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Medicine yr1 > ENDO-sex steroids/menstrual cycle/ fat > Flashcards

ENDO-sex steroids/menstrual cycle/ fat Flashcards

1
Q

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

A

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

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2
Q

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

A
  • > Testosterone
  • > Oestrogen
  • > Progesterone
  • > Androgens (incl. –Testosterone)
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3
Q

what are sex hormones?

A

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

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4
Q

what type of hormones are all androgens?

A

steroid hormones

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5
Q

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

A

zona reticularis

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6
Q

how is testosterone made in males?

A

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

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7
Q

how are oestrogens made in females?

A

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

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8
Q

are oestrogens classed as androgens?

A

no-modified a lot but still steroid hormone

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9
Q

outline the intermediates in steroidogenesis converting cholesterol to androgens.

A

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

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10
Q

which enzyme converts testosterone to oestrogen and androstenedione to estrone?

A

aromatase

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11
Q

what are the roles of LH in women?

A
  • > 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)
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12
Q

what is the role of LH in males?

A

Stimulates testosterone production in the Leydig Cells

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13
Q

what is the role of FSH in males?

A

Stimulates spermatogenesis in the Sertoli Cells

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14
Q

what are the roles of FSH in females?

A
  • > Stimulates oogenesis in the Granulosa Cells

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

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15
Q

what is the role of androgens in males and females?

A

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

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16
Q

what are the roles of testosterone in females?

A
  • > Tends to be used as a precursor to make oestrogens
  • > small influence sexual characteristics
  • > increases bone building.
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17
Q

what are the roles of testosterone in males?

A
  • > Primary sex hormone in males
  • > Influences sexual characteristics
  • > increases bone building ->Increases bone thickness
  • > Increases basal metabolic rate
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18
Q

what are the roles of oestrogen in males?

A

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

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19
Q

what are the roles of oestrogens in females?

A
  • > Primary sex hormone in females
  • > Influences sexual characteristics
  • > decreases bone breakdown
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20
Q

describe the hypothalamic-pituitary-testicular axis.

A

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)

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21
Q

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

A

Testes – Sertoli Cells

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

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22
Q

describe the hypothalamic-pituitary-ovarian axis

A

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)

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23
Q

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

A

Ovaries – Granulosa Cells

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

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24
Q

what is aromatisation?

A

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

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25
Q

where does aromatisation tend to happen?

A

peripheral fat of the body

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26
Q

is aromatisation more important in males or females?

A

females

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27
Q

what is hypogonadism?

A

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

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28
Q

what can hypogonadism lead to?

A

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

29
Q

what is primary hypogonadism?

A
  • > Due to defect at level of the gonad

- >Low levels of oestrogen/testosterone but high levels of LH and FSH

30
Q

what is secondary hypogonadism?

A
  • > Due to defect at level of pituitary or hypothalamus

- >causes reduced Levels of FSH, LH or GnRH secretion as well as oestrogen/testosterone

31
Q

what is the ovarian cycle?

A

Ovarian cycle involves the growth of the ovum and follicle

32
Q

which days make up the follicular phase?

A

0-14

33
Q

which days make up the luteal phase?

A

14-28

34
Q

which 2 phases are in the ovarian cycle?

A

follicular

luteal

35
Q

is the follicular phase oestrogen or progesterone dominant?

A

oestrogen dominant

36
Q

which cells release oestrogen?

A

granulosa cells

37
Q

is the luteal phase oestrogen or progesterone dominant?

A

progesterone dominant

38
Q

which cells release progesterone?

A

corpus luteum

39
Q

which day does LH surge and what does this cause?

A

14

causes ovulation

40
Q

what is the uterine cycle?

A

Uterine cycle involves breakdown and growth of the endometrial wall

41
Q

what are the 3 stages of the uterine cycle?

A

Menses –> Days 0-7

Proliferative Phase –> Days 7-14

Secretory Phase –> Days 14-28

42
Q

what is the role of progesterone?

A

hormone which encourages growth of the endometrium

43
Q

what is adipose tissue?

A

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

44
Q

why do fatty acids need to be stored?

A

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

45
Q

what are the 2 types of adipose tissue?

A
  • white

- brown

46
Q

what is the role of white adipose tissue?

A

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

47
Q

what is the role of brown adipose tissue?

A

Generates body heat (higher in babies)

48
Q

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

A
  • 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)
49
Q

Name the 4 adipose tissue regulators

A
  • adiponectin
  • lepin
  • ghrelin
  • insulin
50
Q

where is adiponectin released from?

A

adipose tissue

51
Q

where does adiponectin bind to?

A

ADIPOR1–>Skeletal muscle, heart

ADIPOR2–>Liver

52
Q

what is the function of adiponectin?

A
  • 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)
53
Q

where is leptin released from?

A

adipose tissue

54
Q

where does leptin bind to?

A

hypothalamus

55
Q

what type of hormone is leptin?

A

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

56
Q

how does leptin work?

A
  • ->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)
57
Q

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

A

hyperphagia (overeating)

58
Q

where is ghrelin released from?

A

stomach

59
Q

where does ghrelin bind to?

A

Hypothalamus

NPY and AgRP receptors

60
Q

what type of hormone is ghrelin?

A

orexigenic hormone

hunger hormone

61
Q

how does ghrelin work?

A

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)

62
Q

where is insulin released from?

A

B cells of pancreas

63
Q

where does insulin bind to?

A

Hypothalamus (Arcuate Nucleus)

[GLUT Receptors]

64
Q

what stimulates the release of insulin?

A

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

65
Q

what type of hormone is insulin?

A

anorexigenic hormone

66
Q

how does insulin work to regulate adipose tissue?

A

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

67
Q

what is the hypothalamic arcuate nucleus (ARC)?

A

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

68
Q

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

A

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

  • ->Dorsomedial Nucleus
  • ->Paraventricular Nucleus
69
Q

which 2 peptide types does the ARC express?

A

–>Orexigenic- NPY and AgRP (ghrelin binds here) (encourages eating)

–>Anorexigenic- POMC (α-MSH is released from here) (discourages eating)

Medicine yr1 (55 decks)

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