Session 4- Puberty and the HPG axis

Question 1

What is puberty

Answer 1

A stage of human development when sexual maturation adnd growth are completed and result in ability to reproduce

Question 2

What is adenarche

Answer 2

Maturation and increase activity of the adrenal glands prior to puberty

Question 3

Gonadarche

Answer 3

Activation of reproductive glands by the pituitary hormones FSH and LH

Question 4

Thelarche

Answer 4

The onset of breast development occurring near the beginning of puberty in girls

Question 5

Pubarche

Answer 5

Onset of the growth of pubic hair

Question 6

Menarche

Answer 6

Teh onset of menstruation at puberty

Question 7

What is thought to have an important influence on puberty

Answer 7

The pineal gland as disorders of this gland can cause early onset puberty

Question 8

What is the SMR

Answer 8

Tanner developed a scale in 1962 that divides the sexual maturity ratings into 5 classes based on Pubic hair and breast in females and pubic and genitalia in males

Question 9

What is the first sign f puberty

Answer 9

Testicular enlargement- males

Breast development - females

Question 10

When does female puberty start

Answer 10

8-13

Question 11

When does male puberty start

Answer 11

9-14

Question 12

What does acccelerated somatic growth depend on

Answer 12

Growth hormone + IGF-1 and sex steroids in both sexes

Question 13

How does accelerated somatic growth end in males

Answer 13

Fusion of epiphysis

Oestrogen closes epiphysis earlier in girls

Question 14

What ones the HPG axis consist of

Answer 14

Hypothalamus

Pituitary

Gonad

Question 15

Describe the HPG axis

Answer 15

Hypothalamus releases GnRH which acts on the pituitary to produce LH and FSH which acts on the gonads to produce androgen and Oestrogen

Question 16

Where is teh GNRH receptor

Answer 16

Anterior pituitary

Question 17

Why is GnRH released in pulsate

Answer 17

Teh receptors will become insensitive to teh GnRH if it is constantly secreted and the cascade will stop

Question 18

When do LH nd FSH levels increase

Answer 18

9-12 years old

Question 19

How does LH work in males

Answer 19

It stimulates Leydig cells in testis which produce testosterone which affects

Question 20

The HPG axis in males

Answer 20

FSH stimulates Sertoli cells which initiate spermatogeneis and causes the developing gametes to produce inhibin. Negative feedback on anterior pituitary - FSH- and possible hypothalamus

LH stimulates Leydig cells
-testosterone released. Negative feedback on hypothalamus and anterior pituitary

Question 21

What cells are present in seminiferous tubules

Answer 21

Supporting cells
Spermatogenic cels
Sertoli cells
-provide nutrition and hormonal support to germ cells allowing sperm formation
-sensitive to FSH
-secreted inhibin by developing gametes- negative feedback on AP FSH

Question 22

The HPG axis- female

Answer 22

FSH stimulates granulosa cells
As follicles envelop get release inhibin which inhibit FSH only.
Granulosa cells a covert androgens to oestrogen

LH stimulates theca interna cells

• release androgens. Converted to oestrogen by granulosa cells
• LH surge is required for ovulation
• LH maintains corpus luteum after ovulation

Question 23

How does oestrogen affect the release of GnRH i females

Answer 23

Moderate tires of oestrogen reduce GnRh secretion
-negative feedbacks

High titres of oestrogen alone promote GnRH secretion

• positive feedback
• LH surge

Question 24

How does progesterone affect FSH nd LH

Answer 24

Increases inhibitory effects of moderate oestrogen
Progesterone prevents positive feedback of high oestrogen
Oestrigen reduces GnRH per pulse, progesterone frequency of pulses

Question 25

What does inhibin do in the female

Answer 25

Inhibits the secretion of FSH and has a small inhibitory effect on LH

Question 26

Where is inhibin produced

Answer 26

Granulosa cells of corpus luteum

sertoli cells

Question 27

Central precocious puberty

Answer 27

Precocious puberty with elevated GnRH

-idiopathic cause/ CNS lesions/ pituitary gonadotropin-secreting tumours

Question 28

pathophysiology of central precocious puberty

Answer 28

premature activaion of the hypothalamo-hypophyseal axis-> abnormally early initiation of pubertal changes -> early development of secondary sexual characteristics and gonarche

Question 29

pathophysiology of central precocious puberty

Answer 29

premature activaion of the hypothalamo-hypophyseal axis-> abnormally early initiation of pubertal changes -> early development of secondary sexual characteristics and gonarche

Question 30

what is peripheral precocious puberty

Answer 30

precocious puberty without elevated GnRH

Question 31

What is delayed onset of puberty

Answer 31

Absent to incomplete development of secondary sex characteristics by the age of 14 in boys or 13 8i. Girls

Question 32

What is Constitutional growth delay

Answer 32

A temporary delay in growth and onset of puberty that is not caused by any pathological process

It is a cause of delayed onset of puberty

Question 33

what is the sequence of pubery events in girls

Answer 33

thelarche- breast bud development 
pubic hair
growth spurt
menarche
pubic haor becomes coarser
breast development

Question 34

what is the sequence of evenst of puberty in males

Answer 34

genital development
pubic hair growth
spermatogenesis
growth spurt
genital enlargement
pubic hair