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πš™πš‘πš’πšœπš’πš˜πš•πš˜πšπš’ 𝟸 : πš›πšŽπš™πš›πš˜πšπšžπšŒπšπš’πš˜πš— > Hypothalamic - Pituitary - Gonadal Axis II > Flashcards

Hypothalamic - Pituitary - Gonadal Axis II Flashcards

1
Q

What is puberty the transition from and to?

A

β†’ Non reproductive to reproductive state

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2
Q

What are the 4 main things that happen during puberty?

A

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

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3
Q

What is gonadarche characterized by?

A

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

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4
Q

What does an increase in LH result in?

A

β†’ Secondary sex characteristics

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5
Q

Why does adrenarche occur?

A

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

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6
Q

What are the adrenal androgens?

A

β†’Dehydro-epiandrosterone (DHEA)

β†’Dehydro-epiandrosterone sulphate (DHEAS)

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7
Q

Where are the adrenal androgens secreted from?

A

β†’ The zona reticularis (cortex)

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8
Q

What is pubarche the result of?

A

β†’ Adrenarche

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9
Q

What appears during pubarche and why?

A

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

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10
Q

What is pubarche associated with?

A

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

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11
Q

What is acne caused by?

A

β†’ Infection and abnormal keratinization

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12
Q

When is puberty considered precocious?

A

β†’ 8 years old in girls

β†’ 9 years in boys

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13
Q

When does gonadarche happen?

A

β†’ several years after adrenarche

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14
Q

What happens during gonadarche?

A

β†’ Reactivation of hypothalamic GnRH

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15
Q

What is the HPG axis required for?

A

β†’ male differentiation during fetal development

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16
Q

When are the GnRH neurons not restrained anymore?

A

β†’ until gonadarche

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17
Q

What does the activation of gonadal steroid production cause?

A

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

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18
Q

What hormones does the hypothalamus produce?

A

β†’ Kisspeptin

β†’ Gonadotrophin releasing hormone

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19
Q

What hormones does the pituitary release?

A

β†’ Gonadotrophin hormones

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20
Q

What is GnRH secreted and synthesized by?

A

β†’ Specialist hypothalamic centres (arcuate nucleus)

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21
Q

When is the HPG axis activated?

A

β†’ at the 16th week of gestation

22
Q

When does pulsatile GnRH secretion continue in the fetus until?

A

β†’ 1-2 years postnatally

23
Q

Around what age are GnRH neurons reactivated?

A

β†’ age 11

24
Q

What is a good measure of GnRH?

A

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

πš™πš‘πš’πšœπš’πš˜πš•πš˜πšπš’ 𝟸 : πš›πšŽπš™πš›πš˜πšπšžπšŒπšπš’πš˜πš— (12 decks)

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