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Science of Reproduction > Disorders of Sexual Differentiation > Flashcards

Disorders of Sexual Differentiation Flashcards

1
Q

What is gonadal dysgenesis?

A

Incomplete sexual differentiation

  • missing SRY in male
  • partial / complete deletion of second X in female

General description of abnormal gonad development

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2
Q

What is sex reversal?

A

Phenotype doesn’t match genotype

May be male genotypically (XY) but externally looks female

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3
Q

What is intersex?

A

Components of both tracts / have ambiguous genitalia

Sex of infant difficult to determine. (e.g. v. large clitoris or v. small penis) - DSD

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4
Q

Describe androgen insensitivity syndrome (AIS)

A

XY individual

Testosterone produced but has no effect

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5
Q

What are the internal and external genitalia of an individual with AIS?

A

Testes form (undescended) and make AMH so Mullerian ducts regress.

No differentiation of Wolffian ducts

No external male genitalia - appear F

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6
Q

What is the incidence rate of complete AIS?

A

Complete AIS - incidence 1:20,000 (46XY)

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7
Q

How may an AIS individual present?

A

Primary amenorrhoea
Lack of body hair

U/s scan and karyotype show male levels androgens

Hormonal puberty causes feminization w/out intervention due to aromatization of endogenous androgens into estrogens = Lacking response to androgen.

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8
Q

What is the incidence rate of partial AIS?

A

Incidence unknown but on a spectrum (46XY)

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9
Q

Describe the spectrum of partial AIS

A

Spectrum of phenotypes including almost normal female external genitalia through ambiguous genitalia (perineoscrotal hypospadias, microphallus, cryptorchidism).

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10
Q

What is the prognosis of partial AIS?

A

Minor genital deviations go unnoticed or may be surgically repaired

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11
Q

How does partial AIS present at puberty?

A

Development of male secondary characteristics not very pronounced

Pubertal gynecomastia can occur (dec androgen : estrogen ratio)

Ambiguous genitalia surgically corrected or via Androgen therapy

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12
Q

What gender do partial AIS individuals identify with?

A

Majority develop identity commensurate with assigned gender

~20% desire to change gender usually in adolescence or adulthood

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13
Q

What is persistent mullerian duct syndrome (PMDS)?

A

XY male unable to produce / respond to AMH in utero

- PMDS I and PMDS II

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14
Q

What causes PMDS I?

A

PMDS type I results from mutations of AMH gene on chromosome 19

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15
Q

What causes PMDS II?

A

PMDS type II results from mutations of the AMH receptor gene (AMH-RII) on chromosome 12.

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16
Q

Describe the mendelian inheritance pattern of PMDS I and II

A

Both autosomal recessive conditions with expression usually limited to XY offspring

1 normal + 1 abnormal = carrier

Homozygous for gene required for mutation

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17
Q

Describe the gonadal formation for PMDS patients

A

Testes form and either fail to make AMH or AMH receptor absent.

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18
Q

Outline the external and internal genitalia of PMDS individuals

A

Mullerian ducts remain.

Differentiation of Wolffian ducts and masculinised external genitalia due to testosterone on genital skin

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19
Q

Describe the varying common presentations of PMDS patients

A

60–70%: intra-abdominal Mullerian structures, testes in position of ovaries

20–30%:one testis in a hernial sac / scrotum together with Mullerian structures

10%: both testes located in same hernial sac (transverse testicular ectopia) along w/ uterine tubes and/or uterine structures.

All have increased risk of malignant transformation.

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20
Q

What are the treatment options for PMDS?

A

surgery

hysterectomy

21
Q

How is surgery used to treat PMDS?

A

Surgery (orchiopexy) to retrieve testes and position them in scrotum

If testes cannot be retrieved, testosterone replacement at puberty is an option.

22
Q

How does a hysterectomy help treat PMDS?

A

Uterus removal, dissection of Müllerian tissue away from vas deferens/epididymis

Laparoscopic hysterectomy may prevent occurrences of neoplastic tissue formation

23
Q

What is the effect of 5-α-reductase deficiency?

A

XY individual can produce testosterone but cannot convert to DHT

24
Q

Describe the external genitalia of someone with 5-α-reductase deficiency

A

Testes form and make AMH so Mullerian ducts regress.

Wolffian ducts develop
No external male genitals.

25
Q

What is the incidence rate of 5-α-reductase deficiency ?

A

5α-reductase deficiency – incidence varies enormously (46XY)

26
Q

Describe the gonadal development of someone with 5-α-reductase deficiency

A

May appear female / have ambiguous genitalia e.g. labioscrotal folds or clitoridean penis

Degree of enzyme block varies and therefore presentation

27
Q

What are the potential risks of 5-α-reductase deficiency

A

High testosterone levels which occur at adrenarche and puberty may induce virilisation

Testosterone and DHT capable of masculinising brain in utero

28
Q

Describe the genotype of someone with Turners syndrome

A

45XO

29
Q

What is the incidence rate of turners syndrome?

A

Incidence 1:3000

30
Q

Describe gonadal development of turners syndrome

A

Ovaries form due to mullerian ducts, wolffian regress = external female genitalia

31
Q

What is the effect of turners on ovarian development?

A

XO = failure of ovarian function

‘Streak’ ovaries - ovarian dysgenesis proves we need two X’s for ovarian development

32
Q

What are the effects of turners?

A

Uterus and tubes present may be small / defects in growth

Wide spectrum of phenotypic disorders and severity

May be fertile / have mosaicism. Female gender.
Hormone support of bones and uterus

33
Q

What is genetic mosaicism?

A

2 or more genetically different sets of cells in body

34
Q

What is congenital adrenal hyperplasia (CAH)?

A

When XX females exposed to high levels of androgens in utero

35
Q

Describe incidence rates of CAH

A

1:15,000

36
Q

Name an example of mineralocorticoids

A

aldosterone

37
Q

Give an example of a glucocorticoid

A

cortisol

38
Q

Name the gonadal steroids?

A

oestrogen, testosterone and progesterone

39
Q

Describe the structures of the gonadal steroids

A

Cholesterol modified by enzymes to form steroids

  • Progestogens: 21C’s
  • Androgens: 19C’s
  • Oestrogens: 18C’s (via aromatase)

E₂(oestradiol), oestrone, oestriol have varying hydroxyl (OH) groups

40
Q

Describe the steroidogenesis step that occurs within the adrenal cortex

A

21’OH adds hydroxyl group to C21

progestogens → mineralo-/glucocorticoids

41
Q

Describe the HPA axis

A

Hypothalamic-Pituitary-adrenal axis

  1. Hypothalamic CRH released
  2. Stimulates ACTH from pituitary
  3. Rapid uptake of cholesterol into adrenal cortex
  4. Upregulates P450scc
  5. Increased glucocortiocid secretion
42
Q

What is P450scc?

A

Cholesterol side-chain cleavage enzyme

43
Q

Describe the effects of high CRH and ACTH levels

A

Increased CRH (GnRH analogue) and ACTH stimulate cholesterol uptake and adrenal cortex activity.

44
Q

What is the consequence of steroidogenesis pathway block?

A

Upregulated ACTH causes increased cholesterol (LDL) brought in - increases progestogen formation into androgens

45
Q

What is the effect of cortisol on the HPA axis?

A

Cortisol provides negative feedback to hypothalamus to limit CRH and ACTH production and release

46
Q

What is the effect of steroidogenesis pathway block?

A

Completeness of the enzyme block varies = CAH

May develop Wolffian structures and ambiguous masculinised external genitalia / hirsutism

47
Q

Why does ‘salt-wasting’ occur in CAH patients?

A

Due to lack of aldosterone CAH patients may excrete salt - this can be lethal.

48
Q

How is salt wasting in CAH treated?

A

Treatment with glucocorticoids to correct feedback

49
Q

What is required for correct sexual development?

A

Correct sexual differentiation requires genetic, anatomical and endocrine components.

Science of Reproduction (32 decks)

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