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Medical Physiology > Hypothalamic Pituitary Gonadal Axis and Sexual Differentiation > Flashcards

Hypothalamic Pituitary Gonadal Axis and Sexual Differentiation Flashcards

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USMLE® Step 1 flashcards
1
Q

function of estradiol/estrogen

A

growth, puberty, decreasing FSH and LH except just before ovulation when estradiol levels rise sharply and become positive feedback for LH

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2
Q

function of testosterone

A

growth, puberty, decrease FSH

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3
Q

function of progesterone

A

supports pregnancy

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4
Q

what does inhibin do

A

decrease FSH (specifically)

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5
Q

what does activin do

A

increase FSH (specifically)

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6
Q

what does anti mullerian hormone do?

A

sexual differentiation: absence of it makes female internal repro develop. (suppresses development of mullerian ducts and prevents female internal development in male)

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7
Q

what structure is conserved through 4 different hormones

A

alpha subunit identical in TSH, LH, FSH, and hCG

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8
Q

what is the 2nd messenger for TSH, LH, FSH, and hCG

A

cAMP

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9
Q

how is GnRH produced

A

as a pre-pro-GnRH, then native GnRH 10AA because in hypothalamic hypophyseal portal system

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10
Q

what is the female pattern of LH release

A

surge and tonic (surges for ovulation)

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11
Q

what is the male pattern of LH release

A

tonic (no ovulation)

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12
Q

what occurs during male brain development

A

testosterone crosses BBB and is aromatized to estrogen quickly. there is estrogenic effects in the male which causes the surge center to NOT develop

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13
Q

what occurs during the female brain development

A

during development, estrogens from placenta and ovary of developing fetus and mothers ovary release estradiol. is lipophilic and travels through the body. in the female, estradiol is bound to alpha-fetoprotein which prevents it from crossing BBB. no estradiol effect in the brain so the surge center develops.

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14
Q

regulation of testosterone

A

negative feedback only from testosterone to hypothalamus and pituitary

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15
Q

regulation of estrogen

A

mostly negative regulation to hypothalamus and pituitary except when about to ovulate

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16
Q

what does the dominant follicle display

A

LH and FSH receptors

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17
Q

what do other follicles display

A

only FSH receptors

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18
Q

what does testosterone and inhibin do?

A

inhibit GnRH, LH, and FSH

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19
Q

what does progesterone, estradiol and inhibin do

A

inhibit GnRH, LH, FSH

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20
Q

what does estradiol alone (increased concentration) do

A

stimulates GnRH, LH and FSH

initiates LH surge

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21
Q

what do luteal cells secrete during luteal phase

A

estrogen, progesterone to maintain pregnancy

“pro-gestation hormone”

22
Q

what does LH do

A

stimulates cholesterol desmolase to start cholesterol forming pregnenolone (eventually to estradiol and testosterone)

23
Q

what does FSH do in the female

A

stimulates aromatase to make estradiol from testosterone

24
Q

what is the primary circulating form of testosterone

A

dihydrotestosterone

25
Q

what does increase in GnRH at age 8 do

A

triggers release of FSH and LH from anterior pituitary which then triggers test and estradiol

26
Q

compare before and after puberty

A

hypothalamus and pituitary are sensitive to testosterone and estradiol. sensitivity decreases allowing high concentration of steroids to stimulate secondary sex characteristics

27
Q

effects of estradiol

A

continuation of folliculogenesis and secondary sex characteristics

28
Q

effects of testosterone

A

initiation of spermatogenesis and secondary sex characteristics

29
Q

what occurs during menopause

A

FSH is increased more than LH because no influence of estrogens or progesterones from corpus luteum

30
Q

what occurs during senescence in males

A

testosterone decreases but sperm capacity and production doesn’t change

31
Q

what do sertoli cells secrete

A

antimullerian hormone, inhibin, androgen binding protein

32
Q

what do leydig cells secrete

A

testosterone

33
Q

what does FSH stimulate

A

sertoli cells to produce inhibin to negatively feedback AP

34
Q

what does LH stimulate

A

leydig cells to make testosterone, direct negative feedback on hypothalamus and AP. acts paracrine on sertoli cells to make inhibin to negative feedback.

35
Q

male 2 cell two gonadotropin complex

A
  1. hypothalamus releases GnRH, stimulates AP to secrete LH and FSH.
  2. LH stimulates leydig cells to release testosterone.
  3. FSH stimulates sertoli cells to release androgen binding protein and inhibin.
  4. ABP binds to testosterone, keeping it at a high concentration.
  5. inhibin is released by sertoli cells, negative feedback to AP.
  6. testosterone negative feedback to hypo and pituitary.
36
Q

what does ABP do

A

causes conformational change in chemistry of testosterone, causes it to become less lipophilic, maintains increased concentration in testis

paracrine control of testosterone

37
Q

what receptors are on the thecal cells

A

LH

38
Q

what receptors are on granulosa cells

A

FSH preselection then LH (dominant follicle)

39
Q

female 2 cell 2 gonadotropin complex

A

theca interna responds to LH only–>cAMP–>PKA–>cholesterol to testosterone.

testosterone freely crosses to the granulosa cell.
FSH and LH bind to receptors and increase cAMP and PKA to make testosterone into estradiol. estradiol goes into bloodstream.

40
Q

describe thecal cells

A

responsive to LH, produce androstenedione (testosterone goes to granulosa cells)

41
Q

describe granulosa cells

A

avascular, preselection responds to FSH alone and produces some estradiol and inhibin.

after selection, responsive to FSH and LH, produces substantial estradiol

42
Q

what do luteal cells do during luteal phase

A

progesterone and estradiol send negative feedback to hypothalamus and AP (if not pregnant)

43
Q

what determines female differentiation

A

no Y chromosome, no SRY gene, no TDF protein, no AMH (internal), no testosterone (external) == girl

44
Q

what determines male differentiation

A

Y chromosome, SRY gene, TDF protein, AMH by sertoli cells, leydig cells making testosterone == boy

45
Q

what is directly responsible for growth of prostate and penis?

A

DHT

46
Q

when does sexual differentiation occur

A

6-10weeks

47
Q

male and female puberty difference

A

female puberty happens earlier than males

48
Q

hypergonadotropic hypogonadism

A

high FSH and LH, low sex steroids

49
Q

hypogonadotropic hypogonadism

A

low FSH and LH, low sex steroids

secondary is more common bc tumors, head trauma, drugs, disease, disorder

50
Q

hypogonadotropic hypergonadism

A

low FSH and LH, high sex steroids

gonad tumors, hyperplasia

51
Q

hypergonadotropic hypergonadism

A

high FSH and LH and sex steroids

precocious puberty, pituitary/gonad tumors?

Medical Physiology (21 decks)

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