Step I estrogen

[ctizzle13498]

I have a question. So I understand that estrogen causes the LH surge. But I also understand that estrogen causes inhibition on FSH and LH. So how can estrogen causes an LH surge AND cause inhibition of LH?????

very confused

 

[rashy]

Because estrogen has something very unique: A positive feedback!
Low levels of estrogen inhibit FSH+LH because of negative feedback, but high levels of estrogen somehow have a positive feedback on the pituitary gland. Thus, at high estrogen levels -> LH surge.

 

[ctizzle13498]

Because estrogen has something very unique: A positive feedback!
Low levels of estrogen inhibit FSH+LH because of negative feedback, but high levels of estrogen somehow have a positive feedback on the pituitary gland. Thus, at high estrogen levels -> LH surge.

But in turners, low levels of estrogen cause an increase in LH and FSH.

 

[rashy]

But in turners, low levels of estrogen cause an increase in LH and FSH.

Of course, because there is no inhibition from estrogen anymore. Ok, maybe i should say "very low levels" of estrogen cause an increase in LH+FSH because there is no estrogen to inhibit this! As FSH+LH increase, estrogen increases and causes a negative feedback.. until high concentrations of it cause the positive feedback

I think what you're missing here is that during the proliferative phase, the oocytes (esp. the dominant one) are able to use this FSH (+LH) more and more "efficiently", so with the same amount of LH+FSH, they are able to produce more and more estrogen. Hope this helps

 

[naseeha]

I agree with rashy. The fact that high levels of estrogen increase LH production through positive feedback is a fact you must just accept and move on, don't dwell on it too much. If it helps, Conrad Fischer said it just happens and there is no real explanation.