[mftrhu]

Both Progynon and Emmenin, the first forms of estrogen used (1928-29), were extracted from the urine of pregnant women. The material for Progynon was initially collected in a Berlin's clinic by Shering [1], and the urine needed for Emmenin was presumably sourced through similar channels. [2] mentions how the supply was scarce, as only women in low-income groups were interested in collecting it, and only while other sources of income were not available.

By 1941-1942 they had moved away from human urine to PREgnant MARe urINe, and Premarin was born.

[1] https://books.google.it/books?id=Z3iTsU6_mHsC&pg=PA119&redir...

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1661006/?page=2