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Science of Repro > HPG Axis > Flashcards

HPG Axis Flashcards

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1
Q

HPG Axis diagram

A
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2
Q

Hypothalamus to Pituitary
structures

A
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3
Q

General Kisspeptin (KISS1/Kiss1) role

what was it also known as?

A

metastin

role: gatekeeper of puberty

Controls synthesis and secretion of GnRH in GnRH neurons

Upstream of GnRH

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4
Q

GNRH neurones are expressed in which two regions?

A
  • Arcuate Nucleus
  • Medial preoptic nucleus
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5
Q

GNRH that is synthesised and secreted move through the what?
to get to the anterior pituitary

A

The hypophyseal portal system

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6
Q

Where is Kisspeptin expressed?

Two spots in something*

A

In the hypothalamus:
- Arcuate Nucleus (ARC)
- Anterventral Periventricular Nucleus (AVPV)

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7
Q

Kisspeptin receptor (GPR54/KISS1R)

Where is it expressed?

A

Expressed on GnRH neurons.

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8
Q

Inactivating mutations of KISS1R and Kisspeptin = ?

A

failure to undergo spontaneous puberty.

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9
Q

Activating KISS1R mutations = ?

A

Can lead to precocious puberty

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10
Q

Kisspepetin neurons and GnRH neurons diagram interaction

A

Kisspeptin neurons send projections to GnRH neurons, and binding to KISS1R expressed on GnRH neurons.

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11
Q

A bolus of Kisspeptin correlates with a…

A

peak of LH secretion

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12
Q

GnRH is secreted in pulses from hypothalamus every…

A

30-120min

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13
Q

Slow frequency GnRH pulse favours..

A

FSHb transcription and FSH release,

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14
Q

Rapid GnrH pulse frequency favours..

A

LHb transcription and LH release

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15
Q

Continuous pulsatile release results in..

A

cessation of response

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16
Q

What is generating the GnRH pulse ?

A

A sub-population of Arcuate Nucleus Kisspeptin Neurons (ARNKISS)

Studies showed:
ARNKISS were all found to exhibit intermittent periods of synchronized electrical activity which had a near perfect correlation with pulsatile LH secretion.

Inhibition of ARNKISS in the mid-caudal region of the arcuate nucleus suppressed pulsatile LH secretion

17
Q

Gonadotrophin hormones: LH, FSH (and hCG)

Features and structure as themselves

A
  • Glycoprotein hormones
  • Heterodimeric
  • Pulsatile (due to B units)
18
Q

Follicle-stimulating hormone (via FSHR) function:

Testis?

A

Regulation of Sertoli cell metabolism

19
Q

Follicle-stimulating hormone (via FSHR) function:

Testis?

A

Regulation of Sertoli cell metabolism

20
Q

Follicle-stimulating hormone (via FSHR) function:

Ovary?

A
  • follicular maturation
  • granulosa cell estrogen synthesis
21
Q

Luteinising-stimulating hormone (via LHR) function:

Testis?

A

Stimulation of Leydig cell androgen synthesis

22
Q

Luteinising-stimulating hormone (via LHR) function:

Ovary?

A
  • theca cell androgen synthesis
  • ovulation
  • progesterone production of corpus luteum
23
Q

General function of gonadotrophins

A

Supports germ cell growth, development and maturation

to produce..

oocyte and sperm, competent for fertilisation

24
Q

Leydig cells?

LHR or FSH expression and why is this then crucial?

A

LHR expression
->
Androstenedione, DHEA, Testosterone production

25
Q

Sertoli cells?

LHR or FSH expression and why is this then crucial?

A

FSHR expression
->
Sertoli cell metabolism (important for spematogenesis)
+ Testosterone –> dihydrotestosterone

26
Q

Theca cells?
LHR or FSH expression and why is this then crucial?

A

LHR expression
—>
Testosterone and Androstenedione

27
Q

Granulosa cells?
LHR or FSH expression and why is this then crucial?

A

FSHR expression –> through aromatase takes Testosterone and Androstenedione and forms Oestradiol and Oestrone

28
Q

Corpus luteum?
LHR or FSH expression and why is this then crucial?

A

LHR (and FSHR) expression
—>
Progesterone (and oestrogens)

29
Q

Inhibin

Features and structure as themselves

A

Peptide hormones

Heterodimers

2 isoforms of inhibin: A and B.

30
Q

Inhibin role

A

inhibits FSH secretion via direct negative feedback to anterior pituitary

31
Q

In males which inhibin is invovled?

A

Inhibin B

32
Q

In females which inhibin is invovled?

A

Inhibin expression is cyclical depending on the phase of the menstrual cycle.

Can switch from inhibin B in the follicular phase to Inhibin A in the luteal phase.

33
Q

Summary of HPG axis in depth

A

Science of Repro (15 decks)

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