Lecture 26: Puberty Flashcards
What’s the definition of normal puberty?
- Central Activation of the H-P gonadal axis
- Progressive sequential changes
- Appropriate rate (over 3-4yrs)
All these things occur “in tempo”!!
Whats the first signs of puberty for boys and girls?
Girls (1st sign) :
- Breast development because eostrogen is the trigger ~10.5 yr
- Then Growth spurt
- Period 2-3 years later ~13-14yr
Boys (1st sign) :
- Increased testicular enlargment ~11-12yr
- >4ml (orchidometer)
- Growth spurt later testosterone > eostrogen 2-3 yrs later ~13-14yr
How many puberties do you have?
3 Puberties of life!!!!
All related back to LH, FSH and sexsteriods
- Pre-natal: We have a huge amount of sex steroids, LH and FSH, (how else would little boys be born with a fallace?)
- Infancy: another little puberty. Biys penile length increases, girls may have a little pubic hair or best budding
- Different to withdrawal bleeding/ baby period which is due to removal from mums high estrogen environment
- Everything goes to sleep
- Adolescent: big, well-known puberty.
What inhibits puberty throughout childhood?
The Gonadostat.
- An area of the brain that actively inhibits puberty
- not able to find if you cut the brain up
- Tonically inhibits throughout childhoduntil at some point it starts to loss that inhibition → 3rd puberty takes off.
- Any damage to this area →early puberty
- if you’re in a car accident and hit your head, or kids wiht meningitis
What do these terms mean?
Thelarche
Pubarche
Gonadarche
Menarche
Gynaecomastia
Thelarche: Breast development (breast budding in a girl)
Pubarche: Pubic hair development
Gonadarche: Gonadal development > makes a bit of eostrogen
Menarche: first menstrual period
Gynaecomastia: breast development in boys
What’s the impact off insulin on ovarian androgen production?
PCOS: Insulin resistant state
High levels of insulin intefere with their androgen production from thecal cells. Why they have male virilised symptoms.
Describe the LH and FSH release during puberty?
Early Puberty LH could be measured at 0 during the day
- Tonic phase increases
- Night Pulses begin
Mid Puberty
- Greater increase in tonic phase
- High amplitude night pulses
Late puberty Measure LH anytime and get a reading
- Day and night pulses
If on COCP, LH level will be 0, as cycle is switched off!
A women who is having extremely irregular periods (~1yr) and we measured her LH levels and found them at 60 (extremely high)
What does this mean?
Tells us the ovaries have shut down = ovarian failure
Eg; women with Turners Syndrome
Nothing to do with brain as it is trying to compensate by increasing LH levels
Describe the Childhood to puberty transition
- Gonadostat turned OFF (loss of inhibitory signal)
- Increased pulsatile GnRH → pulsatile LH/FSH
- Increased Sex steroid production
- Reduced sensitivity to negative feedback from sex steroids (in hypothalamus and pituitary)
Describe Kisspeptin!
- Product of the KISS1 gene
- Expressed where we think Gonadostat is
- Naturally occuring ligand for GPR54 receptor
- Also has a role as a metastasis suppressor gene
- Kisspeptin expressing neurons are located in:
- Arcuate nucleus
- Periventricular nucleus
- Preoptic nucleus
- Therefore they project into GnRH producing areas
- KP neurons send prjections into the preoptic nucleus (GnRH cell bodies)
What evidence supports Kisspeptin as a puberty trigger?
- GPR54 inactivating mutations → don’t go into puberty
- have to give them GnRH
- If you give someone Kisspeptin → prepubertal get LH stimulation and ovulation
- KISS1 and GPR54 expression is increased at the start of puberty
What stimulates inhibin and then what does it inhibit?
What is inhibin produced by?
Inhibin is stimulated by FSH, the acts as a negative feedback to the FSH secretion from Ant. pituitary.
Produced By:
- Leydig Cells (m)
- Granulosa cells (f)
Dimer, 2 chains a and B (variable)
A and B form with indenticle function
What is Adrenarche?
- An increase in adrenal (weak) androgen production (DHEAS hormone)
- Occurs in late childhood (8-10yrs) → pongy smell
- Temporal association with puberty, NOT AN ACTUAL SIGN/stage OF PUBERTY
- Produces pubarche (pubic hair development)
- Trigger is unknown
Big cause of anxiety for kids
DHEAS is produced from?
What can we measure from the adrenal steroid?
DHEA gets sulphated → DHEAS
We can measure Aldosterone, cortisol, DHT, estradiol, DHEA, DHEAS
What does Leptin do in regards to Puberty?
- Leptin: an adipostatic hormone (leptos = thin)
- Increased Leptin → increased fat mass
- Potentailly a facilitatory signal to influence timing of puberty?
- Supported by the fact that obese children have earlier onset of puberty
- 1kg weight gain → lowers age of menarche by 13 days
What will Leptin Deficiency lead to?
Can be due to abnormal leptin hormone or Abnormal leptin receptor.
Sufferers are morbidly obese and don’t go through puberty (no trigger)
- Inject with leptin, to trim down and go through puberty like normal
- Very rare
Leptin levels peak ___________ in boys
Leptin levels peak jsut prior to puberty in boys
What is the current Age of Menarche and what is this dependent on?
- The average age is getting younger, due to increasing weights
- Directly correlated with body fatness
There’s a wide racial variation (body fatness)
- 11.5yrs US black (thicker women> taller, stronger)
- 12.3yrs US white
- 12.8yrs UK
Fallen in US by 0.34 in the past 25yrs
How does body composition change inpuberty for males and females?
Prepubertal male and female are the same in terms of lean, skeletal and fat mass
Puberty:
- Lean and skeletal mass; Males 1.5x more then females
- Fat mass; Females 2x more then males
- Fat
- Males: truncal
- Females: generalised
- There’s increased bone mineral density in both with peak bone mass achieved in early 20’s
