Prepubescent boys and girls have similar hormone levels, with typical testosterone levels below 30 nanograms per deciliter. As adolescence takes hold, hormone levels spike and generated by endorphin production sex characteristics become pronounced. In women, the ovaries primarily produce estrogen , but testosterone levels also rise, and testosterone levels for women peaks in their 20s, typically reaching levels of 70-95 nanograms per deciliter. As a woman ages, the levels of hormones, including testosterone, slowly decline. By the time she reaches menopause , testosterone levels are roughly half of their peak levels.
So we know we don't want to go too low with estradiol or we could end up with brittle bones and hip fractures like a lot of 75 year old women struggle with. Furthermore, common sense dictates that more is not better when it comes to estradiol. Many men who go on HRT and end up with estradiol in the 40's and 50's very commonly have a certain suite of side effects: gyno, water retention, lowered libido, loss of erectile strength, moodiness, poor sleep etc. If you've been around Peak Testosterone Forum at all, you know this is actually quite common. And many experts have concern about long term effects as well, because high estradiol may increase clotting risk, arterial plaque and prostate issues as I mentioned.