Repro: The HPG axis Flashcards
What is the latin name for the anterior pituitary?
Pars distalis (also called adrenohypophysis because it releases hormones
What is the latin name for the posterior pituitary?
Pars nervosa (also called the neurohypophysis as it is nervous tissue, unlike the anterior)
How is the anterior pituitary connected to the hypothalamus?
Via the superior hypophyseal artery
List the hormones produced by the anterior pituitary
- prolactin
- growth hormone
- thyroid stimulating hormone
- adrenocorticotropic hormones
- follicle stimulating hormone
- leuteinizing hormone
What is produced by the posterior pituitary?
Oxytocin and ADH
What is the role of gonado-tropin releasing hormone (GnRH)?
Produced by the hypothalamus
Stimulates the anterior pituitary to secrete FSH and LH
Describe the pattern of release of LH
GnRH release is pulsatile - released every 1-3 hours and LH mirrors this whereas FSH doesnt
Which receptors do FSH and LH use to act on the gonads
G alpha s receptors
In males which cells do FSH and LH act on?
LH acts on the leydig cells (L and L)
FSH acts on the sertoli cells (S and S)
What do leydig and sertoli cells release? What action does this have?
Leydig cells release testosterone which acts on sertoli cells and also stimulates sex hormone synthesis
Sertoli cells cause spermatogenesis and release inhibin
which selectively reduces FSH release
Describe the negative feedback loop from testosterone
Testosterone negatively feedbacks to the anterior pituitary to release less LH
Also negatively feedbacks to the hypothalamus to decrease GnRH which reduces LH AND FSH secretion
What is ABG?
A protein in the seminiferous tubules which binds some testosterone so there is always some available for spermatogenesis
In females which cells do FSH and LH act on?
FSH acts on the granuloSa cells of the corpus luteum
LH acts on the theca cells
What do granulosa and theca cells cells release? What action does this have?
Granulosa cells release oestrogen and inhibin which both act on the hypothalamus to inhibit GnRH release
Theca cells release progesterone
What is the effect of oestrogen on GnRH secretion?
Moderate levels of oestrogen reduce GnRH secretion by negative feedback
High levels of oestrogen alone (in absence of progesterone) promote GnRH secretion by positive feedback causing an LH surge
