Hypothalamic-pituitary-gonadal Axis I

Question 1

What do we need to reproduce?

Answer 1

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

Question 2

What are the hormones released from the hypothalamus?

Answer 2

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

Question 3

What hormones are released from the pituitary?

Answer 3

Stimulating hormones, FSH, LH

Question 4

What hormones are released from the gonads?

Answer 4

Oestradiol (E2), progesterone (P4) in females

Testosterone in females

Question 5

What is the hypothalamic hypophyseal portal system?

Answer 5

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

Question 6

What are the neurones that produce kisspeptin?

Answer 6

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

Question 7

Where does kisspeptin act?

Answer 7

Upstream of GnRH

Question 8

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

Answer 8

Preprokisspeptin

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

Question 9

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

Answer 9

Kp-54

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

Question 10

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

Answer 10

Kp-10

Cheaper

Question 11

Where is GnRH synthesised and secreted from?

Answer 11

GnRH neurons

Question 12

What neurones control the pulsatile secretion of GnRH?

Answer 12

Arcuate (ARC) and medial preoptic (MPN) nucleus

Question 13

What are the ARC and MPN nuclei collectively known as?

Answer 13

The parvocellular system

Question 14

How often is GnRH secreted?

Answer 14

Every 30 - 120 mins

Question 15

What type of pulse frequency favours FSH release?

Answer 15

Slow

Question 16

What type of pulse frequency favours LH release?

Answer 16

Fast

Question 17

What does continuous GnRH cause?

Answer 17

Cessation of response

Question 18

What are the clinical uses of GnRH and their analogues?

Answer 18

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

Question 19

What type of molecule are LH and FSH?

Answer 19

Heterodimer peptides

Question 20

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

Answer 20

Alpha subunits are common and beta subunits are hormone-specific

Question 21

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

Answer 21

N-linked carbohydrate side chains

Question 22

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

Answer 22

Alpha subunits are synthesised in excess and beta are limiting

Question 23

Do LH and FSH require pulsatility to function?

Answer 23

No but they do need it to be released

Question 24

What is the function of LH in males?

Answer 24

Stimulates leydig cells to synthesise androgens

Question 25

What is the function of LH in females?

Answer 25

Theca cell androgen synthesis ovulation progesterone production in the corpus luteum

Question 26

What is the function of FSH in males?

Answer 26

Regulation of the Sertoli cell metabolism

Question 27

What is the function of FSH in females?

Answer 27

Follicular maturation and granulosa cell oestrogen synthesis

Question 28

Where are leydig cells found and what do they do?

Answer 28

In the interstitial cells between the seminiferous tubules | Produce testosterone

Question 29

Where are Sertoli cells found and what do they do?

Answer 29

In the seminiferous tubules | Spermatogenesis

Question 30

Where are theca cells found and what do they do?

Answer 30

In the lining of the antral follicle | Produce androgens

Question 31

Where are granulosa cells found and what do they do?

Answer 31

Immediately surrounding the oocyte | Produce oestrogen

Question 32

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

Answer 32

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

Question 33

What does +ve feedback of oestrogens trigger?

Answer 33

Ovulation

Question 34

What are some examples of oestrogens?

Answer 34

Oestradiol and oestrone

Question 35

When are oestrogens secreted?

Answer 35

Folliculogenesis

Question 36

What are androgens important in?

Answer 36

Spermatogenesis

Question 37

What are some examples of androgens?

Answer 37

Androstenedione Testosterone Dihydrotestosterone

Question 38

What does progesterone do?

Answer 38

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