S4 Puberty And HPG axis Flashcards
What is adrenarche?
Maturation and increased activity of the adrenal glands prior to puberty
What is gonadarche?
Activation of reproductive glands by the pituitary hormones FSH and LH
What is thelarche
The onset of breast development occurring near the beginning of puberty in girls
What is pubarche?
Onset of the growth of public hair
What is menarche?
The onset of mensuration at puberty
What is seen during puberty?
Accelerated somatic growth
Maturation of primary sexual characteristics (gonads and genitals)
Appearance of secondary sexual characteristics (pubic and axillary hair, female breast development, male voice changes)
Menstruation and spermatogenesis begin
What factors are important in the timing of puberty?
- environmental factors
- the pineal gland > disorders of this can cause early onset puberty (evidence shaky)
- body weight (in girls mostly), nutrition and leptin (released from adipose tissue)
- economic/social factors MAY effect (stress)
- genetics
What are sexual maturity ratings (SMR) based on?
Also called a Tanner scale
- based on pubic hair and breasts (female)
- pubic hair and genitalia size (testes. Males)
Scale rating from 1-5
Average range of puberty in girls
8-13
Average age of puberty males
9-14 yrs
Starts with genital development (testes size inc)
Accelerated somatic growth is dependent on?
Growth hormone
IGF 1 (insulin growth factor)- monitor of general growth activity. Greatest peak at puberty.
Sex steroids
(In both sexes)
What ends the accelerated somatic growth
Fusion of growth plates at the end of long bones- epiphyseal fusion
> oestrogen closes epiphytes earlier in girls
Hypothalamus pituitary unit regulates the function of?
Thyroid ( hypothalamic pituitary thyroid axis HPT)
Adrenal (hypothalamic pituitary adrenal axis HPA)
Reproductive glands ( HPX)
also regulates
- somatic growth
- lactation
- milk secretion
- water metabolism
where is GnRH produced? where’s its receptor?
function?
gonadotrophin releasing hormone:
hypothalamus
receptor in anterior pituitary (travels via hypophysial portal system)
- regulates puberty onset, sexual development and ovulatory cyclin females.
describer how GnRH is reread during puberty
as low frequency pulses during the night but after maturation of synaptic connections, it matches the adult pattern
why is it important that release of GnRH is pulsate?
released in bursts so that the receptors don’t develop an insensitivity if exposed to high levels of the hormone for long periods > desensitise HPG pathway >infertility
what is adenohypophysis and neurohypophysis
anterior pituitary
posterior pituitary
hypophysis= pituitary
GnRH stimulates pituitary to release ?
follicle- stimulating hormone (FSH) luteinizing hormone (LH)
high levels of LH and FSH initiate?
gonadal development
level of testosterone in boys is increased when?
Mornings
because the sleep related LH increase which stimulates a nocturnal rise of T
Males: LH stimulates?
Leydig cells in testis > to produce testosterone
*negative feedback on anterior pituitary and hypothalamus
Males: FSH stimulates?
Sertoli cells (responsible for spermatogenesis) > inhibin released
*negative feedback on anterior pituitary n possibly hypothalamus
role of the testes
- contains seminiferous tubules
- interstitial tissue contains Leydig cells
> produce testosterone
role of sertoli cells
- provide nutrition and hormonal support to germ cells allowing sperm formation
- sensitive to FSH (inc sperm production)
- secrete inhibin
