Estradiol valerate is an estradiol ester, or a prodrug of estradiol. As such, it is an estrogen, or an agonist of the estrogen receptors. The affinity of estradiol valerate for the estrogen receptor is approximately 50 times lower than that of estradiol. In addition, estradiol valerate is rapidly cleaved into estradiol and is unable to reach target tissues in concentrations of significance, if at all. As such, estradiol valerate is essentially inactive in terms of estrogenic effect itself, acting solely as a prodrug to estradiol. The molecular weight of estradiol valerate is about 131% of that of estradiol due to the presence of its C17β valerate ester, and hence estradiol valerate contains about 76% of the amount of estradiol of an equal dose of estradiol. Aside from dose adjustment to account for the difference in molecular weight, oral estradiol valerate is considered to be equivalent to oral estradiol. Because estradiol valerate is a prodrug of estradiol, it is considered to be a natural and bioidentical form of estrogen.