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Confusion about negative feedback by Estrogen

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deleted647690

It turns out that at low concentrations of estrogen there is negative feedback on FSH production."

Why would low levels cause negative feedback, further decreasing the levels of estrogen? I understand that positive feedback occurs when there is a high concentration of estrogen because it causes the LH surge. But I would normally think that to increase from the already low concentrations of estrogen, you would need positive feedback.

What causes the first estrogen surge? Just the "proliferation of follicle cells"?
 

theonlytycrane

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From days 0-12, lower levels of estrogen have negative feedback on LH and FSH.

On days 12-14 prior to ovulation, increasing estrogen levels have positive feedback on LH and FSH, which trigger ovulation. (Estrogen, LH, and FSH all spike on the graph)

The increasing estrogen levels are a result of follicle growth prior to ovulation (increased estrogen secretion).
 
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deleted647690

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From days 0-12, lower levels of estrogen have negative feedback on LH and FSH.

On days 12-14 prior to ovulation, increasing estrogen levels have positive feedback on LH and FSH, which trigger ovulation. (Estrogen, LH, and FSH all spike on the graph)

The increasing estrogen levels are a result of follicle growth prior to ovulation (increased estrogen secretion).

I'm just wondering why negative feedback would result from low levels of estrogen. I always thought of negative feedback as occurring because the levels of something are too high and it needs to stop the system from producing whatever it is.
I guess that's just how it is with this concept for estrogen
 

theonlytycrane

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If estrogen (even low levels) always spiked LH (positive feedback) ovulation might occur too early in the menstrual cycle. The negative/positive feedback system helps control the cycle timing.
 
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