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5-alpha-reductase deficiency

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

5-alpha-reductase deficiency (5-ARD) is an autosomal recessive disorder of sex development (DSD, formerly known as intersex) caused by a mutation of the 5-alpha reductase type 2 gene.[1]

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Historical Perspective

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Classification

Overview

There are two isoforms of 5-alpha reductase named type 1 and type 2. Type 1 5-alpha reductase is found mostly in the skin and liver, which can get delivered to the prostate by systemic circulation. Type 2 is found only on prostatic tissue and is the most common form. So, 5-alpha-reductase deficiency is known as 5-alpha-reductase 2 deficiency.

Classification

There is no classification of 5-alpha reductase deficiency as type 2 5-alpha reductase deficiency is the most common one.[[1]]

References

  1. Walter KN, Kienzle FB, Frankenschmidt A, Hiort O, Wudy SA, van der Werf-Grohmann N; et al. (2010). “Difficulties in diagnosis and treatment of 5alpha-reductase type 2 deficiency in a newborn with 46,XY DSD”. Horm Res Paediatr. 74 (1): 67–71. doi:10.1159/000313372. PMID 20395661.

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Pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

The 5-alpha reductase enzyme is responsible for converting testosterone to dihydrotestosterone (DHT) which is a more potent form playing major roles in male sexual development. While Testosterone leads the development of internal male genitalia, DHT develops the external male genitalia. Children with 5-alpha reductase deficiency suffers from defective external genitalia and ambiguous genitalia.

Pathophysiology

5-alpha-reductase is an enzyme that converts testosterone to dihydrotestosterone (DHT) in peripheral tissues. 5-alpha-reductase deficiency-2 is biochemically characterized by low to low normal levels of testosterone and decreased levels of 5α-DHT, creating a higher testosterone/DHT ratio.

Biochemical effects of 5-alpha-reductase deficiency-2 in testosterone biosynthesis. Typically levels of testosterone are elevated, while levels of DHT are significantly decreased, leading to male undervirilization.

DHT is a potent androgen, necessary for the development of male external genitalia in utero.

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Causes
  • SRD5A2 gene mutation
  • Autosomal recessive disorder so commonly found in consanguineous marriages.


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Differentiating 5-alpha-reductase deficiency from other Diseases

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Epidemiology and Demographics

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Epidemiology and Demographics

The number of people with this condition varies geographically, depending on how much of a given population is interrelated. In 1974, Jullianne Imperato-McGinley has estimated an incidence of 1:90 males in the Dominican Republic. This can be seen in that certain regions have evolved terminology for the condition:

Local names

The term Guevedoche or Guevedoces is Spanish slang for the condition. It originated in the Dominican Republic where more than three dozen cases have occurred in the small village of Salinas, all descended from a single individual named Altagracia Carrasco. It stands for the vulgar expression huevo a los doce, which translates literally as “balls at twelve”. It is also known locally as ‘Machihembras’ (‘first women, then man’).

A similar cluster of cases among the Simbari of the Eastern Highlands of Papua New Guinea has the local name ‘Kwolu-aatmwol’ (‘female thing transforming into male thing’).

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Risk Factors

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Screening

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Natural History, Complications and Prognosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Complications

With 5-ARD there is a risk of gender identity disorder as well as infertility, due to underdevelopment of seminal vesicles and prostate.

Gender identity disorder

Although most people with 5-ARD identify themselves as females, some, however, may develop a male gender identity coinciding the with the pubertal virilisation, or can present themselves with apparent gender dysphoria and transgender behavior. Most cases of gender (role) changes have been reported in large families in the Dominican Republic and Sao Pablo. It is unclear if these patients had the means or possibilities to be treated against virilisation. In some cultures it seems to be socially more beneficial to be a man, than an infertile woman. It is unclear whether this has played any part in the above mentioned gender changes.

Infertility

There is an increased risk of cryptorchidism in 5-ARD, causing infertility, but also a higher risk of testicular cancer. Fertility is further compromised by the underdevelopment of seminal vesicles and prostate.

On the other hand, fertility depending on the female characteristics are impossible; Although the external genitalia appear female, the “pseudovagina” consists only of the lower two-thirds of a normal vagina; creating a blind-ending vaginal pouch. Due to the normal action of Müllerian inhibiting factor produced by the testis in utero, individuals with 5-ARD lack a uterus and Fallopian tubes. Thus, individuals with 5-ARD are not able to become pregnant or produce ova.

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Diagnosis

Diagnosis

History and Symptoms | Physical Examination | Laboratory Findings | Molecular Genetic Studies | Genotyping | Pelvic X Ray | CT | Ultrasound | Other Imaging Findings | Other Diagnostic Studies

Treatment

Treatment

Medical Therapy | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies

Case Studies

Case Studies

Case #1

See also

See also

External links


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