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M2M Week3 > Sex Development > Flashcards

Sex Development Flashcards

1
Q

What does sex chromosome aneuploidy mean?

A

Refers to disorders where the affected person doesn’t have the normal number of X or Y chromosomes

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2
Q

What is the genotype of Turner Syndrome?

A

45; X (or 45; XO)

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3
Q

What are the signs at birth of Turner Syndrome?

A

Prenatal cystic hygroma; webbed neck; puffy hands & feet; heart defects like coarctation of the aorta

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4
Q

What are other signs of Turner Syndrome?

A

Short stature; normal intelligence; infertility due to non-functioning ovaries; hormone dysfunction; low set ears; broad chest. Occurs in 1/2500 newborn girls

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5
Q

What is the genotype of Kleinfelter Syndrome?

A

47; XXY

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6
Q

Typical Kleinfelter Syndrome presentation

A

Tall stature; small testes; infertility; hypospadias; gynecomastia; learning disabilities; delayed speech. Occurs in 1/500 - 1/1000 newborn boys

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7
Q

What is the genotype of boys with Jacobs Syndrome?

A

47; XYY

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8
Q

Typical Jacobs Syndrome presentation

A

Learning disabilities; speech/developmental delays; behavioral/emotional difficulties; Autism spectrum; tall stature. Occurs in 1/1000 newborn boys

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9
Q

Genotype of Triple X Syndrome

A

47; XXX

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10
Q

Typical presentation of Triple X Syndrome

A

May be tall; increased risk of learning disabilities; delayed speech/motor; seizures; kidney abnormalities. Occurs in 1/1000 newborn girls

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11
Q

What determines secondary sex characteristics?

A

Gonadal development

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12
Q

What happens in males in the 7th week of conception?

A

Differentiation of genital ridge

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13
Q

In males; what does the genital ridge differentiate into?

A

Sertoli cells and Leydig cells

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14
Q

In the 8th week; what do Leydig cells begin to produce?

A

Testosterone

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15
Q

In the 8th week; what do Sertoli cells begin to produce?

A

Anti-Mullerian Hormone (AMH)

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16
Q

In males; what do the primitive sex cords differentiate into? (in the 8th week)

A

Testis cords & rete testis (eventually become seminipherous tubules during puberty)

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17
Q

What prompts the body to begin developing female human reproductive organs around the 7th-8th week?

A

Absense of SRY & presence of 2X chromosomes

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18
Q

In females; what do the Primitive sex cords dissociate into?

A

Irregular clusters

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19
Q

What happens to the medullary (primitive) cords in females?

A

They cords regress and cortical (secondary) cords are formed

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20
Q

What is the destiny of the cortical cords in females?

A

Destined to become follicular cells of the ovary (Follicular cells will eventually surround an oogonium which together are the primary ovarian follicle).

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21
Q

What are the 2 pairs of genital ducts that are initially present in both males and females?

A

Mesonephric (Wolffian) ducts and Paramesonephric (Mullerian) ducts

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22
Q

Male structures are derived from which ducts?

A

Mesonephric (Wolffian) ducts

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23
Q

Which two genes are responsible for the body choosing the Mesonephric (Wolffian) ducts during development? Are these genes autosomal or sex-linked?

A

SRY gene (on the Y chromosome) & SOX9 gene (This is autosomal gene)

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24
Q

What is the function of SRY and SOX9 genes?

A

They are both transcription factors; responsible for production of Anti-Mullerian Horomone (AMH; aka Mullerian inhibitory Substance - MIS)

25
Q

What does AMH (aka MIS) do?

A

Causes regression of the paramesonephric duct

26
Q

What does the gene FGF9 (fibroblast growth factor 9) do?

A

A protein coding gene; produces a chemotactic factor that causes tubules from mesonephric duct to penetrate the gonadal ridge. This is essential for differentiation of the testis.

27
Q

What do the SF1/NR5A1 genes do?

A

Stimulates differentiation of the Sertoli & Leydic cells

28
Q

Under the influence of testosterone; what do the mesonephric ducts elongate to form?

A

Epidymis; Seminal Vesicles; Vas Deferens

29
Q

What does the WNT4 protein do in relation to the Paramesonephric (Mullerian) Ducts?

A

Extracellular signaling factor responsible for differentiation of the ovary

30
Q

What inhibits WNT4 protein?

A

SOX9

31
Q

What does the DHH gene do in female development?

A

Produces a nuclear hormone receptor.

32
Q

What up-regulated DHH gene? What does it downregulate?

A

Up-regulated by WNT4; Downregulates SOX9

33
Q

What does the RSPO1 gene do?

A

It is a Coactivator of the WNT pathway

34
Q

Under the influence of ESTROGEN (from maternal and placental sources); what structures are formed from the Paramesonephric (Mullerian) Ducts?

A

uterus; cervix; broad ligament; fallopian tubes; upper 1/3 of the vagina

35
Q

Where do both sets of external genitalia orginate?

A

Urogenital sinus

36
Q

What causes male external structures to develop from urogenital sinus?

A

Androgen (dihydrotestosterone) exposure from the testis

37
Q

What influence does androgen exposure have on the external genitalia?

A

Prompts development of penis; scrotum; and the location of the urethral opening at the tip of the penis

38
Q

What causes female external genitalia to develop from the urogenital sinus?

A

Estrogen exposure from maternal and placental sources (aka lack of androgen production)

39
Q

What influence does estrogen exposure have on the external genitalia?

A

Prompts development of clitoris; labia majora and minora; and lower 2/3 of vagina

40
Q

What is the overall pathway of sex development? What determines gonads/2ndary sexual characteristics/external genitalia?

A

Chromosomes determine gonad development; gonads determine external genitalia & secondary sexual characteristics

41
Q

What is the name/rankings for sexual differntiation?

A

Prader scale - rated between ‘no virilization’ to stage 5 (fully male)

42
Q

If a baby is born with ambiguous genitalia; which 5 things should the clinician do on the 1st day of life?

A

1 - obtain FISH studies for Sex Chromosomes & a karyotype or chromosomal microarray 2 - Order hormone studies (LH; FSH; Testosterone; Dihydrotestosterone; +/- AMH) 3 - Consider ultrasound study (check for gonads/uterus) 4 - Surgical consult with urology 5 - Consider consult with specialized team; if available (endocrinology; genetics; urology; psychology)

43
Q

What do you consider if the baby is 46; XY DSD BUT testosterone and dihydrotestosterone are normal or elevated?

A

Androgen Insensitivity Syndrome (AIS) or 5-alpha reductase deficiency

44
Q

What do you consider if the baby is 46; XY DSD and testosterone and dihydrotestosterone are low?

A

WT1 associated diseases (Frasier Syndrome or Denys-Drash); SRY mutations or deletions; DHH mutations; RSP01 mutations

45
Q

What do you consider if the baby is 46; XX DSD and testosterone and dihydrotestosterone are low?

A

Congenital Adrenal Hyperplasia; Ectopic SRY; WNT4 mutations; SOX3 duplications; RSPO1 mutations; MALMD mutations

46
Q

Is the gene responsible for AIS X-linked or Y-linked?

A

X-linked; AR gene

47
Q

What does mutation in AIS cause? What is the phenotype range?

A

Even though the body makes androgens (testosterone); it doesn’t necessarily recognize or respond to it. Phenotypes range from mild under-virilization (Partial AIS) to full sex reversal (Complete AIS)

48
Q

What does mutation in 5-Alpha Reductase Deficiency cause? What is the phenotype range?

A

Mutation causes decreased ability of the body to convert testosterone to dihydrotestosterone. Phenotype shows undervirilized male with increased virilization at the time of puberty

49
Q

Are disorders associated with the SRY gene X-linked or Y-linked?

A

Y-linked

50
Q

What does deletion or absense of the SRY gene cause?

A

Full 46; XY sex reversal and a phenotypically normal female

51
Q

What does the ectopic presence of the SRY gene in a 46; XX individual result in?

A

Phenotypically normal male

52
Q

What do mutations in the SRY gene in a 46; XY individual results in?

A

Decreased or absent production of Anti Mullerian hormone & under virilization of a male

53
Q

What does the WT1 gene do?

A

transcription factor for SRY gene

54
Q

What causes Denys-Drash & Frasier Syndromes?

A

Mutations in the WT1 gene

55
Q

What are the sexual effects of Denys-Drash & Frasier Syndrome?

A

Sex reversal with 46; XY

56
Q

What are the other health effects with Denys-Drash & Frasier Syndromes?

A

Both cause different types of chronic kidney disease (diffuse mesangial sclerosis; focal segmental glomerulosclerosis). Increased risk for Wilms Tumor

57
Q

What are the effects of Congenital Adrenal Hyperplasia?

A

Ambiguous genitalia in 46; XX

58
Q

What causes Congenital Adrenal Hyperplasia?

A

21-hydroxylase deficiency (usually)

59
Q

What else complicates CAH?

A

salt wasting in the first few weeks of life and with times of metabolic stress (Decreased sodium and chloride; Increased potassium)

M2M Week3 (5 decks)

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