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Reproduction > Hypothalamic - Pituitary - Gonadal Axis II > Flashcards

Hypothalamic - Pituitary - Gonadal Axis II Flashcards

1
Q

What is puberty the transition from and to?

A

→ Non reproductive to reproductive state

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2
Q

What are the 4 main things that happen during puberty?

A

→Breast development in females and increased testicular volume in males.
→Secondary characteristics develop

→Profound physiological changes
→Profound psychological changes

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3
Q

What is gonadarche characterized by?

A

→ An increase in GnRH ( measured through FSH and LH)

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4
Q

What does an increase in LH result in?

A

→ Secondary sex characteristics

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5
Q

Why does adrenarche occur?

A

→ Increase in adrenal androgen secretion due to cellular remodelling of adrenal cortex.

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6
Q

What are the adrenal androgens?

A

→Dehydro-epiandrosterone (DHEA)

→Dehydro-epiandrosterone sulphate (DHEAS)

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7
Q

Where are the adrenal androgens secreted from?

A

→ The zona reticularis (cortex)

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8
Q

What is pubarche the result of?

A

→ Adrenarche

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9
Q

What appears during pubarche and why?

A

→Appearance of pubic/axillary hair resulting from adrenal androgen secretion

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10
Q

What is pubarche associated with?

A

→ an increase in sebum production which leads to acne

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11
Q

What is acne caused by?

A

→ Infection and abnormal keratinization

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12
Q

When is puberty considered precocious?

A

→ 8 years old in girls

→ 9 years in boys

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13
Q

When does gonadarche happen?

A

→ several years after adrenarche

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14
Q

What happens during gonadarche?

A

→ Reactivation of hypothalamic GnRH

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15
Q

What is the HPG axis required for?

A

→ male differentiation during fetal development

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16
Q

When are the GnRH neurons not restrained anymore?

A

→ until gonadarche

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17
Q

What does the activation of gonadal steroid production cause?

A

→ The production of viable gametes and the ability to reproduce

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18
Q

What hormones does the hypothalamus produce?

A

→ Kisspeptin

→ Gonadotrophin releasing hormone

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19
Q

What hormones does the pituitary release?

A

→ Gonadotrophin hormones

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20
Q

What is GnRH secreted and synthesized by?

A

→ Specialist hypothalamic centres (arcuate nucleus)

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21
Q

When is the HPG axis activated?

A

→ at the 16th week of gestation

22
Q

When does pulsatile GnRH secretion continue in the fetus until?

A

→ 1-2 years postnatally

23
Q

Around what age are GnRH neurons reactivated?

A

→ age 11

24
Q

What is a good measure of GnRH?

A

→ LH mimics exactly what GnRH does

25
Q

Why is GnRH difficult to measure?

A

→ It is only released in the hypothalamus

26
Q

What stimulates the onset of puberty?

A

→ environmental and genetic factors

→ body fat and nutrition

27
Q

What is the Frisch et al. body fat hypothesis?

A

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

28
Q

What happens as a result of anorexia?

A

→ Reduced response to GnRH
→ Decreased gonadotrophin levels

→ Amenorrhoea

29
Q

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

A

→ Hypogonadism
→ Failure to enter puberty

→ Hypogonadotrophic hypogonadism

30
Q

What happens if there is an activating mutation of KISS1R?

A

→ Precocious puberty

31
Q

What is consonance?

A

→ A smooth ordered progression of changes

32
Q

What are the physical changes in girls during puberty?

A

→ Breasts enlarge
→ Pubic/axillary hair

→ Uterus enlarges
→ Cytology changes
→ Increase in height
→ Body shape

33
Q

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

A

→ Increase in ovarian size and follicular growth

34
Q

Why is menarche not equated with the onset of fertility?

A

→ 80% of menstrual cycles in the first year are anovulatory

35
Q

What are the physical changes in boys during puberty?

A

→ External genitalia grow
→ Facial/ body hair

→ Pubic/axillary hair
→ Vas deferens lumen increases

36
Q

What stimulates spermatogenesis and how?

A

→ Testosterone from Leydig cells stimulate meiosis and spermatogenesis in Sertoli cells

37
Q

What changes the larynx in males and how?

A

→ Androgens lead to an enlarged larynx

→ Voice deepens

38
Q

What is the growth spurt due to?

A

→ Interaction between growth hormone and estrogen

39
Q

What is the biphasic response (growth spurt)?

A

→ Low levels of estrogen → linear growth and bone maturation

→ High levels of estrogen → Epiphyseal fusion

40
Q

What do androgens do at the pilosebaceous units?

A

→ Increase sebum production

41
Q

How does beard formation occur?

A

→ at the vellus pilosebaceous unit there is differentiation

→ Terminal pilosebaceous unit formation

42
Q

What are pubic and axillary pilosebaceous units called?

A

→ APO pilosebaceous units

43
Q

What are the 3 psychological changes in puberty?

A

→ Need for independence
→ Increasing sexual awareness/interest

→ Development of sexual personality

44
Q

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

A

→ Gonadotrophin dependent precocious puberty
→ Gonadotrophin independent precocious puberty

→ Mc Cune Albright syndrome

45
Q

What are the features of gonadotrophin dependent precocious puberty?

A

→ Excess GnRH secretion

→ Excess gonadotrophin secretion → pituitary tumor

46
Q

What are the features of gonadotrophin independent precocious puberty?

A

→ Testotoxicosis - activating mutation of LH receptor

→ Sex steroid secreting tumor or exogenous steroids

47
Q

What are the features of McCune albright syndrome?

A

→ Cafe au lait skin pigmentation
→ Autonomous endocrine function

→ Hyperactivation of adenylate cyclase mediated signalling

48
Q

What classes as pubertal delay?

A

→ Absence of secondary sexual maturation by 13 in girls
→ Absence of menarche by 18

→ Absence of secondary sexual maturation by 18 boys

49
Q

What is constitutional delay?

A

→ Affects both growth and puberty

→ 90% of all pubertal delay cases

50
Q

What is an example of hypogonadotrophic hypogonadiam?

A

→ Kallmans syndrome (impaired GnRH migration)

51
Q

What is an example of hypergonadotrophic hypogonadism?

A

→ Gonadal dysgenesis and low sex steroid levels

Reproduction (12 decks)

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