Stinkin estrogen!

[andafoo]

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I'm a bit confused...

I looked at every post on the menstrual cycle possible and seems like everyone is just barely understanding it.

What about the increase in estrogen causes LH to increase so quickly? Doesn't estrogen inhibit both FSH at the pituitary and GnRH at the hypothalamus?

 

[FutureInternist]

I'm a bit confused...

I looked at every post on the menstrual cycle possible and seems like everyone is just barely understanding it.

What about the increase in estrogen causes LH to increase so quickly? Doesn't estrogen inhibit both FSH at the pituitary and GnRH at the hypothalamus?

Ahhh...the menstrual cycle. How do women expect us simple men to understand them if they are so complicated even at the cellular level 🙁

E does have a negative effect on anterior pit but this applies to the follicular (& luteal) phase of the cycle. As the E amount increases the feedback becomes (+) (in mid-cycle. It is the increase in E concentration that switches the (-) --> (+))

If you have a pregnancy, the trophoblast secretes hCG & maintains the corpus luteum (CL) until the CL itself starts to secrete E & P. Since at this point you do not want ovulation to happen again, E has a (-) effect in the luteal phase

If you did not have fertilisation then the CL dies off so E & P fall & you are back at square one (day 1 of follicular phase)

Hope this is clear. If you have more Qs, post here.

 

[andafoo]

Ahhh...the menstrual cycle. How do women expect us simple men to understand them if they are so complicated even at the cellular level 🙁

E does have a negative effect on anterior pit but this applies to the follicular (& luteal) phase of the cycle. As the E amount increases the feedback becomes (+) (in mid-cycle. It is the increase in E concentration that switches the (-) --> (+))

If you have a pregnancy, the trophoblast secretes hCG & maintains the corpus luteum (CL) until the CL itself starts to secrete E & P. Since at this point you do not want ovulation to happen again, E has a (-) effect in the luteal phase

If you did not have fertilisation then the CL dies off so E & P fall & you are back at square one (day 1 of follicular phase)

Hope this is clear. If you have more Qs, post here.

Well knowing that it happens is not that difficult... pretty much everyone/where can say so. But what makes E able to have two different feedback loops?

It seems like when E is present in high levels, then it will have (+) feeback, but when at low levels, it does have (-) feedback.

Now are there some players involved that we are not aware of? What about inhibin? Also are there some cells/tissues that express certain receptors that cause unexpected behavior (aside from what we expect purely based on +/- feedback loops)?

 

[stn1983]

From my understanding, rising level of estrogen has a positive feedback on the LH secretion because it stimulates GnRH secretion. An increase in GnRH secretion from the hypothalamus will cause an increase secretion of the LH hormone from the anterior pit. You can see this happening from the ovarian hormone graph. The increased in LH hormone secretion in conjuction with the increased in estrogen causes ovulation. HOWEVER, estrogen has a negative feedback on the secretion of LH and FSH when estrogen is secreted WITH progesterone. Progesterone and estrogen TOGETHER inhibits secretion of GnRH, consequently, will inhibit both LH and FSH secretion. This happens in the luteal phase of the menstrual cycle.

-Hope this helps

 

[andafoo]

From my understanding, rising level of estrogen has a positive feedback on the LH secretion because it stimulates GnRH secretion. An increase in GnRH secretion from the hypothalamus will cause an increase secretion of the LH hormone from the anterior pit. You can see this happening from the ovarian hormone graph. The increased in LH hormone secretion in conjuction with the increased in estrogen causes ovulation. HOWEVER, estrogen has a negative feedback on the secretion of LH and FSH when estrogen is secreted WITH progesterone. Progesterone and estrogen TOGETHER inhibits secretion of GnRH, consequently, will inhibit both LH and FSH secretion. This happens in the luteal phase of the menstrual cycle.

-Hope this helps

Then can you explain this:

"Since estrogen circulating in the blood can negatively feed-back to reduce circulating levels of FSH and LH, most oral contraceptives contain a synthetic estrogen, along with a synthetic progestin. Even in men, the major hormone involved in LH feedback is estradiol, not testosterone."

...

I wish your explanation were true, but it doesn't seem logical. GnRH stimulates LH & FSH production, which stimulates estrogen production, which has a positive feedback loop with LH & FSH? That would cause everything to skyrocket!

That would mean someone ingesting estrogen would be guaranteed to undergo ovulation (assuming certain conditions - disclaimer 😀).

 

[FutureInternist]

I asked this question of my endocrinology instructor in med school & her answer was "It just does". There will be many things that have to be filed under this category during 4 years of random facts that is medical school.
As my anatomy instructor told me "Try to understand what you can, memorize what cannot be understood & have the wisdom to know the difference" 😀

 

[andafoo]

I asked this question of my endocrinology instructor in med school & her answer was "It just does". There will be many things that have to be filed under this category during 4 years of random facts that is medical school.
As my anatomy instructor told me "Try to understand what you can, memorize what cannot be understood & have the wisdom to know the difference" 😀

Great quote, I'll work it into my writing sample .

 

[FutureInternist]

It's a med school twist of the Serenity Prayer

"Grant me the serenity to accept the things I cannot change,
the courage to change the things I can,
and the wisdom to know the difference. "