[21] With estradiol as the standard, binding affinity for both estrogen receptor (ER)-α and -ß is equal at 100. [20] Estrone has a binding affinity for ER-α of 60 and for ER-ß of 37.

Both CEE and E2 are classified as natural estrogens and EE as a synthetic estrogen. [11] In terms of human biology, only E2 should be regarded as natural, however, as both of the other estrogen ...