Well what a long and involved thread!
I am like you BrightLight - naturally curious - which is why I studied science in the first place, and still enjoy learning - which is why I enjoy being a member of this forum because I am continually being challenged to look things up that I'm not clear about (sometimes unsuccessfully!) although it all takes up a lot of time!! Having said that I finished my Biology Degree over 40 years ago, and the research I did subsequently was not human biology or anything related so I am looking up everything just as much as everyone else! You had great answers from Dancinggirl and dahliagirl.
In terms of understanding what's going on in our bodies - I think I gave you the link to the article on this site about the biology of the peri-menopause and what happens to the hormones in our menstrual cycle? Now that you've read a lot more you may like to read it again as this is the clearest summary of what happens, without too much complicated biochemistry and terminology. http://www.menopausematters.co.uk/article-perils-of-the-perimenopause.php
The answer to your initial question is is that the biological process will just carry on even if you replace oestrogen through HRT ie HRT will not prevent the decline in ovarian function. However the added oestrogen will prevent the symptomns of oestrogen deficiency. This is why some women experience bleeding at odd times especially when taking HRT early in peri-menopause - because the cycle is doing its own thing. I can't explain how added oestrogen affects the cycling of pituitary hormones and the various hormone feedback mechanisms.
As for excess oestrogen - as CLKD said somewhere on the thread - progesterone normally balances oestrogen throughout your fertile years, because if it didn't, the uterus lining would over-thicken, could lead to endometrial hyperplasia and possibly cancer, and would shed erratically.
There was mention of progesterone in the body – yes it only exists at very high levels during the second half of the menstrual cycle – to prepare for pregnancy, and during pregnancy – which is its main function. However there is a very small amount of progesterone in men, in women during the first half of the menstrual cycle, and post-menopausally – so it is still there carrying out whatever function it does in the body aside from the major changes in pregnancy. That's why it is pointless testing for it.
In terms of oestrogen dominance – I think it's already been mentioned and also as above that oestrogen is dominant during the first half of the natural menstrual cycle – when women usually feel at their best once the period is over. As Dancinggirl says the concept is a distraction because it implies that if it is not “balanced†by progesterone there will be unpleasant symptoms until the balance is restored. The fact is - it is true that progesterone is needed to “balance†oestrogen – but only to protect the uterus lining. If this were not the case, as Dancinggirl points out, no-one who had had a hysterectomy and was on HRT would be able to function without feeling unwell. It is also not helpful because it doesn't take into account the symptoms and problems caused by absolute depletion of oestrogen per se.
Having said that – yes, due to anovulatory cycles additional progesterone may well be needed temporarily (as well as oestrogen), in order to thin the lining and prevent heavy bleeding. This protection cannot be provided by progesterone cream despite what some websites and advocates might suggest.
To keep this post relatively short - I'll comment on some of the other points separately
Hope my ramble is of some help - and doesn't repeat what others have said too much! 
Hurdity x
I do appreciate you taking the time to write, thank you.
I know have the role of hormones clear in the regular cycles and also that HRT tops up our natural hormonal pattern that continues 'underneath' during perimenopause.
I can see that within the cycle progesterone is a balancer to estrogen for the lining etc and without getting hung up on the 'phrase' estrogen dominant my main premise is that both hormones have a role to play both in the reproductive arena and the rest of the body and that some symptoms might respond to progesterone better than estrogen and I really can see that progesterone alone - above and beyond regulating menopausal symptoms alone, could have some uses.
I view it that many woman have an ongoing hormonal imbalance prior to menopause and that menopausal symptoms are just another 'expression' of that imbalance. I can't see why the individuals metabolism of these hormones, whether they are her own or biodentical would change. So HRT might keep the cycle going and the hormones afloat but also might continue to create hyperplasia, polyps, fibroids, cysts etc So I guess I am interested in a wider consideration of hormonal effect and as said earlier, a well woman clinic would help women take a closer look at things and tailor treatment to suit them.
I can see that there are so many useful things that hormones do in our bodies and having read all these useful and informative posts I have a clearer idea about the different approaches, need and solutions that they can provide. Whether they are in the form of conventional HRT, biodentical prescribed, herbs, plants or indeed a yam cream. ALL of it is relevant in my eyes, some has scientific evidence, some symptoms need more sure fire approaches like HRT, some women might benefit from progesterone only cream early in their hormonal imbalanced lives. I can see why it all exists - why it is a mindfield and why it is hard to access individualised support 'out there'. Thanks again for sharing your knowledge
Author
Topic: Can anyone give me a chemistry lesson? (Read 44406 times)