Lecture 27: Puberty Flashcards
Describe the characterisitics of Puberty
- Growth and maturation of p_rimary sexual characteristics_ (gonads and genitals).
- Appearance and maturation of s_econdary sexual characteristics_
- Adolescent growth spurt occurs
- Fertility is achieved
- Profound psychological effects are observed!
These changes result directly or indirectly from
- Maturation of the hypothalamic-pit gonadotropin unit
- Stimulation of the sex organs
- Secretion of sex steroids
Puberty changes result directly or indirectly from
- Maturation of the hypothalamic-pit gonadotropin unit
- Stimulation of the sex organs
- Secretion of sex steroids
What are the first signs of Puberty in Girls and Boys?
1) Breast development
2) Grwoth spurt
1) Increasd testicular enlargement
2) >3ml (orchidometer)
3) Growth spurt later
When do the different puberties occur?
Axis wakes up 3 times.
1) Fetal life
2) First few months of life
3) In Adolescence
Puberty is expected to be suppressed - active (Gonadostatin?)
If a girl is less than ____ years old, it is considered to be early
8 (although this is early)
What is the word for “breast development”?
Thelarche
What is the ord for “pubic hair development”
Pubarche
What is the word for “Gonadal development”
Gonadarche
What is the word for “First menstual period”
Menarche
What is the word for “breast development in boys”
Describe the STAGES of Gential Development in boys
Stage 1:
No development
Stage 2:
1) Scrotum becomes a bit bigger
2) Testes become bigger
3) Scrotal skin becomes thinner
Stage 3
1) Penis starts to enlarge
Stage 4
1) Scrotum becomes a bit darker
Stage 5
ADULT
Describe the stages of Pubic Hair Development (Boys)
Stage 1: No pubic hair at all
Stage 2: Just become more coarse than normal hair
Stage 3: Longer and curlier
Stage 4: Lifted and widened
Stage 5: Lots of pubic hair
Describe the Tanner Stages of breast development
(Mostly describing the areola not the size of the breast)
Stage 1: No development
Stage 2: Earliest- breast bud
Stage 4: Areola lifts up from the breast
Stage 5: Comes down again
Puberty is driven by…
_________ more specifically, ___________ nucleus
HPA axis
Median preoptic nucleus in the hypothalamus
Describe the HPA feedback loops in girls
1) The hypothalamus makes GnRH which travels down to the gonadtroph cell in the anterior pituitary
2) Gonadotroph cell produces FSH and LH
3) LH binds to receptors in the Theca cells which are in the stroma of the ovary. These theca cells make androgens in response (e.g. testosterone)
4) FSH triggers the granulosa cells to aromatase testosterone to estradiol
- also produce progesterone (negatively feedback on the hypothalamus and pit)
- also produce inhibin which feeds back and inhibits the production of FSH and LH (just pit)
Describe the HPA feedback loops in boys
GnRH
LH and FSH
LH binds to leydig and produces testosterone (negative feedback on GnRH and pit)
FSH binds to sertoili cells and produces inhibin (negative feedback on pit)
Describe the LH and FSH release during early, mid and late puberty (separately)
Early
- Topic phase increases
- Night pulses begin
Mid-puberty
- Greater increase in tonic phase
- Higher amplitude night pulses
Late-Puberty
-Day and night pulses
If a child has early-puberty. What can you give them?
Activator of GnRH
Constant binding of GnRH shuts down the whole system
When is the Gonadaostat on for off?
Fetal Life
- Gonadostat is off
- Hypothalalmus makes lot of GnRH
- Strong affect on goands
- Weak negative feedback
Childhood
- Everything is clamped down.
- gonadostat is on
Some GnRH produced
- Small effect on gonads
- Large negative feedback
Puberty
-Everything unclamps
Describe the changes in hormones as a child transits into puberty
- Gonadostat is turned off.
- Increased pulsatile GNRH and LH/FSH secretion.
- Increased s_ex steroid_ production.
- Reduced sensitivity to n_egative feedbac_k from sex steroids.
By early puberty, hypothalamus is released from ___________control.
By early puberty, hypothalamus is released from gonadostat control. The mechanism of this release remains unclear. The hypothalamus and pituitary also become less sensitive to the inhibitory effects of sex steroids.
Note that median preoptic nucleus produces GnRH.
Describe the Gonadostat
I_ntrinsic CNS inhibitory mechanism._ S_ex steroid dependent (turn it off)._
γ aminobutyric acid (GABA) appears to be a potent inhibitor of pulsatile GNRH secretion.
- In prepubertal monkeys, GABA receptor blocker leads to rise in GnRH.
- Glutamate —(GAD)—> GABA
- Enzyme GAD is detectable in median basal eminence
Describe Kisspeptin
Kisspeptin is product of KISS1 gene. It also has a role as metastasis suppressor gene.
- Kisspeptin expressing neurons located in arcuate nucleus, periventricular nucleus, preoptic nucleus.
- Kisspeptin neurons send projections into the preoptic nucleus (triggering GnRH cell bodies).
Kisspeptin is n_aturally occurring ligand_ for GPR54. G protein coupled receptor 54 (GPR54) regulates GnRH secretion and or release from hypothalamus.
Kisspeptin as puberty trigger, according to evidence to support this concept:
- GPR54 mutations leads to failure to go into puberty.
- Kisspeptin administration to prepubertal rats stimulates LH and ovulation.
- KISS1 and GPR54 expression increased at the start of puberty.
Kisspeptin can also cure infertility due to hypothalamic problems due to its potent stimulation of GnRH.
Kisspeptin is product of KISS1 gene. It also has a role as metastasis suppressor gene.
- Kisspeptin expressing neurons located in _____nucleus, _______nucleus, ______nucleus.
- Kisspeptin neurons send projections into the ______nucleus (triggering GnRH cell bodies).
Kisspeptin is naturally occurring ligand for _____________ receptor 54 regulates ______secretion and or release from hypothalamus.
Kisspeptin is product of KISS1 gene. It also has a role as metastasis suppressor gene.
- Kisspeptin expressing neurons located in arcuate nucleus, periventricular nucleus, preoptic nucleus.
- Kisspeptin neurons send projections into the preoptic nucleus (triggering GnRH cell bodies).
Kisspeptin is naturally occurring ligand for GPR54. G protein coupled receptor 54 (GPR54) regulates GnRH secretion and or release from hypothalamus.
Kisspeptin as puberty trigger, according to evidence to support this concept:
- GPR54 mutations leads to failure to go into puberty.
- Kisspeptin administration to prepubertal rats stimulates LH and ovulation.
- KISS1 and GPR54 expression increased at the start of puberty.
Kisspeptin can also cure infertility due to hypothalamic problems due to its potent stimulation of GnRH.
What kick starts puberty?
Kisspeptin as puberty trigger, according to evidence to support this concept:
- GPR54 mutations leads to failure to go into puberty.
Kisspeptin is product of KISS1 gene. It also has a role as metastasis suppressor gene.
- Kisspeptin expressing neurons located in arcuate nucleus, periventricular nucleus, preoptic nucleus.
- Kisspeptin neurons send projections into the preoptic nucleus (triggering GnRH cell bodies).
Kisspeptin is naturally occurring ligand for GPR54. G protein coupled receptor 54 (GPR54) regulates GnRH secretion and or release from hypothalamus.
Describe Inhibin
Inhibin stimulated by FSH, and it is a negative feedback to FSH secretion.
It is produced by sertoli cells (m), granulosa cells (f).
Dimer, 2 chains, α and β (variable). A and B forms with identical function.
Describe Adrenarche
When adrenal glands ‘wake up’- DHEAs
↑ adrenal androgen production (DHEAs) (weak androgen) occurs in _late childhood (_8-10 years).
- Temporal association with puberty, NOT a sign of puberty.
- _Produces pubarche (_pubic hair development).
- Trigger unknown.
Is the development of pubic hair a sign of the beginning of puberty in girls?
No.- begins with breast development
Adrenarche (increased production of DHEAS- produces pubarche)
What causes Pubarche?
Adrenarche-> ↑ adrenal androgen production (DHEAs) (weak androgen) occurs in late childhood (8-10 years).
- Temporal association with puberty, NOT a sign of puberty.
- Produces pubarche (pubic hair development).
- Trigger unknown.
Describe Leptin and its change in puberty
Leptin (leptos = thin) is an adipostatic hormone (produced by the adipocytes)(↑leptin with ↑fat mass).
May be a facilitatory signal (about how much change) to influence timing of puberty.
Obese children have earlier onset of puberty. In girls 1 kg wt gain lowers age of menarche by 13 days.
Leptin levels peak just prior to onset of puberty in boys.
Leptin deficient mice never achieve puberty, however leptin treatment induces puberty.
Compare the differences between a patient who is leptin resistant and someone who is leptin deficient
If we are leptin resistance, then high leptin (body obese, brain starved) due to disrupted feedback loop, thus obese.
If we are l_eptin deficiency,_ then low leptin, _triggers hunge_r and keeps eating thus obese.
What is the pattern of age of menarche?
Age of menarche is getting younger, and directly correlated with body fatness.
There is wide racial variation with body fatness, hence menarche age.
Menarche now are 11.5 yrs US black, 12.3 yrs USA white, 12.8 yrs UK. Fallen in USA by 0.34 yrs in past 25 yrs.
Describe the differences in body composition between males and females before and after puberty
Prepubertal male is equal to female in terms of lean, skeletal and fat mass.
When puberty, male tends to be lean mass, skeletal mass (1.5x>F). Female tends to be more fat mass (2x>M) due to E2.
- Fat: males truncal, f_emales generalised._
- Hips: enlarge in females.
Increased bone mineral density in puberty with peak bone mass achieved in early 20s. Female bone mass increases quicker than male due to E2.
What are the Pubertal growth factors?
(All increased)
1) Sex steroids
2) Growth hormone
3) IGF-1
4) Isulin
