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Physiology 2 > Hypothalamic-Pituitary-Gonadal Axis II > Flashcards

Hypothalamic-Pituitary-Gonadal Axis II Flashcards

1
Q

What is puberty?

A

Transition from a non-reproductive to a reproductive state

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2
Q

What is the clinical definition of puberty?

A

Breast development or increased testicular volume (up to 4ml)

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3
Q

What are the two endocrine events of puberty?

A

Adrenarche and gonadarche

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4
Q

What is adrenarche caused by?

A

The secretion of adrenal androgens

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5
Q

What is gonadarche caused by?

A

LH/FSH

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6
Q

What is adrenarche responsible for?

A

The growth of pubic hair, axillary hair and a growth in height

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7
Q

What is gonadarche responsible for?

A

Steroid synthesis (both LH and FSH), testis growth and folliculogenesis (FSH)

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8
Q

What is adrenarche?

A

A change in adrenal androgen secretion due to cellular remodelling of the adrenal gland

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9
Q

What increases after adrenarche?

A

DHEA and DHEAS

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10
Q

Is there a change in other adrenal steroids during adrenarche?

A

No

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11
Q

Where are the chemicals secreted from in adrenarche?

A

The zona reticularis of the adrenal cortex

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12
Q

What is pubarche associated with?

A

Increased sebum production, infection and abnormal keratinisation which all lead to acne

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13
Q

What is it called if pubarche happens before 8 or 9 years?

A

Precocious pubarche

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14
Q

What happens in gonadarche?

A

Reactivation of the HPG axis and hypothalamic GnRH

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15
Q

When is the HPG axis first activated?

A

16th gestational week

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16
Q

When is pulsatile GnRH secreted?

A

Gestation -> 1-2 years and then reactivated at 11 years

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17
Q

Why do you test for LH instead of GnRH?

A

It mimics the activity but is much easier to access

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18
Q

What is puberty stimulated by?

A

A maturational event in the CVS, possibly helped by the inherent maturation of GnRH neurons, environmental/genetic factors or body fat/nutrition

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19
Q

How does anorexia nervosa/ intense physical training lead to amenorrhoea?

A

Reduced response to GnRH which leads to a decrease in gonadotrophin levels

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20
Q

What do inactivating mutations of Kiss1R or kisspeptin lead to?

A

Hypogonadism, failure to enter puberty and hypergonadotrophic hypogonadism

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21
Q

What do activating mutations of Kiss1R cause?

A

Precocious puberty

22
Q

What is consonance?

A

The order of pubertal changes is uniform

23
Q

What is the average age of puberty onset?

A

12.5

24
Q

What are the tanner stages of puberty?

A

Pubic and axillary hair growth -> testicular volume and penile length or Breast development

25
Q

What are the external physical changes in female puberty?

A

Breasts enlarge
Pubic/axillary hair
Height
Body shape

26
Q

What are the internal physical changes in female puberty?

A

Uterus enlarges, cytology changes and secretions in response to E2
Uterine tubes
Vagina
Cervical changes
Increase in ovarian size and follicular growth

27
Q

What percentage of menstrual cycles are anovulatory in the first year?

A

80

28
Q

What is the meaning of anovulatory?

A

Without ovulation/ egg

29
Q

What are the external physical changes in male puberty?

A 
Increase in testicular volume
Growth of penis, scrotum and scrotal skin changes 
Facial/ body/ pubic hair
Larynx 
Height
Body shape
30
Q

What causes the enlargement of larynx in male puberty?

A

Androgens

31
Q

What are the internal physical changes in male puberty?

A

Increased vas deferens lumen
Seminal vesicles and prostate
Stimulation of spermatogenesis

32
Q

What do low levels of oestrogen cause?

A

Linear growth and bone maturation

33
Q

What do high levels of oestrogen cause?

A

Epiphyseal fusion

34
Q

What are the psychological changes in puberty?

A

Increased need for independence, sexual awareness/ interest and development of sexual personality

35
Q

What is classed as precocious sexual development?

A

Development of any secondary sexual characteristic before the age of 8 (female) or 9-10 (male)

36
Q

What can cause gonadotrophin-dependant precocious puberty?

A

Excess GnRH secretion or excess gonadotrophin secretion

37
Q

What causes excess GnRH secretion?

A

It can be idiopathic or secondary

38
Q

What causes excess gonadotrophin secretion?

A

Pituitary tumour

39
Q

What can cause gonadotrophin-independant precocious puberty?

A

Testotoxicosis, McCune Albright syndrome or a sex steroid secreting tumour or exogenous steroids

40
Q

What is testotoxicosis?

A

An activating mutation of LH receptor

41
Q

What is classed as pubertal delay?

A

The absence of secondary sexual maturation by 13 (female) or 14 (male)

42
Q

What are the three things that can cause a delayed HPG axis activation?

A

Constitutional delay, hypogonadotrophic hypogonadism, or hypergonadotrophic hypogonadism

43
Q

What causes constitutional delay?

A

Secondary to chronic illness (eg diabetes or cystic fibrosis)

44
Q

Which sex is constitutional delay more common in?

A

Male

45
Q

What is hypogonadotrophic hypogonadism?

A

Low LH and FSH

46
Q

What is hypergonadotrophic hypogonadism?

A

High LH and FSH

47
Q

What can cause hypogonadotrophic hypogonadism?

A

Kallman’s syndrome or other mutations causing defects in GnRH production

48
Q

What can cause hypergonadotrophic hypogonadism?

A

Gonadal dysgenesis and low sex steroid levels

49
Q

What causes kleinfelters syndrome?

A

An extra X chromosome

50
Q

What are the symptoms of kleinfelters syndrome?

A 
(In males) 
Wide hips
Female pubertal hair pattern
Chest development 
Small testicles

Physiology 2 (38 decks)

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