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KPH - Week 3 > Puberty Regulation > Flashcards

Puberty Regulation Flashcards

1
Q

what is puberty characterised by?

A

-appearance of secondary sexual characteristics
-pubertal growth spurt
-physiological, cognitive and social changes

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2
Q

what makes up the HPG axis?

A

hypothalamus
pituitary
gonadal axis

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3
Q

what is the fetal HPG axis?

A

plays a major role in the. differentiation and maturation of the foetal reproductive tract

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4
Q

what is the process of the fetal HPG axis?

A

-hypothalamus produces lots of GnRH
-GnRH stimulates the pituitary gland
-pituitary stimulates high LH/FSH levels
-high levels act on the testes and increase sex steroid hormone levels
-stimulation of the differentiation of the reproductive tract

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5
Q

when is the next drive of HPG axis after the fetal one?

A

for a short period after birth

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6
Q

what effect does neurotransmitter gaba have on the HPG axis?

A

major inhibitory signal during the pre pubertal period

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6
Q

what is the status of the HPG axis during the pre pubertal period?

A

it is inhibited

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7
Q

what is thought to be one of the main stimulus of the pubertal HPG axis?

A

kisspeptin

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8
Q

what is the onset of puberty?

A

the reawakening of the HPG axis
(generally GABA stops inhibiting)

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9
Q

what is kisspeptin?

A

released from the hypothalamus
stimulatory of the HPG

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10
Q

what effect does FSH and LH have on the ovaries/testes?

A

production of sex steroid hormones increases
size of gonads increases

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11
Q

what is the release of GnRH like?

A

pulsative manner
one pulse corresponds to one secretion of gonadotrophin and in turn one release of one pulse of LH

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12
Q

what are the first signs of puberty?

A

breast development in females
testicular enlargement in males (radius of 2.5cm is puberty)

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13
Q

when does the release of GnRH occur?

A

during the night normally

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14
Q

what are the secondary signs of puberty?

A

axillary hair
body odour
pubic hair
acne
growth spurt
changes in body composition

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15
Q

what is the onset of puberty for females?

A

10 and a half years
normal range is fro 8-13 years

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16
Q

what is the onset of puberty for males?

A

11 years
normal range from 9 and 14 years

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17
Q

what does the tanner staging indicate?

A

stage 1 - complete pre pubertal state
stage 5 - final adult appearance

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18
Q

how long does it take to reach stage 5 of thr tanner staging scale?

A

3-5 years

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19
Q

what is precocious puberty?

A

unusually early puberty
below age of 8 or 9

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20
Q

what is delayed puberty?

A

girls - no sign of breast development by 13
boys - no signs of testicular enlargement by 14

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21
Q

what is gonadotrophin dependent precocious puberty?

A

-tumours on hypothalamus or pituitary
-cerebrl malformations
-injuries to CNS
-idiopathic
-genetic

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22
Q

what is gonadotrophin independent precocious puberty?

A

-tumours on gonads or liver
-adrenal gland hyperplasia (CAH)
-exogenous androgenic or oestrogen steroids
-genetics

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23
Q

what are the clinical signs of gonadotrophin dependent precocious puberty?

A

girls - breast development before 8
boys- testicular development before 9

24
Q

what are the clinical signs of gonadotrophin independent precocious puberty?

A

girls - only pubic/axillary hair before age 8
boys - only pubic/axillary hair before age 8

25
Q

what investigations can be done to investigate precocious puberty?

A

-gonadotrophins
-sex steroids
-bone age

26
Q

what are some of the reasons for delayed puberty?

A

hypergonadotrophic hypogonadism
hypogonadotrophin hypogonadism
constitutional delay of growth

27
Q

what would cause hypergonadotrophic hypogonadism?

A

high conc of gonadotrophin
can be due to bilateral gonadal insufficiency which is often due to a genetic factor eg Turner syndrome (one X chromosome for girls)
klinfelter syndrome ( extra X chromosome)

27
Q

what would be looked for in a physical exam testing for delayed puberty?

A

tanner stage
height and weight
are there any signs of malnutrition
visual fields exam (tumours)
dysmorphic features

28
Q

what is kisspeptin?

A

kisspeptin neurons present in the brain in regions that control reproduction
54 amino acid long kisspeptin

29
Q

which kisspeptins are present in the synapse within the hypothalamus?

A

kisspepsin 54 and 10

30
Q

which 2 disctinct regions are kisspeptins found within the synapse?

A

AVPV (anterior ventral peri ventricular nucleus)
ARC nucleus

31
Q

what is the role of kisspeptin?

A

positively acts with GABA to initiate reproductive development
induce puberty and regulate the HPG axis and normal reproductive cycles and some other reproductive processes

32
Q

why is kisspeptin 10 so important in research?

A

shorter so can easily be made synthetically and used in research cheaply
stimulate the pathway to observe
can make antibodies easily to look at distribution in tissues
KP-10 used to create inhibitors to use in cell and animal models

33
Q

what are the levels of ARC kiss pepsin been shown like in rodents?

A

levels peak prenatally and then decrease at birth
postnataly kisspeptin neutrons are higher in the female brain from PND1 through puberty

34
Q

what happens with KiSS1 neurons during pregnancy?

A

levels increase in the AVPV of the hypothalamus and the number of neurons that contact GnRH neurons increases as well as the amount of KiSS1 receptor (GPR54) on GnRH neurons

35
Q

why is the increase in kisspeptin in puberty larger in females than males?

A

testosterone exposure in neonatal life

36
Q

what happens to kiss pepsin secretion during pregnancy?

A

increases and becomes pulsatile with 60 minute intervals that correlate with CnRh pulses

37
Q

what secretes leptin?

A

fat cells

38
Q

what happens when we reach the correct height to weight ratio for reproduction to occur?

A

high levels of leptin stimulate increase in the number of kisspeptin neurons in the hypothalamus so the leptin acts in accurate nucleus and AVPN to increase the number of neurons there

39
Q

what effect does the R386P mutation have?

A

activates kisspeptin receptor and leads to precocious puberty (early puberty)

39
Q

what is the most common kisspeptin mutations?

A

most mutations inactivate the kisspeptin receptors leading to the child having idiopathic hypogonadotrophic hypogonadism (delayed puberty)

40
Q

how often is kisspeptin released in adulthood?

A

every hour in impulses

41
Q

what controls the release of GnRH by directly contacting GnRH neurons?

A

kisspeptin

42
Q

where is the kisspetin receptor on GnRH?

A

on the cilia

43
Q

what is the impact of GnRH release?

A

release of LH and FSH from anterior pituitary

44
Q

where is FSH and LH released from?

A

anterior pituitary

45
Q

what controls the release of kisspetin?

A

feedback from the gonads
(estrogen, progesterone and testosterone

46
Q

where does kisspetin reside?

A

hypothalamus

46
Q

what is positive kisspeptin feedback dependent on?

A

directly on oestrogen receptors on kisspetin neurons

47
Q

how does negative feedback of kisspeptin work?

A

another neutron inhibits kisspetin in the ARC

48
Q

what receptor for kisspeptin does the placenta display and where?

A

placental extravillosu trophoblast cells express the kisspeptin receptor GPR54

49
Q

what happens if we stimulate extravillois trophoblast cells with kisspeptin?

A

activates intracellular signalling pathways to increase calcium

50
Q

what effect does kisspeptin have on the trophoblast cells?

A

inhibits migration of trophoblast cells (rescued by kisspeptin inhibitor, p234)

51
Q

what is the role of kisspeptin in relation to the placenta?

A

to ensure the trophoblast does not invade too far

52
Q

what happens to kisspeptin levels during the 1st trimester?

A

increase 1000 fold in the 1st trimester

53
Q

what happens to kisspeptin levels in the 3rd trimester?

A

increase 9000 fold

54
Q

what happens to kisspeptin levels after delivery?

A

return to pre pregnancy levels

55
Q

why is kisspeptin important for pregnancy?

A

-stimulates firing of oxytocin during late pregnancy and lactation
-involve din labour and milk maturation

KPH - Week 3 (7 decks)

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