FGSS 2140 Lecture Notes - Lecture 13: Sex Steroid, Endometrium, Pituitary Gland
31 Oct 2016
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2-cell 2-gonadotropin model (cont"d: delta 5 pathway used to make androgens, progesterone (p4) is not produced; e2 feeds back on theca and granulosa to keep p4 low, e2 acts as negative feedback on progesterone, but not androgen production. D. and hence, estradiol in cows and sheep, increase in lh pule frequency as p4 declines during luteolysis converts a dominant follicle into a preovulatory follicle capable of making lots of e2. D: so, e2 has positive feedback on the follicle during the time when preovulatory follicle is growing. The more e2 it makes, the more granulosa cells there will be. If we removed the ovary during follicular phase, lh and fsh would become very high. If we remove e2, they would drop again. C. the surges of fsh and lh, causing ovulation in rat: steroids appear to feedback on both hypothalamus and pituitary (control gnrh and control pituitary levels) in monkey: feedback only on pituitary; hypothalamus keeps sending.
