Disorders of Sexual Differentiation Flashcards
What is gonadal dysgenesis?
- Sexual differentiation is incomplete.
- Usually missing SRY in male, or partial or complete deletion of second X in female.
- Also used as a general description of abnormal development of the gonads.
What is sex reversal?
Phenotype does not match genotype, ie may be male genotypically but externally look like a female
What is an intersex person?
They have some components of both tracts or have ambiguous genitalia. Sex of infant difficult to determine.
What happens if in an XY individual testosterone is made but has no effect?
They have androgen insensitivity syndrome (AIS)
What happens in complete androgen insensitivity syndrome?
- Testes form and make AMH so Mullerian ducts regress.
- DHT still made
- Androgen receptor does not detect androgens (testosterone and DHT)
- No differentiation of Wolffian ducts
- Undescended testes.
- No uterus or fallopian tubes
- External genitalia appear female - abbreviated blind vaginal pouch.
- Usually present with primary amenorrhoea (no period). Lack of body hair is a clue.
- Hormonal puberty may be feminizing without intervention due to aromatization of endogenous androgens to estrogens. Lacking response to androgen.
What can help detect AIS?
Ultrasound scan and karyotype with male levels of androgens can help detect it.
What is partial AIS and why does this happen?
- When the patients genitals appear ambiguous
- Spectrum of phenotypes including almost normal female external genitalia through ambiguous genitalia.
- Minor genital deviations go unnoticed or may be surgically repaired.
- At puberty development of male secondary characteristics may not be very pronounced – testosterone increase at puberty but not enough to fully develop male parts.
What happens if XY male is unable to make or respond to AMH in utero?
They have persistent Mullerian duct syndrome.
How does Persistent Mullerian duct syndrome (PMDS) happen?
- PMDS type I results from mutations of the gene for AMH on chromosome 19.
- PMDS type II results from mutations of the gene for the AMH receptor (AMH-RII) on chromosome 12.
- Both autosomal recessive conditions with expression usually limited to XY offspring
What happens in PMDS?
- Testes form and either fail to make AMH or AMH receptor absent.
- Mullerian ducts remain.
- Differentiation of Wolffian ducts and masculinised external genitalia still happens
What is the common presentation of PMDS?
- 60–70% of cases have intra-abdominal Mullerian structures and testes in a position simulating that of the ovaries
- 20–30% have one testis in a hernial sac or scrotum together with Mullerian structures.
- 10% have both testes located in the same hernial sac (transverse testicular ectopia) along with the uterine tubes and/or uterine structures.
- All have increased risk of malignant transformation.
What are the treatments for PMDS?
- Surgery to retrieve the testes and position them in the scrotum. If testes cannot be retrieved, testosterone replacement at puberty is an option.
- Removal of uterus dissection of Müllerian tissue away from the vas deferens/epididymis.
- Laparoscopic hysterectomy may prevent the occurrences of neoplastic tissue formation.
What happens if in an XY individual testosterone is made but not DHT?
They have 5-α-reductase deficiency
What happens in 5-α-reductase deficiency?
- Testes form and make AMH so Mullerian ducts regress.
- Wolffian ducts develop
- No external male genitalia – ambiguous or female genitalia
- Need to assess potential as high testosterone level which will occur at adrenarche and puberty – may induce virilisation.
- Both testosterone and dihydrotestosterone (DHT) are capable of masculinising the brain in non-human primates so some brain masculinisation in utero possible with this condition.
What is Turners syndrome?
- When there’s only one X chromosome
- Failure of ovarian function.
- Will have ‘Streak’ ovaries = ovarian dysgenesis - illustrates that we need two X’s for normal ovarian development.
- Uterus and tubes are present, may be small or other defects in growth and development. Wide spectrum of phenotypic disorders and severity.
- They have mosaicism if the X is lost later during development – some patients may still be fertile
- Hormone support of bones and uterus.