I found this article, which might be a clue. Estradiol starts as a cooking oil by-product. Hubei seems to be a hot spot for cooking oil plants, and I did find a few in that general area, although most of China’s production appears to be located northeast of there. That’s about as far as I got. I’m questioning the veracity of this, but it’s not worth it to me to prove it one way or the other. Details are becoming more difficult to dig up.