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Phys Exam Focus Areas > Gonadotropins and Repro Hormones > Flashcards

Gonadotropins and Repro Hormones Flashcards

1
Q

Role of FSH in female reproductive cycles.

A
  • Follicular development
  • In combination w/ LH = secretion of oestrogen
  • Stimulates granulosa cells to convert androgens to oestrogens
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2
Q

Role of FSH in male reproductive cycles.

A

Stimulates sustentactuar cells (sertoli cells) in seminiferous tubules = spermatogenisis.

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3
Q

Role of LH in female reproductive cycles.

A

Induces ovulation

Promotes oestrogen and progesterone secretion

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4
Q

Role of LH in male reproductive cycles.

A

Stimulates the productions of androgens (testosterone) in the interstitial (Leydig’s Cells).

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5
Q

Compare and contrast GnRH release in males and females.

A

Males: GnRH secretion occurs in 60-90min pulses

Affects secretion of FSH, LH and testosterone.

Pulses Remain steady throughout life.

Female: GnRH regulates reproductive function

Pulse frequence and amplitude varies across ovarian cycle.

Affects LH and FSH

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6
Q

What mechanisms control the release of gonadotropins from the pituitary gland?

A

Males:

  • Testosterone inhibits GnRH secretion.
  • Under FSH stimulation, sertoli cells produce inhibin which potentially has an inhibitory effect on GnRH secretion.

Females:

  • GnRH pulse frequency controlled by oestrogen (stimulation) and progesterone (inhibiton)
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7
Q

What hormonal mechnisms control testicular growth and function?

A

Testosterone, the hormone responsible for the secondary sexual characteristics that develop in the male during adolescence, stimulates spermatogenesis, or the process of sperm production in the testes.

Sertoli cells support the differentiation and physical maturation of spermatozoa. Under FSH Stimulation, secretes inihibin = inhibits FSH. Secretes Androgen binding protein

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8
Q

How is testosterone formed and what is its role in the male.

A

Synthesized from cholesterol or acetyl-CoA by Leydig cells which are stimulated by LH from ant.pit.

Cholesterol -> DHEA -> Androsternedione -> Testosterone

Testosterone promotes the production of functional sperm, maintains secretory glands, and determines main secondary sexual charcteristics.

Affects metabolic reactions around the body- stimulates muscle growth, produces aggressive behavorial responses.

Circulates blood bound to Gonadal Binding Protein (GBP)

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9
Q

How long is the uterine cycle?

A

24-35 days

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10
Q

Describe the Menstrual Phase of the Uterine Cycle:

A
  • Periodic discharge of blood, tissue fluid, mucous and epithelial cells of the stratum functionalis.
  • Caused by sudden reduction of Oes. + Prog. (decrease due to degradation of corpus luteum.)
  • Decreased Oes. + Prog. stimulates release of prostaglandins= vasocontriction of endomtrial blood vessels.
  • New Stratum functionalis formed from underlying stratum basalis.
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11
Q

Describe the Proliferative phase of the uterine cycle:

A
  • After 5-8 Days.
  • Newly-developed follicles, under influence of FSH and LH, secrete sufficient amount of Oes. + Prog.
  • Oes. stimulates repair and growth of new endometrium,
  • Phase lasts from end of menses -> ovulation.
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12
Q

Describe the Secretory Phase of the Uterine Cycle:

A
  • Following ovulation, corpus luteum is formed (CL) = increased Oes. + Prog.
  • Prog. prepares endometrium to recieve fertilised ovum
  • Uterine changes:
  1. Vascularisation of superficial layer of endometrium.
  2. Thickening of endometrium
  3. Glycogen storage by epithelial cells
  4. increase in amount of tissue fluid
  5. increased secretory activity by endometrial glands.
  • If fertilisation doesnt occur, CL degenerates = Oes. + prog. decline
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13
Q

Role of LH and FSH during Follicular phase:

A
  • 6-13 days
  • Initially, FSH is predominant, LH increases closer to ovulation.
  • High FSH = one follicle attains maturity
  • Oes. repairs endometrium
  • LH->Thecal cells -> Cholesterol to Androgen
  • FSH->Granulosa cels -> Androgen -> Oestrogen
  • FSH and LH inhibited by low levels of oes. from developing follicle + inhibin.
    • Inhibin targets Ant.pit., Oes targets Hypothalamus and Ant.Pit.
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14
Q

Describe the roles of LH and FSH during ovulation.

A
  • High Oes. levels = Pos. feedback -> HypoT + Ant.Pit = Increased GnRH and LH.
  • Inhibin (from granulosa cells) = Neg. Feedback -> Inhibits FSH.
  • As Oestrogen Inceases, so does LH w/out drastic increases in FSH
  • LH surge = Graafian follicle rupturing = ovulation
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15
Q

LH and FSH during Post-ovulatory phase.

A
  • High LH = development of corpus luteum (CL)
  • Graafian follicle collapses -> clot -> corpus haemorrhagicum -> reabsorbed.
  • During Days 15-28
  • FSH and LH still ‘switched off’ by high oes.
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16
Q

LH and FSH during Early to mid-luteal phase

A
  • CL secretes Oes. and Prog. = Inhibits LH + FSH
  • Progesterone is functionally dominant.
17
Q

FSH and LH during late luteal phase

A

If fertilisation and implantation do not occur:

  • CL degenrates = corpus albicans
  • Therefore Prog. + Oes. levels decline
  • Therefore increases GnRH pulses -> starts to increase FSH+LH = new cycle
18
Q

Describe role of Oestrogen during Follicular stage

A

Early Follicular:

Low Oes. = Prostaglandin release= endometrial vasoconstriction.

Oes. increases slightly due to secretion from follicular cells = pos feedback to granulosa cells and neg feedback to LH and FSH.

Mid-Late Follicular: Neg feedback to GnRH changes to pos feedback inducing LH surge. Oes increases to its peak prior to ovulation.

19
Q

Role of oestrogen in early-mid luteal phase

A

Oes + Prog= pos feedback on LH + FSH switches to negative feedback (CL)

20
Q

Role of Oestrogen in late luteal phase

A

Levels decrease due to degeneration of CL = Decrease Oes + prog

21
Q

Describe Oestrogen synthesis in Ovary

A
  1. LH stimulates Thecal Cells
  2. Thecal cells convert Cholesterol -> Androstenedione
  3. Androgen diffuses into granulosa cells
  4. FSH stimulates granulosa cells to convert Androstenedione -> estradiol (enzyme used = aromatase
  5. Part of oestrogen secreted into blood
  6. Part remains and contributes to antral formation
  7. Local Oestrogen + FSH stimulates proliferation of granulosa cells
22
Q

3 Significant Oestrogens:

A

Beta-Oestradiol

Oestrone

Oestriol

23
Q

Oestrogen 3 main functions:

A

Development and maintanence of female reproductive structures: endometrial lining of the uterus, secondary sexual characteristics & breasts.

Controls fluid and electrolyte balance

Inceases protein anabolism (synergistic effect with GH)

24
Q

Describe role of Corpus Luteum

A

CL secretes Oes + Prog to inhibit release of LH and FSH in late Luteal phase.

If fertilisation and impantation do occur:

  • For 8-10 weeks CL continue to secrete Oes + Prog until role is taken over by placenta.
25
Q

Role of Progesterone

A
  • Prepares uterus for arrival of developing embryo
  • Accelerates movement of oocyte or embryo along uterine tube
  • Works w/ other hormones to enlarge mammary glands.
  • High levels of Prog also inhibit GnRH secretion.
26
Q

Endocrine functions of Placenta

A

Secretes Prog and Oes and glycoprotein hormones

After 7 weeks, produces enough prog. to maintain pregnancy

After CL regresses, (10-12wks) placenta become major sex-steroid producing hormone. Also produces large amounts of hCG, hCD, GH, TSH, ACTH

27
Q

hCG=

A

human Chorionic Gonadotropin

Rescues CL for first 6-8wks of pregnancy

continues secretion throughout pregnancy but role is unknown

28
Q

hCS=

A

human Chorionic Somatomammotropin (aka huan placental lactogen)

Secreted in large amounts by the placenta

100x conc other hormones released, constantly increases

strong prolactin-like activity (big boobies)

“Diabetic affect”= stimulates lipolysis + Increase [FA]. Decreases maternal utilisation of glucose and increases [blood glucose]

29
Q

Role of Oestrogen and Progestrone during pregnanacy

A

Oestrogen promotes uterine blood flow which ensures survival of foetus

warm and fluffy

Progesterone inhibits contractions

End of gestation, oestrogens >progesterone therefore, labour.

30
Q

Why is the placent an ‘incomplete’ endocrine organ?

A

Requires precursors to produce oestrogen and progesterone.

For progesterone, cholesterol is required from mother. Once formed, its passes to steroid-producing tissues in the foetus and is convrted to other androgens and oestrogen

31
Q

Hormones of labour

A

Oxytocin = contraction, protects against haemorrhaging (acts as tourniquet)

Relaxin = relaxation of symphysis pubis and dilation of cervix.

Phys Exam Focus Areas (17 decks)

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