Disorders of Sexual Differentiation Flashcards

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1
Q

What is gonadal dysgenesis?

A
  • 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.
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2
Q

What is sex reversal?

A

Phenotype does not match genotype, ie may be male genotypically but externally look like a female

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3
Q

What is an intersex person?

A

They have some components of both tracts or have ambiguous genitalia. Sex of infant difficult to determine.

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4
Q

What happens if in an XY individual testosterone is made but has no effect?

A

They have androgen insensitivity syndrome (AIS)

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5
Q

What happens in complete androgen insensitivity syndrome?

A
  • 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.
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6
Q

What can help detect AIS?

A

Ultrasound scan and karyotype with male levels of androgens can help detect it.

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7
Q

What is partial AIS and why does this happen?

A
  • 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.
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8
Q

What happens if XY male is unable to make or respond to AMH in utero?

A

They have persistent Mullerian duct syndrome.

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9
Q

How does Persistent Mullerian duct syndrome (PMDS) happen?

A
  • 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
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10
Q

What happens in PMDS?

A
  • 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
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11
Q

What is the common presentation of PMDS?

A
  • 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.
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12
Q

What are the treatments for PMDS?

A
  • 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.
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13
Q

What happens if in an XY individual testosterone is made but not DHT?

A

They have 5-α-reductase deficiency

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14
Q

What happens in 5-α-reductase deficiency?

A
  • 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.
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15
Q

What is Turners syndrome?

A
  • 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.
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16
Q

What happens if XX female is exposed to high levels of androgens in utero?

A

Congenital adrenal hyperplasia

17
Q

What are all steroid hormones made of?

A

Cholestrol

18
Q

What’s the structure of cholesterol?

A

Cholesterol has three 6 sided rings, a 5 sided ring and a carbon chain – has 27 carbons in total

19
Q

How is pregnenolone and progesterone made?

A
  • The carbon chain (containing carbons 22-27) is removed
  • 17 alpha hydroxylase adds a hydroxyl group on carbon 17 – makes 17 hydroxyprogesterone
  • Add oxygen to carbon 3 of pregnenolone – makes progesterone
20
Q

How are androgens made?

A
  • If you take off carbons 21 and 20 off pregnenolone it makes androgens
  • the difference between androgens in the placement of the oxygens and hydroxyls
21
Q

How are oestrogens made?

A
  • Aromatase take off a carbon (carbon 19) from androgens to make oestrogens
  • there’s types of oestrogens and they’re different due to whether they have hydroxyl groups and how many groups they have
22
Q

What are the different oestrogens?

A
  • Oestrone (1 hydroxyl group)
  • oestradiol
  • oestratriol
23
Q

What are the sex hormones?

A
  • Progesterogens, androgens and oestrogens

- made in the testis and ovaries

24
Q

Where are the adrenal glands found?

A

on top of the kidney

25
Q

What do adrenal glands make?

A

aldosterone and cortisol

26
Q

How are aldosterone and cortisol made?

A
  • 21-hydroxylase is needed for the production of aldosterone and cortisol
  • Progesterone made first before making aldosterone – it has 21 carbon atoms
  • Cortisol is a glucocorticoid – 21 carbon atoms
27
Q

What does cortisol do normally?

A
  • Gives negative feedback in the hypothalamic pituitary adrenal axis
  • Normally Corticotropin releasing hormone is released by hypothalamus which stimulates pituitary to secrete ACTH
  • ACTH stimulates rapid uptake of cholesterol into the adrenal cortex and upregulates cholesterol side-chain cleavage enzyme (P450scc).
  • ACTH Increases glucocorticoid (cortisol) secretion.
  • The cortisol then feeds back to the pituitary and hypothalamus
28
Q

How does congenital adrenal hyperplasia cause its symptoms?

A
  • There’s no negative feedback
  • Increased CRH and ACTH levels
  • ACTH causes an upregulation of cholesterol side chain cleavage enzyme
  • Progesterone levels rise
  • They convert into androgens – androgens levels rise
  • Build up and release of androgens as aromatase isn’t present in women until puberty either
  • Adrenal glands get bigger trying to make cortisol and aldosterone
29
Q

Symptoms of congenital adrenal hyperplasia.

A
  • No SRY so no testes and no AMH.
  • Mullerian ducts remain.
  • Masculinised external genitalia due to 5-alpha reductase making DHT from the androgens
  • Androgen levels not usually high enough to rescue Wolffian ducts.
  • Completeness of the enzyme block varies. May have developed Wolffian structures and ambiguous masculinised external genitalia or hirsutism.
  • Possibility of ‘salt-wasting’ due to lack of aldosterone, this can be lethal.
  • Treatment with glucocorticoids to correct feedback.