Puberty And The HPG Axis

Question 1

What is adrenarche?

Answer 1

Maturation of the adrenal glands prior to puberty

Question 2

What is gonadarche?

Answer 2

Activation of the reproductive glands by pituitary hormones FSH and LH

Question 3

What is Thelarche?

Answer 3

Onset of breast development occurring near the beginning of puberty in girls

Question 4

What is pubarche?

Answer 4

Onset of pubic hair growth

Question 5

What is menarche?

Answer 5

Onset of menstruation at puberty

Question 6

What factors influence puberty?

Answer 6

Body weight
Pineal gland
Leptin (adipose tissue)

Question 7

What is the critical weight for menarche in females?

Answer 7

47kg

Question 8

What is the first visible sign of puberty in males?

What is it in females?

Answer 8

Testicular enlargement,

Breast development.

Question 9

When does puberty begin in females?

When does it begin in males?

Answer 9

8-13,

9-14.

Question 10

Why do boys tend to grow larger than girls?

Answer 10

dependant on amount of growth hormone and IGF-1, which males tend to have larger amounts of. Oestrogen closes epiphyseal growth plates sooner in girls.

Question 11

What is the sequence of hormones governing puberty in both boys and girls?

Answer 11

Hypothalamic GnRH - pituitary LH and FSH - gonadal androgens (oestrogen and progesterone for women and testosterone for men)

Question 12

Which gene is responsible for production of GnRH?

Answer 12

GnRH-1 gene, expressed in the pituitary (why lol?)

Question 13

What feedback do testosterone and oestrogen (at low levels specifically) exhibit on the hypothalamus?

Answer 13

Negative feedback

Question 14

What does LH stimulate in males?

Answer 14

Leydig cells and production of testosterone from cholesterol precursors

Question 15

What does FSH stimulate in males?

Answer 15

Sertoli cells - responsible for nurturing and providing nutrition to growing spermatozoa - spermatogenesis

Sertoli cells also secrete inhibin!

Question 16

What does FSH stimulate in females?

Answer 16

Granulosa cells - follicular development and conversion of androgens to oestrogen. These also release inhibin.

Question 17

What does LH stimulate in females?

Answer 17

Theca interna cells - release androgens to be converted to oestrogen by granulosa cells.

Question 18

At high titres of oestrogen alone, what is caused?

Answer 18

Positive feedback on the HPG axis and increased GnRH secretion

Question 19

What effect does progesterone have on oestrogen?

Answer 19

At moderate oestrogen levels - increases inhibitory effect on HPG axis
At high titres - inhibits positive feedback

Question 20

What hormonal changes promote the pubertal growth spurt?

Answer 20

Growth hormone secretion of the pituitary
Increased TSH
Increased androgens

Question 21

What is the function of leptin and what is its role in puberty?

Answer 21

Adipocyte driven hormone that signals energy levels to the CNS. Accelerates onset of reproductive function as perceived more favourable nutrient state.
Regulates GnRH independent of LH

Question 22

What is central precocious puberty?

What causes it?

Answer 22

Precocious (early) puberty with elevated GnRH levels
Often idiopathic,
CNS lesions,
Obesity related,
Tuberous sclerosis,
Neurofibromatosis.

Question 23

What is peripheral precocious puberty and what are its causes?

Answer 23

Puberty without elevated GnRH levels
Increased androgen production eg ovarian cyst,
Congenital adrenal hyperplasia,
Leydig cell tumours,
HCG secreting germ cell tumour
Obesity related due to compensatory hyper insulinaemia

Question 24

What is the most common cause of pubertal delay?

What are other causes

Answer 24

Constitutional growth delay. Physiological not pathological.

Pathologically: malnutrition, IBD, hypothyroidism, hypogonadism.