Ambiguous Genitalia Flashcards

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1
Q

Genitalia of embryo at 6 weeks

A

Undifferentiated gonads

Mullerian ducts

Wolffian ducts

Undifferentiated external genitalia

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2
Q

What can be developed from Mullerian ducts?

A

Uterus

Fallopian tubes

Upper vagina

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3
Q

What can be developed from Wolffian ducts?

A

Epididymis

Vas deferens

Seminal vesicles

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4
Q

If Y chromosome is present, What does happen to genitalia after 6 weeks?

A

Undifferentiated gonads >>> Testes >>> produces testosterone & MIF (Mullerian inhibiting factor)

  • MIF acts upon Mullerian ducts >>> Mullerian duct regresses
  • Testosterone acts upon Wolffian ducts >>> develops into epididymis, vas deferens, seminal vesicles
  • Testosterone turns into dehydro-testosterone >>> acts upon undifferentiated external genitalia >>> develops into male genitalia
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5
Q

Which enzyme does convert testosterone to dehydrotestosterone?

A

5-alpha reductase

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6
Q

If Y chromosome is absent, What does happen to genitalia after 6 weeks?

A

Undifferentiated gonads >>> ovaries >>> NO MIF & NO testosterone

  • Due to lack of testosterone >>> Wolffian ducts regress
  • Due to lack of MIF >>> nothing to inhibit Mullerian ducts >>> Mullerian ducts turn into uterus, fallopian tubes, uuper vagina
  • By default: undifferentiated external genitalia >>> turns into female genitalia
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7
Q

Divisions of ambigous genitalia

A
  • Undermusculinisation of a male foetus (46, XY)
  • Musculinisation of a female foetus (46, XX)
  • Mosaicism of a cell line containing a Y chromosome & another that does not (45X or 46XY mosaic)
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8
Q

Causes of undermusculinised male foetus (46, XY)

A
  • Partial testicular failure
  • Partial androgen insensitivity
  • 5-alpha reductase deficiency
  • Rare forms of CAH (Congenital adrenal hyperplasia)

e.g. 3beta-hydroxylase

17alpha-hydroxylase

  • Rare syndromes: Smith-Lemil-Opitz (AR)
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9
Q

Causes of musculinised female foetus (46, XX)

A
  • External androgens, e,g, OCP ​
  • Endogenous androgens, e.g.

1. Common forms of CAH (Congenital adrenal hyperplasia)

  • ​21-hydroxylase
  • 11-beta hydroxylase

​2. Virilising tumours

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10
Q

Examples of abnormal chromosome/mosaicism

A

45X

46XY mosaic

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11
Q

Appearence of genitalia in case of complete testicular failure

A

Normal female genitalia

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12
Q

Appearence of genitalia in case of complete androgen insensitivity (= testicular feminisation syndrome)

A

Normal female genitalia

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