in 239 patients from 187 families. A total of 118 families had homozygous mutations, 63 had compound heterozygous mutations and six had undetermined genotypes. Mutations occurred in all 11 exons and were missense (55%), splice-site (29%), small deletions and insertions (7%), nonsense (5%), and multiple exon deletions and duplications (2%). Several mutations were recurrent and missense mutations at codon 80 and the splice-site mutation c.277+4A>T each represented 17% of all mutated alleles. These findings may be useful to those involved in the clinical management and genetic diagnosis of this disorder.

Pubertal Development in 17Beta-Hydroxysteroid Dehydrogenase Type 3 Deficiency

BACKGROUND

17β-hydroxysteroid dehydrogenase (17β-HSD) type 3 deficiency is an autosomal recessive disorder with diminished testosterone synthesis and consequently underandrogenisation. 46,XY patients with 17β-HSD type 3 deficiency are often assigned a female sex at birth but have a high virilisation potential at the time of puberty.

METHODS

We studied four 46,XY patients with 17β-HSD type 3 deficiency at puberty with regard to the underlying mutations, the hormone values, and the clinical findings.

RESULTS

Three patients were initially assigned a female sex and 1 was assigned a male sex. All had relevant mutations in the HSD17B3 gene. The 2 patients with deleterious mutations had lower testosterone values at the time of puberty than the patients with possible residual activity of 17β-HSD type 3. One of the latter patients changed to male gender.

CONCLUSION

All 4 patients with 17β-HSD type 3 deficiency synthesized relevant amounts (>0.7 µg/L) of testosterone at puberty, which lead to variable androgenisation. In patients with presumable residual activity of the mutated enzyme, testosterone values in the male reference range can be achieved, thereby inducing male pubertal development. These patients should possibly be assigned a male sex. Any surgical intervention should be avoided until the patients are old enough to consider their options of medical and surgical intervention.
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17β-Hydroxysteroid dehydrogenase 3 deficiency: Three case reports and a systematic review

17β-Hydroxysteroid dehydrogenase 3 deficiency is a rare autosomal recessive cause of 46, XY disorders of sex development resulting from HSD17B3 gene mutations, however, no case has been reported in East Asia. The aim of this study was to report three Chinese 46, XY females with 17β-HSD3 deficiency in a single center and perform a systematic review of the literature. Clinical examination, endocrine evaluation and HSD17B3 gene sequencing were performed in the three Chinese phenotypically females (two sisters and one unrelated patient). Relevant articles were searched by using the term "HSD17B3" OR "17beta-HSD3 gene" with restrictions on language (English) and species (human) in Pubmed and Embase. All the three phenotypically female subjects showed 46, XY karyotype, inguinal masses, decreased testosterone and increased androstenedione. Two novel homozygous mutations (W284X and c.124_127delTCTT) in HSD17B3 gene were identified. A systematic review found a total of 121 pedigrees/158 patients, with 78.5% (124/158) of patients assigned as females, 15.2% (24/158) from females to males, and 5.1% (8/158) raised as males. The most common mutation was c.277+4C>T (allele frequency: 25/72) for patients from Europe, and R80Q (allele frequency: 21/54) for patients from West Asia. The testicular histology showed normal infantile testicular tissue in 100% (9/9) infantile patients, normal quantity germ cells in 44.4% (8/18) prepubertal patients and 19.0% (4/21) pubertal and adult patients. We reported the first East Asian 17β-hydroxysteroid dehydrogenase 3 deficiency cases. Additional literature reviews found founder effects among patients with different ethnic background and early orchiopexy may benefit fertility in patients assigned as males. These findings may significantly expand the clinical, ethnic and genetic spectrum of 17β-hydroxysteroid dehydrogenase 3 deficiency.

46,XY disorder of sex development (DSD) due to 17β-hydroxysteroid dehydrogenase type 3 deficiency

17β-hydroxysteroid dehydrogenase 3 deficiency consists of a defect in the last phase of steroidogenesis, in which androstenedione is converted into testosterone and estrone into estradiol. External genitalia range from female-like to atypical genitalia and most affected males are raised as females. Virilization in subjects with 17β-HSD3 deficiency occurs at the time of puberty and several of them change to male social sex. In male social sex patients, testes can be safely maintained, as long as they are positioned inside the scrotum The phenotype of 46,XY DSD due to 17β-HSD3 deficiency is extremely variable and clinically indistinguishable from other causes of 46,XY DSD such as partial androgen insensitivity syndrome and 5α-reductase 2 deficiency. Laboratory diagnosis is based on a low testosterone/androstenedione ratio due to high serum levels of androstenedione and low levels of testosterone. The disorder is caused by a homozygous or compound heterozygous mutations in the HSD17B3 gene that encodes the 17β-HSD3 isoenzyme leading to an impairment of the conversion of 17-keto into 17-hydroxysteroids. Molecular genetic testing confirms the diagnosis and provides the orientation for genetic counseling. Our proposal in this article is to review the previously reported cases of 17β-HSD3 deficiency adding our own cases.

Severe Undervirilisation in a 46,XY Case Due to a Novel Mutation in HSD17B3 Gene

17-β-hydroxysteroid dehydrogenase type 3 (17β-HSD3) is an important enzyme involved in the final steps of androgen synthesis and is required for the development of normal male external genitalia. 46,XY individuals with deficiency of this enzyme present a wide clinical spectrum from a female appearance of the external genitalia through ambiguous genitalia to a predominantly male genitalia with micropenis or hypospadias. This paper reports a one-year-old 46,XY patient with 17β-HSD3 deficiency who presented with female external genitalia and bilaterally palpable gonads in the inguinal region. The low T/Δ4 ratio after human chorionic gonadotropin (hCG) stimulation suggested 17β-HSD3 deficiency. A homozygous mutation, c.761_762delAG, was determined at the intron 9/exon 10 splice site of the HSD17B3 gene. To the best of our knowledge, this mutation has not been reported thus far, but its localization and type would imply a complete disruption of the 17β-HSD3 which may explain the phenotype of our patient.

Isolated mild clitoral hypertrophy may reveal 46,XY disorders of sex development in infancy due to 17βHSD-3 defect confirmed by molecular analysis

AIMS

17-β-Hydroxysteroid dehydrogenase type 3 (17βHSD-3) is expressed exclusively in the testes where it converts Δ4 androstenedione (Δ4) to testosterone (T). Here, we report a patient with a rare mutation at a critical site in HSD17B3 gene leading to deficiency of 17β HSD-3 enzyme.

METHODS

We describe a 3-year old healthy female of consanguineous Lebanese descent, who presented to the endocrine service with isolated mild clitoromegaly. Adrenocorticotropic hormone (ACTH) and human chorionic gonadotrophin (hCG) stimulation tests were performed. Genes for sex-determining region Y (SRY), steroidogenic factor-1 (SF-1) and 17βHSD-3 (HSD17B3) were sequenced.

RESULTS

The post-hCG stimulation T levels and T/Δ4 ratio was low. Patient had a 46,XY karyotype. Sequence analysis of the HSD17B3 gene revealed a homozygous R80W missense mutation on exon 3. No mutation was found in SRY and SF1 genes. Mullerian structures were not detected on pelvic imaging.

CONCLUSIONS

A low T/Δ4 ratio is indicative of 17βHSD-3 deficiency and associated with isolated clitoromegaly. The R80 site is critical for NADPH binding, thus the mutation at this site leads to 17βHSD-3 deficiency presenting as 46,XY disorder of sex development.

46,XY DSD due to impaired androgen production

Disorders of androgen production can occur in all steps of testosterone biosynthesis and secretion carried out by the foetal Leydig cells as well as in the conversion of testosterone into dihydrotestosterone (DHT). The differentiation of Leydig cells from mesenchymal cells is the first walk for testosterone production. In 46,XY disorders of sex development (DSDs) due to Leydig cell hypoplasia, there is a failure in intrauterine and postnatal virilisation due to the paucity of interstitial Leydig cells to secrete testosterone. Enzymatic defects which impair the normal synthesis of testosterone from cholesterol and the conversion of testosterone to its active metabolite DHT are other causes of DSD due to impaired androgen production. Mutations in the genes that codify the enzymes acting in the steps from cholesterol to DHT have been identified in affected patients. Patients with 46,XY DSD secondary to defects in androgen production show a variable phenotype, strongly depending of the specific mutated gene. Often, these conditions are detected at birth due to the ambiguity of external genitalia but, in several patients, the extremely undervirilised genitalia postpone the diagnosis until late childhood or even adulthood. These patients should receive long-term care provided by multidisciplinary teams with experience in this clinical management.