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Reprooooooooo > Hypothalamic pituitary gonadal axis 2 > Flashcards

Hypothalamic pituitary gonadal axis 2 Flashcards

1
Q

What is puberty?

A

Puberty is the transition from non-reproductive to reproductive state

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2
Q

In puberty, what are the gonads able produce?

A

Gonads produce mature gameres

  • Testis–>Spermatozoa
  • Ovaries –>Oocytes
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3
Q

What is puberty defined as?

A

Defines as breast development in females and increased testicular volume in males

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4
Q

What characteristics develop in puberty and what profound changes are there?

A

Secondary characteristics develop

Profound physiological and psychological changes

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5
Q

How many endocrine events of puberty are there?

A

Two endocrine events

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6
Q

What is the first endocrine event of puberty and what is it and what does it result in?

A

The first is adrenarche:

  • It is the result of adrenal androgen secretion
  • Results in the growth of pubic and axillary hair and growth in height
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7
Q

What is the second endocrine event of puberty and what is it and what does it result in?

A

The second is gonadarche:

  • It is the reawakening of the HPG axis
  • Results in the development in secondary sexual characteristics
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8
Q

What do both adrenarche and gonadarche result in?

A

Both of these events result in complete puberty

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9
Q

What is adrenarche and what secretion do we get?

A

Adrenarche is the change in adrenal androgen secretion due to cellular remodelling of adrenal
-Get secretion of DHEA and DHEAS

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10
Q

Is there any other change in steroids in adrenarche?

A

No other adrenal steroid change

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11
Q

Where are both DHEA and DHEAS secreted from?

A

DHEA and DHEAS are secreted from the zona reticularis of adrenal cortex

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12
Q

What is pubarche the result of?

A

Is the result of adrenarche

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13
Q

What does pubarche result in the appearance of?

A

Results in the appearance of pubic/axillary hair

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14
Q

What is pubarche associated with?

A

Associated with:

  • Increase in sebum production=acne
  • Infection, abnormal keratinization=acne
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15
Q

When is pubarche known as precocious?

A

If pubarche is before 8 yrs old in girls or 9 yrs old in boys, this is known as precocious

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16
Q

When does gonadarche occur?

A

Occurs several years after adrenarche

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17
Q

What is gonadarche?

A

Is the reactivation of hypothalamic GnRH

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18
Q

What do we see the activation of in gonadarche and what does this lead to?

A

We see the activation of gonadal steroid production which leads to the production of viable gametes and ability to reproduce

19
Q

What is GnRH synthesized and secreted by?

A

Synthesised and secreted by specialist hypothalamic centres-GnRH neurons

20
Q

When is HPG axis first activated?

A

HPG axis first activated at 16th gestational week

21
Q

What secretion is there in a foetus and until when?

A

There’s pulsatile GnRH secretion in foetus until 1-2 years postnatally when it ceases

22
Q

When are GnRH neurons restrained?

A

GnRH neurons restrained during postnatal period

23
Q

What happens at puberty to the release of GnRH?

A

At puberty there’s a gradual rise in pulsatile release of GnRH

24
Q

What does anorexia nervosa/intensive physical training result in in terms of reproduction?

A

-Reduced response to GnRH
-Decreased gonadotropin levels
-Amenorrhea
Restored when nourished/exercise stopped

25
Q

What does inactivating mutations of KISS1R or the gene coding for KISSpeptin result in?

A

Results in:

  • Hypogonadism
  • Failure to enter puberty
  • Hypogonadotropic hypogonadism
26
Q

What does activating mutation of KISS1R result in?

A

Results in:

-Precocious puberty

27
Q

What is consonance?

A

Consonance is smooth ordered progression of changes in puberty

28
Q

What are the physical changes in girls during puberty?

A
  • Breasts enlarge
  • Pubic/axillary hair
  • Uterus enlarges, cytology changes
  • Uterine tubes
  • Vagina
  • Cervical changes
  • Height increase
  • Body shape
  • HPG axis
    - Increase in ovarian size and follicular growth
29
Q

What are physical changes in boys during puberty?

A
  • External genitalia
    - Increase in testicular volume
    - Growth in penis, scrotum, scrotal skin changes
  • Vas deferens
    - Lumen increases
  • Seminal vesicles and prostate
  • Facial/body hair
  • Pubic/axillary hair
  • Larynx - androgens –> enlarge larynx(adam’s apple)
  • Height
  • Body shape
  • Onset of fertility
30
Q

What is a growth spurt a complete interaction between?

A

Is a complete interaction between:

  • Growth hormones
  • Oestrogen
31
Q

In what gender is growth spurts earlier in?

A

Earlier in girls

32
Q

What is the biphasic effect of oestrogen on epiphyseal growth?(LOW LEVELS OF OESTROGEN)

A

-Linear growth and bone maturation

33
Q

What is the biphasic effect of oestrogen on epiphyseal growth?(HIGH LEVELS OF OESTROGEN)

A

-Epiphyseal fusion

34
Q

What are psychological changes due to puberty?

A
  • Increasing need for independence
  • Increasing sexual awareness/interest
  • Development of sexual personality
35
Q

What is precocious sexual development defined as?

A

Defined as the development of any secondary sexual characteristic before the age of 8 in girls and before the age of 9-10 in boys

36
Q

What is precocious puberty?

A

Is when pubertal changes are early but in consonance

37
Q

Premature activation of HPG axis

A

-Is gonadotropin dependent precocious puberty in consonance:
-Can result from excess GnRH secretion-idiopathic or
secondary
-Or result from excess gonadotropin secretion-pituitary
tumor
-Is also gonadotrophin independent precocious puberty-loss of consonance:
-Results from testotoxicosis where an activating mutation . of LH receptor results in premature maturation of
external genitalia.
-Also results from sex steroid secreting tumor or administration of exogenous steroids

38
Q

What is Mccune albright syndrome the most common thing?

A

The most common gonadotrophin independent precocious puberty

39
Q

What is Mccune albright syndrome caused by?

A

Caused by mutation in the GNAS1 gene

40
Q

What does Mccune albright syndrome result in?

A

Results in café au lait skin pigmentation

41
Q

What is there a hyperactivity of in Mccune albright syndrome?

A

Hyperactivity of signalling pathways and overproduction of hormones

42
Q

What is pubertal delay?

A

Is the absence of secondary sexual maturation by 13 yrs in girls or 14 yrs in boys

43
Q

What causes pubertal delay?

A

Delayed activation of HPG axis:
-Constitutional delay
-Affecting both growth and puberty
-Hypogonadotropic hypogonadism(Low LH and FSH)
-Rare but can occur due to kallman’s syndrome due to
impaired GnRH migration
-Can occur due to other mutations causing defects in
GnRH production
-Hypergonadotropic hypogonadism(High LH and FSH)
-Presents at gonadal dysgenesis and low sex steroid
levels

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