Steroids are hormones that occur naturally in the body. Steroid medicines are man-made and are similar to the natural hormones made in the body. The letters α and β[18] denote absolute stereochemistry at chiral centers—a specific nomenclature distinct from the R/S convention[19] of organic chemistry to denote absolute configuration of http://www.stes.tyc.edu.tw/xoops/modules/profile/userinfo.php?uid=2413040