Confusion about negative feedback by Estrogen

[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"?

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[betterfuture]

Where did you read that low levels of estrogen has a negative feedback mechanism on FSH?

 

[deleted647690]

Where did you read that low levels of estrogen has a negative feedback mechanism on FSH?

In Berkely Review, in the chapter on reproduction and development

 

[theonlytycrane]

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).

 

[deleted647690]

View attachment 206079

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]

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.