ENDO-sex steroids/menstrual cycle/ fat

Question 1

What does the hypothalamic-pituitary-gonadal axis refer to?

Answer 1

Refers to all of the hormones that are released from the hypothalamus, pituitary and gonads (testes or ovaries)

Question 2

what are the main hormones involved in the hypo-pit-gonadal axis?

Answer 2

• > Testosterone
• > Oestrogen
• > Progesterone
• > Androgens (incl. –Testosterone)

Question 3

what are sex hormones?

Answer 3

These are only the steroid hormones released by the gonads (ovaries or testes), and their precursors (called androgens)

Question 4

what type of hormones are all androgens?

Answer 4

steroid hormones

Question 5

which part of the adrenal gland uses cholesterol to make androgens?

Answer 5

zona reticularis

Question 6

how is testosterone made in males?

Answer 6

Androgens used by Leydig cells (testes) to make testosterone (still classified as androgen)

Question 7

how are oestrogens made in females?

Answer 7

Androgens will undergo an aromatization reaction inside granulosa cells to make oestrogens, such as oestradiol

Question 8

are oestrogens classed as androgens?

Answer 8

no-modified a lot but still steroid hormone

Question 9

outline the intermediates in steroidogenesis converting cholesterol to androgens.

Answer 9

CHOLESTEROL—–>PREGNENOLONE—->PROGESTERONE/ TESTOSTERONE —->DIHYDROTESTOSTERONE/ OESTROGEN

Question 10

which enzyme converts testosterone to oestrogen and androstenedione to estrone?

Answer 10

aromatase

Question 11

what are the roles of LH in women?

Answer 11

• > Stimulates the release of androgen/testosterone by Theca Cells
• > A surge of this hormone on Day 14 of a female’s menstrual cycle will cause ovulation (release of an egg)

Question 12

what is the role of LH in males?

Answer 12

Stimulates testosterone production in the Leydig Cells

Question 13

what is the role of FSH in males?

Answer 13

Stimulates spermatogenesis in the Sertoli Cells

Question 14

what are the roles of FSH in females?

Answer 14

• > Stimulates oogenesis in the Granulosa Cells

- >Stimulates the conversion of androgen/testosterone —>oestrogen

Question 15

what is the role of androgens in males and females?

Answer 15

Released from the Zona Reticularis of the adrenal gland and will be used to make testosterone and oestrogens

Question 16

what are the roles of testosterone in females?

Answer 16

• > Tends to be used as a precursor to make oestrogens
• > small influence sexual characteristics
• > increases bone building.

Question 17

what are the roles of testosterone in males?

Answer 17

• > Primary sex hormone in males
• > Influences sexual characteristics
• > increases bone building ->Increases bone thickness
• > Increases basal metabolic rate

Question 18

what are the roles of oestrogen in males?

Answer 18

Has less influence in males but does influence sexual characteristics and decreases bone breakdown

Question 19

what are the roles of oestrogens in females?

Answer 19

• > Primary sex hormone in females
• > Influences sexual characteristics
• > decreases bone breakdown

Question 20

describe the hypothalamic-pituitary-testicular axis.

Answer 20

GnRH released from hypothalamus

—>ant. pit. releases LH from gonadotrophs—–>Leydig cells (testes) are stimulated by LH—>produce testosterone—>estrogens (aromatisation)

AND

–>ant. pit. releases FSH from gonadotrophs—->sertoli cells are stimulated by FSH—->spermatogenesis/ estrogens
(by aromaisation)

Question 21

how is the release of FSH/ LH inhibited in the hypo-pit-test axis?

Answer 21

Testes – Sertoli Cells

Release Inhibin B to stop the release of FSH and LH –>negative feedback loop

Question 22

describe the hypothalamic-pituitary-ovarian axis

Answer 22

GnRH released from hypothalamus

—>ant. pit. releases LH from gonadotrophs—->LH stimulates theca cells in ovaries to release testosterone—->estrogens (aromatisation)

AND

–>ant. pit. releases FSH from gonadotrophs—>FSH stimulates granulosa cells to release estrogens/ oogenesis (aromatisation)

Question 23

how is the release of FSH/ LH inhibited in the hypo-pit-ovarian axis?

Answer 23

Ovaries – Granulosa Cells

Release Inhibin B to stop the release of FSH and LH–> negative feedback loop

Question 24

what is aromatisation?

Answer 24

process by which enzyme aromatase takes different androgens (e.g. androstenedione, testosterone) and converts them into oestrogens (specifically, oestradiol)

Question 25

where does aromatisation tend to happen?

Answer 25

peripheral fat of the body

Question 26

is aromatisation more important in males or females?

Answer 26

females

Question 27

what is hypogonadism?

Answer 27

When male testes or female ovaries produce little or no sex hormones

Question 28

what can hypogonadism lead to?

Answer 28

Leads to underdevelopment of gonads due to lack of oestrogen and testosterone

Question 29

what is primary hypogonadism?

Answer 29

- >Due to defect at level of the gonad | - >Low levels of oestrogen/testosterone but high levels of LH and FSH

Question 30

what is secondary hypogonadism?

Answer 30

- >Due to defect at level of pituitary or hypothalamus | - >causes reduced Levels of FSH, LH or GnRH secretion as well as oestrogen/testosterone

Question 31

what is the ovarian cycle?

Answer 31

Ovarian cycle involves the growth of the ovum and follicle

Question 32

which days make up the follicular phase?

Answer 32

0-14

Question 33

which days make up the luteal phase?

Answer 33

14-28

Question 34

which 2 phases are in the ovarian cycle?

Answer 34

follicular | luteal

Question 35

is the follicular phase oestrogen or progesterone dominant?

Answer 35

oestrogen dominant

Question 36

which cells release oestrogen?

Answer 36

granulosa cells

Question 37

is the luteal phase oestrogen or progesterone dominant?

Answer 37

progesterone dominant

Question 38

which cells release progesterone?

Answer 38

corpus luteum

Question 39

which day does LH surge and what does this cause?

Answer 39

14 | causes ovulation

Question 40

what is the uterine cycle?

Answer 40

Uterine cycle involves breakdown and growth of the endometrial wall

Question 41

what are the 3 stages of the uterine cycle?

Answer 41

Menses --> Days 0-7 Proliferative Phase --> Days 7-14 Secretory Phase --> Days 14-28

Question 42

what is the role of progesterone?

Answer 42

hormone which encourages growth of the endometrium

Question 43

what is adipose tissue?

Answer 43

tissue dedicated to lipid storage --> safely stores fatty acids as triglyceride

Question 44

why do fatty acids need to be stored?

Answer 44

fatty acids are toxic when they’re circulating in the blood -->must be stored if they’re not being used

Question 45

what are the 2 types of adipose tissue?

Answer 45

- white | - brown

Question 46

what is the role of white adipose tissue?

Answer 46

-->lipid storage tissue -->has receptors for insulin, adrenaline and sex steroids --> these hormones can trigger lipolysis (breakdown) of white adipose tissue to generate energy

Question 47

what is the role of brown adipose tissue?

Answer 47

Generates body heat (higher in babies)

Question 48

what is the difference between fasting and post-prandial phase?

Answer 48

- Fasting --> triglyceride undergoes lipolysis (hydrolysis reaction) to FAs and glycerol (to produce ATP/provide energy) - Post-Prandial --> FAs and glycerol undergo lipogenesis (esterification) to form triglyceride (to store)

Question 49

Name the 4 adipose tissue regulators

Answer 49

- adiponectin - lepin - ghrelin - insulin

Question 50

where is adiponectin released from?

Answer 50

adipose tissue

Question 51

where does adiponectin bind to?

Answer 51

ADIPOR1-->Skeletal muscle, heart ADIPOR2-->Liver

Question 52

what is the function of adiponectin?

Answer 52

- enhances a cell’s response (sensitivity) to insulin/ makes it easier to uptake glucose - good marker for whether or not someone has developed insulin resistance (Diabetes)

Question 53

where is leptin released from?

Answer 53

adipose tissue

Question 54

where does leptin bind to?

Answer 54

hypothalamus

Question 55

what type of hormone is leptin?

Answer 55

anorexigenic hormone--->released after you eat high fat foods-tells you to stop eating

Question 56

how does leptin work?

Answer 56

- ->binds to leptin receptors in the hypothalamus to modulate activity of the thyroid gland and HPO axis to tell you to stop eating - ->uses up your existing fat storage (leptin keeps you thin!) (increases lipolysis)

Question 57

what happens if there is a mutation in the leptin gene?

Answer 57

hyperphagia (overeating)

Question 58

where is ghrelin released from?

Answer 58

stomach

Question 59

where does ghrelin bind to?

Answer 59

Hypothalamus | NPY and AgRP receptors

Question 60

what type of hormone is ghrelin?

Answer 60

orexigenic hormone | hunger hormone

Question 61

how does ghrelin work?

Answer 61

binds to NPY and AgRP receptors in the hypothalamus to stimulate you to eat, and to store any fat that you then eat in your meal (increases lipogenesis)

Question 62

where is insulin released from?

Answer 62

B cells of pancreas

Question 63

where does insulin bind to?

Answer 63

Hypothalamus (Arcuate Nucleus) [GLUT Receptors]

Question 64

what stimulates the release of insulin?

Answer 64

Glucagon-like Peptide 1 is released after eating-and stimulates insulin release

Question 65

what type of hormone is insulin?

Answer 65

anorexigenic hormone

Question 66

how does insulin work to regulate adipose tissue?

Answer 66

-binds to the Arcuate Nucleus in the hypothalamus and promotes storage of glucose

Question 67

what is the hypothalamic arcuate nucleus (ARC)?

Answer 67

an area of the hypothalamus that is key for regulation of appetite.

Question 68

which other nuclei in the hypothalamus does the ARC work with?

Answer 68

-->Ventromedial Nucleus = ‘Satiety Centre’ Stimulating it will decrease eating A lesion (disease) will result in overeating - ->Dorsomedial Nucleus - ->Paraventricular Nucleus

Question 69

which 2 peptide types does the ARC express?

Answer 69

-->Orexigenic- NPY and AgRP (ghrelin binds here) (encourages eating) -->Anorexigenic- POMC (α-MSH is released from here) (discourages eating)