Very brief notes.
Growth spurt
- females 2 years earlier than males
- due to steroid hormones, GH, insulin-like growth hormone
- adrenal androgens not involved
Changes
- male increase muscle mass
- female increase fat deposition in hips & breast
- increase in sebaceous glands & thickness of secretion in male
- female have oestrogens: more fluid
- larynx enlarge in males
- increase androgens
- pubic & axillary hair
Stages of development of genitals, pubic hair and breast
- read from notes
Sequence of male puberty
- testes growth
- penis, scrotum & pubic hair growth
- axillary hair
- 1st ejaculation (wet dream)
- growth spurt
- facial hair
- adult height
Sequence of female puberty
- breast buds appear (thelarche)
- pubic hair appear (pubarche)
- growth spurt
- axillary hair
- pubic hair matures
- breast mature
- menarche (1 year after peak growth)
- adult height
Mechanism of puberty
3 changes in the endocrine homeostatic function
- Adrenarche
- selective maturation of zona reticularis
- increase DHEA
- cause axillary and pubic hair growth
- 2 year of growth spurt & menarche
- Decrease repression of the gonadostat
- hypothalamic-pituitary system regulating LH/FSH
- From late infancy to 8 yo, LH & FSH remain low
- hypothalamus & pituitary highly sensitive to the –ve feedback of low levels of oestrogen?
- intrinsic central inhibition of GnRH
- Gradual amplification of the peptide-peptide (GnRH-LH/FSH) and peptide-steroid (FSH/LH-steroids) interaction leading to gonadarche
Pubertal onset
- Gradual loss of sensitivity of gonadostat
- hypothalamic maturation
- noctural pulsatile GnRH secretion
- increase amplitude & frequency GnRH pulses
- Increase LH & FSH
- LH pulses initially in sleep throughout the day
- Oestrogen & testosterone?
- gonadarche
- 2nday characteristics
- menarche, ovulation
Critical weight hypothesis
- Critical weight must be attained before the activation of the hypothalamo-pituitary-gonad axis & growth spurt can occur
- Critical weight for growth spurt: 30kg
- Critical weight for menarche: 47kg