Puberty

Question 1

What is Puberty?

Answer 1

A stage of human development where sexual maturation and growth are completed giving an individual the ability to reproduce. This stage will involve physiological and behavioural changes.

Question 2

When are primary sexual characteristics established?

Answer 2

Before Birth

Question 3

When does activation of the reproductive system happen?

Answer 3

Puberty

Question 4

Which gender tends to hit puberty first?

Answer 4

Girls

Question 5

List 4 events of puberty

Answer 5

• accelerated somatic growth
• maturation of primary sexual characteristics
• Secondary sexual characteristics appear (hair, breasts and voice changes)
• Menstruation and spermatogenesis

Question 6

List the environmental influences of puberty

Answer 6

Pineal gland (tumours)
Melatonin- day length/ light levels

Question 7

What is the most important factor in the age of onset of puberty?

Answer 7

Body weight

Question 8

What is the critical weight for onset of menarche?

Answer 8

47kg

Question 9

What is the average age of menarche in the UK at present and is this rising or falling?

Answer 9

13 years old

falling

Question 10

Describe the role of leptin in triggering puberty.

Answer 10

Leptin may be involved in signalling the onset of puberty. Leptin is secreted by adipocytes, thus the higher the amount of fat the stronger the leptin signal to the CNS- this may indicate that there is enough body weight to support a pregnancy.

Question 11

What is thelarche and when does it happen?

Answer 11

Appearance of breast buds- the first sign of female puberty

seen at age 9-13 years

Question 12

What is adrenarche?

Answer 12

Growth spurt and menstruation onset

Question 13

What stimulates pubic hair growth in both males and females?

Answer 13

Testosterone

Question 14

Why do women have less circulating active testosterone?

Answer 14

Testosterone binding proteins

No testis kicking out extra testosterone

Question 15

Which hormone closes the epiphyseal plates at the end of the growth spurt?

Answer 15

Oestrogen

Question 16

What staging system can be used to grade puberty?

Answer 16

Tanners staging

Question 17

When do boy genitalia start to mature?

Answer 17

10-14years

Question 18

What is the first sign of sexual maturation in men?

Answer 18

Increase in testicular volume

Question 19

Compare the growth spurt in men and women?

Answer 19

Men have a later onset, longer duration and faster rate of growth in their growth spurt compared to females

Question 20

List events of male puberty

Answer 20

Increase testicular Volume
Increase in genital size
Pubic Hair
Growth spurt

Question 21

What is accelerated somatic growth dependent on?

Answer 21

Growth hormones

Sex steroid hormones

Question 22

What stimulates genital maturation in men?

Answer 22

Testosterone

Question 23

Why do women stop growing earlier?

Answer 23

Oestrogen closes epiphyseal plates in both sexes- oestrogen levels higher in women so close earlier.

Question 24

What age do boys tend to start puberty and what sign indicates its onset?

Answer 24

12.5 yrs (10-14)

Testicular volume up to 4ml (G2 Tanner)

Question 25

How much do boys grow in a year during their accelerated growth compared to girls?

Answer 25

10.3 cm per year in boys | Girls only grow 9 cm/year

Question 26

How long does it take to establish menarche?

Answer 26

2.4 years plus or minus 1.1 year

Question 27

Once a boy has started puberty how long until the testis are adult size (duration of puberty in boys)?

Answer 27

3.2 years +/- 1.8 years

Question 28

When do girls start puberty?

Answer 28

11.5 years (appearance of breast bud- B2 Tanner)

Question 29

Which axis is switched on in puberty?

Answer 29

HPG axis | Hyothalamo-Pituatry-Gonadal Axis

Question 30

Which hormone is released do the Hypothalamus via the hypophyseal portal system to the ant pituitary?

Answer 30

GnRH | Gonadotrophin releasing hormone

Question 31

What is the effect of pulsatile GnRH on LH?

Answer 31

Increases frequency and amplitude of LH pulses

Question 32

What hormone class are LH and FSH?

Answer 32

Gonadotrophins

Question 33

What is the action of gonadotropins?

Answer 33

Gonad actions- stimulates secretion of sexual steroids | Extragonadal hormonal changes- elevation of IGF-1 and adrenal steroids

Question 34

Deletion of which gene would result in puberty not starting?

Answer 34

GnRH-1

Question 35

Where is the GnRH-1 gene exclusively expressed?

Answer 35

Discrete population of neutrons in the hypothalamus

Question 36

Which hormone could you give to stimulate the onset of puberty?

Answer 36

GnRH pulsatile

Question 37

What happens if you block GnRH?

Answer 37

No gonadotrophins secreted by the gonadotrophs of ant pituitary and lack of reproductive development

Question 38

How are the GnRH pulses regulated?

Answer 38

Biological clock which is controlled by light signals from the external environment.

Question 39

What is the action of hypothalamic releasing hormones on the specific membrane receptors of the pituitary?

Answer 39

Specific membrane receptors transduce the signal to second messengers. This stimulates release of stored pituitary hormones, production of more hormones and the hypertrophy and hyperplasia of the pituitary cells. Note the releasing hormones regulate their own receptors.

Question 40

How much of the anterior pituitary is made up of gonadotrophs?

Answer 40

5-10%

Question 41

Which two hormones do gonadotrophs release?

Answer 41

LH and FSH

Question 42

What two inputs are there to GnRH release?

Answer 42

Light | Leptin

Question 43

FSH acts on which cells in women?

Answer 43

Cumulus cells and Mural cells of the ovary

Question 44

Thecal cells and mural cells respond to which hormone?

Answer 44

LH

Question 45

Which hormone acts on Sertoli cells?

Answer 45

FSH

Question 46

Which cell does LH act on in the testis?

Answer 46

Leydig cells

Question 47

Which hormones negatively feedback on the hypothalamus?

Answer 47

Estradiol | Testosterone

Question 48

High levels of leptin in a child may do what?

Answer 48

Accelerate the onset of puberty

Question 49

Leptin has a pulsatile release is closely associated with surges in ....

Answer 49

LH (LH and leptin have similar patterns and thus don't negatively feedback on one another)

Question 50

What could negatively feedback on leptin?

Answer 50

Gonadal steroid hormones

Question 51

Which hormone stimulates the rise in GH that leads to the accelerated growth hormone?

Answer 51

GHRH

Question 52

What action does GH have on the liver?

Answer 52

IGF-1 increases

Question 53

List actions of GH secretion from the pituitary.

Answer 53

Increases TSH Increases metabolic rate (stimulating the thyroid) Promotes gowth Increases androgens (retains minerals for bone and muscle growth) ----- GROWTH SPURT-----

Question 54

How long is the GnRH peptide?

Answer 54

10 aminoacids

Question 55

Lh mirrrors the GnRH pulse- describe the pulse timings?

Answer 55

Every 1-3 hours

Question 56

If GnRH release is more frequent of more intense what does this say about its stimulus?

Answer 56

Strong stimulus

Question 57

Which artery connect the hypothalamus and the ant pituitary?

Answer 57

superior hypophyseal artery

Question 58

What tissue type is seen in the anterior pituitary?

Answer 58

Glandular tissue (NOT neuronal)

Question 59

Name the 6 peptides made by the anterior pituatary.

Answer 59

``` Prolactin Growth Hormone TSH ACTH FSH LH ```

Question 60

What happens to LH in adolescent boys while they sleep?

Answer 60

Increases

Question 61

Whats the side effects of increased LH in adolescent boys as they sleep?

Answer 61

Nocturnal testosterone increases

Question 62

Which comes first, the nocturnal GnRH pulsatility of the phenotypic changes?

Answer 62

The nocturnal GnRH pulsatile release by years

Question 63

What rises with the onset of puberty?

Answer 63

FSH and LH

Question 64

What is precocious puberty?

Answer 64

Early puberty

Question 65

What stops the reproductive system working as if adult before puberty?

Answer 65

Low hormones from lack of GnRH

Question 66

What stimulates gonadal development? It is low levels of these that stop gonadal function as children.

Answer 66

LH and FSH

Question 67

LH and FSH increase between ....-.... age and the .... of pulses .... especially during sleep.

Answer 67

9-12 amplitude increases

Question 68

The output of the hyothalamohypophyseal portal system controls which glands?

Answer 68

Thyroid Adrenal Glands Reproductive glands

Question 69

Somatic growth, lactation and water metabolism are all controlled by what?

Answer 69

Hypothalamus-pituatary unit

Question 70

What are steroid hormones derived from?

Answer 70

Cholesterol

Question 71

Name a male steroid hormone

Answer 71

Testosterone

Question 72

Do testosterone levels fluctuate after puberty?

Answer 72

Not really, they stay quite constant

Question 73

Which cells make testosterone?

Answer 73

Leydig

Question 74

What affects testosterone production?

Answer 74

Circadium rhythm | Environmental stimuli

Question 75

How many seminiferous tubules are seen in a lobule of the testis?

Answer 75

1-4

Question 76

Where does spermatogenesis happen?

Answer 76

seminiferous tubule which is 90% of the testicular volume

Question 77

What is between the seminiferous tubules?

Answer 77

Interstitial cells (leydig making testosterone) loose connective tissue and blood vessels.

Question 78

Leydig cells are needed for normal function of what?

Answer 78

Seminferous tubules

Question 79

Name the two epithelial cell types that line the seminiferous tubules.

Answer 79

Supporting/Sertoli cells | Germ cells

Question 80

What is the role of the sertoli cell?

Answer 80

Provide nutrition and hormonal support to germ cells FSH sensitive (will increase sperm production) Secrete inhibin that will negatively feedback on FSH production by the ant pit.

Question 81

Why do the seminiferous tubules need tight junctions?

Answer 81

Blood sperm barrier to avoid an immune response to gametes

Question 82

Which cells in the testes make testosterone?

Answer 82

Leydig

Question 83

FSH and LH act on what subtype of GPCR generally?

Answer 83

GalphaS | increases andenyl cyclase

Question 84

What are the target ovary cells for FSH and LH?

Answer 84

Granulosa cells -FSH | Theca interna-LH

Question 85

What are the effects of FSH and LH at the ovary?

Answer 85

Stimulate synthesis of sex hormones | Controls gamete production

Question 86

What releases Progesterone in females ovaries?

Answer 86

Old ruptured follicle

Question 87

High concentrations of oestrogen do what to GnRH?

Answer 87

Positive feedback and so will give an LH surge

Question 88

Oestrogen at moderate concentrations has what effect on GnRH?

Answer 88

Negative feedback

Question 89

How does progesterone (in the pill) stop ovulation at high doses?

Answer 89

Negative feedback of moderate oestrogen level is enhanced with progesterone so no GnRH pulse and thus absent LH surge

Question 90

Progesterone and oestrogen will negatively feedback on GnRH, describe there effects.

Answer 90

Oestrogen reduces GnRH release amplitude | Progesterone reduces GnRH frequency

Question 91

Where are the granulosa cells and what do they make?

Answer 91

Found in the corpus luteum Make inhibin

Question 92

In females what is the effect of inhibin on LH

Answer 92

small inhibitory action