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Endocrinology > Lec 12 - Puberty > Flashcards

Lec 12 - Puberty Flashcards

1
Q

what is puberty

A

when immature individual acquires the physical and behavioural attributes which will allow them to reproduce

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2
Q

what released from hypothal to trigger gonadotrophin release from apg

A

gonadotrophin releasing hormone (GnRH)

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3
Q

the 2 gonadotropins

A

Luteinising Hormone (LH)
Follicle Stimulating Hormone (FSH)

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4
Q

what do gonadotropins do to the gonads

A

stimulate gonads to:
1. produce/mature gametes
2. sex steroids release

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5
Q

what are male sex steroids

A

mainly androgens
e.g. testosterone

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6
Q

what are female sex steroids

A

mainly oestrogen and progesterone

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7
Q

what do sex steroids do

A

play a role on gonads themselves,
also have endocrine role:
- accessory reproductive organs
- secondary sexual characteristics

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8
Q

what happens during juvenile pause

A
  • CNS dampens the GnRH pulse generator in the hypothalamus
  • So = low gnhr activity
    And low gonadotrophin production
  • also sensitive negative feedback from sex steroids
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9
Q

where is the GnRH pulse generator likely to be

A

hypothalamus = probably in arcuate nucleus

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10
Q

how is puberty initiated

A

inhbition from CNS released (mechanism unknown)
low level pulses of GnRH begin
and the sensitivity to negative feedback decreases

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11
Q

what kind of rhythm is gonadotropin released in

A

early on in puberty, has diurnal release (at night)
later on the dirunal release is lost

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12
Q

what is adrenarche

A

contribution of adrenal gland to puberty
= start of production of androgens

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13
Q

what are the androgens produced by adrenal gland

A

androstenedione
DHEA

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14
Q

what does androstenedione and DHEA get converted to

A
  • testerone
  • DHT = potent version of testosterone
    (is converted in peripheral tissues)
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15
Q

what is the trigger for adrenarche

A

not sure of the trigger:
- independent of ACTH and cortisol
- may be indicated to IGF1 and growth hormone
- But people you have Addison’s disease (no adrenal function) STILL go into puberty, so not essential

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16
Q

first sign of puberty in males

A

Growth of testes usually first sign
- increasing mass of seminiferous tubules
- controlled by testosterone
Pubic hair development

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17
Q

what system used to assess puberty in males and females

A

Tanner grading system

18
Q

progression of puberty in males

A
  1. No pubic hair; testes < 2.5cm
  2. Hair at base of penis; testes > 2.5cm
  3. Hair spread & coarser; testes & penis growth
  4. More hair but no spread to thighs; further
    enlargement of testes & penis
  5. adult appearance achieved
19
Q

male secondary sexual characteristics

A

Other secondary sexual characteristics
increased laryngeal size
deepening of the voice
increased bone mass
increased mass & strength of skeletal muscle
thickened skin
increased & thickened hair on trunk, axillae & face
(last characteristic to appear – fully mature at age 25)

20
Q

first sign of puberty in females

A

Breast development usually first sign
controlled by estrogen
= maybe asymmetrical

Pubic hair development
- controlled by testosterone

21
Q

puberty in females developmetn

A

Preadolescent
Breast bud
Enlargement of breast & areola
Protruding 2º mound of areola
Adult size; recession of areola

22
Q

other secondary sexual characteristics in females

A

keratization of vaginal mucosa
enlargement of labia minora and majora
uterine enlargement
increased fat deposition in hips & thighs

23
Q

average age of menarche

A

12.8 +or- 1.2 in Caucasian girls
usually at tanner stag 4

24
Q

what sex hormone increases GH secretion

A

estrogen
(in males, androgens would get aromatised to estrogen)

25
Q

how do sex steroids directly afffect height

A

affect epiphysial plate
AR and ER expressed in all zones

26
Q

what 2 things account fo the diff in male and female height

A
  • 2 years earlier in girls (so males get 2 extra years of growth at childhood rate)
  • girls have slower rate of growth during spurt
27
Q

how has age of menarche changed over time

A

decreased from avg age of ~17 in 1800s to about 12-13 now (in developed countries)

28
Q

what might the decrease in age of menarche be caused by

A

improved socioeconomic stability and nutrition
- possibly need particular body weight for puberty to occur

29
Q

what is delayed/advanced puberty associated with

A

malnutriotion
elite athletes
= delayed

moderate obesity
= advanced

30
Q

evidence that estrogen is locally produced in growth plate

A

transplant of growth plate from one animal to another
= found that closure of growth plate depended on donor and not recipient
= indicating locally produced estrogen

31
Q

how come leptin was indicated as a possible hormone that triggered onset of puberty after certain weight reached

A
  • expressed in adipose tissue
  • levels increase at start of puberty
  • k/o mice have low Gn levels & underdeveloped gonads
  • similar phenotype in humans with mutations in leptin or receptor
  • abnormalities reversed by leptin therapy
32
Q

why is leptin NOT directly the trigger

A

not expressed by GnRH neurones

33
Q

what is kisspeptin produced by

A

CNS = infundibular neurones
Peripheray = gonads, GI tract, placenta

34
Q

where does kisspeptin act

A

at GPR54 = which is expressed by GnRH neurones
and stimulates GnRH release

35
Q

what are mutations in GPR54 linked to

A

delayed puberty

36
Q

how might kisspeptin be regulated by leptin

A

leptin receptor exists in kiss1 neurones

37
Q

what is consitutional delay in puberty

A

normal delayed puberty in comaprison ot peers
(late bloomers)

38
Q

what can gonadotropin deficiency be caused by

A

e.g. tumour

39
Q

what can gonadal failure lead to

A

low sex steroids = low negative feedback so can lead to high Gn

40
Q

what can gonadal failure be caused by

A

chemotherapy

41
Q

what is precocious puberty

A

too early
caused by premature activation of HPG axis

42
Q

what can precocious puberty be caused by

A

brain damage e.g.
Tumour, meningitis, head trauma

Endocrinology (25 decks)

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