Definition: Pregnenes with one double bond or more than three double bonds which have undergone ring contractions or are lacking carbon-18 or carbon-19..
Gestodene [ Gestoden,SH B 3331,13-ethyl-17-hydroxy-18,19-dinor-17 alpha-pregna-4,15-dien-20-yn-3-one,17-alpha-ethinyl-13-ethyl-17 beta-hydroxy-4,15-gonadien-3-one,Gestodene, ((17alpha)-(+-))-isomer ] synthetic steroid with progestational activity; RN given refers to (17alpha)-isomer