• Friday July 10,2020

5-alpha reductase type 2 deficiency

5-alpha reductase type 2 deficiency is a congenital disorder of male sexual development due to the absence or diminished presence of the hormone dihydrotestosterone. Due to the disturbed development of the external sexual characteristics, the boys are usually born as alleged girls. A clear development of male sexual characteristics takes place only during puberty through a significantly increased testosterone levels.

What is a 5-alpha reductase type 2 deficiency?

5-alpha reductase type 2 deficiency is a congenital disorder of male sexual development due to the absence or diminished presence of the hormone dihydrotestosterone.

5-alpha reductase type 2 deficiency is a rare autosomal recessive inherited disease that causes a differentiation disorder in male sexual development.

This results in a disruption of the metabolism of the hormone testosterone to dihydrotestosterone. There is an intersexuality, more precisely a pseudohermaphroditism masculinus. The external genitals appear female or ambiguous, but the set of chromosomes is male.


The cause is a genetic disorder of the testosterone metabolism. Due to the deficiency of the enzyme 5-alpha-reductase not enough unbounded dihydrotestosterone from testosterone is formed. The hormone dihydrotestosterone at the androgenic receptors has a two and a half times greater biological activity than the testosterone itself.

In addition, the dihydrotestosterone is significantly involved in the fetal development of the external genitalia, urethra and prostate. There are two genes in the human genome that code for the two isoenzymes of 5-alpha reductase. On chromosomes 2 and 5, the type 1 enzyme and the type 2 enzyme are encoded.

The isoenzyme 5-alpha reductase type 2 is characterized by the gene SRD5A2, which occurs on chromosome 2. The type 2 5-alpa reductase occurs in high concentrations in the prostate, but also in the seminal vesicles, sebaceous glands, kidneys, testes and brain. These are all tissues that are sensitive to androgenic hormones. In total, over 90 different mutations of the SRD5A2 gene are known.

Symptoms, complaints & signs

The severity of the disease can vary greatly. From an externally completely female appearance to the clearly male appearance with mild symptoms of diminished masculinization. Signs of a possible 5-alpha reductase deficiency may be a micropenis, a urethral malformation, a so-called hypospadias, an undescended testicle or an enlargement of the clitoris.

Most patients either develop a female genital externally with a clitoral enlargement or have a micropenis with varying degrees of hypospadias. Rarely, isolated micropenis or a normal female genitalia occur. In genetic girls, this metabolic disorder has no influence on the sex development.

Diagnosis & History

The diagnosis of newborns or children who have not entered puberty can be very difficult due to the great variability of the external genitalia. If a 5-alpha reductase type 2 deficiency is suspected, a laboratory test is carried out. In this case, both the amount of testosterone and dihydrotestosterone is determined and formed the ratio to each other.

This study is repeated after stimulation with HCG, the human chorionic gonadotropin. If deficient, the ratio of testosterone to dihydrotestosterone increases to more than 10: 1 due to a lack of dihydrotestosterone. However, in some patients this ratio is not clear so that only analysis of the gene coding for type 2 5-alpha reductase can provide definitive information.

The natural course of the disease in boys is initially characterized by the apparently female external genitalia. The education takes place accordingly in the childhood of a girl. In puberty, when it comes to profound hormonal changes, the clitoris suddenly grows into a penis and the testicles enter the scrotum.

In addition, it comes to the typical beard growth, muscle mass increase and sebaceous gland changes. In principle, the testes can form sperm, but it can come to infertility due to the previous undescended testis itself or due to a hormonal underdevelopment of the prostate. About 80 percent of boys continue to live as men after puberty. The disease is symptomless in women, however.

When should you go to the doctor?

In many cases, it is relatively difficult to identify or diagnose 5-alpha reductase type 2 deficiency. However, the disease manifests itself in most cases by a masculinization of the body and the appearance. Should it therefore come to these complaints, then in any case a doctor should be consulted. This is especially the case when it comes to the formation of a micropenis or when the clitoris of the patient has increased significantly.

Even with external complaints, such as increased hair growth on the skin, a doctor should be asked for advice. These symptoms usually occur during puberty. In many cases, surgical procedures can be performed right after birth. However, these are only possible if the complaints on the urethra due to the 5-alpha-reductase type 2 deficiency were detected early. Even with sudden disturbances of the metabolism, which occur especially during puberty, a doctor should be consulted in any case.

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Treatment & Therapy

If diagnosed early, it is advisable to support male identification, as the subsequent strong formation of testosterone during puberty produces a distinctive male gender identity. In particular, a psychosexual therapy may be necessary, as the affected boys were unknowingly educated like girls in childhood and now suddenly have to be sexually reoriented in adolescence.

Usually, at a young age, according to the current doctrine between the 3rd and 18th month of life, a malformation of the urethra or an undescended testicle must be surgically repaired in order to prevent further consequences. In later life, due to an untreated urethral malformation, pain, inflammation or mental stress, due to aesthetics, may occur.

Leaving undescended testicles can lead to infertility of the man. During puberty, the hormones testosterone and dihydrotestosterone are substituted to ensure normal development of the external sexual characteristics. Fertility may be limited, but is often compensated by artificial insemination.

In some cases the boys decide to continue living as girls after diagnosis. Then there is the substitution with female hormones, the estrogens, as well as, if necessary, corrective operations with removal of the testicles during puberty.

Outlook & Forecast

Due to the 5-alpha-reductase type 2 deficiency, it comes mainly in the male patients to disorders in the development of gender. The male sexual characteristics usually develop only when puberty occurs. The penis is greatly reduced and it may come to the formation of a clitoris.

The 5-alpha-reductase type 2 deficiency can also lead to significant mental health problems. Children can also be victims of bullying and teasing at a young age. In many cases, disorders of the metabolism occur, which make the everyday life of the affected considerably more difficult.

The symptoms and symptoms of 5-alpha-reductase type 2 deficiency can in most cases be treated without complications and difficulties. Only in rare cases surgical interventions are necessary. The treatment is done with the help of hormones.

If no treatment is given, pain and other discomforts may occur in the kidneys and urethra. Similarly, many patients require psychological treatment. The life expectancy is not limited by the deficiency and there are no more complaints in adulthood.


A preventive measure to prevent the genetic disorder of testosterone metabolism is not known. In case of a familial accumulation a chromosome analysis of the affected couple can be carried out in case of planned pregnancy. Likewise, an analysis of the set of chromosomes of the unborn child can be made. However, appropriate risks of intrauterine intervention should be weighed, as in the worst case, miscarriage may occur.


In most cases, 5-alpha reductase type 2 deficiency has no aftercare option as it is a congenital disorder that can not be fully treated. Likewise, a causal treatment is not possible, so that those affected are dependent on a purely symptomatic therapy. If the affected person wishes to have children, counseling may be advisable in order to avoid the further transmission of 5-alpha-reductase type 2 deficiency.

However, the life expectancy of the patient is not diminished by the disease. Since the lack is often associated with mental health problems, depression or other moods, conversations with friends or with one's own family often make sense. Similarly, the contact with other stakeholders of the 5-alpha-reductase type 2 deficiency may be useful, since it can lead to an exchange of information that can facilitate life.

Other malformations can be treated with surgical intervention. After such an intervention, the affected person should rest and spare. From physical effort is to be seen. For serious mental health problems that occur through bullying or teasing, however, a proper psychological treatment is useful.

You can do that yourself

In a known 5-alpha reductase type 2 deficiency, self-help is the most important factor. Medical measures are usually uncomplicated. The necessary hormone therapy is well observed by the parents of those affected and in recognizable abnormalities of a mental or physical nature, the attending physician should be consulted.

Much more important, however, is the psychological accompaniment of the affected children. Here, the family environment plays the biggest role. It is advisable to consult an experienced child psychologist, both for the affected child and the parents. A visit to a self-help group for the mutual exchange of experience should also be considered. Parents must be a great support to their child in this genetic disease and sensitive to the gender education. Children should generally not be pressed into a solid role model and be allowed to deal with both sexes. This is a natural phase that every child should go through for a healthy mental development.

However, in order to avoid later psychological stress, strict education according to the female role model - exclusively due to the optical conditions - must be prevented. Affected boys should be able to identify with their own gender from the beginning. In case of existing bullying parents should often seek the conversation with their child and the involved educators. In pedagogical literature parents will find suggestions on how to playfully strengthen the self-esteem of their child.

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