Lecture 25: Puberty

Question 1

What is the definition of puberty?

Answer 1

The physical and biochemical changes associated with activation of the hypothalamic-pituitary-gonadal axis, that lead to adult reproductive function
HPG axis needs to work in concert for this to work

Question 2

What is puberty recognized by?

Answer 2

Maturation of genitalia
Development of secondary sexual characteristics
Acceleration in growth
Change in affect
Occurrence of menstruation in females

Question 3

What is the neonatal period marked by?

Answer 3

Gonadotropin levels are high after birth for 2 years

High FSH in females and High LH in males in early infancy

Question 4

What are the characteristics of prepuberty?

Answer 4

Both FSH and LH levels are suppressed

Question 5

When will LH levels spike in midpuberty?

Answer 5

During sleep

Question 6

When will LH levels spike in adulthood?

Answer 6

In the morning and throughout the day

Question 7

What are the characteristics of puberty in females?

Answer 7

Normal adult LH pulse frequency and amplitude
Gonadotropin secretion leads to estrogen production by ovaries
In midpuberty, sufficient gonadal estrogen secretion leads to proliferation of endometrium and first menstruation
First 1-2 years of menarche are typically anovulatory

Question 8

What are the characteristics of puberty in males?

Answer 8

Normal LH pulse frequency and amplitude
LH secretion leads to production of testosterone by Leydig cells
Spermatogonia 600 million in each gonad is produced
Growth of testes is first sign of puberty in the male

Question 9

How do you know HPG axis is suppressed in childhood at level of hypothalamus?

Answer 9

Because children with gonadal dysgenesis have FSH and LH levels similar to normal children
GnRH will stimulate FSH and LH secretion in agonadal children

Question 10

A child with gonadal dysgenesis will have what type of FSH and LH levels?

Answer 10

In childhood, same FSH and LH levels as normal kids

Question 11

What are the two stages of puberty in both male and female?

Answer 11

1. Adrenarche

2. Gonadarche

Question 12

What is adrenarche?

Answer 12

Increase in secretion of androgen precursors from the zona reticularis of the adrenal gland (DHEAS)
Leads to axillary and pubic hair
Not under direct control of ACTH

Question 13

What is gonadarche?

Answer 13

1. Activation of sex steroid secretion by the ovary or testis
2. Leads to growth of breast tissue, sexual maturation

Question 14

What happens when adrenarche occurs in individuals without functioning gonads?

Answer 14

Turner Syndrome

Question 15

What is the takehome point of association between adrenarche and gonadarche?

Answer 15

Adrenarche and gonadarche are mutually EXCLUSIVE

Gonadarche can occur normally in individuals with primary adrenal insufficiency

Question 16

If a patient has pubic and axillary hair development, does that necessarily mean that puberty has hit?

Answer 16

No, because this says nothing about GONADARCHE
Gonads could be undeveloped even though hair grows (adrenarche)
Adrenarche and gonadarche are exclusive

Question 17

What is thelarche?

Answer 17

Breast development

Question 18

What is pubarche?

Answer 18

Devo of pubic/axillary hair

Question 19

What is the pubertal sequence in girls?

Answer 19

Adrenarche (6-7)
Thelarche (9.8 yo)
Pubarche (10.5 yo)
Growth spurt (12 yo)
Menarche (12.8 yo)
Order doesnt matter

Question 20

What is the pubertal sequence in boys?

Answer 20

Adrenarche (8)
Testes growth (10)
Pubarche (10)
Penis growth (11)
Growth spurt (14)
Order doesnt matter

Question 21

What is the tanner staging of puberty?

Answer 21

Based on English school girls lmao

This is what we base puberty staging of females…

Question 22

Does the sequence or timing of normal pubertal events vary between ethnic groups?

Answer 22

Sequence of pubertal events the same
Evidence that timing of normal pubertal events differs from ethnic groups
Important to recognize what is normal in your patient population
If there is no breast development at 13, then it’s a problem
If there is breast development before 8, then it’s a problem

Question 23

Which racial group reaches puberty first?

Answer 23

African americans reach puberty earlier than Caucasians (thelarche)

Question 24

Can ovulation occur prior to menarche?

Answer 24

yes

Question 25

When breasts develop, when does menses occur?

Answer 25

2 years later is normal

If no menses by age 16, primary amenorrhea, needs an evaluation, may be physiologic

Question 26

What emotional changes do you experience in puberty?

Answer 26

1. Family conflicts increase
2. Interest in opposite-sex companions increase while interest in same-sex companions decreases with pubertal maturation if youre not gay lol
3. Increased ability and preference for abstraction
4. Increase in imaginative responses
5. Increased judgement

Question 27

What signal initiates pubertal changes?

Answer 27

Unknown

Question 28

What is leading hypothesis for puberty?

Answer 28

Concept that an increased release in pulsatile GnRH is responsible for gonadarche is well founded

Question 29

What happens in agonadal children?

Answer 29

Demonstrate same suppression of FSH and LH….levels are slightly higher

Question 30

What are the factors that turn on puberty in hypothalamus?

Answer 30

1. Genetic
2. Environmental
3. Toxic Exposures
4. Nutritional status
5. Hormonal factors

Question 31

What are earlier puberty associated with?

Answer 31

1. urban environment
2. closer to equator
3. lower altitudes

Question 32

What is decreasing age of menarche attributed to?

Answer 32

Better nutrition
Less physical activity
Higher incidence of obesity

Question 33

What governs resumption of GnRH pulsatility?

Answer 33

GnRH control is extra-gonadal
-agonadal primate and human models show increased GnRH pulsatility
GnRH control may differ by sex

Question 34

What are the upstream signals being investigated that lead to puberty?

Answer 34

1. GABA
2. Neuropeptide Y
3. TGF-alpha
4. Leptin
5. Kisspeptin
6. Glutamate
7. CCK

Question 35

What is the association of GABA and puberty?

Answer 35

Receptor in GnRH neurons
Key in female gonadarche
Inhibits GnRH
GABA declines as GnRH increases at gonadarche

Question 36

What is the association of neuropeptide Y and puberty?

Answer 36

Inhibits GnRH
Key in male gonadarche
NPY central administration arrests GnRH pulses in monkeys
Increased NPY associated with delayed puberty

Question 37

What is the association between leptin and puberty?

Answer 37

-receptor in hypothalamus and anterior pituitary
Leptin increases during childhood until onset of puberty
Leptin soluble receptor decreases in puberty
Inverse relationship between serum leptin and menarche age
Leptin is not consistently elevated before GnRH pulsatility

Question 38

What is the association between Kisspeptin and puberty?

Answer 38

Synthesized in Hershey, PA
Stimulates release of GnRH when administered to male rhesus monkeys
Key role in activation of gonadotropic axis at puberty but not primary trigger
Hottest area of research

Question 39

What is the signal that is most likely to initiate puberty?

Answer 39

E. The signal that initiates puberty is unknown

-Kisspeptin-GPR54-GnRH neuron axis is most promising