True about estrogen:

All C18 steroids, including estrone, estradiol, and estriol, are commonly referred to as estrogens. Estriol is a weak estrogen; it is an oxidative product derived from both estradiol and estrone, with the conversion occurring mainly in the liver. The estrogenic potency of b-estradiol is 12 times that of estrone and 80 times that of estriol Estradiol-17b is also one of the most potent regulators of osteoblast and osteoclast function. Estrogen promotes survival of osteoblasts and apoptosis of osteoclasts, thereby oring bone formation over resorption.