Hypothalamic-pituitary-gonadal Axis I Flashcards

1
Q

What do we need to reproduce?

A

Correct sex determination and differentiation process
Sexual maturation
Production and storage of sufficient supply of eggs and sperm
Sexual intercourse
Fertilisation, implantation, embryonic and placental development

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2
Q

What are the hormones released from the hypothalamus?

A

All releasing hormones, gonadotropin releasing hormone (GnRH) and kisspeptin

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3
Q

What hormones are released from the pituitary?

A

Stimulating hormones, FSH, LH

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4
Q

What hormones are released from the gonads?

A

Oestradiol (E2), progesterone (P4) in females

Testosterone in females

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5
Q

What is the hypothalamic hypophyseal portal system?

A

Kisspeptin acts on the GnRH neurones to produce GnRH, which acts on the anterior pituitary to release FSH and LH into circulation

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6
Q

What are the neurones that produce kisspeptin?

A

Arcuate (ARC) nucleus and the anteroventral periventricular (AVPV) nucleus of the hypothalamus

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7
Q

Where does kisspeptin act?

A

Upstream of GnRH

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8
Q

How does kisspeptin start and what is it cleaved down into?

A

Preprokisspeptin

Kisspeptin-54 -> Kp-14, -13 or -10

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9
Q

What type of kisspeptin is favoured for in vivo clinical studies and why?

A

Kp-54

It’s the most efficient at crossing the blood-brain barrier

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10
Q

What type of kisspeptin is favoured for in vitro clinical studies and why?

A

Kp-10

Cheaper

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11
Q

Where is GnRH synthesised and secreted from?

A

GnRH neurons

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12
Q

What neurones control the pulsatile secretion of GnRH?

A

Arcuate (ARC) and medial preoptic (MPN) nucleus

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13
Q

What are the ARC and MPN nuclei collectively known as?

A

The parvocellular system

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14
Q

How often is GnRH secreted?

A

Every 30 - 120 mins

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15
Q

What type of pulse frequency favours FSH release?

A

Slow

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16
Q

What type of pulse frequency favours LH release?

A

Fast

17
Q

What does continuous GnRH cause?

A

Cessation of response

18
Q

What are the clinical uses of GnRH and their analogues?

A

Ovulation induction and IVF, prostate cancer, ovarian and endometrial cancers, breast cancer, endometriosis, PCOS and uterine fibroids

19
Q

What type of molecule are LH and FSH?

A

Heterodimer peptides

20
Q

What are the common and hormone specific subunits of LH and FSH?

A

Alpha subunits are common and beta subunits are hormone-specific

21
Q

What are required for the biological function of LH and FSH?

A

N-linked carbohydrate side chains

22
Q

Which hormone subunits are synthesised in excess and which are the limiting factor?

A

Alpha subunits are synthesised in excess and beta are limiting

23
Q

Do LH and FSH require pulsatility to function?

A

No but they do need it to be released

24
Q

What is the function of LH in males?

A

Stimulates leydig cells to synthesise androgens

25
Q

What is the function of LH in females?

A

Theca cell androgen synthesis
ovulation
progesterone production in the corpus luteum

26
Q

What is the function of FSH in males?

A

Regulation of the Sertoli cell metabolism

27
Q

What is the function of FSH in females?

A

Follicular maturation and granulosa cell oestrogen synthesis

28
Q

Where are leydig cells found and what do they do?

A

In the interstitial cells between the seminiferous tubules

Produce testosterone

29
Q

Where are Sertoli cells found and what do they do?

A

In the seminiferous tubules

Spermatogenesis

30
Q

Where are theca cells found and what do they do?

A

In the lining of the antral follicle

Produce androgens

31
Q

Where are granulosa cells found and what do they do?

A

Immediately surrounding the oocyte

Produce oestrogen

32
Q

Where is the corpus luteum found and what does it do?

A

Has both LHR and FSHR to produce progesterone and oestrogen in the Luteal phase

33
Q

What does +ve feedback of oestrogens trigger?

A

Ovulation

34
Q

What are some examples of oestrogens?

A

Oestradiol and oestrone

35
Q

When are oestrogens secreted?

A

Folliculogenesis

36
Q

What are androgens important in?

A

Spermatogenesis

37
Q

What are some examples of androgens?

A

Androstenedione
Testosterone
Dihydrotestosterone

38
Q

What does progesterone do?

A

Prepares the uterus for egg implantation and maintains conditions needed for the early stages of pregnancy