Puberty Flashcards
Factors influencing age of puberty onset
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)
Term for when period stops because too fit
amenorrhea
Average age of puberty onset in industrialized countries
Female: 12-13
Male: 13
What occurs during female puberty
Secondary sexual characteristics appear
- breast development
- pubic hair
- ability to procreate
- growth spurt
- hip and thigh adipose tissue
How is puberty initiated
Gonadotropin secretion
- GnRH increases and becomes pulsatile
When is GnRH pulsatile in human years
Child- no
Puberty- at night
Reproductive years- all the time
How do breast change and what hormones
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
Where is mucus secreted in females? What hormone allows this
Vagina/uterus, fallopian tubes
Progesterone
What hormone causes pubic and axillary hair growth in females
Adrenal androgens
What hormone causes the increase in fat deposition in subcutaneous tissue in females (where is subcutaneous tissue found)
Estrogen
- subcutaneous is located under skin
Female vs male fat placement
Female- subcutaneous fat- under skin
Male- visceral fat- around organs
What hormone fuses epiphyseal plates
Estrogen
- think females shorter
Name four possible triggers for the increase in gonadotropin that initiates puberty
- decreased melatonin
- decreased inhibition of GnRH
- increased leptin
- increased kisspeptin
Explain “decreased inhibition” trigger that causes initiation of puberty
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
Explain “increased leptin” trigger that causes initiation of puberty
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
Where are leptin receptors found, what does leptin increase
In hypothalamus, anterior pituitary, ovaries
Leptin increases FSH and LH secretions and adiposity
Explain “increased kisspeptin” trigger that causes initiation of puberty
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
What does kisspeptin regulate, where is kisspeptin located. Explain pathway importance
Kisspeptin from arcuate nucleus
Arcuate nucleus dictates pulsatility of GnRH (so kisspeptin regulate GnRH)
Cause high and pulsatile GnRH— so high LH and FSH
Explain “decreased melatonin” trigger that causes initiation of puberty
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
How can increasing leptin change other puberty initiation factors
Increase leptin will
Decease melatonin
Reducing inhibition on kisspeptin
Therefore higher GnRH secretion
More LH/FSH release
overall reduced inhibition of puberty
What develops during male puberty
Secondary sexual characteristics
Penis, testes, scrotum enlarged (testes grow before penis)
Pubic hair
Growth spurt
Ability to procreate
What is puberty
Transition between juvenile state and adulthood, during which secondary sexual characteristics appear, adolescent growth spurt, ability to procreate
When is sign male puberty onset
First conscious ejaculation or testes > 2.5 cm
When are testosterone peaks during male lifespan
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
Name some actions of testosterone
- larynx male voice
- muscle mass
- sperm production
- visceral fat
- beard growth
What is the D2:D4 ratio
Sexually dimorphic trait marker of prenatal hormone exposure
How does the D2:D4 ratio work
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
