Flashcards in Hypothalamic - Pituitary - Gonadal Axis II Deck (51)
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1

What is puberty the transition from and to?

β†’ Non reproductive to reproductive state

2

What are the 4 main things that happen during puberty?

β†’Breast development in females and increased testicular volume in males.
β†’Secondary characteristics develop
β†’Profound physiological changes
β†’Profound psychological changes

3

What is gonadarche characterized by?

β†’ An increase in GnRH ( measured through FSH and LH)

4

What does an increase in LH result in?

β†’ Secondary sex characteristics

5

Why does adrenarche occur?

β†’ Increase in adrenal androgen secretion due to cellular remodelling of adrenal cortex.

6

What are the adrenal androgens?

β†’Dehydro-epiandrosterone (DHEA)
β†’Dehydro-epiandrosterone sulphate (DHEAS)

7

Where are the adrenal androgens secreted from?

β†’ The zona reticularis (cortex)

8

What is pubarche the result of?

β†’ Adrenarche

9

What appears during pubarche and why?

β†’Appearance of pubic/axillary hair resulting from adrenal androgen secretion

10

What is pubarche associated with?

β†’ an increase in sebum production which leads to acne

11

What is acne caused by?

β†’ Infection and abnormal keratinization

12

When is puberty considered precocious?

β†’ 8 years old in girls
β†’ 9 years in boys

13

When does gonadarche happen?

β†’ several years after adrenarche

14

What happens during gonadarche?

β†’ Reactivation of hypothalamic GnRH

15

What is the HPG axis required for?

β†’ male differentiation during fetal development

16

When are the GnRH neurons not restrained anymore?

β†’ until gonadarche

17

What does the activation of gonadal steroid production cause?

β†’ The production of viable gametes and the ability to reproduce

18

What hormones does the hypothalamus produce?

β†’ Kisspeptin
β†’ Gonadotrophin releasing hormone

19

What hormones does the pituitary release?

β†’ Gonadotrophin hormones

20

What is GnRH secreted and synthesized by?

β†’ Specialist hypothalamic centres (arcuate nucleus)

21

When is the HPG axis activated?

β†’ at the 16th week of gestation

22

When does pulsatile GnRH secretion continue in the fetus until?

β†’ 1-2 years postnatally

23

Around what age are GnRH neurons reactivated?

β†’ age 11

24

What is a good measure of GnRH?

β†’ LH mimics exactly what GnRH does

25

Why is GnRH difficult to measure?

β†’ It is only released in the hypothalamus

26

What stimulates the onset of puberty?

β†’ environmental and genetic factors
β†’ body fat and nutrition

27

What is the Frisch et al. body fat hypothesis?

β†’ A certain body fat % is required for menarche 17% and to maintain female reproductive ability

28

What happens as a result of anorexia?

β†’ Reduced response to GnRH
β†’ Decreased gonadotrophin levels
β†’ Amenorrhoea

29

What happens if someone has an inactivating mutation of the KISS1R gene?

β†’ Hypogonadism
β†’ Failure to enter puberty
β†’ Hypogonadotrophic hypogonadism

30

What happens if there is an activating mutation of KISS1R?

β†’ Precocious puberty

31

What is consonance?

β†’ A smooth ordered progression of changes

32

What are the physical changes in girls during puberty?

β†’ Breasts enlarge
β†’ Pubic/axillary hair
β†’ Uterus enlarges
β†’ Cytology changes
β†’ Increase in height
β†’ Body shape

33

What changes occur in girls due to the activation of the HPG axis?

β†’ Increase in ovarian size and follicular growth

34

Why is menarche not equated with the onset of fertility?

β†’ 80% of menstrual cycles in the first year are anovulatory

35

What are the physical changes in boys during puberty?

β†’ External genitalia grow
β†’ Facial/ body hair
β†’ Pubic/axillary hair
β†’ Vas deferens lumen increases

36

What stimulates spermatogenesis and how?

β†’ Testosterone from Leydig cells stimulate meiosis and spermatogenesis in Sertoli cells

37

What changes the larynx in males and how?

β†’ Androgens lead to an enlarged larynx
β†’ Voice deepens

38

What is the growth spurt due to?

β†’ Interaction between growth hormone and estrogen

39

What is the biphasic response (growth spurt)?

β†’ Low levels of estrogen β†’ linear growth and bone maturation
β†’ High levels of estrogen β†’ Epiphyseal fusion

40

What do androgens do at the pilosebaceous units?

β†’ Increase sebum production

41

How does beard formation occur?

β†’ at the vellus pilosebaceous unit there is differentiation
β†’ Terminal pilosebaceous unit formation

42

What are pubic and axillary pilosebaceous units called?

β†’ APO pilosebaceous units

43

What are the 3 psychological changes in puberty?

β†’ Need for independence
β†’ Increasing sexual awareness/interest
β†’ Development of sexual personality

44

What are the three disorders when there is premature activation of the HPG axis?

β†’ Gonadotrophin dependent precocious puberty
β†’ Gonadotrophin independent precocious puberty
β†’ Mc Cune Albright syndrome

45

What are the features of gonadotrophin dependent precocious puberty?

β†’ Excess GnRH secretion
β†’ Excess gonadotrophin secretion β†’ pituitary tumor

46

What are the features of gonadotrophin independent precocious puberty?

β†’ Testotoxicosis - activating mutation of LH receptor
β†’ Sex steroid secreting tumor or exogenous steroids

47

What are the features of McCune albright syndrome?

β†’ Cafe au lait skin pigmentation
β†’ Autonomous endocrine function
β†’ Hyperactivation of adenylate cyclase mediated signalling

48

What classes as pubertal delay?

β†’ Absence of secondary sexual maturation by 13 in girls
β†’ Absence of menarche by 18
β†’ Absence of secondary sexual maturation by 18 boys

49

What is constitutional delay?

β†’ Affects both growth and puberty
β†’ 90% of all pubertal delay cases

50

What is an example of hypogonadotrophic hypogonadiam?

β†’ Kallmans syndrome (impaired GnRH migration)

51

What is an example of hypergonadotrophic hypogonadism?

β†’ Gonadal dysgenesis and low sex steroid levels