[chrishoney]

As for estradiol vs estradiol valerate: estradiol is the most powerful estrogen in the body. Estradiol valerate is an artificial chemical version of estradiol which the body can absorb and convert to estradiol.

Just for clarification, manufacturers need to modify estradiol ever so slightly to get it to be more soluble in the oil used for intramuscular injection (typically peanut or soy oil). The oil is relatively insoluble in the interstitial fluid of the tissue into which it is injected and thus creates a kind of slow release "depot" so that all of the estradiol isn't absorbed into your system right after the injection. The 'valereate' part is the side chain that makes the estradiol more soluble in oil. An injection typically takes about a week to be fully absorbed.

For all intents and purposes, estradiol and estradiol valereate are considered to be identical in terms of their estrogenic action in the body.