Puberty and the HPG axis Flashcards
what is precocious puberty
puberty before the age of 8
why might precocious puberty be stimulated by meningitis
as menignitis infers with the pulsating release of GnRH, disrupting the axis
will individuals who have had precocious puberty be taller or shorter and why
shorter - as their epiphyseal growth plates will close sooner
what scale is used to asses points of puberty
tanner scale
define puberty
a stage of human development when sexual maturation and growth are completed and result in the ability to reproduce
the secretion of what hormone from the pineal gland assists in puberty
melatonin
what role does leptin play in puberty
leptin determines when the child (particularly girls) have enough adipose tissue to sustain reproductive life
what is the critical weight for girls to enter puberty
47kg
what can cause precocious puberty
Brain injury, hydrocephalus, meningitis, congenital adrenal hyperplasia, pituitary tumour, pineal tumour
when does puberty begin in girls
9-13
what is aromatase
an enzyme which converts testosterone into oestrogen
what causes the closure of epiphyseal growth plates
oestrogen
when does puberty start in boys
10-14
what does HPG stand for
hypothalamo-pituitary-gonadal axis
what hormone is released from the hypothalamus in the HPG axis
GnRH
what does GnRG stand for
gonadotrophin releasing hormone
what causes the release of GnRH
leptin and photoperiod
in what pattern type if GnRH secreted
pulsatile pattern
where does GnRH go
to the anterior pituitary gland to stimulate the release of hormones
what hormones are released in response to GnRH
luteinising hormone and follicle stimulating hormone
how is the HPG axis controlled
though positive and negative feedback
when do LH secretions increases
during sleep
in males what does LH do
stimulates leading cells to produce testosterone
in males what does FSH do
stimulates Sertoli cells to help mature sperm cells and release inhibin
what does inhibin do
causes a negative feedback loop to FSH
why dos Sertoli cells have tight junctions
to prevent sperm from entering the blood stream as they have different antigens so are seen as foreign
in females where does LH go
goes to the theca interna cells
in females where does FSH go
granulose cells
what negative feedback occurs in the female HPG axis
normal oestrogen levels give negative feedback to the hypothalamus
inhibin gives negative feedback to FSH
what cells in females produce inhibin
granulose cells
describe the positive feedback occurring in the female HPG axis
high levels of oestrogen send positive feedback signals to the hypothalamus causing a LH surge
