Puberty Flashcards
What is puberty?
- developmental event
- leading to somatic and sexual maturation
-profound physiological, psychological and physical changes - reproductive perspective: goal to produce mature gametes (spermatozoa and oocyte)
- breast development in females and increased testicular volume in males
What is adrenarche characterised by?
- first endocrine process of puberty
- occurs around 6-8 y/o
characterised by re- instigation of adrenal androgen secretion- DHEA (after 5yrs).
-androgen secretion from zona retcularis
-no change in cortisol
What are two endocrine events of puberty?
- Adrenarche->adrenal androgens
- Gonadarche -> LH/FSH
How does adrenal remodelling occur during development?
- fetus /neonate = DHEA produced
- infant - 5 y/o = no DHEA
-6 y/o = functional ZR developed - DHEA and 12- 13 ZR expansion.
histology of adrenal gland
outside -> inside
- zona glomerulosa (ZG)
-Zona fasciculata (ZF)
-Zona reticularis (ZR
-medulla (M)
How is DHEA made?
- cholestrol is the main precursor
-cholestrol -> pregnenolone -> 17 alpha hydroxypregnenolone -> DHEA -> DHEA - sulfate
What is the function of DHEA?
adrenal -> circulation -> peripheral tissue (hair follicle, genital skin for pubic hair)
Can ACTH instigate adrenarche?
- ACTH?
-children with ACTH receptor mutation fail to undergo adrenarche so maybe ACTH is involved
=> but no change in ACTH/cortisol during adrenarche so maybe not
What other factors instigate adrenarche?
- POMC?
- proximal 18 AA region that positively regulated adrenal androgen production.
-in vitro studies did not substantiate this - POMC - related peptides?
- b- lipotrophin and b-endotrophin plasma levels correlate with increase DHEA/S at adrenarche but no direct causal link - other factors ruled out include , IGF- 1 and insulin
=> no conclusive mechanism for control of adrenarch e
What comes first?
Adrenarche before gonadarche
What is gonadarche?
- reactivation of the HPG axis
- several years after adrenarche (typically ~11yrs)
- driven by hypothalamic GnRH and pituitary gonadotrophins
-puberty depends on reactivation of GnRH release
Why can we find out gender only on week 20 scan?
- HPG axis needs to be switched on to identify gender
- only switched on in week 16 and switched off just after birth then again switched on between 1-2
GnRH and puberty
Neurones restrained during postnatal period until 10 years or more.
At puberty a gradual rise in pulsatile release - around 1 year before breast budding is observed.
GnRH levels high at night
What is consonance?
- individual goes in order from stage 1 to 5 of the tanner stages of puberty.
- what varies is the duration a person stays at each stage
What are the 5 stages of Tanner stages?
- 3 categories : breast development(girls), pubic hair development, genital development (boys)
- 1 : no breast, no pubic hair and prepupertal genital
-2: breasts bud , few hairs, testis enlarged to 4mL
-3: enlarged breast and areola , more pigmented hair , penis enlarges in length.
-4: projection of areola above breast , small adult configuration, growth of penis in length and diameter
-5: papilla projects out of areola, adult configuration with hair spread onto inner thighs, testis, scrotum and penis adult size.