Lecture 25: Puberty Flashcards
What is the definition of puberty?
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
What is puberty recognized by?
Maturation of genitalia Development of secondary sexual characteristics Acceleration in growth Change in affect Occurrence of menstruation in females
What is the neonatal period marked by?
Gonadotropin levels are high after birth for 2 years
High FSH in females and High LH in males in early infancy
What are the characteristics of prepuberty?
Both FSH and LH levels are suppressed
When will LH levels spike in midpuberty?
During sleep
When will LH levels spike in adulthood?
In the morning and throughout the day
What are the characteristics of puberty in females?
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
What are the characteristics of puberty in males?
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
How do you know HPG axis is suppressed in childhood at level of hypothalamus?
Because children with gonadal dysgenesis have FSH and LH levels similar to normal children
GnRH will stimulate FSH and LH secretion in agonadal children
A child with gonadal dysgenesis will have what type of FSH and LH levels?
In childhood, same FSH and LH levels as normal kids
What are the two stages of puberty in both male and female?
- Adrenarche
2. Gonadarche
What is adrenarche?
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
What is gonadarche?
- Activation of sex steroid secretion by the ovary or testis
- Leads to growth of breast tissue, sexual maturation
What happens when adrenarche occurs in individuals without functioning gonads?
Turner Syndrome
What is the takehome point of association between adrenarche and gonadarche?
Adrenarche and gonadarche are mutually EXCLUSIVE
Gonadarche can occur normally in individuals with primary adrenal insufficiency
If a patient has pubic and axillary hair development, does that necessarily mean that puberty has hit?
No, because this says nothing about GONADARCHE
Gonads could be undeveloped even though hair grows (adrenarche)
Adrenarche and gonadarche are exclusive
What is thelarche?
Breast development
What is pubarche?
Devo of pubic/axillary hair
What is the pubertal sequence in girls?
Adrenarche (6-7) Thelarche (9.8 yo) Pubarche (10.5 yo) Growth spurt (12 yo) Menarche (12.8 yo) Order doesnt matter
What is the pubertal sequence in boys?
Adrenarche (8) Testes growth (10) Pubarche (10) Penis growth (11) Growth spurt (14) Order doesnt matter
What is the tanner staging of puberty?
Based on English school girls lmao
This is what we base puberty staging of females…
Does the sequence or timing of normal pubertal events vary between ethnic groups?
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
Which racial group reaches puberty first?
African americans reach puberty earlier than Caucasians (thelarche)
Can ovulation occur prior to menarche?
yes
When breasts develop, when does menses occur?
2 years later is normal
If no menses by age 16, primary amenorrhea, needs an evaluation, may be physiologic
What emotional changes do you experience in puberty?
- Family conflicts increase
- Interest in opposite-sex companions increase while interest in same-sex companions decreases with pubertal maturation if youre not gay lol
- Increased ability and preference for abstraction
- Increase in imaginative responses
- Increased judgement
What signal initiates pubertal changes?
Unknown
What is leading hypothesis for puberty?
Concept that an increased release in pulsatile GnRH is responsible for gonadarche is well founded
What happens in agonadal children?
Demonstrate same suppression of FSH and LH….levels are slightly higher
What are the factors that turn on puberty in hypothalamus?
- Genetic
- Environmental
- Toxic Exposures
- Nutritional status
- Hormonal factors
What are earlier puberty associated with?
- urban environment
- closer to equator
- lower altitudes
What is decreasing age of menarche attributed to?
Better nutrition
Less physical activity
Higher incidence of obesity
What governs resumption of GnRH pulsatility?
GnRH control is extra-gonadal
-agonadal primate and human models show increased GnRH pulsatility
GnRH control may differ by sex
What are the upstream signals being investigated that lead to puberty?
- GABA
- Neuropeptide Y
- TGF-alpha
- Leptin
- Kisspeptin
- Glutamate
- CCK
What is the association of GABA and puberty?
Receptor in GnRH neurons
Key in female gonadarche
Inhibits GnRH
GABA declines as GnRH increases at gonadarche
What is the association of neuropeptide Y and puberty?
Inhibits GnRH
Key in male gonadarche
NPY central administration arrests GnRH pulses in monkeys
Increased NPY associated with delayed puberty
What is the association between leptin and puberty?
-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
What is the association between Kisspeptin and puberty?
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
What is the signal that is most likely to initiate puberty?
E. The signal that initiates puberty is unknown
-Kisspeptin-GPR54-GnRH neuron axis is most promising
