Oestradiol is a steroid hormone that accounts for 80% of the oestrogen in the female body. It is also found in men at much lower levels. Oestradiol is a steroid hormone that accounts for 80% of the oestrogen in the female body. It is also found in men at much lower levels. Both men and women need to have optimal levels of oestradiol as it is essential for bone strength, libido and sexual function, and fat distribution. In women, oestradiol is secreted by the ovaries, adrenal glands and placenta during pregnancy. It is responsible for developing and maintaining reproductive structures, including fat distribution, preparing the follicle in the ovary for the release of an egg, and helping maintain bone density.