Puberty

Question 1

Factors influencing age of puberty onset

Answer 1

Sex- females earlier
Ethnicity- earliest in black females, latest at high altitudes in Asia
Nutritional status- lower status starts later
Genetics
Adiposity- obese girls earlier (fat to carry baby)
Endocrine status
Exogenous estrogen exposure (endocrine disruptors)- environmental factors
Distance from equator- dark/light cycles, circadian rhythm, melanin (farther from equator = more melatonin production = later period onset)
Intensive training with energy restriction- period later in super fit individuals (not enough fat)

Question 2

Term for when period stops because too fit

Answer 2

amenorrhea

Question 3

Average age of puberty onset in industrialized countries

Answer 3

Female: 12-13
Male: 13

Question 4

What occurs during female puberty

Answer 4

Secondary sexual characteristics appear
- breast development
- pubic hair
- ability to procreate
- growth spurt
- hip and thigh adipose tissue

Question 5

How is puberty initiated

Answer 5

Gonadotropin secretion
- GnRH increases and becomes pulsatile

Question 6

When is GnRH pulsatile in human years

Answer 6

Child- no
Puberty- at night
Reproductive years- all the time

Question 7

How do breast change and what hormones

Answer 7

Estrogen- duct development, accumulation of adipose tissue, increased size of nipple/areolus
Progesterone- lobular/alveolar proliferation and development
Growth hormone/ IGF-1 (insulin like growth factor)
Prolactin

Question 8

Where is mucus secreted in females? What hormone allows this

Answer 8

Vagina/uterus, fallopian tubes
Progesterone

Question 9

What hormone causes pubic and axillary hair growth in females

Answer 9

Adrenal androgens

Question 10

What hormone causes the increase in fat deposition in subcutaneous tissue in females (where is subcutaneous tissue found)

Answer 10

Estrogen
- subcutaneous is located under skin

Question 11

Female vs male fat placement

Answer 11

Female- subcutaneous fat- under skin
Male- visceral fat- around organs

Question 12

What hormone fuses epiphyseal plates

Answer 12

Estrogen
- think females shorter

Question 13

Name four possible triggers for the increase in gonadotropin that initiates puberty

Answer 13

• decreased melatonin
• decreased inhibition of GnRH
• increased leptin
• increased kisspeptin

Question 14

Explain “decreased inhibition” trigger that causes initiation of puberty

Answer 14

Child- gonadotropin release is very sensitive to inhibition from gonadal sex steroids (even low estrogen and progesterone levels turn off pathway). Turn off fast and easily
Puberty- higher levels of estrogen and progesterone needed to inhibit gonadotropin release- decreased sensitivity
experimentally proven

Question 15

Explain “increased leptin” trigger that causes initiation of puberty

Answer 15

Leptin is a satiety hormone. Promotes adiposity. Higher leptin levels = high fat reserve
experimentally proven leptin fed animals have earlier onset puberty
- leptin animals ate less because less of an appetite
- no leptin but diet same as leptin animals had slow puberty onset and decreased adiposity
- no leptin but amount of food unlimited (third group not much to say)
- leptin is permissive but is not sufficient for puberty onset

Question 16

Where are leptin receptors found, what does leptin increase

Answer 16

In hypothalamus, anterior pituitary, ovaries
Leptin increases FSH and LH secretions and adiposity

Question 17

Explain “increased kisspeptin” trigger that causes initiation of puberty

Answer 17

Kisspeptin (protein) only initiated at puberty - neurological break that inhibits kisspeptin release must be removed at puberty
- might be by neurological ‘pubertal clock’ or somatometer that senses growth

Question 18

What does kisspeptin regulate, where is kisspeptin located. Explain pathway importance

Answer 18

Kisspeptin from arcuate nucleus
Arcuate nucleus dictates pulsatility of GnRH (so kisspeptin regulate GnRH)
Cause high and pulsatile GnRH— so high LH and FSH

Question 19

Explain “decreased melatonin” trigger that causes initiation of puberty

Answer 19

GnIH- don’t know what is actually is, might be melatonin! It’s role is to inhibit GnRH until puberty. We know GnIH is produced by the pineal gland which is also where melatonin is secreted.
- know when pineal gland destroyed there is earlier puberty (therefore something in gland must inhibit puberty until ready)
High daylight hours have earlier puberty onset
experimentally proven low melatonin inversely correlated with rising LH/ FSH/ T. Know melatonin levels drop at puberty

Question 20

How can increasing leptin change other puberty initiation factors

Answer 20

Increase leptin will
Decease melatonin
Reducing inhibition on kisspeptin
Therefore higher GnRH secretion
More LH/FSH release
overall reduced inhibition of puberty

Question 21

What develops during male puberty

Answer 21

Secondary sexual characteristics
Penis, testes, scrotum enlarged (testes grow before penis)
Pubic hair
Growth spurt
Ability to procreate

Question 22

What is puberty

Answer 22

Transition between juvenile state and adulthood, during which secondary sexual characteristics appear, adolescent growth spurt, ability to procreate

Question 23

When is sign male puberty onset

Answer 23

First conscious ejaculation or testes > 2.5 cm

Question 24

When are testosterone peaks during male lifespan

Answer 24

3-6 months in gestation (medium)
First year of birth (small)
Climb during puberty (13) til peak hold at adult (18)
- constant T as adult. Highest level achieved

Question 25

Name some actions of testosterone

Answer 25

• larynx male voice
• muscle mass
• sperm production
• visceral fat
• beard growth

Question 26

What is the D2:D4 ratio

Answer 26

Sexually dimorphic trait marker of prenatal hormone exposure

Question 27

How does the D2:D4 ratio work

Answer 27

FEMALES
- shorter index finger (D2) than ring (D4) (smaller ratio D2/D4) indicates higher T in utero- linked to later puberty onset
- D2>D4- low T in utero- early puberty
——————
MALES
- D2<D4- high T- early puberty onset
- D2>D4- low T- late puberty