Puberty and HPG axis Flashcards
What is thelarche
Breast development
What is adrenarche
Maturation and increase adrenal gland activity
What is gonadarche
Activation of reproductive glands by pituitary hormones FHS and LH
What is menarche
Onset of menstruation
What factors affect the onset on puberty
Weight, nutrition, sleep, pineal gland
What scale can we use
Tanners
What does Tanners use
Males: pubic hair and testicular and penis volume/size
Females: pubic hair and breast size
Why does female growth spurt last shorter than mens
Oestrogen causes fusion of epiphyseal plates earlier
What does the hypothalamus pituitary system regulated function of
Thyroid, adrenal, reproductive, growth, lactation, water metabolism
What is the onset of puberty associated with
LH and FSH secretion
Why doesn’t the reproductive system work before puberty
GnRH secretion not pulsatile so hormone levels too low
What does GnRH regulate
Puberty onset, sexual development, ovulatory cycles
Where is the GnRH receptor
Anterior pituitary
How does GnRH affect change when it binds to receptor
G coupled
Conformational change and intracellular pathways activated
Modulation of genes in target cells via phosphorylation events
What is the adult pattern of GnRH release
Males pulses after 2 hours
Females depends on cycle phase
What happens if GnRH release isn’t pulsatile
Desensitisation by loss of receptors
What is adenophyphysis
Anterior pituitary
What does the anterior pituitary release
LH, FSH, ACTH, GH, LPH, MSH, prolactin
What is the effect of LH and FSH secretion
Gonadal development
Why is there negative feedback from oestrogen and testosterone
Don’t want constant GnRH release or will be desensitized.
What does LH stimulate in males
Leydig cells –> testosterone
What affects testosterone production
Circadian rhythm, time of day, environment
What does FSH stimulate
Sertoli cells –> spermatogenesis and inhibin release
What does inhibin feedback to
Anterior pituitary
What does testosterone feedback to
Hypo and ant p
What is the role of seminiferous tubules
Spermatogenesis
Where are they Leydig cells
Interstitial fluid of testes between seminiferous tubules
What 2 cells do the S tubules contain
Sertoli and Germ cells
What is the role of sertoli cells
Nutrition and hormonal support to germ cells = sperm formation
Secrete inhibin
Sensitive to FSH
What does FSH stimulate in females
Granulosa cells = follicular development
Inhibin release which only inhibits FSH
Convert androgens to oestrogen
What does LH stimulate in females
Theca cells = androgen release
LH surge
Maintains corpus luteum as release progesterone and oestrogen
In females, what is inhibited by inhibin release
FSH
In females what inhibits GnRH
Moderate oestrogen
In females what promotes GnRH release
High levels of oestrogen so we get LH surge
Effects of GH secretion
Increase TSH = increase metabolic rate = tissue growth promoted
Retention of minerals to support bone and muscle growth = spurt
Role of Leptin
Energy store information to CNS important for neuroendocrine function
What does excess or deficiency of Leptin cause
Early puberty onset
Reproductive dysfunction
What is central precocious puberty
Early puberty with elevated GnRH
What causes central precocious puberty
Lesions, tumours, obesity,
What is the mechanism of CPP
Premature activation of HPA leading to early development of secondary sexual characteristics and gonadarche
What would lab results of CPP show
Basal LH and FSH: elevated
GnRH stimulation test increase Lh and FSH
High androgen
What is Peripheral precocious puberty
Early puberty without elevated GnRH
Causes of PPP
High androgens Ovarian cyst Congenital adrenal hyperplasia Leydig-cell tumour Granulosa cell tumour Hepatoblastoma- B HCG produced Primary hypothyroidism
What would PPP lab tests show
High androgens, decrease LH and FSH
When is it called delayed onset of puberty
Absent or incomplete by 14 boys and 13 girls
What are the causes of delayed onset of puberty
Constitutional - low bone age- they will catch up
Malnutrition
Hypogonadism
What will lab tests show with delayed onset of puberty
No increase in LH and FSH to drive puberty
