 While its chemical structure is close to that of progesterone, these changes result in dydrogesterone having improved oral activity and metabolic stability, among other differences, in comparison to progesterone.Other retroprogesterone derivatives, and analogues of dydrogesterone, include trengestone (1,6-didehydro-6-chlororetroprogesterone) and Ro 6-3129 (16α-ethylthio-6-dehydroretroprogesterone).Dydrogesterone is synthesized and manufactured by treatment of progesterone with ultraviolet light exposure.