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Life Cycle Exam 1 > Embryology and CAH > Flashcards

Embryology and CAH Flashcards

1
Q

True or false: Richardson syndrome is 45, YO.

A

False. 45, YO is lethal.

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2
Q

Presence of __________ determines male development, regardless of number of X chromosomes.

A

SRY (the Sex-determining Region of Y)

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3
Q

How does SRY determine male sexual development?

A

It is a transcription factor that activates a cascade of genes that determines male development.

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4
Q

What is WT1?

A

Wilms Tumor-related gene

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5
Q

The genital ridges form just medial to the proliferating ________________.

A

mesonephros

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6
Q

WT-1 deletions and mutations are associated with _________________.

A

gonadal dysgenesis and Wilms tumors

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7
Q

NR5A-1 is also called __________.

A

Steroidogenic Factor-1 (SF-1)

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8
Q

SF-1 regulates development of ________________.

A

the adrenal glands and genes involved in gonadal development

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9
Q

SF-1 deletions result in gonadal dysgenesis and ____________.

A

adrenal failure

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10
Q

Germ cells migrate from the ____________.

A

yolk sac

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11
Q

The primitive sex cords development into the ____________.

A

Sertoli cells

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12
Q

One of the most important transcription targets of SRY is _______________.

A

SOX-9; mutations in this result in gonadal dysgenesis and skeletal dysplasia (due, in part, to lowered levels of anti-Müllerian hormone)

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13
Q

The urogenital ridge develops into the ________________.

A

bipotential gonad

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14
Q

Duplication of the DAX gene results in ________________.

A

dysgenesis of the testes; this is normal in females, but if a male has a DAX duplication, then he will develop small testes

(“It AXes the testes.”)

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15
Q

Which genes stimulate ovarian development?

A

Wnt/RSPO1 -> beta-catenin
FOXL2
DAX1

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16
Q

In females, what happens to the medullary sex cords?

A

They degenerate. The cortex becomes the cords.

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17
Q

AMH is secreted by ____________; this must occur by the 8th week.

A

Sertoli cells

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18
Q

What two hormones are needed for proper development of the internal ducts in males?

A

AMH and testosterone

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19
Q

What two hormones are needed for proper development of the internal ducts in females?

A

Trick question –females need absence of AMH and testosterone to develop properly

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20
Q

The paramesonephric ducts development into _____________.

A

fallopian tubes, uterus, and the upper portion of the vagina

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21
Q

In ________________ syndrome, women have absent Müllerian structures.

A

Rokitansky (46, XX)

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22
Q

What two molecular abnormalities can lead to persistent Müllerian structures in 46, XY males?

A

Defects in the AMH receptor or AMH synthesis

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23
Q

The ____________ develops into the glans penis in males and the clitoris in females.

A

genital tubercle

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24
Q

What structure becomes the labia majora in females and scrotum in males?

A

The labioscrotal swellings

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25
Q

The urethral folds develop into __________ in females and ____________ in males.

A

labia minora; penile urethra

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26
Q

In males, the Müllerian duct develops into the _______________.

A

prostatic utricle

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27
Q

What is the main determining factor in the development of the external genitalia?

A

Testosterone

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28
Q

Development of the male external genitalia is complete by _____________, so the addition of androgens after that time – in a male who was deficient earlier –will not correct the abnormality.

A

13 weeks

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29
Q

What occurs to females exposed to excess androgens before and after 13 weeks’ gestation?

A

Prior: insertion of urethra into vagina
After: clitoromegaly

30
Q

What would palpable gonads in the labial folds indicate?

A

Testes (and likely an XY baby)

31
Q

The two broad categories of disorders of sexual development (DSD) are _____________________.

A
  • 46, XX (virilized)

- 46, XY (undervirilized)

32
Q

95% of 46, XX DSD is _________________.

A

congenital adrenal hyperplasia

33
Q

Underexpression of SOX9 will lead to _________________.

A

gonadal dysgenesis in a male

34
Q

Testicular regression is most often due to _________________.

A

vascular insults in utero

35
Q

In those with 5-alpha reductase deficiency, the testes are usually in ______________.

A

inguinal canal or labioscrotal folds

36
Q

Those with ______________ lack a uterus and have a feminizing puberty.

A

congenital androgen insufficiency (46, XY)

37
Q

Bilateral hernia repairs (due to testes) is a symptom of ______________.

A

CAIS

38
Q

Why will girls with CAIS develop breasts at puberty?

A

Because they still have testosterone –it’s just not binding to androgen receptors –and the testosterone gets converted to estrogen.

39
Q

True or false: 21-alpha hydroxylase deficiency is almost always fatal in the first few months of life if undetected.

A

False. There are actually milder forms that present in adolescence.

40
Q

How does 21-alpha hydroxylase deficiency present in males?

A

Hyponatremia and hyperkalemia with hypotension (the virilziing effects are not of consequence)

41
Q

StAR syndrome results in what phenotype?

A

All female, regardless of chromosomal status (because no androgens are produced); it is also called lipoid adrenal hyperplasia, because cholesterol accumulates in the adrenal gland yet cannot be converted to any of its usual derivatives

42
Q

If yolk sac cells fail to migrate, then _____________ develops.

A

streak gonads

43
Q

When does yolk sac cell migration occur?

A

6 weeks’ gestation

44
Q

Until when are the gonads undifferentiated?

A

7 weeks’ gestation (when SRY begins to differentiate in the male)

45
Q

You know that hCG stimulates Leydig cells. Why is this important?

A

Males need testosterone to develop, but they don’t start making LH until the second trimester. As such, maternal hCG needs to stimulate LH receptors in the first trimester.

46
Q

Without _____________, the Wolffian structures regress.

A

high local concentrations of testosterone

47
Q

What needs to occur (and when) for the labial folds to fuse?

A

Exposure to excess androgens prior to 12 weeks’ gestation

48
Q

How does androgen insensitivity present?

A

With no uterus or ovaries because the male XY chromosomes produce AMH, but external female genitalia because androgens are needed for male genitalia development. Also, testosterone is needed for maturation of the Wolffian duct structures so male gonads are present intra-abdominally but without the epididymis.

49
Q

ACTH regulates which enzyme?

A

20,22-desmolase

50
Q

True or false: 21-hydroxylase deficiency presents with normal internal sex organs in an XX child.

A

True! XX females will lack SRY and thus lack testes and AMH and thus normal ovaries and uterus will develop.

51
Q

An elevated _____________ is diagnostic of CAH.

A

17-hydroxy progesterone

52
Q

Which two genes elevate AMH levels?

A

SF-1 and SOX9

53
Q

Which cells secrete AMH?

A

Sertoli cells

54
Q

At birth, what are normal stretched penile and clitoral lengths?

A

Penile: greater than 2.5 cm
Clitoris: less than 1.0 cm

55
Q

What is the overview timeline of sex development in the embryo

A

3 weeks: germ cells are in the yolk sac
6 weeks: germ cells migrate and invade the genital ridge, also expression of the SRY and differentiation of the testes begins
8 weeks: internal duct differentiation begins (leydig cells start producing testosterone), continues testicular and ovarian development
13 weeks: development of external genitalia is complete

56
Q

When can you test for fetal sex?

A

10 weeks: cffDNA

20 weeks: ultrasound

57
Q

What type of cells make up the primitive sex cords?

A

Epithelial cells

58
Q

What does FGF9 do?

A

It maintains SOX9 expression

59
Q

What is the function of DAX1?

A

A nuclear receptor that antagonizes SRY, NR5A1, and SOX9

60
Q

What is the function of WNT4?

A

Ovarian development and maintained education, regulation of Müllerian duct formation and ovarian steroidogenesis. Also does development of the kidney, adrenals, pituitary, mammary tissue.

61
Q

What is the function of RSPO1?

A

Suppression of Sox

So with loss of function mutation, can develop an overestimate in an XX individual

62
Q

What is the function of FOXL2?

A

Granulosa cell differentiation, follicle development, and maintenance during fetal life

63
Q

Describe the timeline of testicular descent

A

Reach the inguinal region by week 12

Reach the scrotum by week 33

64
Q

what is 17B-hydroxysteroid dehydrogenase deficiency?

A

mutations in 17B-hydroxysteroid dehydrogenase type 3 (expressed in the testes) which converts androstenedione to testosterone. Causes undervirilization of XY fetuses, female external genitalia, wolffian structures usually present with virilization at puberty becuase of extratesticular conversion to testosterone.

65
Q

StAR Protein deficiency

A

a muation in the StAR protein that helps transfer cholesterol from the outer to inner mitochondrial membrane allowing it to convert from cholesterol to pregnenolone. It is a congenital lipoid hyperplasia (accumulation of cholesterol esters in the adrenocortical tissue). These children will appear female and have salt wasting.

66
Q

17a hydroxylase deficiency

A

causes HTN due to buildup of deoxycorticosterone, hypokalemia, females fail to develop 2nd sex characteristics, males are undervirillized.

67
Q

3B-hydroxysteroid dehydrogenase deficiency

A

causes virilization in females, undervirilization in males, and salt wasting

68
Q

21 hydroxylase deficiency

A

causes buildup of 17-OH progesterone (screen for this on newborn screen), causes hyperkalemia, hyperpigmentation, hyponatremia, hypoglycemia, and hypotension
causes virilization of females because shunting through testosterone, no change outward in males.

69
Q

what causes false positive 21 hydroxylase deficiency tests?

A

stressed, premature, and low birthweight infants.

70
Q

how to treat 21 hydroxylase deficiency

A

replace deficient hormones (give glucocorticoids, mineralicorticoids,) and suppress ACTH overproduction

71
Q

11B hydroxylase deficiency

A

virilization similar to 21HD
no salt wasting because 11 deoxycorticosterone has mineralicorticoid activity
HTN

Life Cycle Exam 1 (26 decks)

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