I truly think that for some of us the transition starts LOOOONG before mainstream medicine thinks it does. For me mid to late 30's. My bloodwork is perfect. My hormone levels are perfect. In face, on paper, I'm absolutely perfect, but have felt like I'm dying a lot of the time over the last few years. I think some of us ( likely a whole lot that end up on these boards) are very sensitive to hormonal changes and fluctuations ( be they low or high).
There is a fair bit of evidence that absolute estrogen values don't drop dramatically until the year before you stop having periods. That means if you're perimenopausal and having regular periods you are making estrogen. Plenty of estrogen i think. The neurologic changes I had over the last few years were like my brain was 'wired'. Jitters/anxiety, headaches, fog, etc. Makes me wonder if my brain is amping up my levels of estrogen to try to 'force' an ovulation. In very early menopause is it too much estrogen that's the problem??? I certainly can induce all my neurologic symptoms with a 50 ug estrogen patch. Right down to the freezing chills, brain fog, panic attacks and weeping. Remove the patch, and I"m back to normal in less than 8 hours. hmmmmm