Estradiol (E2) is the only estrogen with FDA-approved products; estrone (E1) and estriol (E3) lack FDA approval but are available through compounding.

“Now, the FDA only has a battery of approved products around the second estrogen, which is the dominant estrogen. There's no FDA approved product for estrone. Um, and there's no FDA approved product for estriol, but there are plenty of compounded uh, opportunities around that.”