12. Biochemistry of the Main Gonadal Hormones

Question 1

What are the main gonadal hormones in females?

Answer 1

Oestrogen and progesterone

Question 2

What are the main gonadal hormones in males?

Answer 2

Testosterone and DHT

Question 3

Which axis is involved in the control of female gonadal hormones?

Answer 3

Hypothalamic-Pituitary-Gonado Axis

Question 4

What type of hormone is GnRH?

Answer 4

Peptide

Question 5

Where is GnRH released from?

Answer 5

Hypothalamus

Question 6

What is the function of FSH?

Answer 6

Stimulates follicular development in females

Spermatogenesis in sertol cells in males

Question 7

What is the function of LH?

Answer 7

Maintain structure and secretory function of corpus luteum in females
Secretion of testosterone in males

Question 8

What are the functions of progesterone?

Answer 8

Converts endometrium to the secretory stage

Prepares uterus for implantation

Question 9

What is the function of inhibin?

Answer 9

Inhibits secretion of FSH

Question 10

Where is inhibin secreted from?

Answer 10

Granulosa cells in ovary

Question 11

What are the events of day 1-5 of the menstrual cycle?

Answer 11

Menses: shedding of the endometrium

Question 12

What are the events of day 5-13 of the menstrual cycle?

Answer 12

follicular phase
Ovum maturation
Endometrium proliferates
Oestrogen levels gradually rise

Question 13

What are the events of day 14 of the menstrual cycle?

Answer 13

Ovulation

Question 14

What are the events of day 15-28 of the menstrual cycle?

Answer 14

Luteal phase
Increased progesterone
Decreased gonadotropins
If no fertilisation occurs, progesterone is no longer secreted and menses occured
If fertilisation does occur then the corpus luteum continues to secrete progesterone

Question 15

What are the 3 primary roles of oestrogen?

Answer 15

Secondary sex characteristics
Control reproductive cycle
Stimulates linear bone growth

Question 16

What are the female secondary sex characteristics?

Answer 16

Enlargement of the breasts
Body hair
Thigh muscles behind femur
Widening of hips
Increased oil and sweat glands
Change in distribution of fat

Question 17

Where is oestrogen made?

Answer 17

Ovaries, testes, adrenal cortex

Question 18

What are the other actions of oestrogen?

Answer 18

1. Fertility control (follicle development, timing of follicular phase
2. Preparation of the uterus for implantation (proliferation and vascularisation of endometrial cells and induction of progesterone receptors)
3. Inhibit FSH release
4. Retention of Na+ and water
5. Increases HDL and decreases LDL
6. Increased coagulability of blood
7. Maintains bone density and elasticity of skin and blood vessels

Question 19

What are the 3 forms of oestrogen?

Answer 19

Estrone (menopause)
Estradiol
Estriol (pregnancy)

Question 20

Which adrenal cortex hormone is a major source of androgenic activity in females?

Answer 20

Androstenedione

Question 21

What are the functions of aromatase?

Answer 21

Converts testosterone to estradiol in the ovary

Converts androstenedione to estrone in peripheral adipose

Question 22

Where is progesterone secreted from?

Answer 22

Corpus luteum, placenta, testes, adrenal cortex

Question 23

What are the effects of progesterone?

Answer 23

Maturation of the endometrium

Supports gestation and embryogenesis

Question 24

Where are glycoproteins produced?

Answer 24

Anterior pituitary, chorion, placenta

Question 25

What type of hormones are gonadotropins?

Answer 25

Glycoproteins | Have a shared alpha subunit and a different beta one

Question 26

What controls the release of gonadotropins?

Answer 26

GnRH is secreted in a pulsatile manner from the hypothalamus

Question 27

What do low frequency pulses of GnRH from the hypothalamus result in?

Answer 27

Release of FSH

Question 28

What do high frequency pulses of GnRH from the hypothalamus result in?

Answer 28

Release of LH

Question 29

What converts testosterone to DHT?

Answer 29

5a-reductase

Question 30

What are the male secondary sex characteristics?

Answer 30

``` Hair Thigh muscle in front of femur Enlargement of larynx and deepening of voice Increase in stature Heavier skull and bone structure Increased muscle mass and strength Broadening of shoulders and chest Increased secretion of oil and sweat glands Higher waist-to-hip ratio than females ```

Question 31

What happens in a 5a-reductase deficiency?

Answer 31

Testosterone is not converted to DHT Boys are born with ambiguous external genitalia Full virilization occurs at puberty ('penis at 12' syndrome)