Hypothalamic-Pituitary-Gonadal Axis II

Question 1

What is puberty?

Answer 1

Transition from a non-reproductive to a reproductive state

Question 2

What is the clinical definition of puberty?

Answer 2

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

Question 3

What are the two endocrine events of puberty?

Answer 3

Adrenarche and gonadarche

Question 4

What is adrenarche caused by?

Answer 4

The secretion of adrenal androgens

Question 5

What is gonadarche caused by?

Answer 5

LH/FSH

Question 6

What is adrenarche responsible for?

Answer 6

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

Question 7

What is gonadarche responsible for?

Answer 7

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

Question 8

What is adrenarche?

Answer 8

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

Question 9

What increases after adrenarche?

Answer 9

DHEA and DHEAS

Question 10

Is there a change in other adrenal steroids during adrenarche?

Answer 10

No

Question 11

Where are the chemicals secreted from in adrenarche?

Answer 11

The zona reticularis of the adrenal cortex

Question 12

What is pubarche associated with?

Answer 12

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

Question 13

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

Answer 13

Precocious pubarche

Question 14

What happens in gonadarche?

Answer 14

Reactivation of the HPG axis and hypothalamic GnRH

Question 15

When is the HPG axis first activated?

Answer 15

16th gestational week

Question 16

When is pulsatile GnRH secreted?

Answer 16

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

Question 17

Why do you test for LH instead of GnRH?

Answer 17

It mimics the activity but is much easier to access

Question 18

What is puberty stimulated by?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What do inactivating mutations of Kiss1R or kisspeptin lead to?

Answer 20

Hypogonadism, failure to enter puberty and hypergonadotrophic hypogonadism

Question 21

What do activating mutations of Kiss1R cause?

Answer 21

Precocious puberty

Question 22

What is consonance?

Answer 22

The order of pubertal changes is uniform

Question 23

What is the average age of puberty onset?

Answer 23

12.5

Question 24

What are the tanner stages of puberty?

Answer 24

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

Question 25

What are the external physical changes in female puberty?

Answer 25

Breasts enlarge Pubic/axillary hair Height Body shape

Question 26

What are the internal physical changes in female puberty?

Answer 26

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

Question 27

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

Answer 27

80

Question 28

What is the meaning of anovulatory?

Answer 28

Without ovulation/ egg

Question 29

What are the external physical changes in male puberty?

Answer 29

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

Question 30

What causes the enlargement of larynx in male puberty?

Answer 30

Androgens

Question 31

What are the internal physical changes in male puberty?

Answer 31

Increased vas deferens lumen Seminal vesicles and prostate Stimulation of spermatogenesis

Question 32

What do low levels of oestrogen cause?

Answer 32

Linear growth and bone maturation

Question 33

What do high levels of oestrogen cause?

Answer 33

Epiphyseal fusion

Question 34

What are the psychological changes in puberty?

Answer 34

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

Question 35

What is classed as precocious sexual development?

Answer 35

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

Question 36

What can cause gonadotrophin-dependant precocious puberty?

Answer 36

Excess GnRH secretion or excess gonadotrophin secretion

Question 37

What causes excess GnRH secretion?

Answer 37

It can be idiopathic or secondary

Question 38

What causes excess gonadotrophin secretion?

Answer 38

Pituitary tumour

Question 39

What can cause gonadotrophin-independant precocious puberty?

Answer 39

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

Question 40

What is testotoxicosis?

Answer 40

An activating mutation of LH receptor

Question 41

What is classed as pubertal delay?

Answer 41

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

Question 42

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

Answer 42

Constitutional delay, hypogonadotrophic hypogonadism, or hypergonadotrophic hypogonadism

Question 43

What causes constitutional delay?

Answer 43

Secondary to chronic illness (eg diabetes or cystic fibrosis)

Question 44

Which sex is constitutional delay more common in?

Answer 44

Male

Question 45

What is hypogonadotrophic hypogonadism?

Answer 45

Low LH and FSH

Question 46

What is hypergonadotrophic hypogonadism?

Answer 46

High LH and FSH

Question 47

What can cause hypogonadotrophic hypogonadism?

Answer 47

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

Question 48

What can cause hypergonadotrophic hypogonadism?

Answer 48

Gonadal dysgenesis and low sex steroid levels

Question 49

What causes kleinfelters syndrome?

Answer 49

An extra X chromosome

Question 50

What are the symptoms of kleinfelters syndrome?

Answer 50

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