Estrace is a bio-identical form of estradiol, a plant-based version of the same estrogen made by our ovaries. It comes in two forms—oral (systemic) and vaginal (localized). I use very little oral estrogen in my practice, because we've learned that transdermal estrogen (delivered by patch, gel, or spray or other forms that deliver it through the skin) is safer than oral. Because it's not metabolized by the liver, it doesn't carry the same risk of thrombosis.
Vaginal Estrace is great from a therapeutic perspective—that is, it's very effective for treating vaginal atrophy. Because it's a cream, though, many of my patients don't love it: Some find creams messy to apply. It's important to find a form of localized hormones that each patient will actually use!