Ovarain cycle

[yellowjellybean]

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This has always confused me but I think I've narrowed it down to a few questions that if I can get answered will help tremendously.

Before ovulation, how is the estrogen able to steadily rise when there is the negative feedback system? Is there estrogen coming from somewhere other than the theca cells? How is the LH able to surge/ what about the negative feedback loop?

 

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Hormone interactions are very complex. While lower levels of estrogen are inhibitory to gonadotropins, higher levels are stimulatory to them. Estrogen and LH have a positive feedback on each other during this process, where LH causes androgen production and conversion to estrogen, which then upregulates LH receptors and thereby increases its effects. This eventually results an LH surge which causes follicular rupture (ovulation)